Author Topic: Green Twin Oscillator Cast/Build  (Read 24135 times)

MetalCaster

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Green Twin Oscillator Cast/Build
« on: July 27, 2013, 04:27:07 PM »
A little history about how I got into model building, and my approach to the same.
I have had a lifelong interest in steam engines, and build my first one as a 12th grade science project, along with a boiler that was about 18" dia, 36" tall, vertical fire tube type with injector.

Life has been busy since 12th grade, and I always had the intention of getting back to building steam engines and boilers.

My dad got into the modeling hobby about 2001, and build a ludicrous number of model steam and hot air engines, and some full sized ones too.
My intention was always to get with dad and build some models too, but again it was not to be.

About 2002, I was working as an engineer at a large firm, and a very ambitions and rather ruthless junior engineer pulled some corporate political strings, pushed out the head of our department, took over, and then fired the entire department to "clean the slate" and install his own loyal people.
He lasted about a year at that business, and then quit and took "his people" with him to start his own firm.

I decided that the old adage "Fool me once, shame on you, fool me twice, shame on me" was something I had to adhere to, so in 2003 I started my own consulting engineering business, and have been running it as a one-man operation ever since.
While the last few years have been nothing short of brutal, and one man in his own firm has to wear a lot of hats (I am the janitor, secretary, financial planner, marketer, draftsman, designer, you name it, I do it), there are some redeeming things about working for yourself, such as the fact that I have been the "employee of the month" every single month going on 11 years now.

My dad died in 2006, and so I accumulated his machine tools and shop equipment.
Building models seemed rather rudimentary to me, after all, dad made so many, and made it look so easy.
But it was anything but rudimentary.  I realized I was floundering in 2009 after getting the shop and equipment set up, so I discovered online model building forums, and began the process of learning how to machine engines from bar stock.

Several things became evident very quickly, which were 1. I sucked at machining.  2. Machining can be extremely tedious and boring for someone like me with a short attention span.  3. Machining engines from bar stock generally required machining anywhere from 50% to 90% of the metal off into chips which fall on the floor and fly in every direction, and have to be cleaned up daily.

I was bound and determined to make the brute-force method work for me, and so I drew a couple of my dad's engines in 2D CAD, and set about to build copies of them.
After a year or so of what seemed like banging my head against the wall, I decided there must be another way.

Offline awemawson

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Re: Green Twin Oscillator Cast/Build
« Reply #1 on: July 27, 2013, 04:37:37 PM »
And the "Green Twin Oscillator Cast/Build " ??????????????????????????
Andrew Mawson
East Sussex

MetalCaster

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Re: Green Twin Oscillator Cast/Build
« Reply #2 on: July 27, 2013, 04:39:52 PM »
Several things became apparent at this time.
1. Too much metal was being wasted to get the part into the shape I wanted.
2. Too many tool bits were being worn out to make the parts.
3. The parts never really assumed the shape/appearance that I wanted them to have.

My dad had lamented that if he had enough space, he would have cast his engines.
I really did not have the space either, but I considered getting into castings.

Then I ran across Rob Wilson's work, got the 3D bug, and then discovered that with 3D, I could visually see the engine, as well as assemble the parts, and check for alignment, fit, and actually run the engine virtually.

So I decided to give the casting thing a go.
I tried a charcoal melt, to no avail, and then purchased a propane burner.
I melted aluminum first, and had pretty good success with that for a beginner.
I found a casting forum and leaned heavily on the information found there and in videos online, many by members here.
My funace design comes directly from Rob Wilson's (thanks again Rob).

You may ask, why does my furnace look so shabby, when Rob's looks superb?
Well, I quickly realized that while my interests in self-discovery are high, my time and money are limited, and I am no spring chicken, I only have a limited amount of time to make a go of the casting thing.
So my method has been to use the information available on the internet to maximum advantage to hone in quickly on workable (granded ugly) furnace, burner, equipment, etc.
Trade-off's don't bother me as long as the focus is on the final product, and so that has been my approach.

MetalCaster

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Re: Green Twin Oscillator Cast/Build
« Reply #3 on: July 27, 2013, 04:40:37 PM »
And the "Green Twin Oscillator Cast/Build " ??????????????????????????

I got to have a lead-up to the story of the green twin.
I will get there shortly.

Chafing at the bit are we?

Edit:
I attended a concert one time and the musician came out and began talking incessantly, and finally someone yelled "Are you daft man, stop yammering and get on with the show", and he said "righto", and the show began without further ado.
« Last Edit: July 27, 2013, 05:13:38 PM by MetalCaster »

MetalCaster

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Re: Green Twin Oscillator Cast/Build
« Reply #4 on: July 27, 2013, 04:44:15 PM »
So then one day, I was doing a group build on another forum, and a guy says "I am going to build a green twin oscillator" that I saw on Preston's services.

