MadModder

The Shop => Metal Stuff => Topic started by: vtsteam on May 25, 2013, 03:28:14 PM

Title: Sawed off cupola
Post by: vtsteam on May 25, 2013, 03:28:14 PM
I've been asked for pics of my new furnace in Rob Wilson's cupola thread, so I figured I better open a new thread for this one which has more of a Depression era aesthetic than his fine workmanship!

It's actually not new now -- I built it last fall from a discarded industrial vacuum cleaner barrel. The main body was stainless steel. The intent was to make a short single charge cupola, that might double as a small crucible furnace. It already has had a trial by fire melting a couple of aluminum pours (as a crucible furnace). But has yet to be used for iron.

The cupola's single tuyere is blocked up presently and the tap hole has been used for blast.

I haven't had a lot to spend on it, so I used materials I had on hand to line it -- hard firebrick and sand and fire clay (Hawthorn). The lining is 4" thick and the bore is 7".

I bent up a 4" wide ring for a lid -- but haven't lined that yet or made a lift mechanism for it. For the aluminum melts I used an older 2" thick lid I salvaged from my old popcorn tin melter. But for Iron, I want to have the bigger lid.

This is the furnace I want to try hardwood charcoal with -- there is no source for coke locally that I can find. Though just this weekend I did find a source for blacksmith coal -- don't know if that could be converted to coke or not for an occasional melt.

The capacity of the furnace I hope, will be about 10 lbs of iron, but that remains to be seen. I'll post pics of it here as I can.

First, the salvaged vacuum cleaner can. I took the wire basket and hose outlet off, after this pic.


(http://www.vtsteam.com/SawedOffCupola/FurnaceVac.jpg)





Title: Re: Sawed off cupola
Post by: vtsteam on May 25, 2013, 03:30:18 PM
First course of fire brick set in place. An aluminum tube was set in the bottom to act as a form for the tap hole area.


(http://www.vtsteam.com/SawedOffCupola/FurnaceFirstCourse.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on May 25, 2013, 03:34:00 PM
The lid form. Some steel reinforcing mesh was welded into it for support of the lining.


(http://www.vtsteam.com/SawedOffCupola/FurnaceTop.jpg)

Title: Re: Sawed off cupola
Post by: vtsteam on May 25, 2013, 03:36:36 PM
First course of firebrick completed. You can see a piece of steel pipe on the right, which would be the tuyere for the furnace as a cupola.  The hole above that will be closed in -- it was where the vacuum hose fitting was removed.


(http://www.vtsteam.com/SawedOffCupola/FurnaceFirstCourseDone.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on May 25, 2013, 03:40:23 PM
Second course of brick in and the top screeded off. Some wood chips are in the bottom on top of sand, getting ready to fire the lining.


(http://www.vtsteam.com/SawedOffCupola/FurnaceSecondCourseIn.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on May 25, 2013, 04:27:40 PM
Ready to fire. It was getting cold, toward evening with snow threatening.


(http://www.vtsteam.com/SawedOffCupola/FurnaceReady.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on May 25, 2013, 04:28:57 PM
A wood fire was gradually built up.

(http://www.vtsteam.com/SawedOffCupola/FurnaceFiring.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on May 25, 2013, 04:39:07 PM
After the wood had burned down, a layer of charcoal briquettes was poured in. When lit successive layers were added until the furnace was filled. It was left to heat soak for 30 minutes, and then blast air was applied to the tapping hole to bring the furnace up to temperature. Charcoal briquettes were added to keep it topped up over the next 3 hours of firing. It was dark and beginning to snow when I finally cut the air and bricked off the hole in the cover and the inlet.


(http://www.vtsteam.com/SawedOffCupola/FurnaceFiring1.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on May 25, 2013, 04:44:22 PM
The next morning the furnace was sitting in a melted area after the snow. I walked over to feel the exterior to see if the outer shell was still warm. Yeooowwch, I jerked my hand away!  :wack:   :loco:   It was really hot 11 hours after it had been shut down, in subfreezing temperatures.


(http://www.vtsteam.com/SawedOffCupola/FurnaceMorning.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on May 25, 2013, 04:49:05 PM
It was cool enough to open by evening. Here's what the fired lining looked like. Not bad, only one real crack through the lining at the top of the furnace.


(http://www.vtsteam.com/SawedOffCupola/FurnaceFired.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on May 25, 2013, 04:55:39 PM
What I removed. This clinker shows how much junk there is in store bought charcoal briquettes. But I did take it as a positive sign for ultimately melting iron. In my older furnace, briquettes formed a lot of loose powder ash. But it was never fused like this was. So temps were clearly a lot higher in the new furnace even thought the fuel was a poor one.


(http://www.vtsteam.com/SawedOffCupola/FurnaceClinker-1.jpg)
Title: Re: Sawed off cupola
Post by: Rob.Wilson on May 26, 2013, 03:21:15 AM
Hi Steve

Your lining has fired well  :clap: :clap: your allot  closer to melting Iron than I  :ddb:


Rob

 
Title: Re: Sawed off cupola
Post by: Mayhem on May 27, 2013, 06:21:15 AM
Thanks for posting this.  I will be watching with interest.
Title: Re: Sawed off cupola
Post by: vtsteam on May 27, 2013, 06:15:39 PM
Thanks Mayhem.

Some accessories for the cupola. Made the botting irons and tapping bars this week from reinforcing rod.


(http://www.vtsteam.com/SawedOffCupola/CupolaTools.jpg)


The blower was actually once a turbine, believe it or not. I originally built it to see if I could harness a valveless pulsejet's output by attaching a turbine. It worked.

Basically a pulsejet puts out low velocity, low pressure high volume exhaust. Some people online have suggested that a Tesla disk turbine might be run off of one, but I thought that was wrong. Having built and run a disk turbine, I knew that it was a high pressure device, completely mismatched to a pulsejet's output.

So instead I went in the opposite direction and decided that a turbine shaped like a flat bladed scroll fan, and calculated the same way you would a blower requirement, would match up much better. And possibly wouldn't interfere with the resonance of a valveless pulsejet -- another problem when people have tried to do this in the past. I had used a manometer to measure the exhaust velocity of a pulsejet, and built the fan/turbine to suit

After I sized the fan for the output , I built it with ABEC 7 roller skate bearings and aluminum vanes. The bearing housing was a pipe flange, and a section of water pipe. The disk on the end is half black and half reflective to check RPM with a laser tach. Of course the aluminum vanes melted during the first trial in about 45 seconds! I replaced them with steel. After the switch to steel blades it ran fine. I hit it right on the numbers for RPM, too.

Back to cupolas.... this becomes just a fan if you rotate it with a motor, so I think I'll try to use it for the cupola. Assuming the output is suitable. I will have to try step up or down pulleys with a motor and a manometer to check the output.  I also built a manometer back when I was making this as a turbine.  Hope this fan is the right size for the cupola.

(http://www.vtsteam.com/SawedOffCupola/CupolaTools2.jpg)
Title: Re: Sawed off cupola
Post by: Mayhem on May 30, 2013, 09:00:04 AM
OK - what are tapping irons and blotting bars used for?

Any pics of the build of the blower?  I note that both you and Rob Wilson have built them and this would be a good project log...
Title: Re: Sawed off cupola
Post by: vtsteam on May 30, 2013, 01:31:16 PM
Mayhem basically they are used for corking and uncorking your cupola!

The botting iron gets a plug of clay sand refractory mix ( a bot) and you push it into the tapping hole when melting iron. At a point when it is judged the iron is running and hot enough to be useful. Sealing it off allows it to begin collect behind the bot in the well.

The tapping bar has a chisel point on the end and is used to knock out the bot to let the iron out and down the spout into the waiting pre-heated pouring ladle. The spout is lined with refractory. The dam at the bottom of Rob's spout is there to hold the refractory in and something to pack it against. The actual channel for the metal would be above that.

I'll try to get some photos of the blower construction this evening. Can't now -- must work on legs for furnace. Rob is surging ahead......
Title: Re: Sawed off cupola
Post by: vtsteam on May 30, 2013, 07:31:57 PM
Okay, fan first.

Taking off the cover. Lots of nuts. You can see one of the ABEC 7 skate bearings. There are two.

The arbor was a piece of 5/16" drill rod. The arbor casing is a 3/4" pipe nipple. The pipe nipple was cleaned up on the outside on the lathe, and then bored to take the ball bearing races. With the nipple still in the chuck, the pipe flange was screwed onto one end and it was faced in the lathe. This made everything true and square to the arbor, and the bearings aligned true.

The fan casing was made of thin plate. The flare at the end was made of stovepipe and is very thin. I flame welded a lot of this as I didn't have a good enough arc welder to work with thin metal -- just a Lincoln tombstone buzzbox stick welder.



(http://www.vtsteam.com/SawedOffCupola/cupolafan1.jpg)



Title: Re: Sawed off cupola
Post by: vtsteam on May 30, 2013, 07:39:37 PM
The cover off. You can see the flare and a lotta ugly welds! didn't clean much up here, but didn't ever expect to show this and I was anxious to see the results of my experiment.

I'm no welder.  :palm:


(http://www.vtsteam.com/SawedOffCupola/cupolafan2.jpg)
Title: Re: Sawed off cupola
Post by: dsquire on May 30, 2013, 08:07:34 PM
VT

As long as you keep the air movin fast it won't have time to see if the welds are purty or not.  :lol: :lol: :lol:


It looks good enough for me and if your satisfied with it then that is all that matters. I enjoy following along with your build and with Rob Wilson as well. I don't care who get finished first because I know that you will both be winners.  :D :D

Cheers  :beer:

Don
Title: Re: Sawed off cupola
Post by: vtsteam on May 30, 2013, 08:11:11 PM
I stick welded pieces of threaded rod all around. To get them to align with the holes, I drilled the holes first, then threaded nuts onto the studs and placed thm in the holes. They were then welded in place.


(http://www.vtsteam.com/SawedOffCupola/cupolafan3.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on May 30, 2013, 08:13:39 PM
Thank you kindly Dsquire!  :beer:
Title: Re: Sawed off cupola
Post by: vtsteam on May 30, 2013, 08:23:53 PM
The guts.

The original blades were made of aluminum, as I said. They melted almost instantly in the heat of the pulsejet. As did the ball retainers (plastic) in the cages of the cheaper ball bearings (skate) I had used.

I replaced with steel blades (made from stovepipe) and better bearings, and all was well. The blades are fastened in place with steel pop rivets. I used a hub from a discarded utility fan for the hub here and welded it in place.


(http://www.vtsteam.com/SawedOffCupola/cupolafan4.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on May 30, 2013, 08:41:26 PM
It's funny, to size the turbine (fan) I built some of the equipment normally used to power a cupola furnace. I built a manometer (blast gage) and used it on the pulsejet to characterize exit pressure and velocity. That was what told me they were surprisingly low -- indicating to me that the volume was good and it might respond to a broad flat blade fairly well.  Just like a spinnaker or square sail is a good running sail for high volume low velocity air by comparison with a Marconi rig. on a sailboat -- I was pretty familiar with those.  Because velocity was low, blade area needed to be big, and RPM low. If I remember correctly I shot for about 3500 RPM in the design of the turbine, and hit it pretty close in reality,

Anyway, the funny thing is I have never used the manometer to characterize the fan. So I have no idea how it will perform when I add a motor. Normally you'd build a fan for the requirements of the cupola and then  blast gauge to characterize the fan output. So it's all going to be new to me, though I've had this stuff for many years.

Here's the manometer (blast gauge) that I built.  (Needs some water -- a lot has evaporated.)  believe I used David Gingery's fan book to build both, Though Steve Chastain repeats a lot of that information in his cupola furnace book.


(http://www.vtsteam.com/SawedOffCupola/CupolaBlastGage1.jpg)
Title: Re: Sawed off cupola
Post by: Mayhem on May 30, 2013, 08:47:47 PM
VT - thanks for the info.  That is really useful stuff.
Title: Re: Sawed off cupola
Post by: vtsteam on May 30, 2013, 08:57:14 PM
You're welcome Mayhem.  :beer:

The end of the probe for the blast gauge is what is called a pitot tube. Pilots are familiar with those. They measure relative airspeed. They can also measure dynamic pressure.

This one was made from some copper tubing. The end is a turned brass plug and has a hole drilled in it. A very thin copper tube is soldered to the plug internally and runs inside the outer copper tube to the far end of the probe where it exits in a tee fitting. I believe I used the tubing from a heating furnaces pilot light probe. These are available as replacement parts.

You can also see a ring of small holes drilled further back in the outer tube. This outer tube also exits from a different leg of the tee fitting.



(http://www.vtsteam.com/SawedOffCupola/CupolaBlastGage2.jpg)


Title: Re: Sawed off cupola
Post by: vtsteam on May 30, 2013, 09:25:57 PM
You can see the two separate connections for the tubes here at the tee fitting at the bottom of the pitot. Both are connected to a U-shaped tubing gauge with colored water in it. A ruler is located in the gauge to judge the relative heights of the water on each leg of the U. The difference between the two heights is a measure of the pressure that the pitot tube is sensing. For a furnace this is called blast pressure. And traditionally, in this country at least, it was measured in "inches of water column". This can of course be converted to any measurement system.

BTW if you want a great converter for your computer -- look up Josh Madison's "Convert" online. It's free software. I use it constantly.

(Just checked it -- unfortunately It doesn't calculate inches of water column, but you can add that in its custom tab and then it will in future. 1 inch water column = .00249 bar = .0361 PSI)

Actually, most texts on cupola furnace operation use inches of water column -- so it's usually unnecessary to convert to anything else. And its easy to make a guage if you have a ruler graduated in inches.



(http://www.vtsteam.com/SawedOffCupola/CupolaBlastGage3.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on May 30, 2013, 09:33:06 PM
Okay, back to the cupola.

Salvaged materials: a steel packing crate for a tractor mounted chipper. A few pieces of cutoffs from a galvanized fence top rail. A piece of bent semi flattened 2' pipe I found somewhere.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst1.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on May 30, 2013, 09:39:41 PM
I cut up some of the crate with a grinder and cut the fence rail with the bandsaw. I put the tube into a container of muriatic acid to get rid of the galvanizing.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst2-1.jpg)[/URL]
Title: Re: Sawed off cupola
Post by: vtsteam on May 30, 2013, 09:44:25 PM
Cut to length and mitered some pieces of angle iron.



