Author Topic: Foundry Furnace for the Tiny Shop  (Read 35661 times)

Offline DavidA

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Re: Foundry Furnace for the Tiny Shop
« Reply #50 on: March 02, 2015, 01:30:38 PM »
VT,

Am I correct in saying that you have no insulation between the refractory and the outer steel wall ?

I'm thinking about making something similar for aluminium,  just to get some practice at casting.

I have insulation that I got from Norman,  but don't want to use it on the aluminium furnace if it isn't necessary .

Dave.

Offline vtsteam

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Re: Foundry Furnace for the Tiny Shop
« Reply #51 on: March 02, 2015, 01:44:18 PM »
No David, it isn't necessary. The 2" of refractory acts as insulation for the relatively short heating times of aluminum in a furnace this size.

The outside near the bottom was "hottish" after a full day of baking the shell when I first built it, but not hot enough to even bother the paint, and I could touch it briefly.  Wouldn't want to hold my hand for long on it, but that's about how hot it was. Higher up it was just warm.

A twenty mnute to half hour aluminum melt barely warms the outside.
I love it when a Plan B comes together!
Steve
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Offline DavidA

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Re: Foundry Furnace for the Tiny Shop
« Reply #52 on: March 02, 2015, 01:54:02 PM »
VT,

Thanks,

 Something else to add to my 'to - do' list.

Dave.

Offline vtsteam

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Re: Foundry Furnace for the Tiny Shop
« Reply #53 on: March 02, 2015, 08:49:05 PM »
With the morning's pour having worked with propane, I thought about it for awhile and then decied late in the day to go for a pulley pour. This meant clearing enough bench space to do the moulding, estimating the amount of aluminum needed, locating the baked sand cores I'd made and re-conditioning the sand.

I weighed out 56 oz of aluminum, which seemed like it would be enough, though this particular mould would have a very long sprue (for me) in a 3 part flask, and a riser. Moulding took quite awhile, I haven't cast anything in a year and a half, and this one had a bked core and a hanging greensand core in the cope, and a sprue running through cope and cheek. I didn't want to mess up, and with darkness coming I wouldn't have a chance to remake the flaask.

Everything worked while moulding, nothing dropped out even though I did a couple of rolls, and the core fit the prints holes when put together. The wind had picked up worse than it was this morning, it was really whipping. Temp was -7C. I re-oriented the furnace to take advantage of the wind direction, and piled up bricks to shield it from low pressure. I started the furnace at 4:05, and had 56 oz of molten aluminum a half hour later.

I gave it a little extra time in the furnace to pour hot with the chilled mold, skimmed and poured. Well unfortunately, I had underestimeated by probably 4 oz, and the sprue and riser didn't top out. Ahhhh, well! There's alway still hope til you open these things.


« Last Edit: April 30, 2018, 09:54:32 PM by vtsteam »
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Offline vtsteam

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Re: Foundry Furnace for the Tiny Shop
« Reply #54 on: March 02, 2015, 09:02:09 PM »
I kinda peeled off the layers one at a time, hoping all went well. The first one showed the inverted greensand core had stayed in place, and the baked core looked crumbly. No shrink cavities, the shorted riser had been just enough:

« Last Edit: April 30, 2018, 09:55:21 PM by vtsteam »
I love it when a Plan B comes together!
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Offline vtsteam

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Re: Foundry Furnace for the Tiny Shop
« Reply #55 on: March 02, 2015, 09:09:53 PM »
And pulling off the drag showed the bottom pulley looked good. not tears around the baked core, and it was still positioned okay:

« Last Edit: April 30, 2018, 09:55:46 PM by vtsteam »
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Offline vtsteam

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Re: Foundry Furnace for the Tiny Shop
« Reply #56 on: March 02, 2015, 09:13:30 PM »
The core was soft and easily dug out. the pips are from the vent wire:


« Last Edit: April 30, 2018, 09:56:09 PM by vtsteam »
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Offline vtsteam

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Re: Foundry Furnace for the Tiny Shop
« Reply #57 on: March 02, 2015, 09:41:42 PM »
Finally, the break-out. Everything looks good!

« Last Edit: April 30, 2018, 09:56:33 PM by vtsteam »
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Offline vtsteam

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Re: Foundry Furnace for the Tiny Shop
« Reply #58 on: March 02, 2015, 09:53:25 PM »
Ready to machine, I couldn't have asked for a better result, particularly under the circumstances. With all the changes in thickness, I figured this one for a bear, but everything worked first time out. Really happy with it!!