(http://www.vtsteam.com/SawedOffCupola/Cupolaconst3.jpg)

Title: Re: Sawed off cupola
Post by: vtsteam on May 30, 2013, 09:49:58 PM
Welded them together.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst4.jpg)[/URL]
Title: Re: Sawed off cupola
Post by: vtsteam on May 30, 2013, 09:55:12 PM
Ground it.

(http://www.vtsteam.com/SawedOffCupola/Cupolaconst5.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on May 30, 2013, 10:00:57 PM
And started to put legs on. Got two welded and two tacked by supper time.



(http://www.vtsteam.com/SawedOffCupola/Cupolaconst6.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on May 31, 2013, 07:03:51 PM
(http://www.vtsteam.com/SawedOffCupola/Cupolaconst7.jpg)
Title: Re: Sawed off cupola
Post by: Rob.Wilson on June 01, 2013, 03:44:51 AM
Lookin good Steve  :thumbup: ,,, were is your tapping hole ?  :scratch:

Rob
Title: Re: Sawed off cupola
Post by: vtsteam on June 01, 2013, 09:16:01 PM
Thanks Rob.

The tapping hole 's on the right side, low down, you can't see it from this angle. It doesn't have a spout yet. I had been using it as a tuyere when I melted aluminum as a crucible furnace.

The cupola tuyere is on the left where the elbow is -- it was formerly plugged. There is no wind belt on this small furnace.

Today I cut out the bottom of the furnace. I just used a stick to do that -- the stainless is very thin -- I measured .020 on the drop.

I started to make up a new bottom -- I don't have much for sheet steel, but found an old disk shape that was almost exactly the right size -- the OD was 17", perfect. But the hole was 6" dia. and I needed 7"

So I found a circle cutting attachment I made for my torch several years ago and took a strip of steel and tacked it across the hole to give me a center point. Then I punched the center.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst8.jpg)



Title: Re: Sawed off cupola
Post by: vtsteam on June 01, 2013, 09:20:53 PM
Here is the circle cutter assembled to the torch.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst9.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 01, 2013, 09:25:46 PM
And the hole it cut.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst10.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 01, 2013, 09:35:29 PM
I decided to make the drop door. I don't have much height to work with -- I wanted to keep the cupola low. And since the max melt is 10 lbs (I hope) the height of a ladle is probably going to be only about 6".

Anyway, It occurred to me that the door might be better as the traditional double doors seen on much larger furnaces, to keep them short when in the down position.

Also, I only had two pieces of 3/8" plate available. one was too narrow for a single door, but wide enough for a double, so I tacked my wider plate to it and put the tacks right where the circle centers would be. Then punched them.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst11.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 01, 2013, 09:39:45 PM
And cut them out.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst12.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 01, 2013, 09:47:45 PM
Cut up some water pipe for hinges and welded two sections to the doors.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst13.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 01, 2013, 09:54:55 PM
And welded the other hinge barrels to the bottom plate. The wavy edge on the left is just an old upside down garbage can I was welding on. My welding table. Some day I'll have a better one...

I need to turn some better fitting pins than the 5/8 all-thread here. It was time to quit for the day.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst14.jpg)
Title: Re: Sawed off cupola
Post by: Rob.Wilson on June 02, 2013, 01:47:28 AM
 :D Doors turned out well Steve  :clap: :clap: me thinks I may be loosing  the race  :lol: :lol: :lol:


Rob
Title: Re: Sawed off cupola
Post by: Mayhem on June 02, 2013, 02:02:07 AM
Best pull your finger out then Rob!
Title: Re: Sawed off cupola
Post by: Rob.Wilson on June 02, 2013, 02:05:15 AM
Best pull your finger out then Rob!

 :lol: :lol: I no Darren  :Doh:  , must admit I am looking forward to seeing Iron flowing from Steve's furnace  :ddb:


Rob
Title: Re: Sawed off cupola
Post by: Mayhem on June 02, 2013, 02:10:41 AM
I want to see both in action, so I know which one to copy  :borg:

Just think - if you finish yours Rob you can cast a new mill instead of spending all that time trying to get your Chester square - or is that a sore point  :poke:
Title: Re: Sawed off cupola
Post by: Rob.Wilson on June 02, 2013, 02:15:43 AM
You planning on building cupola Darren ?

 :lol: No the Chester mill is all all nice and square now , I will probably still fined something to moan about on it further down the line  :lol:  :Doh:


Rob
Title: Re: Sawed off cupola
Post by: Mayhem on June 02, 2013, 02:36:03 AM
Its in the back of my mind Rob - along with hundreds of other projects, many of which may never see the light of day.  I still have to finish off my babington burner (http://www.metalworkingfun.com/showthread.php?tid=83&highlight=babington) and then get my furnace built. 

The burner worked fine when I had it set up on retort stands with a gravity drip feed to see if it was plausible to actually build.  Since then there have been little problems crop up with progressing it to a self contained unit with an oil pump and sump.  Now that winter is upon us and the fire bans lifted, I can play a bit more with it.  Once it is running I'll start on the furnace and see how it performs.

If there is any interest in it, I'll start a thread on here when (if) I get the kinks ironed out...
Title: Re: Sawed off cupola
Post by: Rob.Wilson on June 02, 2013, 02:41:52 AM
Aye Darren  get a tread started  :poke:


Rob
Title: Re: Sawed off cupola
Post by: vtsteam on June 02, 2013, 04:31:06 PM
Rob, you know I'd be happy if you poured first. But the friendly cupola wars is a great motivator to actually get the darned thing done, for me. Maybe we'll pour on the same day. That would be cool!

Well, it just started storming so I quit for the day. Here's what I did:

Welding the hinges on really warped up the 1/8" plate, so I weighted it down and clamped it to the base to keep it flat while I welded it in place.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst15.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 02, 2013, 04:39:57 PM
I welded the disk on. I wanted to avoid more distortion, so I didn't continuous weld it on, but put two welds per angle section. Then I ground the tops of the welds down flush with the plate. Not pretty, but it was flat.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst16.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 02, 2013, 04:47:44 PM
I was thinking about what to put on the bottom of the legs as pads. I don't have any heavy bar stock. I did have two lefover pieces of angle iron I'd removed from the pallet. These seemed just the right size to weld on as runners. I didn't even have to cut them. They also had some tabs and slots which I could have removed, but it also just worked out that they were in the right positions for possible lifting eyes. So I left them on.



(http://www.vtsteam.com/SawedOffCupola/Cupolaconst17.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 02, 2013, 04:51:47 PM
There was enough length to cut and bend one end of each into a sled like profile.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst18.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 02, 2013, 05:00:11 PM
Welded and ground a bit. I think this will work better for me on grass and sand than pads would have, and I don't have a paved place for casting. Maybe some day.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst19.jpg)
Title: Re: Sawed off cupola
Post by: micktoon on June 02, 2013, 05:06:15 PM
 That looks like a rare occasion where something is actually ready to use without totally changing it ...............or it could be cunning design work making whats there do the job needed  :thumbup: , it looks like it will do the job to me , you will have to watch you dont go downa dead end as no reversing by the look of things  :D


 Cheers Mick
Title: Re: Sawed off cupola
Post by: vtsteam on June 02, 2013, 05:16:48 PM
Ha ha, thanks Micktoon!

Ah well, all in Plan B,  for reversing or turning I do have a 5 foot shifting bar that I remove boulders with. Tends to come in handy If I don't line up the tractor perfectly with an implement. (I have plenty of practice with stubborn objects!)

Just before the rain I also worked on the doors:

Drilled 1/4" holes on 1" centers. But I also realized the clearances in the hinge are too close. When it heats there may be some binding, so I'll have to grind those back. It would have been wise to put washers in the gaps before welding the hinges to the base plate. I ground the gap between the doors a little to prevent binding that way.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst20.jpg)
Title: Re: Sawed off cupola
Post by: doubleboost on June 02, 2013, 05:21:57 PM
Ha ha, thanks Micktoon!

Ah well, all in Plan B,  for reversing or turning I do have a 5 foot shifting bar that I remove boulders with. Tends to come in handy If I don't line up the tractor perfectly with an implement. (I have plenty of practice with stubborn objects!)

Just before the rain I also worked on the doors:

Drilled 1/4" holes on 1" centers. But I also realized the clearances in the hinge are too close. When it heats there may be some binding, so I'll have to grind those back. It would have been wise to put washers in the gaps before welding the hinges to the base plate. I ground the gap between the doors a little to prevent binding that way.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst20.jpg)

With a big enough lever you could move the world

It is coming on fast now
John
Title: Re: Sawed off cupola
Post by: vtsteam on June 02, 2013, 05:29:48 PM
Thanks John.  :beer:  It only took me three years of backing the tractor multiple times, trying to get those pins to line up, cursing, jumping on and off the tractor to re-start and shift it a little to finally figure out that a lever might be a good idea!   :loco:


After drilling all those holes I added a piece of bar as a lip.

(http://www.vtsteam.com/SawedOffCupola/Cupolaconst21.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 02, 2013, 05:40:07 PM
And tried the barrel on for size. Right after I took this pics, some big drops started falling and I had to dash to get everything put away and covered up. We have severe thunderstorms  and hail predicted for tonight. The garden seedlings are going to take a beating if so!


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst22.jpg)

Title: Re: Sawed off cupola
Post by: vtsteam on June 02, 2013, 05:57:23 PM
Ha ha, I was just imagining that cupola on runners heading downhill in winter with a heat on! My neighbor might be in for a bit of a surprise....
Title: Re: Sawed off cupola
Post by: Mayhem on June 02, 2013, 09:25:10 PM
Looking good va - I'm keen to learn more about the way this style of cupola works, given that there is no wind belt on yours.  I'm off now to see what Rob has been up to on his (I think he is taking this race seriously, as I've not seen any CAD plans or renderings!).

...With a big enough lever you could move the world...

Yes - but what would you use as your fulcrum?
Title: Re: Sawed off cupola
Post by: vtsteam on June 02, 2013, 09:43:16 PM
va? omg, never confuse vt with va! btw how's the weather in NZ?

(vtsteam, purveyor of additional mischief)
Title: Re: Sawed off cupola
Post by: Mayhem on June 03, 2013, 12:01:46 AM
:doh: at least I didn't call you vd 
Title: Re: Sawed off cupola
Post by: vtsteam on June 03, 2013, 07:41:41 AM
Just kidding Mayhem, I've lived in both states!

 :lol:   :ddb:
Title: Re: Sawed off cupola
Post by: Mayhem on June 03, 2013, 08:38:32 AM
VA and VT I hope, not VD  :jaw:

 :lol:
Title: Re: Sawed off cupola
Post by: Rob.Wilson on June 03, 2013, 10:36:25 AM
L  I'm off now to see what Rob has been up to on his (I think he is taking this race seriously, as I've not seen any CAD plans or renderings!).

Too right its SERIOUS ! Darren this is like an international bake off , well cupola off , now if your got your arse in gear and built one it could be global.  :lol: :lol:

As Steve said ,
Quote
But the friendly cupola wars is a great motivator to actually get the darned thing done, for me
it is more a motivation thing , all done with good humor , well at least my rain dance worked a bit , it did slow him up a tad  :lol:


Looking good Steve  :thumbup: I like the doors   :dremel: ,



Rob


PS , I now have 50 kg of metcoke   :ddb:
Title: Re: Sawed off cupola
Post by: vtsteam on June 03, 2013, 11:44:54 AM
VD? Never been there, by golly. And never want to go there agin!
 :lol:

Now for more serious matters. Since it's raining today, time to do a little calculating. Result, I have some small doubts my fan is going to cut it. I was hoping for 2 oz of blast pressure (ideal, theoretical) to give me some leeway with this sawed off single charge melter. I don't know, everything is so experimental here with nothing to go by. This is not a normal cupola. Or even a normal fuel.

Two oz. theoretical looks like I would require turning the fan at about 5700 RPM with ideal output @100 cuft/min. Not sure if that RPM would be a problem. That would absorb 0.12 hp so the 5/16 drill rod fan shaft could probably take it. Not sure about the bearings. Maybe. Anyway, wouldn't need much of a motor. 1/4 hp 3450 rpm preferable and pulleys say 1.5" and 2.5".

Rain stopped.....getting sunny out there......back at it.
Title: Re: Sawed off cupola
Post by: vtsteam on June 03, 2013, 11:51:19 AM
PS , I now have 50 kg of metcoke   :ddb:

Oh sure, rub it in.....  :hammer:
Title: Re: Sawed off cupola
Post by: vtsteam on June 03, 2013, 05:24:45 PM
Very little out of him today. Has his metrocoke. Probably bought it off a street corner. Heaven knows what he's up to.  I like it better when he posts pictures. Is he trying to psych me out? Must not falter. Must squelch doubts. Must keep forging ahead...... Aaaach school board planning committee meeting at 2:00. Wash off grinding dust....back again at 3:30....don welding duds. Then another school board meeting at 6:15. Probably dark when I get back. 600 feet to house. Must avoid thinking about bear...... or Rob and cupola....

Well, here's all I got done today:

(http://www.vtsteam.com/SawedOffCupola/Cupolaconst23.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 04, 2013, 11:44:11 AM
Checking the fit:


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst24.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 04, 2013, 12:29:49 PM
I wanted to weld some relatively thin steel tube to the furnace base. Normally I'd burn a hole right through the tube sooner or later even using 1/16" welding rod. Not to mention the furnace shell which is .020" stainless -- backed by insulating refractory. I wouldn't even have to look at that with a stick welder before there'd be a ragged hole in it. (For the stainless shell, I've decided it's fastenings and clamps all the way.)

But I thought about brazing the thin steel tube to the steel furnace base. Starting to run out of acetylene though I noticed this morning. But then I remembered I've also had the correct hoses and a spare gauge to switch over from oxy-acetylene to oxy-propane -- still in boxes. Just never actually set it up.

Well I have a full 20 lb tank of propane and this morning I thought I'd give it a try, so I hooked up the propane hoses to the torch, and switched over to a #2 (Victor style) welding tip to try some propane brazing.

Welding is not supposed to be possible w/oxy-prop, but cutting and brazing are. Propane is considerably cheaper than acetylene, and far more available. Brazing has always been a little difficult for me -- I like gas welding better, but perhaps I just didn't have the right tip for the job. Seemed to take forever to heat up to flowing, and by then I'd burn the braze.

Anyway, The #2 welding tip was a cheap one from Harbor Freight -- purchased just for trying out brazing w/propane, and so I tried it. First problem was that since it was really an acetylene tip, the flame blew out immediately when cranked even slightly -- plus it was a very windy day.

But from reading online, I knew this would happen, and heeded the suggestion I read somewhere to drill the tip slightly to form a recessed flame holder.So I used a 3/32" drill bit and went in maybe 1/16th". Well, that really made a difference and I was able to maintain a flame. Cranking the flame up still proceeded in a couple stages, but I got it to a very slight hissing flame easily.

So then I thought I'd try a really tough test, and grabbed a really crappy piece of bent cracked and rained-on coated brazing rod to try to get some braze on a piece of rusty reinforcing bar lying in the dirt. NO surface prep. Was this a planned torture test? Nah -- they were both handy to where I was standing with the torch lit! I had little expectation of braze doing anything but balling up and rolling off the rod.

Imagine my surprise when after seconds of heating, the stuff started to just flow over the end of the rebar. I could not believe it! Man that propane puts out some decent spot heat! The flame was pinpoint accurate. I don't think the rebar behind the end was even hot. You can see the rust isn't even turned black a half inch back.

I think I'm going to like brazing with propane!  :ddb:



(http://www.vtsteam.com/SawedOffCupola/Cupolaconst25.jpg)


Title: Re: Sawed off cupola
Post by: Rob.Wilson on June 04, 2013, 01:40:37 PM
 :lol: :lol: Hi Steve ,

I am no trying to psych you out  :lol: , just work is getting in the way  :palm: Maybe I will get a bit done tomorrow night .

Furnace looks great on the stand  :thumbup:  , so were going all out and doing paint jobs as well  :med:

Rob
Title: Re: Sawed off cupola
Post by: vtsteam on June 04, 2013, 02:45:42 PM
Thanks Rob. If I welded like you, I would never paint anything.   :bow:
Title: Re: Sawed off cupola
Post by: vtsteam on June 04, 2013, 05:05:36 PM
Finished up the day working on the lid and lift mechanism:


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst27.jpg)


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst26.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 05, 2013, 02:07:53 PM
Working on the lid lift mechanism today. Strictly speaking, this isn't a part of a cupola, but something that will be a help if I also use it as a crucible furnace.

I'm using 3/4" water pipe as the lift lever. The unpainted vertical pipe leads up to the lid. Both were cut from the same scrsap piece of pipe. Under the lift stanchion is a small plate, welded to the lever. I'm checking the position of the pivot bolt in order to make a bracket as a fulcrum.

After the bracket is made, the bolt will be reversed, and run through the bracket, and the head will be welded to the bracket.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst28.jpg)


Title: Re: Sawed off cupola
Post by: vtsteam on June 05, 2013, 02:13:21 PM
The lever comes up and terminates under the cupola. That's because I don't want anything sticking out when I have to move it, and also probably will also be better when it is operating as a cupola.

An extension  made from a piece of 1" electrical conduit will be slipped over the lever when the furnace is used with a crucible. Then you just step on the extension to lift the lid.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst29.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 05, 2013, 02:15:03 PM
The bracket and bolt welded in place.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst30.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 05, 2013, 02:17:37 PM
Cupola with lid swung out of the way, and showing the lever extension. Might be a little long, but depending on how hot that furnace and lid is, might seem a little short!


We have rain predicted for the next three days, so that should slow things down a bit.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst31.jpg)
Title: Re: Sawed off cupola
Post by: Rob.Wilson on June 06, 2013, 11:48:31 AM
Looks like your getting close to the finishing line Steve

I like the lid lift arrangement   :clap: :clap: :clap:


Rob
Title: Re: Sawed off cupola
Post by: vtsteam on June 06, 2013, 04:35:37 PM
Thanks Rob!

Luckily the rain held off today, and I was able to work on the belt clamp.

First I cut up another piece of that pallet to make brackets:

(http://www.vtsteam.com/SawedOffCupola/Cupolaconst32.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 06, 2013, 04:40:24 PM
Then welded two of the brackets to the furnace base:

(http://www.vtsteam.com/SawedOffCupola/Cupolaconst33.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 06, 2013, 04:45:35 PM
Then I bent a strap out of 1/8" x 2" and welded the other two brackets to that:


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst34.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 06, 2013, 04:49:51 PM
The strap and base before adding the barrel:


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst35.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 06, 2013, 04:53:49 PM
And the barrel bolted in place:


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst36.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 06, 2013, 05:00:31 PM
The furnace mostly finished:



(http://www.vtsteam.com/SawedOffCupola/Cupolaconst37.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 06, 2013, 05:12:03 PM
Because the welding was finished, I moved the cupola up to where it will be tried out. I live on steep ground, so I wanted to get it up there before it started to rain because even the tractor won't make it in mud. We have heavy rains predicted for 2 days. It is supposed to clear up Sunday.

The next job is filling the lid with refractory. I found some lightweight fire brick given to me many years ago by a friend who was rebuilding a kiln. The lid will be quite heavy, since it's 4" thick, so I thought I'd break these up into chunks and plaster them into the mix to lighten it up.

I'll leave a 1" thick layer of pure fireclay and sand as a hot face, since these brick aren't rated at as high a temperature, I believe.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst38.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 06, 2013, 05:21:48 PM
I had a 1/4 bag of fireclay that was in a storage area that was recently flooded with an inch of water. The clay was probably a perfect consistency for making pottery, but poor for mixing with sand to make refractory!

I spent about an hour kneading in sand by hand, then switched to the riddle and put it through that twice using a firebrick as a muller. That was a lot of work!

Finally it seemed to be mixed and stick together reasonably well. I covered it and put it aside, even though I really wanted to ram up the lid. But with rains imminent, I knew that firing it wouldn't protect it, since I couldn't cover a hot lid with plastic sheet, and I could imagine trying to save the whole thing at night in the rain. Bad idea. So, uncharacteristic patience for me -- I put the furnace aside until Sunday.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst39.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 09, 2013, 05:46:18 PM
It's Sunday finally, our one day of sun predicted before we return to rains until Wednesday. Couldn't get much done because of a retirement party for a friend and neighbor this afternoon, but did work on the lid.

Here is the bare metal ring and some scrap reinforcing:



(http://www.vtsteam.com/SawedOffCupola/Cupolaconst40.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 09, 2013, 05:48:41 PM
Cutting up soft firebrick with an old pruning saw (never worked well on wood). Cuts quite easily. The bottom of the lid was rammed up first with about 2 inches of refractory before adding the brick:


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst41.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 09, 2013, 05:50:03 PM
Checking the brick for fit. The spray can is there to provide a form for the exhaust hole.



(http://www.vtsteam.com/SawedOffCupola/Cupolaconst42.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 09, 2013, 05:55:37 PM
The fire brick was mortared in place with premixed "refractory cement" mixed with Perlite. I had both left over for a few years from other projects. Neither is a super high temp product, but I hope that the 2" of fireclay and sand refractory below will keep the upper portion of the lid within a reasonable temperature range.

I hoped that the refractory cement would provide a better bond to the brick and steel. It contains sodium silicate and fireclay and some kind of non-asbestos fiber. Sticky stuff.

I hoped the perlite would help lighten the lid (as would the insulating firebrick).

Guess we'll find out.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst43.jpg)[/URL]
Title: Re: Sawed off cupola
Post by: vtsteam on June 09, 2013, 05:58:05 PM
Cooking the lid:

(http://www.vtsteam.com/SawedOffCupola/Cupolaconst44.jpg)[/URL]
Title: Re: Sawed off cupola
Post by: Rob.Wilson on June 10, 2013, 11:55:26 AM
Nice work Steve  :thumbup:

You must be dam close to a test run  :headbang:


Rob
Title: Re: Sawed off cupola
Post by: vtsteam on June 10, 2013, 01:01:12 PM
Not too close yet Rob. I need proper tuyere attachment, patching lining (it's taken a beating with all the metal work and moving), make pouring shank, need to mix iron molding sand, make ingot molds, make blower /motor assembly, test fan output, make skimmer, line ladle, make more charcoal, break up and clean iron pieces, get weights for flasks, figure out a ladle heater. Seems like there's a never ending list ! And it will be raining through Wednesday. I'm going to guess a week 'til I get a nice hot ladle full of slag!!
 :lol: :lol: :lol: :lol:
Title: Re: Sawed off cupola
Post by: vtsteam on June 10, 2013, 08:47:31 PM
Decided as long as it was raining today I'd take an hour drive down to a town in Massachusetts that has a pottery supply business, and buy some silica sand. It's getting hard to find, and expensive for the real stuff because of health concerns.

They had the pure stuff in #60 mesh. I had read a recommendation for #70 from Stewart Marshall, but 60 was all they had. So I bought 200 lbs of it and trucked it back. Brought plastic bins with me to keep it dry.

I'm going to use Ironman's mix of 85% sand, 7.5% Bentonite, 3.5% coal dust (I might have found a source for some coal I can pulverize -- but can I substitute charcoal dust?), and 4% water.

Ironman's video:



(Ironman, if you read this, is this greensand composition by weight or volume. I'm assuming weight. Thanks!)
Title: Re: Sawed off cupola
Post by: Swarfing on June 11, 2013, 03:04:47 PM
Vsteam not sure about your side of the pond? but a good source for silica sand is the stuff they use for brushing in between block paving. Here it is qute fine and i use it with good results
Title: Re: Sawed off cupola
Post by: ironman on June 11, 2013, 08:38:51 PM
vtssteam It is by weight. The coal dust burns and slightly lifts the metal of the sand to give it a smooth surface. Coal dust may be hard to find so you could use other things that burn ie. sawdust or wheat flour.
Title: Re: Sawed off cupola
Post by: vtsteam on June 11, 2013, 09:23:54 PM
Thank you Swarfing, I will look into that for silica sand.

Ironman, would powdered charcoal work? That would be easy to get/make. I'd prefer not to use other things like flour and sawdust that can decompose.

I could carbonize sawdust -- I have quite a bit of that from my homemade sawmill.
Title: Re: Sawed off cupola
Post by: awemawson on June 12, 2013, 03:46:53 AM
Recalling something I read in one of my early foundry books, I think the coal is added to stop 'blistering' where the sand fuses to the cast. If I remember correctly the coal dust breaks down forming a gas layer that cushions the sand from the metal. Also improves surface finish.

If the above is correct powdered charcoal wouldn't work as the gases have already been driven off.
Title: Re: Sawed off cupola
Post by: vtsteam on June 12, 2013, 07:45:56 AM
Thanks awemawson, I think the gas involved is CO2 or CO so any of the above might work.
Title: Re: Sawed off cupola
Post by: awemawson on June 12, 2013, 09:48:40 AM
Google "why is coal added to foundry sand" There are many references to the coal partially burning and off gassing organic compounds - here is one on wikipedia


http://en.wikipedia.org/wiki/Molding_sand


My feeling is charcoal won't work as the majority of the organic stuff has been driven off in the making process.
Title: Re: Sawed off cupola
Post by: vtsteam on June 12, 2013, 04:03:04 PM
CO2 and CO are organic compounds that are off-gassed during partial combustion of coal. And charcoal.

Graphite has recently come into favor in commercial practice for replacing sea coal to reduce unwanted emissions. Graphite is pure carbon.

Most references I found online said seacoal was used to produce a reducing atmosphere. There was not specific mention of the need for VOCs to do that, just a reducing atmosphere,.....which a mix of CO2 and CO would produce, since they have absorbed and continue to actively absorb oxygen.

I'd still like to hear from Ironman on this, or anyone who has actual experience using charcoal in greensand for iron casting.
Title: Re: Sawed off cupola
Post by: ironman on June 13, 2013, 03:45:59 AM
vtsteam Charcoal will not do anything because as awemawson has said it burns and forms a gas  layer.

I used to add coal dust to my sand after every melt but I don't do it anymore. Each time the cast iron burns the coal dust it turns to coke which is an inert byproduct that I don't need or want in my sand. The sand becomes very brittle after a while and so more bentonite has to be added to give the sand more strength.

 I now make a facing sand with coal dust and use it to cover the pattern only so the sand lasts for many years. When I added coal dust to the sand after every melt I would throw out the sand about every 12 months.

If you want to don't use any additives and just wire brush or sand blast the castings
Title: Re: Sawed off cupola
Post by: vtsteam on June 13, 2013, 08:49:55 AM
Thanks Ironman, so coal only in the facing sand. That is easier for me to come by, since I have some coal that I can pulverize, and I wouldn't need much of it

I'm still confused about the charcoal since all of the online talk is that you want a reducing layer of gas between the metal and mold surface to get a good finish, and that seacoal produces it. But charcoal also seems to produce it, but now it is seen as a negative. Maybe because it burns more easily, and produces too much gas? Would reducing the amount help that?

Anyway experience is more important than theory, and you have that, more than most people doing iron on the scale we are interested in. So I won't add coal or charcoal to the molding sand, but only to facing sand.

I suppose I could do some small batch experiments with various amounts of ingredients just to satisfy my curiosity about all of the above. I also have some plumbago (graphite) that I could try. Since it doesn't have to be in my main casting sand, there's less of a concern that I'm going to wreck it all by mixing in the wrong ingredients right now at the start.

Title: Re: Sawed off cupola
Post by: vtsteam on June 13, 2013, 10:52:31 AM
One more accidental addition to the gear....the propane torch I'm experimenting with in another thread -- trying to get it to braze -- no good for that so far, but would probably work fine as a ladle heater.
Title: Re: Sawed off cupola
Post by: ironman on June 14, 2013, 02:51:34 AM
I was about to suggest doing experiments to see what works and what does'nt, that is  the way I learnt. We all come from different parts of the world so what we use may not the same and give a different result.

I have heard about this method but never tried it, is using CO2 gas from a bottle and filling up the mold so there is no oxygen left. The castings have a nice colour and skin because there is no air to oxidize the surface.