You can see the double sprue here. Final weight of pulley casting, 42 oz. One more to go.

« Last Edit: April 30, 2018, 09:57:00 PM by vtsteam »
I love it when a Plan B comes together!
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Offline awemawson

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Re: Foundry Furnace for the Tiny Shop
« Reply #59 on: March 03, 2015, 02:33:32 AM »
Excellent Steve

It must be rather nice to be back casting after a year or so.. It's now over seven years since I had mine set up, something else always is crops up!
Andrew Mawson
East Sussex

Offline PekkaNF

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Re: Foundry Furnace for the Tiny Shop
« Reply #60 on: March 03, 2015, 03:47:54 AM »
Wow, all that looks like magic! I tired "green sand" like 20 years ago. Never worked out for me, none of it! I did have some success with oil-sand. Paid something ridiculous of few kilos. That was pre internet....

Thanks for showing - really inspirational.

Pekka

Offline Manxmodder

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Re: Foundry Furnace for the Tiny Shop
« Reply #61 on: March 03, 2015, 04:01:03 AM »
Happy days,looks a right good casting does that  :clap: :clap:

The wire vents you mention,are they serving pretty much the same purpose as piercing with a hacksaw blade,as I have seen others do?......OZ.
Helixes aren't always downward spirals,sometimes they're screwed up

Offline awemawson

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Re: Foundry Furnace for the Tiny Shop
« Reply #62 on: March 03, 2015, 06:44:44 AM »
Happy days,looks a right good casting does that  :clap: :clap:

The wire vents you mention,are they serving pretty much the same purpose as piercing with a hacksaw blade,as I have seen others do?......OZ.

I made up a set of 'prickers' - just  bits of oxy-acetylene welding wire about 9" long with a loop bent in one end (so it looked like a kids bubble blower) to hold it by. Gently feel it down to the pattern in several places to let the gases escape freely.
Andrew Mawson
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Offline RobWilson

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Re: Foundry Furnace for the Tiny Shop
« Reply #63 on: March 03, 2015, 10:01:36 AM »
 :clap: :clap: :clap: :clap: :clap: very nice Steve  :thumbup:

Bottom gating worked well .

Is it one of a pair of pulleys   or do you just need the one  ?


Hopefully I may get a wee  bit of casting done this year , some new foundry toys arrived today  :)


Oh yes , did you do the  :ddb: dance  :lol: :lol:


Cheers Rob 

Offline mattinker

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Re: Foundry Furnace for the Tiny Shop
« Reply #64 on: March 03, 2015, 11:07:38 AM »
Interesting, you cut a very small gate! I'm glad it worked out!

Regards, Matthew

Offline tom osselton

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Re: Foundry Furnace for the Tiny Shop
« Reply #65 on: March 03, 2015, 11:24:08 AM »
Casting looks good!

Offline vtsteam

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Re: Foundry Furnace for the Tiny Shop
« Reply #66 on: March 03, 2015, 08:22:41 PM »
Andrew thanks so much! You must get back into casting. I forgot about the sheer fun of it (when it works!) -- breaking away some dirt to see what you've got -- and the playing with fire.... you know what I mean!

Pekka, thanks kindly! it's probably just being familiar with whatever materials you've got, through trial and error. Every sand is different, but I believe most are workable for aluminum at least. It's just doing it enough with your particular ingredients. The feel of the sand - tempering is very important, and the proportion of clay to sand also. But not necessrily the pedigree or cost.

This casting was made with 13 year old greensand made from fireclay and sand, not even Bentonite. The very same sand I cast my lathe, accessories, and everything else aluminum with.

I'm used to it, I know how it should feel, and how hard to ram it and how to vent it, etc. And I'm sure that would all be different if I changed to a different sand.

In fact casting was all brand new again the other summer when I did so with iron. Everything was different, and I had to re-learn it. Coming back to this stuff, wth aluminum in a foundry the size of my original, with my old sand, everything was familiar, and second nature.

Oz thanks! re. using a venting wire to poke holes. Everybody is different, but I would never vent with a hacksaw blade. I prefer just the opposite -- a fine straight wire, 1 mm (.040"), stainless steel spring wire.

I started out with coarser wire -- bare house electrical copper wire -- it was too thick, not straight enough, and dug out divots and tended to crumble the mold surface if poked through from the inside (I frequently do this -- not just venting from the outsode toward the pattern).

I later went to aircraft SS tie-wire -- still not stiff and straight enough, and too coarse, though better. Finally I found a a kitchen baking tool for poking pastry just perfect for the job. It had a coin sized flat plastic handle, 1 mm stainless spring wire, perfectly straight (so it didn't tend to disturb the sand when pulled out) and very thin. I think it cost $3. That's what I use. It really helps make a clean mold.