With your ladle heater it might be easier to place the ladle on top of your exhaust vent to recover the waste heat coming from your furnace. It also means you do not waste propane heating your ladle. I wanted to try this method with my own cupola but my the ladle was too heavy to lift to the top so I scrapped the idea because of safety concerns.
Title: Re: Sawed off cupola
Post by: vtsteam on June 14, 2013, 07:48:39 AM
Thanks Ironman. I just ran across a reference in Stewart Marshall's book to yet another facing dust -- from store bought charcoal briquets. He doesn't like them for iron use otherwise, but mentions the dust  So maybe I could try a test of all 4 types of facing powders in sand so far mentioned and see what happens.

I had thought about an exhaust ladle heater, but when I saw yours in action it was glowing really yellow, and I was wondering if the exhaust from my sawed off cupola with a lid could really get a ladle to glow.

Definitely would be nice to save propane if possible, so just one more thing to find out.



Title: Re: Sawed off cupola
Post by: vtsteam on June 14, 2013, 06:16:22 PM
Rain stopped this morning, I think we got 8" total since last week with 1 day of sun.

Thought I'd try to fire the cupola lid a little harder with a propane weed torch, but the thought of dragging a full tank 300 feet up the saturated hill wasn't apealing.

I remembered the wheels and handle I'd taken off of the cupola shell (it was originally a commercial vacuum cleaner), and decided to make a oxy-propane welding cart with the remnants. A little rebar, a cutoff of 1/8" sheet, and an old discarded toolbox were assembled, and I tried out my oxy-propane rig for the first time as a cutting torch by simply changing the cutting tip. It cut the sheet and rebar easily, so I'm very happy with the changeover from acetylene.

Everything that went into this was a discard -- the wheels and handles twice over. The rebar was just short cutoffs, so I welded them together to get a usable length. In short, this is a total work of scrap!

It rolls and balances very well, and I may actually take a grinder and a paintbrush to it to give it some respectability. It sure is nice to have -- Just as I finished taking the picture a monster gray cloud rolled up and it started to rain again.!! But wheeling the rig back into shelter was the work of a moment and It was very pleasing to be able to do that.


(http://www.vtsteam.com/SawedOffCupola/Cart1.jpg)


(http://www.vtsteam.com/SawedOffCupola/Cart2.jpg)
Title: Re: Sawed off cupola
Post by: dsquire on June 14, 2013, 07:12:16 PM
VT

Darn it, you would be a handy guy to have around my junk treasure pile.  :lol: :lol:

It's a good thing that you and Rob Wilson are on seperate Continents. I can't imagine what we would all see if the two of you got together.  :Doh: :Doh:


That cart looks pretty darn good. With a lick of paint nobody will ever know where it came from.  :D :D


Cheers  :beer:

Don
Title: Re: Sawed off cupola
Post by: NeoTech on June 15, 2013, 03:19:40 AM
So now we should start the get the madmodders onto the same scarpyard project? ;)
Title: Re: Sawed off cupola
Post by: awemawson on June 15, 2013, 03:47:31 AM
I reckon your next project needs to be a Funicular railway up that hill of yours - save all that hassle  :clap:
Title: Re: Sawed off cupola
Post by: vtsteam on June 15, 2013, 08:36:14 PM
Thanks Dsquire -- Rob has some pretty talented friends over there already -- apparently involved with tool grinders at the moment! Did manage to add a fender under the hose to prevent rubbing, grind some of the worst looking parts and empty a spray can of paint at the thing, before the honey-do list ad to be attended to -- since we actually had sunshine all day. Basically I mowed with a push mower from 2:00 to 6:00 PM. Grass was 6 " tall -- where it was low!

Sure Neotech, join in the junkyard fun anytime!

Awemawson, I wish -- that would be fantastic. I've dreamt of a scenc railway through this property. But funicular in spots, for sure!
Title: Re: Sawed off cupola
Post by: awemawson on June 16, 2013, 04:12:17 AM
Basically I mowed with a push mower from 2:00 to 6:00 PM. Grass was 6 " tall -- where it was low!


I'll lend you some sheep if you like  :lol:
Title: Re: Sawed off cupola
Post by: Rob.Wilson on June 16, 2013, 04:22:05 AM
Hi Steve

Thats a nice compact set you have there  :thumbup: , thinking of doing similar , due to space and cost of fuel gas .

I may go down the Propane route too .


Rob
Title: Re: Sawed off cupola
Post by: vtsteam on June 16, 2013, 09:20:35 AM
Basically I mowed with a push mower from 2:00 to 6:00 PM. Grass was 6 " tall -- where it was low!


I'll lend you some sheep if you like  :lol:

That would be great! Sheep are making a comeback here after wool industry collapsed many moons ago. Specialty cheeses are the reason. Guess I'd have to figure out what to do about Eastern Coyote (wolf mix) which are also new upon the scene. Our little mutt is half border collie, but half dachshund, so he'd basically make a meal for them!
Title: Re: Sawed off cupola
Post by: Mayhem on June 16, 2013, 09:49:13 AM
Throw a couple of alpaca's into the heard - they protect the sheep from canine threats.
Title: Re: Sawed off cupola
Post by: vtsteam on June 16, 2013, 10:03:57 AM
Hi Steve

Thats a nice compact set you have there  :thumbup: , thinking of doing similar , due to space and cost of fuel gas .

I may go down the Propane route too . Rob

I like propane a lot, Rob, now that I've tried it. Took me a bunch of cuts to understand the difference. Preheat is a little longer, but not much -- but you do need to keep the flame about an inch above the cut to preheat, not touching the blue cones as in Acetylene.

But you lower when you hit the oxygen to normal cutting height -- didn't realize that at first and so was interrupting cuts. Makes sense now because, of course it's the oxygen jet that cuts, not the propane (or acetylene). 

I like the compactness of the rig, too -- and there is 170 cu ft of propane in there instead of the 40 cu ft of acetylene in the B size tank that matches the oxygen tank. Plus propane is 2500 btu/cu. ft, and acetylene is 1750 btu/cu ft. Costs the same to fill the propane tank as the B size acetylene tank, and much more widely available. Also just a lot more stable a gas than acetylene, with its tricky storage medium and critical flow rates. so generally I feel better about just having a tank of it around.

Changeover for me was just buying a T rated hose ($35) and a propane cutting tip for my torch ($15). I had a spare acetylene gauge which I'm using. I've kept my acetylene tank in case I want to flame weld, but if that doesn't happen often enough, I'm thinking about trading it in for a second oxygen tank.

Title: Re: Sawed off cupola
Post by: vtsteam on June 17, 2013, 04:24:58 PM
I got a chance to work on a tuyere for the cupola today. I took an old piece of 2" pipe with an elbow attached that I had found half buried in a field . It was well rusted together, and filled with dirt.  I sawed off the pipe to a 3" stub. Then welded  a bandsaw cutoff from a 1-1/2" pipe with threads to the elbow. That made it into a Tee and will serve as a peep hole. I cut out the connecting hole through the elbow inside the new fitting using the oxy- propane torch.

Then I bent a piece of 1/8" plate to fit the barrel curvature, and burned a hole in it. I then welded the tuyere to the plate. The plate will serve as a mounting flange to attach to the furnace barrel. The barrel skin is very thin stainless and I'll probably rivet the tuyere plate in place. This is what it looked like, and a pic of test fitting it in place on the furnace. It isn't attached yet. A thunderstorm came up and I had to get tools under shelter.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst45.jpg)



(http://www.vtsteam.com/SawedOffCupola/Cupolaconst46.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 18, 2013, 08:13:47 PM
Riveted the tuyere on tonight and patched the lining and lid.
Title: Re: Sawed off cupola
Post by: vtsteam on June 19, 2013, 09:38:51 PM
Sunsine!!! This morning I decided to try to fire the patched lining and lid, and to do that I would try using my new propane burner. I  took the oxy bottle off of the new propane cart and wheeled it up the hill to the furnace position in what was once cleared dirt, and more recently, mud. But today with the sunf and a breeze, the mud dried up.

To fire it I also needed a prop to keep the cupola doors shut, so I welded a length of chain onto a section of 2" pipe, and scrounged a square of 1/4" plate as a base. I didn't weld this to the pipe because I think it would more likely hang up that way.

Anyway, I got everything set up, dialed 5 PSI on the gauge, which seems to be a nice even flame for this burner. The Mako burner, which this one is similar to, has a range of 5 PSI to 15 PSI. I wasn't in any hurry to fire the lining, and I've never had it up to 15.

I just propped the burner in the cupola's tap hole and there was a muffled roar, much quieter than running a blower with charcoal. I figured I'd run it an hour.



(http://www.vtsteam.com/SawedOffCupola/Cupolaconst47.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 19, 2013, 09:46:19 PM
Naturally as soon as you start heating up a furnace, you think, why not use that heat? I didn't have a mold ready, and the sand isn't in condition anyway, but I figured I might try to melt a chunk of aluminum that has been a challenge to my bandsaw. Not the best stuff for casting -- 6061 t6 I think, but I might be casting some flasks like ironman's, and surface finish wouldn't be important. Some of the best structural aluminum types are not too pretty when cast.

Anyway I figured I'd take this recalcitrant 4 pound chunk and see whether I could reduce it to muffin ingots. The darn thing would hardly fit in the pot!


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst48.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 19, 2013, 09:57:29 PM
And it fought bravely for about an hour, but finally succumbed to gradually increasing furnace temps. I have 4" thick walls and lid, so the furnace has a fair amount of heat inertia. And with a modest burn rate set on the propane burner, I didn't expect to set any records. But it definitely turned into a full to the brim pot of the silvery stuff, and poured nice as you please into 9 muffins.  :thumbup:

Well that just fired the enthusiasm up, and I repeated the same thing with another chunk that might have been its twin brother.  It melted in half the time with the furnace temps up. By the time two hours was up I had done four melts -- the last were pieces of a Chevy bell housing and a heavy cast aluminum tray from the thrift shop. These, having been cast items made much better looking aluminum than the 6061 had. All in all about 15 pounds of muffin ingots.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst49.jpg)


Title: Re: Sawed off cupola
Post by: vtsteam on June 19, 2013, 10:11:40 PM
Well things were going along great when my 6 year old daughter came up and said, Daddy do you think you can make a picnic table in 5 days?

Sure, I said, I promised you. Her birthday party is coming up and she said she wanted a picnic table from me as a birthday present. Unusual level headed and practical 6 year old!  She also has her mothers sense of urgency when it comes to chores.

Seemed like the furnace had baked long enough, anyway, so I turned off the burner and checked the tank. Not even cold. No condensation, and at least a half tank left. Pretty economical, I guess -- I don't know. My first experience with propane in a furnace.

So switched gears, drove an old pine log onto the sawmill with the cant dog. Slicked off the bark with a flat shovel, poured about a cup of gas into the motor, turned the stopcock, gave it the choke and it started instantly. First pull. As if it hadn't sat all winter.

I did a rough job on the boards -- blade needs sharpening after sitting, but I got it done. By afternoon I was bolting the table together.

Good day! Nice to see sun again.


(http://www.vtsteam.com/SawedOffCupola/Picnic1.jpg)



(http://www.vtsteam.com/SawedOffCupola/Picnic2.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 20, 2013, 06:29:02 PM
Made another load of charcoal today. Made up the sand bottom in the cupola. Lined the breast with refractory and lined the spout. Checked the ladle fit under the spout.



(http://www.vtsteam.com/SawedOffCupola/Cupolaconst50.jpg)

Title: Re: Sawed off cupola
Post by: Mayhem on June 20, 2013, 08:19:45 PM
Looking good VT - is the chain to pull the doors or to keep the guard dog in close proximity.
Title: Re: Sawed off cupola
Post by: vtsteam on June 20, 2013, 08:49:37 PM
It pulls out the prop holding the doors shut.
Title: Re: Sawed off cupola
Post by: vtsteam on June 21, 2013, 11:43:10 AM
Measuring capacity and charcoal this morning. Looks like, if filled to the brim, the furnace will hold 9.5 liters (a full US 2.5 gal bucket) of charcoal, which weighs 1735 gm, (3.8 lbs).

Somewhat more than half of the barrel is above the tuyere, but let's say the bed is less than half -- that gives me say 1.5 pounds of carbon in the charge. That should mean maybe 6 to 9 pounds of iron, depending on how well it melts (if at all!).

So, maybe start out with 6 lbs of iron?
Title: Re: Sawed off cupola
Post by: Rob.Wilson on June 21, 2013, 11:59:27 AM
Must be getting very close to a melt in cupola mode  Steve  :thumbup:

I will keep my fingers crossed all goes well  :med:


Rob
Title: Re: Sawed off cupola
Post by: vtsteam on June 21, 2013, 02:11:27 PM
I could probably try it tomorrow, Rob if I could work on it straight from here on out. But commitments to work today and through the weekend, and Monday all day will push it off, I think. Weather has been perfect.

Tuesday prediction looks do-able.

Unless I can sneak it in Sunday evening.... :zap:
Title: Re: Sawed off cupola
Post by: vtsteam on June 21, 2013, 02:18:40 PM
(http://www.vtsteam.com/SawedOffCupola/Cupolaconst51-1.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 21, 2013, 05:13:39 PM
Another two to check off the list.

(http://www.vtsteam.com/SawedOffCupola/Cupolaconst52.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 21, 2013, 08:36:31 PM
Mixed up 50 lbs of new greensand tonight after supper. 50 lbs F60 quartz sand with 3.75 lbs Bentonite (ceramic grade) and 2 lbs water.

I put it in a wheelbarrow and applied the Strongarm (tm) muller first the sand, then water gradually, and finally the clay.

Wonderful stuff, very fluffy and uniform compared to my ten year old sand -- which was sand and fireclay.

Well, it stood me in good stead for a long time -- built my lathe and much else. But I think I'm really going to love this new stuff!

Funny how you can get excited over some sand! :lol:
Title: Re: Sawed off cupola
Post by: Rob.Wilson on June 22, 2013, 04:26:26 PM
Hi Steve


 :lol: :lol: nothing wrong with having a sand fetish  :)


I hope the weather holds for you  :thumbup:


Rob
Title: Re: Sawed off cupola
Post by: vtsteam on June 22, 2013, 04:34:47 PM
I'm more pleased with the new sand than anything else!  Keep going out and making little clumps of it and breaking it apart. Nice clean break. This stuff is pure white.

I must be nuts. :loco:
Title: Re: Sawed off cupola
Post by: vtsteam on June 22, 2013, 08:49:25 PM
Well was able to sneak in a couple minor things after supper -- painted the handles different colors so I know what is what quickly, and won't lose a tool in the grass.

And I soaked some broken up steam radiator pieces in a little dilute muriatic acid for a couple hours to remove scale and most of the rust. Then rinsed and set out to dry. That's about 18 lbs ready to go --  3 charges @ 6lbs ea. in case they are needed.

Getting there little by little!


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst53.jpg)



(http://www.vtsteam.com/SawedOffCupola/Cupolaconst54.jpg)


Title: Re: Sawed off cupola
Post by: Rob.Wilson on June 24, 2013, 06:19:19 PM
Hi Steve

I like the easy find tools , very bright  :thumbup:  , looks like you cant be far off now  :poke:


Rob
Title: Re: Sawed off cupola
Post by: vtsteam on June 24, 2013, 08:44:57 PM
Thanks Rob. Tomorrow was the day planned, but had a little setback this evening. Part of the lid flaked off while it was hanging off to the side. I patched it tonight, but the real problem was that I didn't add enough water to the clay/sand mix when I originally rammed it up. Most books say to keep it relatively dry, similar to molding sand. But every time I've done that on a furnace lid or repair I get flaking. I think it ought to be mixed thinner like mortar -- then it seems to stick well. It does shrink, and sometimes crack a little with more water, but it's usually solid.

The problem with this lid is it's 4" thick, as is the furnace lining. And it really doesn't get vitrified except above where the bore is. The rest just stays clay and sand.

I'm thinking that a much better way to do it would be to arch the inside upwards (hollow it) so the rim is the only area of contact with the furnace barrel. Then the whole top would be exposed to the heat and vitirify. Plus you'd have a little more room for fuel. I bet the arch would be just as stable against flaking as a shape, if not more so. Being in compression. And the lid would be lighter in weight. There's just a lot of wasted uncooked material in it now. So if it flakes again, I'll do the arch thing.

Anyway still lots to do if I'm to try an iron melt tomorrow -- the blower isn't sorted ( I do have my fan -- but without motor, and a choice of a small shop vac, and an older larger one). I might skip my fan for the first try and go with a vac. But still need to pipe it and make some kind of blast gate/control. Need to mix bodding. Should have done that today.

And need to mould a pattern in the new sand. Don't just want to pour ingots if this actually works!

Dental appointment at 11 -- and thunderstorms predicted for late afternoon. But it could all happen tomorrow..... :zap:
Title: Re: Sawed off cupola
Post by: vtsteam on June 25, 2013, 07:08:12 PM
Well, gave it a go, but it didn't work. I'm not sure how badly it didn't work because I decided to just kill the blast and close it up instead of drop the bottom. The tap hole was never closed, and nothing issued from it. I doubt I melted iron. From the looks of it through the peep hole I got the iron bright orange and that was it. We'll see tomorrow when it's cool. Big thunderstorm right now.

I think the problem is not enough height even for a single charge cupola -- or --  using charcoal instead of coke. It might have worked if either of those two had been changed, but the combination didn't provide enough heat for long enough time to melt.

It looked to me like the charcoal charge burned through in only a couple minutes before the metal had dropped (hot but intact) to the level of the tuyere. Too short a time. It should be more like 5 to 10 minutes. So that would mean more height for a deeper charge. Or coke, which probably doesn't burn as fast, being denser.

I would also think the tuyere could be lower in this type of cupola, and the bore could also be larger for the same amount of melt.

Oh well.

I can remedy the height by adding an extension, though this will mean modifying the top lift.

I also think two tuyeres would be better than one so the bed doesn't burn with a slope -- that tends to drop the iron even faster, as it slides down hill  toward the tuyere. Stewart Marshall suggested that a single tuyere could work on a small 7" cupola -- so I tried that -- maybe this would also be more true for a coke charge than a charcoal charge. But I think performance would definitely be better with two tuyeres when using charcoal.

Charcoal tends to blow out the top very easily with a strong blast, again coke probably does this less since it is denser. Flying embers limits the permissible blast pressure -- I don't want to start a forest fire.

The good things about today were getting practice at a full iron run through. Getting the ladle lined and heated. Practice with the botting, and seeing how the whole thing should work.

I think it may work with a taller rig. I still don't have any access to furnace coke. The other possibility would be to oil fire the furnace as a crucible melter. I'm pretty sure that would work.
Title: Re: Sawed off cupola
Post by: ironman on June 25, 2013, 08:35:21 PM
Think of the Wright brothers, it took a while for them to deal with the problems they faced. In the end they did fly and had no internet to help them. In my first melt with a cupola I got lucky and had lots of iron coming from the tap hole but I used a cold crucible to pour the iron. Cold iron does not work very well. Cupolas have a steep learning curve, everything has to be right for it to work.
Title: Re: Sawed off cupola
Post by: vtsteam on June 26, 2013, 07:59:31 AM
Thank you, ironman! I'll have to think about what to do.
Title: Re: Sawed off cupola
Post by: vtsteam on June 26, 2013, 08:45:23 AM
What I found this morning:

(http://www.vtsteam.com/SawedOffCupola/CupolaTrial1.jpg)

It was up on top of about 7 inches of un-burnt charcoal. Extinguished when I shut off the openings. I don't think there is any metal pooled at the bottom, but it's too hot in there to get the charcoal out yet by hand to find out. Still hot at the bottom 16 hours later.

Lining looks in perfect shape, and the top fired well. Yesterday I chipped away at older parts of the top and relined so the top had the concave shape I wanted. I think it fired all the way across. So that's a plus.
Title: Re: Sawed off cupola
Post by: vtsteam on June 26, 2013, 10:21:36 AM
I removed the charcoal from the bottom. Lining is perfect. No puddle of iron. But a fair number of frozen droplets mixed in ith the bottom charcoal. Here's all the metal removed from the furnace, arranged by melting range. Sifting this stuff out feels a little like an archaeological dig.  :borg:



(http://www.vtsteam.com/SawedOffCupola/CupolaTrial1a.jpg)


Title: Re: Sawed off cupola
Post by: awemawson on June 26, 2013, 10:26:43 AM
So you were close in temperature but not quite high enough. Either not enough air or possibly too much air over cooling the burn. I suspect the former as you have unburnt charcoal left. Did you get white sparks out of the top or only orange? Many cupola designs pre- heat the blast air using heat lost in the walls.
Title: Re: Sawed off cupola
Post by: vtsteam on June 26, 2013, 11:02:27 AM
Thanks awemawson.  Air might have been a factor but the biggest problem was not enough fuel height -- at least that's what I think.

The charge burned through in at most a couple minutes. Didn't time it, but should be more like 5-10 minutes for the iron to drop through.

I measured the furnace and the 2" tuyere is centered 7" above the sand floor, and 11" below the top of the furnace barrel.

So that's only an 11" bed height. From readings, a lidded cupola furnace can get away with a shorter bed height. That may be true, but how much shorter? and charcoal would seem to require a higher bed height normally. So I think it might have worked with either coke, or more bed height.

So, options:

1.) I have a nice strip 10" x 48" of clean steel sheet that I can bend into a furnace extension. That would give me 21" of bed height as opposed to the present 11". It will be less of a "sawed off cupola" however, and I will have to modify the lid lifting mechanism as well as make the new extension. The space for a drop may now be insufficient under the furnace, but I suppose I could raise it on blocks, and or trench a little under it.

2.) I could make an oil burner pretty easily and run it as a waste oil crucible furnace, with no other modifications.

3.) I do  not think this furnace will work as a charcoal crucible iron melter -- though I could still try that. But I believe that would require a bigger bore to seat more fuel around the crucible. My crucibles are about 5" in diameter, and with a 7 " bore, most of the charcoal would have to be sitting on top of the crucible, and wouldn't drop past it. A plinth would also block fuel. Wish I'd made the bore larger -- that would have helped the cupola mode as well, I think.  I don't know if crucibles are ever set floating, to drop with the fuel -- that would be the only possibility I think, of melting iron with charcoal in a crucible in this furnace.
Title: Re: Sawed off cupola
Post by: Rob.Wilson on June 26, 2013, 02:41:25 PM
So close Steve  :(

Stick with it I no you will crack it  :thumbup: ,,,,,,,,,,, at least you have had iron and fuel in yours unlike yours truly  :palm:


Rob
Title: Re: Sawed off cupola
Post by: vtsteam on June 26, 2013, 03:25:24 PM
Thanks Rob!! I'll keep going. But I'm starting to lean toward oil, just to see some liquid iron without doing another week of work. Feel like that's cheating, but I can always make the charcoal cupola extension, too.

It has also been threatening rain off and on all day -- rained last night. So out of a mixture of curiosity mixed with frustration at the weather, I thought I'd try a quick crucible run with my remaining charcoal and about 2 lbs of iron pieces. It seemed to me that I had more crucible side clearance than I'd remembered. So maybe it would work.

I made a top for the crucible out of sand/fire clay mix -- a patty. I put the iron pieces in the crucible, sprinkled in a small amount of sodium carbonate (aka soda ash, aka washing soda) and filled the crucible to the rim with charcoal pieces and covered with the top.

Then I lit the furnace with about 1/4 full charcoal, applied light blast to get it going, added more charcoal, more blast, etc until almost full. Then added the crucible and surrounded and covered that with charcoal.

Then I put the furnace cover down, applied blast, and after about ten minutes the crucible had dropped to the plinth. I then re-filled with charcoal, applied blast. When that burned down, I then re-filled with charcoal and applied blast. So charcoal three times total. Time was about 30 minutes from start.

The crucible was glowing orange in the furnace. I maneuvered the top off, and the internal charcoal was also bright orange. Couldn't see past that. I pulled the crucible out of the furnace and simply poured the contents out into the ingot mold.

Unfortunately it was just bright orange pieces of iron. No melting, but close, I think. If I hadn't run out of charcoal, a 4th or 5th round might have done it. The furnace did have to start from cold, and it does take an hour to heat the walls up. This was only a half hour, and the walls above the halfway mark weren't glowing. Normally with more time I pre-heat with a wood fire.

I'm pretty sure if it had been bronze it would have been molten even now, so I guess the crucible side of things still has possibilities.
Title: Re: Sawed off cupola
Post by: awemawson on June 26, 2013, 04:50:16 PM
Years back I had an oil fired furnace. A Morgan No. 5. The burner was simple in the extreme. I used a central heating circulating pump to push red diesel through a small jet (0.8mm if I remember correctly, but it was a long time ago. The air blower produced 150 inches water gauge pressure, and if tested running on the foundry floor had a habit of sucking up small bits of grit and embedding them in my ankles! - it was powered by a 2HP motor. Fan was a 'shrouded radial blade type' of about 28" diameter and 4" wide. Lighting consisted of dumping an oily rag into the pit having lit it, turning on the fan, heavily choked back (simple gate valve) and slowly opening the oil feed. Then it was a case of adjusting the oil and air just as you would the gas and air with a bunsen burner to get the right flame colour. Flame was maintained by the glowing furnace and crucible.

Had to stop using it when my neighbour sold the bottom of his garden and a house was built 10 foot from my foundry  :(
Title: Re: Sawed off cupola
Post by: vtsteam on June 26, 2013, 05:48:01 PM
Wow, awemawson, that's heavy duty! Too bad about the neighbor.  :(

I happened  to have just about everything needed for a Kwiky style burner so I'm making one up right now. We'll see if it's man enough to do the job  :dremel:



(http://www.vtsteam.com/SawedOffCupola/Cupolaconst55.jpg)



Title: Re: Sawed off cupola
Post by: awemawson on June 27, 2013, 04:32:18 AM
Mine was like this only slightly bigger and oil fired:

http://www.canfieldjoseph.com/foundry/furnaces/mms/gasoroilliftoutcruciblefurnace.pdf

Some useful data in that link
Title: Re: Sawed off cupola
Post by: vtsteam on June 27, 2013, 08:06:18 AM
Nice furnaces!

I guess mine would be about 1/4 the smallest capacity listed. Though I think the warm up time (from experience) is about the same -- you need an hour to get my furnace up to temp with its traditional refractory  4" thick lining.

Among other problems so far, I don't believe I've properly warmed up the furnace in my last few tries. I should plan on at least an hour of full blast to get the walls glowing. Once it is up to temperature, It will become more economical of fuel, and more than one melt would probably be a good idea once it's hot. It takes a long time to cool down afterwards. It just needs to be handled and thought of in a more old fashioned way. Particularly with charcoal.
Title: Re: Sawed off cupola
Post by: vtsteam on June 27, 2013, 10:04:37 PM
Small things completed on the furnace today - it threatened rain most of the day.

First, I drilled out the rivets holding the cupola tuyere plate on, and removed the tuyere. This will be held on with screws in future so I can substitute an oil burner here, now, yet convert back when operating as a cupola, which I still intend to do (and with charcoal.)

A couple problems re. this oil conversion presented themselves -- the tuyere hole is centered 7" above the bottom, and it is also directed 90 degrees to the bore. Ideally for an oil burner it would be near the bottom and directed tangentially to the bore.

I didn't want to put another hole in the casing and lining. It would be difficult to make a diagonal (tangential) hole through firebrick on edge without really tearing up the lining. Also I don't want additional holes to fill when used as a cupola. That inner surface and well need to be tight.

After thinking for awhile, I solved both tuyere position problems (I hope) by simply adding about 3" of sand to the bottom, and using a half fire brick oriented vertically as a plinth. The brick is located and oriented so that it acts as a deflecting vane to give a tangential swirl to the burner flame. The furnace is tall enough that raising the bottom and adding the brick puts the crucible right where it should be with clearance under the lid and supported just above the burner entry. So that looked good.

I also completed the burner jet -- several parts needed to be silver soldered. I then tested and adjusted the atomization of the burner jet with water, and briefly with waste oil @ 30 lbs of air pressure. No attempt at fire yet, but it draws oil very well and atomizes it. I'm confident it should flame.