Seems a small point -- but it what works best for me.

I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Foundry Furnace for the Tiny Shop
« Reply #67 on: March 03, 2015, 09:06:52 PM »
Thanks Rob!!!! Oooh, I forgot!

             :ddb:

My daughter loves that one! Always wants me to put them in posts if she sees me typing.

I do have to make a matching pulley -- except for the hole -- it goes on a 5/8" arbor.

I'm not sure it's worth coring 1/2" -- might just make it solid. Probably better if I core it, though -- I didn't get shrinkage at the top this time -- that might not hold with an even thicker center. I think I might have some old 1/2 cores stashed away.....

New foundry toys????? Whadidjaget??  Huh? Huh? Huh?  :drool:

Thank you Matt. (I think it was the right size!)  :beer:

Thank you Tom! Your own castings looked great, out of the starting gate!  :beer:

No further progress today guys.....it was Town Meeting Day in Vermont -- our once a year indulgence in local participatory democracy. Townspeople propose, debate, modify and vote every aspect of the budget for the upcoming year.
I love it when a Plan B comes together!
Steve
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Offline RobWilson

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Re: Foundry Furnace for the Tiny Shop
« Reply #68 on: March 04, 2015, 03:53:07 PM »


New foundry toys????? Whadidjaget??  Huh? Huh? Huh?  :drool:


Hi Steve ,

I bought myself , a few of each /different sizes  ;  Scotch cleaner ,English cleaner , Scotch club cleaner ,flange cleaner ,girder tool ,flange bead  upset ,boss tool ,straight bead ,spoon tool , and a few I have not found the names of yet  :lol: :lol: :lol: you did ask  :) all moulding tools  :dremel: 

Rob

Ill take a bonny photo of them at the weekend .

Offline Will_D

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Re: Foundry Furnace for the Tiny Shop
« Reply #69 on: March 04, 2015, 04:03:09 PM »
Talking of foundry tools - does anyone have any recommended designs for the more common crucible tools we use for these:

A2, A4, A6

In particular lifting out the furnace tongs either straight or with a 90 degree offset.

Pouring handles

Its not so much the diameters to match the crucibles its more about the length and strength of the sections needed. Also safety features that are not always shown in the basic undimensioned drawings.

I don't want to buy stock lengths of the wrong sized steel
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Offline RobWilson

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Re: Foundry Furnace for the Tiny Shop
« Reply #70 on: March 04, 2015, 04:12:24 PM »
Hi Will

If you can hang fire untill the weekend I will measure up my crucible gear , easy to make , simple ,been using them  for years   :thumbup:

Re bar makes for good poring shanks and the likes (nice and grippy)  cheap to .


Rob
 

Offline Will_D

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Re: Foundry Furnace for the Tiny Shop
« Reply #71 on: March 04, 2015, 04:19:23 PM »
Cheers Rob,

No rush! Waiting for the weather to improve before cutting down the gas bottle etc.

Yet another question:

Using a butane/Propane tank as the basic for a charcoal/coke furnace do people build in a dump grate to empty the ashes or leave as is (much safer if a crucible breaks)?
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Offline RobWilson

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Re: Foundry Furnace for the Tiny Shop
« Reply #72 on: March 04, 2015, 04:30:33 PM »
Never Charcoal fired Will , thats one for Steve .

As to the safety hole ,mmm  personally I  think its safer that the molten metal stays in the furnace ,let it cool, break out solidified metal and repair/patch furnace lining ,so I have never had a safety hole in the bottom of any of my furnaces .


Rob

 

Offline Will_D

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Re: Foundry Furnace for the Tiny Shop
« Reply #73 on: March 04, 2015, 04:56:20 PM »
Rob,

I didn't mean a safety hole.

Some solid fuel furnace designs I have seen incorporate a "Dump Flap" that allows you to drop the coals out of the cold furnace.
(In paricular cupola designs).

Otherwise you have to turn it upside down to empty it out!
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Offline vtsteam

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Re: Foundry Furnace for the Tiny Shop
« Reply #74 on: March 04, 2015, 04:57:45 PM »
Mmmmmmmmmm, rebar!  :drool:

1/2" dia, here. Actually these are mostly cupola tools....... but you get the idea!





« Last Edit: April 30, 2018, 10:01:21 PM by vtsteam »
I love it when a Plan B comes together!
Steve
www.sredmond.com