I still need to locate the burner jet assembly into a pipe casing and then mount that to the furnace Also, connect the blower, which will probably be my small shop vac.

The only drawback I can see to this kind of oil burner is that it requires an air compressor as well as a blower. But mine is on wheels so not a big problem to bring to the site. There are simpler burners out there, but just thought I'd try this one.

I would really like to put the heat on tomorrow but we have 100% rain predicted tonight and tomorrow, as well as severe thunderstorm warnings. So it's unlikely I can.

I may make the 10" cupola extension ring tomorrow indoors, for use when I try to melt with charcoal again as a cupola.

Title: Re: Sawed off cupola
Post by: vtsteam on June 28, 2013, 06:51:55 PM
3 inches of rain overnight. Yuck. Rained off and on today. But I managed to quickly set up the new oil burner for a couple tests.

Here's the burner end on. You can see the orifice. Behind it is a mig tip jet that supplies compressed air at 30 psi:


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst57.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 28, 2013, 06:56:51 PM
Here it is quickly set up very temporarily to test. Rainwater everywhere!

Performance with kerosene (paraffin) was pretty impressive. With waste oil, inadequate. Mixed, the burner ran okay, but I wasn't happy with the heat output for melting iron using any proportion of waste oil. Feed rate definitely slowed with viscosity. I'm not sure what the exact problem is, because videos of the Kwiky burner do better on oil than mine did. Will have to figure that out.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst56.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 29, 2013, 12:39:29 PM
Solved the waste oil problem. I had a really good test burn this afternoon with a lot of heat produced.

The change I made was to increase the taper at the back side of the pipe plug used in the Kwiky burner. I did this with a 60 degree countersink.

The pipe plug I was using may have been different than the Kwiky's designer. I believe his had a counterbored recess at the back of the plug, as purchased. Mine was solid.

I did counterbore slightly, anticipating the difference. But performance was greatly improved after countersinking it and going as deep as the diameter of the plug allowed. This new smooth taper really increased flow through the nozzle, as well as vaporizing the oil more fully.

Here is a link to the Kwiky burner instructions:

http://metalshop.homestead.com/How-to-Build-The-Kwiky-all-Fuel-Foundry-Burner.html

My rig is pretty temporary at present. I need to work on a small oil leak that drips back along the underside of the burner housing, and build a shutter to control the blower airflow, as well as fasten the whole burner in more permanently and caulk with lining mix.

But it looks quite hopeful for waste oil and melting iron!

Title: Re: Sawed off cupola
Post by: awemawson on June 29, 2013, 01:23:37 PM
Well done  :beer: :beer: :beer:

We demand PICTURES of that beast burning  :ddb:
Title: Re: Sawed off cupola
Post by: vtsteam on June 29, 2013, 06:36:16 PM
Thanks awemawson!

It's hard to tell from a photo, so I took a video.

[embed=500,371]<iframe src="http://player.vimeo.com/video/69389468" width="500" height="371" frameborder="0" webkitAllowFullScreen mozallowfullscreen allowFullScreen></iframe> <p><a href="http://vimeo.com/69389468">Test of Modified Kwiky Burner</a> from <a href="http://vimeo.com/user9419463">vtdiy.</a> on <a href="http://vimeo.com">Vimeo</a>.</p>[/embed]
Title: Re: Sawed off cupola
Post by: vtsteam on June 29, 2013, 06:41:40 PM
What you're seeing:

At first the blower is off but compressed air is on. I open the fuel a bit, and you can see the vapor. Then I light the vapor with a Mapp gas torch. You see my temporary blower adjustment (a purposely misaligned vacuum cleaner hose held by a brick!)  Then I turn on the vacuum cleaner blower. Flame is high. Then I reduce the fuel supply a little so I can get a closer shot of the furnace barrel.

The video doesn't quite give the feel of it in bright daylight. That's quite a bit of flame!
Title: Re: Sawed off cupola
Post by: vtsteam on June 29, 2013, 07:07:26 PM
Secrets of the TurboPlinth revealed:



(http://www.vtsteam.com/SawedOffCupola/TurboPlinth.jpg)


In short........it's a brick.
Title: Re: Sawed off cupola
Post by: vtsteam on June 29, 2013, 07:15:51 PM
Other things accomplished today (due to sunshine):

Crucible tongs made from blacksmith tongs plus rebar plus sections of 4" pipe scrap.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst58.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on June 29, 2013, 07:27:00 PM
....and a pouring shank.



(http://www.vtsteam.com/SawedOffCupola/Cupolaconst59.jpg)
Title: Re: Sawed off cupola
Post by: dsquire on June 29, 2013, 08:16:41 PM
Thanks awemawson!

It's hard to tell from a photo, so I took a video.


Steve

What happened at 1:08? Is that when the camera melted and dropped into the fire?  :lol: :lol: :lol:

Nice to see you persevering on this. A lot of people as well as yourself are going to benefit by it. Thanks for sharing it with us Steve.  :D

Cheers  :beer:

Don

Title: Re: Sawed off cupola
Post by: awemawson on June 30, 2013, 05:17:14 AM
Looking good!

It may change as the walls of the furnace heat up, but that flame is too yellow to melt iron - not hot enough. I think that you need more air in the equation - you need to aim for blue / almost invisible flame.
Title: Re: Sawed off cupola
Post by: vtsteam on June 30, 2013, 03:41:24 PM
(http://www.vtsteam.com/SawedOffCupola/Cupolaconst62.jpg)



WahhhhHooooo!!!!!!
Title: Re: Sawed off cupola
Post by: dsquire on June 30, 2013, 03:56:20 PM
Steve

It looks like sucess. I guess we will have to wait for the details. Glad to see that it is starting to all come together for you.  :D :D

Cheers  :beer:

Don

Title: Re: Sawed off cupola
Post by: SemiSkilled on June 30, 2013, 03:59:55 PM
Well done fella  :nrocks: :nrocks: :nrocks: :beer:

Lee
Title: Re: Sawed off cupola
Post by: awemawson on June 30, 2013, 04:22:33 PM
Excellent, you obviously got it hot enough to melt iron  :thumbup: Now tell us what you tweaked  :coffee:
Title: Re: Sawed off cupola
Post by: doubleboost on June 30, 2013, 04:27:48 PM
Very nice  :thumbup: :thumbup: :thumbup: :thumbup:
John
Title: Re: Sawed off cupola
Post by: Rob.Wilson on June 30, 2013, 05:10:19 PM
:ddb: :ddb: :ddb: WAY TO GO  STEVE  :ddb: :ddb: :ddb: :ddb:


I am chuffed for you  :thumbup: , ,,,,,,,,,,,,,just new you could do it  :clap: :clap: :clap: :clap:


Rob
Title: Re: Sawed off cupola
Post by: vtsteam on June 30, 2013, 08:05:33 PM
Rob,  Don, Andrew, Lee, John, Thank you all!   Wow, what a great feeling....I've really been waiting for years to do this! Seems like a small thing, but it really is something to me.

Man that casting is so HEAVY!  That's what comes of casting so much aluminum. I keep picking the thing up and going, that's a heavy casting. Well, I know, it only weighs about 3 pounds or so....

Andrew, the tweak was only to my courage -- i was pretty nervous, there was a fair amount of water around from the rains, though I got a tractor bucket load of sand and put it around the furnace area. Also just running something that hot for that long (total time was an hour and a half) and just the unknown of what molten iron was like -- I didn't know what to expect. I'd read about "white hot" but it didn't seem so -- just bright yellow.

The skimming had me worried, too, plus wondering if I'd get the iron fluid enough. But that all went perfectly. The equipment functioned just as it was supposed to, and the amount of metal was EXACTLY correct -- a little closer than I usually try to get -- the mold filled right to the top of the sprue and then there was no more. I didn't pour any ingots, though I had the mold ready.

For skimming, I am indebted once again to Dave Gingery for a suggestion to set the crucible tilted so the molten surface was even with the lip. I set up sand and firebricks that way in advance as a prop area, with the shank ring at the bottom, so it was just tilt and scrape and lift and pour.

Thanks to Ironman for many things -- sand mix, and all his videos and suggestions. WC Ammens for suggesting a little charcoal in the crucible with soda ash and lid. The slag was very fluid.
Title: Re: Sawed off cupola
Post by: vtsteam on June 30, 2013, 09:04:50 PM
Also Terry Aspin for his books, Stewart Marshall for many aspects of this furnace, Steve Chastain for great books and engineering information, and Madmodders website for the encouragement and a place to talk about it. Otherwise I'd have been the only one to know what I did today.

Back to the interesting stuff for you guys. The lining was in perfect shape after the melt. It just had a very thin brown glaze on it, which I might even count as an improvement. Here's a pic -- the broken up stuff on the bottom is fused sand -- I broke it up when it was an orange sticky taffy mass, as I didn't want it glued to the furnace brick. I also freed the "TurboPlinth" since it served so valiantly. It is also intact, though slightly glazed now.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst63.jpg)

I made no changes to the Kwiky burner, other than the countersinking I mentioned earlier. I ran it at partial throttle all the way through because with my full volume of the vacuum cleaner blower any more throttle would have created smoke in the exhaust. I look forward to completing a dedicated (and quieter) blower.

Andrew, I never had a blue flame, but once temps were up it was impossible to distinguish a flame from the glowing walls anyway. I just went by whether I was generating sooty smoke out of the top of the furnace. I will say that the hottest period toward the end was the result of a slightly rich (reducing) setting which gave max flame size.


Title: Re: Sawed off cupola
Post by: vtsteam on June 30, 2013, 09:25:47 PM
I'm very gratified to report that standard hard firebrick, available almost everywhere, can be used as a furnace lining to melt iron. That was an unknown for me -- I'd received a few hints otherwise elsewhere.

Also I believe end-on is the most heat resistant and strongest way to do that. I believe this furnace will last a very long time with minimal repairs required

Also that a 4" thick clay/sand and firebrick lining will retain enough heat and has enough insulating value to melt iron.

Also that a physically small burner made of standard plumbing fittings, burning waste motor oil will melt iron.

Also that a brick may be used to deflect a burner flame so that it acts as a tangential swirl burner, and can double as a plinth. No need to make a diagonal hole through a furnace barrel -- particularly a firebrick lined one.

I wasn't sure of any of the above, though reading in books and internet suggested that it would -- just figured it should all be able to be put together to allow low expense, and simplicity of construction, which I hope will allow others to achieve their dream of casting in iron. Now I can say,

Yes it can be done.  :thumbup:


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst64.jpg)


This will be a new upper valve case for my rotary valve 4 cycle to steam engine conversion.

Title: Re: Sawed off cupola
Post by: vtsteam on June 30, 2013, 09:52:16 PM
Backside when first broken out -- you can see the channel from the greensand core -- also how very close I was to running out of metal in this pour! The sprue was full when poured, and did shrink down on cooling -- but I don't want to cut it that close again!


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst61.jpg)


Total metal loaded in the crucible was 5 pounds. Total weight of casting and sprue was 4 pounds 3 ounces. I don't know where the other 13 oz. went as I didn't scrape a lot of slag, just a reasonable amount. Maybe I mis-measured?

Also -- just checked the iron with a file -- it files "like buttah". Nice grey iron.

Title: Re: Sawed off cupola
Post by: dsquire on June 30, 2013, 09:59:55 PM
Steve

I'm glad to see that all your hard work and research has paid off. The anticipation of knowing it is going to work but not having proved it yet can get the adrenaline flowing.

Thank you so much for taking the time to document all of the steps that you have taken to get to this stage of casting iron. For many it was a very good lesson in back yard DIY casting. I have enjoyed following along and will continue to look for more posts on this and other subjects.

Good luck and pour safe.  :D :D

Cheers  :beer:

Don

Title: Re: Sawed off cupola
Post by: vtsteam on June 30, 2013, 10:19:43 PM
Don, thanks!

And on the "pour safe" well wishes, -- very apropos -- I do want to point out that it was just a test, and I plan to rebuild most of the burner assembly since what I have here is clearly temporary makeshift. I don't favor open plastic tanks, clear vinyl fuel line, my present loose mounting plate with a couple of screws, etc. But in the interests of a preliminary test It was handy to see the fuel flow and change from kero to waste oil, etc. I don't recommend anyone else copy what I did today.

I'll be improving the whole setup -- and in fact making an improved burner as this one could be better in some respects. Also a new blower, mount, tanks, and better ducting and plumbing, now that I know it works.

And of course, I haven't yet succeeded with charcoal, the original intended fuel, or as a cupola. I'm still going to take a shot at that.
Title: Re: Sawed off cupola
Post by: vtsteam on July 02, 2013, 07:43:41 PM
Worked on improving the oil burner today.

One problem with the Kwiky burner on this furnace is a result of its construction. The oil orifice is located in a Tee fitting and a leg of that fitting comes out of the burner tube and connects to the oil supply. What this means is that the orifice is located right at the outer skin. The leg prevents you from pushing the burner nozzle further in.

My furnace shell and lining is 4" thick, so the atomized jet has to travel 4" in to reach the furnace interior.

The original Kwiky also has a nice small size tube housing -- 1-1/4" in diameter. And this size suits the size of the 1/8" plumbing fittings to center the orifice in the tube in a very simple manner.

The problem for me comes because of the long distance and narrow diameter of the tube. The orifice effectively sprays a fan, hitting the tube walls, and spray condenses there and flows down into a drip. That effectively defeats a lot of the purpose of an atomized spray. Probably half of the oils is simply dripping into the furnace, or, worse dripping back out along the bottom of the pipe, unless it is oriented downhill inwards.

The designer of the Kwiky also noted a drip and mentions orienting the tube down and in.

I decided that I wanted to extend the orifice away from the oil inlet tee almost all the way into the furnace so that the spray pattern does not hit the walls of the housing.

The problem with extending with 1/8"pipe is that the tee gives lots of clearance for the oil, but the 1/8" pipe does not -- it is a fairly close fit to the 1/4" copper tube airline which runs inside, concentric with the oil flow.

Here's a pic of the air line inside the oil line:

(http://www.vtsteam.com/SawedOffCupola/Cupolaconst65.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on July 02, 2013, 08:17:08 PM
So the only way to extend the nozzle into the furnce would be to increase the oil feed pipe size from 1/8" to 1/4" ID.

The problem with that was that the pipe fittings would be that much larger and would block more airflow through the outer blower pipe.

I decided to see if I could eliminate any 1/4" pipe fittings but still use a 1/4" iron pipe. The first thing was to check to see if I could internally thread a 1/4" iron pipe to take the 1/8" pipe plug that is used as an oil nozzle in the original Kwiky.  I suspected this could be done but had never tried to internally thread one pipe size to fit another. If it wasn't possible, I decided I'd make a press in plug for the pipe, and drill and tap that to fit the nozzle plug.

Internal threads would eliminate the need for an air inhibiting 1/4" pipe coupler (and 1/4" plug nozzle).

I also decided to silver braze the 1/4" pipe to the existing 1/8" oil tee. This would eliminate a 1/4" to 1/8" reducer.

Here is a picture of the setup for brazing these two.

Oh, it also turned out that, yes, the 1/4" iron pipe could be successfully threaded internally to take the pipe plug nozzle -- shown here on top:


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst66.jpg)

Title: Re: Sawed off cupola
Post by: vtsteam on July 02, 2013, 08:18:58 PM
And silver brazed together:

(http://www.vtsteam.com/SawedOffCupola/Cupolaconst67.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on July 02, 2013, 08:24:48 PM
Here are various mods. The .024" Mig tip has been re-shaped to a bullet outer profile, and the threads at the base turned off to fit inside a 1/4" copper tube. This will be silver brazed in. It will create a compressed air jet to blow oil out through the plug orifice -- something like an injector.

The modded brass plug orifice has been countersunk 60 degrees on the inside, and has a 3/32" hole for exit of the oil and air mix.

Also shown is the 1/4" iron pipe extension that has been brazed to the Tee and threaded internally to take the orifice plug.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst68.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on July 02, 2013, 08:31:42 PM
Here's the completed assembly. The compressed air comes in on the left line. It travels through the coaxial 1/4" copper line and mig tip. The oil comes in on the right line. It fills the 1/4" iron pipe section. The gap between the mig tip and brass plug pipe orifice is adjustable by screwing the plug in. The compressed air @ 30 psi forces the oil in the gap through the orifice and atomizes it.

Not shown is the outer 1-1/4 tube housing that is inserted into the furnace and forms the duct for the blower.

I hope this new burner will outperform the old one with a full spray, and eliminate the drip.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst69.jpg)
Title: Re: Sawed off cupola
Post by: ironman on July 02, 2013, 08:42:18 PM
It is great to see you melting cast iron. You have joined a very exclusive club!

Does this mean that the cupola iron melting idea is gone forever?  :bow:  :bow:  :bow:  :clap:  :clap:  :clap:
Title: Re: Sawed off cupola
Post by: vtsteam on July 02, 2013, 09:17:50 PM
It is great to see you melting cast iron. You have joined a very exclusive club!

Does this mean that the cupola iron melting idea is gone forever?  :bow:  :bow:  :bow:  :clap:  :clap:  :clap:

No Ironman, I almost made up the 10" cupola furnace extension today, but decided to upgrade the oil burner instead because it was, again, RAINING. And I didn't want to weld in the rain.

I have never seen a wetter late spring and early summer. It rained right after my first iron pour, and has rained every day since and is predicted to rain through the end of the week. Two year ago we had a drought and were without water for two months. I'm not complaining but.......crikey!

I'm also going to reduce the size of the tuyere to fit the oil burner but add a second one opposite for use when a cupola -- two tuyeres will help prevent the slope of the charcoal that the iron slid down prematurely to tuyere level on my first try -- and the doubling of the bed height should help, too.
Title: Re: Sawed off cupola
Post by: vtsteam on July 03, 2013, 05:10:08 PM
Rain held off. Started on the second tuyere. Decided to make both 2" dia and line with steel tube. So I cut two sections of tube with angled ends. They will both mount pointing downward towards the center of the barrel,

Here I'm drilling out the location for the second tuyere opposite the original one with a carbide masonry drill. It went right through the stainless steel jacket and easily drilled through the firebrick lining. Took about 5 minutes to do.



(http://www.vtsteam.com/SawedOffCupola/Cupolaconst70.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on July 03, 2013, 05:13:20 PM
And here is the tubing liner installed:


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst71.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on July 03, 2013, 05:16:47 PM
And the new liner on the first tuyere. Black stain is soot from the oil burner drip. I had to chisel the firebrick a little on this side to be able to angle the tuyere downward. The upper hole is from a fitting removed from the original vacuum cleaner that forms the housing.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst72.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on July 03, 2013, 05:20:25 PM
And finally today I bent up and welded together a ten inch cupola extension.

To do: Line the extension, extend the top lift rod, make some sort of wind manifold -- not sure if it will be a full fledged wind belt or not.

The furnace as it stands now:


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst73.jpg)

Title: Re: Sawed off cupola
Post by: vtsteam on July 05, 2013, 04:08:29 PM
Today I lined the cupola furnace extension. I was a little concerned about building it with firebrick on the table and then transporting it to the furnace. Not much wet strength compared to the weight, and I could imagine the whole thing collapsing out of the steel ring. But I couldn't dry it very easily without heating it on the furnace, so it did have to be moved.

Finally I decided to just build it right on top of the furnace. But to prevent sticking the wet clay to the furnace top, I put a layer of cardboard between them. I hoped the cardboard would burn out once fired.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst74.jpg)




Title: Re: Sawed off cupola
Post by: vtsteam on July 05, 2013, 04:17:50 PM
A base layer of fire clay and sand was put down and the firebricks were pressed into ring.

The brick edges were buttered with premix refractory furnace cement -- the type with sodium silicate in it. I had a gallon of the stuff, and though it isn't refractory enough to handle iron melting temperatures, the outer edges of the furnace probably never have reached as much as 400 F.

But one great advantage of the furnace cement is that it is a very good adhesive compared to the clay/sand mix. So I was able to effectively glue the brick to the steel outer ring with a good bond, and I hoped this would help prevent any collapse of the extension lining when it is finally heat cured.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst75.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on July 05, 2013, 04:20:15 PM
Adding more firebrick. The spaces between the bricks were filled with clay sand mix and chunks of broken up firebrick. Each section was progressively filled and rammed.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst76.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on July 05, 2013, 04:26:10 PM
And finally the extension lining was completed with a cap of fireclay and sand.

After this photo, I loaded the cupola with wood and kept the fire burning for 4 hours. The draft through the 2 new 2" dia tuyeres was sufficient for a good draw without a blower. Toward the end of the burn, I covered the cupola with the lid. I haven't tried to remove the extension yet as it is very hot, but I think it baked well.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst77.jpg)
Title: Re: Sawed off cupola
Post by: Rob.Wilson on July 06, 2013, 03:12:54 AM
Hi Steve


You have been busy  :thumbup:  , nice job making the extension piece , looks like you will have room for allot more fuel .


Rob 
Title: Re: Sawed off cupola
Post by: vtsteam on July 06, 2013, 09:07:17 AM
Thanks Rob!  :beer:  Your encouragement has kept me going on this thing.  :nrocks:

Guess I've got to make more charcoal now.

Title: Re: Sawed off cupola
Post by: vtsteam on July 06, 2013, 08:22:45 PM
Family and company for last couple days for the 4th, so not much time for the furnace. But pulled the extension off this morning to have a peek. Here it is. Cardboard pattern and wrinkles were reproduced faithfully in  the refractory.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst78.jpg)


I trimmed out the excess flash in the center and smoothed the whole with a fire brick used as a sanding block. Very effective!

I hope to make some charcoal tomorrow, and try to work out the air supply for the two tuyeres.
Title: Re: Sawed off cupola
Post by: vtsteam on July 08, 2013, 02:03:46 PM
Twin pipes:

(http://www.vtsteam.com/SawedOffCupola/Cupolaconst79.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on July 08, 2013, 06:10:53 PM
Trying out tubing hook up lengths. The nice thing about PVC pipe is that it is the same size as iron pipe, so plastic solvent glue type fittings are a good firm slip fit on metal. The I.D. also fit some flexible hose I had, and this in turn fits my small shop vacuum. So This looks like it will work.

I chose plastic because a welded steel crossover wouldn't have been removable (to switch over to the oil fired burner.) Also the weight of  iron pipework needs lots of external support.

I made up the Y fitting by splitting two elbows and gluing the halves together (I didn't have a Tee in the junk box). But I will probably replace that with a manifold box with an external bleed shutter so i can control the blast.

Anyway, this gives me an idea how things will eventually be arranged.

(http://www.vtsteam.com/SawedOffCupola/Cupolaconst80.jpg)
Title: Re: Sawed off cupola
Post by: doubleboost on July 08, 2013, 06:15:11 PM
This is looking great
Like a big stethoscope  :lol: :lol: :lol: :headbang: :headbang: :) :)
John
Title: Re: Sawed off cupola
Post by: vtsteam on July 08, 2013, 08:45:50 PM
Thanks John!  :beer: :beer:

I guess the blower is the heartbeat of the furnace. Especially when it was bellows!  Pumping that for a couple hours must have been interesting!  :whip:
Title: Re: Sawed off cupola
Post by: awemawson on July 09, 2013, 03:58:03 AM
I have visions of you stopping the blower, the tuyers heating up and the plastic fittings dribbling down  :lol:
Title: Re: Sawed off cupola
Post by: vtsteam on July 09, 2013, 11:59:46 AM
I don't think that will be a problem for a number of reasons awemawson including the fact that the plastic slip fittings are removable, your explanations of strict one way convection in our earlier discussions of chimney function, and the obvious natural draft of this cupola previously mentioned here, but never say never!   If they melt, I can always replace them with metal.  :)
Title: Re: Sawed off cupola
Post by: vtsteam on July 09, 2013, 06:05:37 PM
Mmmmmmm, charcoal!


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst81.jpg)


About 9 gallons above, representing the usable yield from one burn in the charcoal barrel, minus fines and brands.

The cupola holds 4.5 gallons. I'm guessing 18 gallons should be a minimum to have on hand before trying a melt.

The barrel reloaded for another burn tomorrow morning:


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst82.jpg)
Title: Re: Sawed off cupola
Post by: NeoTech on July 10, 2013, 06:51:28 AM
Is there any thread on your charcoal making ... bucket..  I have seen many versions of making charcoal but the almost always have a double walled solution.. your seems to be open fired from below.. ?
Title: Re: Sawed off cupola
Post by: vtsteam on July 10, 2013, 08:04:54 AM
Here you go, NeoTech:

http://madmodder.net/index.php/topic,8484.0.html

It actually fires all through, just lit from below. It's actually very similar to existing charcoal methods with a lifted metal kiln ring and propped up metal lid -- though considerably smaller than those!

Here's a video by Amy Smith that shows the method using corn stalks, and also simple briquetting:


Title: Re: Sawed off cupola
Post by: vtsteam on July 10, 2013, 11:02:57 AM
A few differences from the video -- mine doesn't have a perforated bottom -- it's completely open. Mine works with wood -- preferably 1-3 inches thick. And I used a circular lid.

Mine works even if the barrel you find has only one end on it. I also modulate the fire with the lid, and sand at the base once it is burning well. I try to keep it just slightly smoking -- a wisp or two -- rather than running it full out. I believe this gives a greater yield. 

There is also some suggestion lately that it is helpful to retain some of the volatiles -- not sure if I subscribe to that yet, but I accept that as a possibility worth exploring. Also another heresy that pine charcoal is better than hardwood charcoal from a Japanese style sword making source. Though what kind of "pine" and "hardwood" have been compared is not yet clear. White pine and yellow pine are very different woods and fuels, as are cottonwood and red oak, for instance. So pine vs hardwood might be apples and oranges, so to speak!

Anyway, about to light off the second batch (if I can manage to light it) and the rain holds off. Everything was doused last night. My hardwood today is red maple and black (sweet) birch, for comparison sake.

BTW -- one could easily melt aluminum -- probably a sizable quantity -- in the heat given off during the charcoaling process. Thus a single load of wood could be used for two separate melts. You would have to find a way to suspend a crucible in the barrel (I've found that even 1/2" rebar across the opening sags like a noodle in the charcoaling heat) and a way to observe and remove it when ready. Sticking even gloved hands or head anywhere near the opening is not advised -- at least with a hardwood burn.
Title: Re: Sawed off cupola
Post by: vtsteam on July 10, 2013, 03:45:58 PM
The sun came out and it got hot and muggy, so I started the charcoal burn. When it was just done, and I'd covered everything with sand, the clouds rolled in and we got inundated with rain.   :bang: :bang: :bang:

The furnace area flooded, as did the charcoal barrel. I hope it didn't wash the sand down from the lid into the fresh charcoal below.  Looks like it did from here....:(

This is the wettest summer I have ever seen.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst83.jpg)
Title: Re: Sawed off cupola
Post by: awemawson on July 10, 2013, 04:10:24 PM
Bad luck. You need a simple bothy type building - four poles and a corrugated roof leaving the sides open to let you carry on playing.
Title: Re: Sawed off cupola
Post by: vtsteam on July 10, 2013, 04:29:33 PM
Thanks, yes awemawson, that would be nice. But limited budget means even the galvy roofing would be difficult.

I'm doing better than local farmers, though. Almost none of the hayfields have been cut for the June hay. All turned brown and gone to seed. I don't know if they will be able to get it down and try for a second hay if this continues. They need a week of drying weather just to get out into the fields.

Between thunderstorms I ran out and knocked the barrel over -- was surprised to see most of the charcoal clean and dry. I salvaged enough and got it under cover to bring the total on-hand to 14 gallons. The furnace takes 4-1/2 to fill. So I may try it when the weather improves.
Title: Re: Sawed off cupola
Post by: vtsteam on July 11, 2013, 05:50:13 PM
Rained this morning, but cleared by afternoon and was able to work while ground dried. Today's cupola work:

Added view ports to both tuyeres...


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst85.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on July 11, 2013, 05:51:50 PM
Added a support fixture to the lift rod for pre-heating the ladle:

(http://www.vtsteam.com/SawedOffCupola/Cupolaconst84.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on July 11, 2013, 05:54:16 PM
It's just a scrap pipe nipple quickly carved into a sort of spiral with the hand grinder. Not a thing of beauty, but it works well.

(http://www.vtsteam.com/SawedOffCupola/Cupolaconst86.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on July 11, 2013, 05:58:59 PM
It grips the rebar shank. Stays put even when I rotate the lid of the cupola as seen here, yet is easily removed with a twist and lift motion.


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst87.jpg)


Today I also made up the sand bottom of the cupola. Everything is looking ready except maybe a formal means of moderating blast. Weather tomorrow is predicted at 30% chance of rain mainly after 5 PM, so I may have a go at cupola casting with with charcoal, second time around.
Title: Re: Sawed off cupola
Post by: andyf on July 11, 2013, 07:04:01 PM
I'm just an interested observer of this topic; molten metal is well out of my league. However, it does occur to me that your weather reports aren't encouraging me to visit Vermont. It will soon be 40 days and nights; time to stop gathering animals two by two and charcoaling wood which might be better employed in building an ark.

Andy
Title: Re: Sawed off cupola
Post by: vtsteam on July 11, 2013, 07:53:28 PM
We're really not responsible Andy, we get our weather second-hand from New York state.
Title: Re: Sawed off cupola
Post by: vtsteam on July 11, 2013, 08:17:31 PM
Here's an ark, of sorts, I built 22 years ago in Vermont. Took it 1700 miles down the coast and across the center of Florida. Lived aboard, off and on for 10 years in Florida and later Louisiana. Finally towed it back to Vermont, and used it as a base camp on land while building my present house.

Launch day, November 1991:

(http://www.vtsteam.com/SawedOffCupola/Gesso1.jpg)

(http://www.vtsteam.com/SawedOffCupola/Gessolaunch.jpg)

Interior:

(http://www.vtsteam.com/SawedOffCupola/Houseboatinterior.jpg)


Base camp ten years later back in VT, October 2001. Frost is on the field again.


(http://www.vtsteam.com/SawedOffCupola/Houseboat.jpg)




Title: Re: Sawed off cupola
Post by: vtsteam on July 12, 2013, 06:44:53 PM
Tried the cupola on charcoal today. Even with the extension the charcoal burned down very quickly. A few minutes and it was down 18 inches. Melting was more thorough than last time but not good enough. The melt froze in the well -- never went completely fluid. I did have one small stream of metal start out the tap hole before freezing . \

Here I'm getting ready to chip out the blockage. I never did get to bod it off. The bod rods are at the ready in the cinderblock in this picture, and the ladle is heating on top of the cupola. The flame had been impressive out the top, but by the time this picture was taken it had died down as the cupola had burned most of its fuel.

I did try a second charge after refilling with charcoal, but had no better results. In the end I dropped the bottom and chiseled the slag off the barrel.


(http://www.vtsteam.com/SawedOffCupola/CupolaSecondTry2.jpg)
Title: Re: Sawed off cupola
Post by: vtsteam on July 12, 2013, 08:03:32 PM
When the cupola cooled off enough to remove the extension, I pulled the tuyeres off, plugged up the far one with bod mix on the inside, remade the bottom, installed the new oil burner, and the plinth. Brought up the compressor, the oil and kerosene, and tried an oil burn. Figured I might as well try to fill the mold I'd made while the main furnace body was still hot.

But, no luck there, either. The new burner had an air leak in a silver solder joint, so wouldn't draw the fuel. Just bubbled in the container.

So I took the burner apart cleaned it and re-brazed it. Took two tries to finally get rid of the leak. Tried it again, and it seemed to work, but wasn't drawing fuel as well as the first one had. Not sure why -- maybe there is a blockage in  the jet. There was definitely enough draw for kero, but waste oil draw was weak.

I probably could have melted with kerosene, but it was getting late and general discouragement was taking over. Decided to just put everything away and call it a day. :(
Title: Re: Sawed off cupola
Post by: vtsteam on July 12, 2013, 09:54:47 PM
I think I'm going to stop the charcoal cupola experiments for awhile and just melt iron with oil.

My feeling about the charcoal side of things is that it would really need a much larger bore for increasing the heat available to a single charge. You really can't just go upwards -- most cupolas fit several charges in a taller height. That wouldn't work here. You basically need more charcoal between each charge, and the only way to do that is to increase bore.

I think mine might have worked with a much smaller charge than the 6 pounds (x 2) I tried. Maybe 2 or 3 pounds. But then the well is far too large for that quantity (7" dia x 8" high) so it wouldn't be hot enough to keep it fluid.

I'd say that to successfully melt iron with charcoal -- in usable quantity -- I would want something about a foot in bore diameter, minimum, whether a crucible furnace or cupola. The well on a cupola would be short -- the tuyeres much lower than in coke melting practice, and a higher bed height.

I don't think my 7" cupola is going to work with charcoal therefore -- maybe with 2 pounds of iron it might, but that's a lot of work both in construction, pour preparation, and fuel making for such a small quantity of metal. And I bet it would pour cold.

I'm pretty certain it would work with coke, and it is proven as a crucible iron furnace with oil. Aluminum and the copper metals should be doable with charcoal. Or propane.

I'm pretty much "burned out" on furnace experimentation and construction at this point -- other than finishing up the oil burner tank and piping.

Maybe in the fall I may try a short big bore charcoal iron crucible furnace using a half 55 gallon drum -- I would still like to melt iron with charcoal at some point, but I think my cupola days are over.

Title: Re: Sawed off cupola
Post by: Rob.Wilson on July 13, 2013, 12:03:23 AM
Hi Steve ,

Dont be too disheartened , It was a valiant effort too try and get a charcoal fired cupola to melt iron,no one could have done more .  :bow: :bow: :bow: , Step back ,take a break, you have been at this project for a wile now , spend a bit time on another project   :dremel:   

At the end of the day you still have a very capable oil fired furnace  :)



Rob
Title: Re: Sawed off cupola
Post by: awemawson on July 13, 2013, 04:01:17 AM
Steve,

Bad luck with the melt - you've put a lot of effort into this.

- you are re-charging with fuel as the burn progresses aren't you? - when I've seen cupolas working they've all had to have several re-charges of fuel to get up to temp then several fuel / iron batches added as the melt progresses.

The only one I've personally attended (rather than seen on film) the fellow had many buckets all pre-prepared - some just coke, and others coke / iron / limestone mixes all weighed out.
Title: Re: Sawed off cupola
Post by: NeoTech on July 13, 2013, 04:20:46 AM
Thats still a great furnace however you choose to fire it.  =)
Title: Re: Sawed off cupola
Post by: vtsteam on July 13, 2013, 05:04:39 PM
Thanks greatly, Rob, Andrew, NeoTech!  :bow: :beer: You make it useful to report this kind of thing.

Andrew, in answer to your question yes I did keep adding charcoal, -- I went though all of the charcoal I had --  but only after I realized it had evaporated so fast. And even later added a second metal charge (which didn't help anything). I went through 14 gallons of charcoal. The furnace had been preheated with wood for an hour with blast on, and charcoal, as well as a heat soak period with metal.

Just as observations which may help others on this particular path, I do believe that the iron layer tended to choke up the exhaust and force it out the tap hole. The tap hole was left open to look for the first iron, per most cupola books. But it hardly showed up. I do believed the open tap robbed some heat from the upper cupola and kept it low -- near the tuyeres -- but probably there just wasn't enough heat altogether for the quantity of metal. If there'd been an excess, fire would have come out of every nook and cranny! Well maybe the lid contributed to this upper restriction problem. The lid also tends to stop you from adding -- you can't see what's going on inside, and don't want to cut the blast to check, while melting. So maybe the lid was part of the problem, too.

I should some day try it with the lid off, and try melting a 3 pound charge. But don't have the motivation right now. Not saying it would work, but might be useful to just see what the difference was.

I'm going to work on the oil fired side of iron melting in this furnace. I really want to do some casting and think less about the furnace construction itself. Thank you all again.   :beer:

(Shot of one fused chunk of cast iron found in the drop -- shaped roughly like the well. About 5 pounds.)


(http://www.vtsteam.com/SawedOffCupola/Cupolaconst88.jpg)
Title: Re: Sawed off cupola
Post by: awemawson on July 13, 2013, 05:08:57 PM
Steve,

Have a beer or two - sleep on it, finish off a few more bits awaiting 'round tuits' , then come back afresh. I bet it'll work then

 :beer: :beer:

Andrew
Title: Re: Sawed off cupola
Post by: Mayhem on July 14, 2013, 12:24:12 AM
Bad luck Steve but I'm glad you are placing this part on the back burner and not giving up completely. 

I'm having similar issues with my babington burner.  It worked when I had it cobbled together with retort stands and clamps but is behaving badly now I have it in a self contained unit.  I played with it a little yesterday and think I may be on to something but who knows  :zap:

I look forward to seeing your results of using the oil burner, as if I cannot get the babington burner to work I will be heading down that path.
Title: Re: Sawed off cupola
Post by: vtsteam on July 15, 2013, 12:40:24 PM
Thanks both of you! Perhaps another cupola some day, and maybe even a try or two with this one in a few months time if I thought there was value to it.

This furnace will continue to melt iron at present as an oil burner. We'll see where we go with that -- plenty of scope for improvement there. That first pour must have been beginner's luck! Anyway I'll open another thread for it as an oil burner if anything interesting comes up.

Cheers!  :beer:
Title: Re: Sawed off cupola
Post by: tom osselton on July 16, 2013, 02:35:58 AM
Vsteam have you tryed a bigger blower or maybe another vacum one for each tyure by the look of your pic it came close to melting it may just be low blast presure.
Title: Re: Sawed off cupola
Post by: vtsteam on July 16, 2013, 08:24:37 AM
I suppose it's possible Tom. But charcoal embers were flying out of the top as is -- I have a burn on my ear to prove it.

Maybe more air rather than more pressure. One possible way to do that would be to leave the lid off to reduce back pressure.


I also don't think the well was hot enough. not sure what to do about that except lower the tuyeres.

One more thought -- charcoal is supposedly hotter burning than coke. The problem is that it burns so fast. Maybe larger charcoal would be better. I tried to mimic coke size (3/4") for this size furnace (7")  but maybe that was a mistake. Larger pieces burn more slowly, plus they let air through more easily. Maybe that would compensate for the charcoal characteristic of too much too quickly. A flash in  the pan...

Lots to think about.
Title: Re: Sawed off cupola
Post by: Meldonmech on July 16, 2013, 10:12:08 AM
What a fantastic effort, you have achieved a great deal and aquired invaluable experience. I know you must be disheartened  but am convinced you will succeed after you have had a break from it. Can't wait for your next attempts. The build has been both interesting and informative.

                                                                         Well Done  David
Title: Re: Sawed off cupola
Post by: vtsteam on July 16, 2013, 07:44:19 PM
Thanks so much, David!  :beer:
Title: Re: Sawed off cupola
Post by: vtsteam on January 06, 2018, 02:44:11 PM
All photos restored after Photobucket broke links.
Title: Re: Sawed off cupola
Post by: vtsteam on January 07, 2018, 11:25:14 AM
Having revisited this thread now several years later, I think I understand the charcoal fuel problem better. And possible solutions.  :coffee:

I think I missed the point that though charcoal may be hotter burning, it is also much less dense than coke. So to melt the same amount of iron (with the same amount of heat -- regardless of burn temperature) I would have needed the same weight of charcoal per unit weight of iron. And the burning zone would have needed to be proportionately larger to produce the same amount of local heat.

There are two ways to increase the amount of charcoal available to the burning zone -- increase the diameter of the cupola, or increase the height.

Increasing the diameter would increase fuel mass as the square of  the dimensional increase. Increasing the height would increase the mass of fuel linearly.

Since the burn time was so short, more height would help with that. A sawed-off cupola isn't ideal for much burn time. Even with the short extension, it wasn't adequate, although better.

Increasing the diameter would increase the temperature of the hot area. And this would have possibly been a benefit in melting sufficient metal to fill the well and keep it hot. It's also more efficient with less proportionate heat loss to insulation.

The proportion of charcoal to metal in a charge would probably needed to be higher than with coke (even by weight).
As the metal charge and fuel drops down the cupola barrel, it basically determines metal feed rate to the molten puddle. With a fast burning fuel like charcoal, that metal feed rate is faster as well, since the iron is dropping into the heat zone faster, coming along for the ride with the charcoal.

So, in general, I'm going to say, a specifically designed charcoal cupola might better be taller even than a conventional coke cupola, and the fuel to metal ratio would likely need to be higher. Blast will likely need to be be lower since the charcoal is less dense, and the weight of oxygen needed is proportionate to the weight consumed of a less dense fuel.

Anyway, I think I can see what might have needed changing.  :smart:  :wack:
Title: Re: Sawed off cupola
Post by: RotarySMP on January 09, 2018, 09:11:17 AM
Thanks for reposting the photos to your thread. It is a great thread.

Another avenue which springs to mind would be using smaller lumps of iron. Smashing up iron small is a PITA, but might help. It would be cool to you have another go with the larger lunps of charcoal, and smaller iron.
Mark
Title: Re: Sawed off cupola
Post by: vtsteam on January 12, 2018, 04:57:02 PM
I think if I tried again, I might use the same cupola with anthracite. It is obtainable here. And I already have some.

Anthracite requires a hot blast to work, as I understand it, so the blast would have to be routed through the exhaust gasses. You'd need some other fuel to heat it to start with, as well. Maybe load wood, charcoal or charcoal briquets in the cupola first, then when the exhaust and  intake gets up to temp, add the anthracite. Once that's going, add the iron charge.

The other possibility, for a true charcoal cupola would be to build a much taller and possibly wider cupola. Better insulation and a softer blast would seem to be advantages. The melting capacity would be in proportion to the weight of the charcoal, which is considerably less dense than coke.
Title: Re: Sawed off cupola
Post by: RotarySMP on January 13, 2018, 07:15:48 AM
How about a mix of charcoal and coal? Could you turn coal to coke in you charcoal burner?
Mark
Title: Re: Sawed off cupola
Post by: vtsteam on January 13, 2018, 03:19:49 PM
Neither would work with anthracite.