So he designed on it for a while, and I offered some ideas/suggestions, and it got complicated, and not wanting to see it all go by the wayside, I jumped into the design.

Luckily my wife was gracious enough to give up her two-car garage and half the driveway, and without even divorcing me (yet).

So I started in earnest on the green twin, and about a year and a half ago, I got the mother of all work projects, and all work on the green twin ground to a halt.
I am just getting to the point of catching up at work to begin on the twin again.

So here is where I left off with the green twin.

MetalCaster

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Re: Green Twin Oscillator Cast/Build
« Reply #5 on: July 27, 2013, 04:50:30 PM »
The design was eyeballed from the Preson Services photo, and turned out like this:

MetalCaster

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Re: Green Twin Oscillator Cast/Build
« Reply #6 on: July 27, 2013, 04:55:02 PM »
I tried my hand at making a pattern for the flywheel, but my equipment and pattern making skills were just not ready for that.
A 3D print was dispatched, and it looked like this, made from the 3D design, and printed with the appropriate oversize for shrinkage.

Offline doubleboost

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Re: Green Twin Oscillator Cast/Build
« Reply #7 on: July 27, 2013, 04:59:21 PM »
You have my attention
Get on with it :lol: :lol: :lol: :lol: :lol: :lol:

John

MetalCaster

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Re: Green Twin Oscillator Cast/Build
« Reply #8 on: July 27, 2013, 05:00:45 PM »
I was certain I could make the pattern for the base of the engine, and so I begain building one from balsa.
The first pattern went rather badly, and so I had to redouble my efforts and really pay attention to detail.

Here is my second attempt at the base pattern.

It is a hybrid affair with some of it printed in 3D and some of it made from balsa.
It was a parallel effort by two of us (the guy who originally decided he wanted to model the engine and myself).

I was quite proud of this group-effort, and all seemed to be going fine..............
(Note:  If you ever think things are going fine, just wait a little while and things will change.)


MetalCaster

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Re: Green Twin Oscillator Cast/Build
« Reply #9 on: July 27, 2013, 05:06:12 PM »
And the cylinder and some of the other parts were printed in various places around the world, and shipped in.

The best 3D print was the flywheel, but I did not have to pay for that one.
The cylinder and some of the other parts were made on an inferior 3D printer, and so lots of extra work to finish them (an ongoing process).


MetalCaster

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Re: Green Twin Oscillator Cast/Build
« Reply #10 on: July 27, 2013, 05:12:57 PM »
I started trying to learn all the strange new terms required for casting, such as cope, drag, sprue, runner, gate, shrinkage allowance, machining allowance, ect. etc.


I tried to melt cast iron with propane as I had seen Rob do, but no luck with that.
I had to find a better burner, and without the problems of vaporization of the propane tank.
I started playing around with kerosene and a paint sprayer, blowing huge flames across the driveway much to my wife and the neighbor's horror.

I built a very ugly but well functioning furnace, and build an oil burner from a cutting torch tip.
The cutting torch burner worked well, but required a heck of a lot of compressed air for atomization.

Then I ran across a Delavan siphon nozzle, and made a great duel-fuel (propane-oil) burner which melts cast iron like butter.

The cope/drag thing and moulding in general was very confusing, and I confess I hardly had a clue as to what I was trying to do other than fill the mould with molten metal.
Here is an early attempt at a cope/drage layout.  I would probably do it different now.
This is before I read the "Basic Gates and Risering" book.

MetalCaster

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Re: Green Twin Oscillator Cast/Build
« Reply #11 on: July 27, 2013, 05:34:40 PM »
One very critical casting term that I was aware of, but an idea that was further impressed upon me as I progressed was the all critical "draft angle".

Not a more important term in casting than that (in my humble opinion).

I attempted to cast the base in aluminum, and had a lot of trouble with the lower mould breaking off (the part that protrudes up into the bottom of the base).
I finally used a sodium silicate core in the drag, and petrobond in the cope.

But who would dream that you have to put weights on top of your flask to counteract the hydraulic forces, and so while I was on track for an excellent cast, the mould blew out, and the casting was ruined.

The sand used for the core was too coarse, and so the finish underneath was terrible.

I have made several other attempts at casting the base, using various sand types, mixtures, grain sizes, mould layouts, etc. and each has been a failure for one reason or another.  A good learning experience though, and I think I have the issues sorted out.


MetalCaster

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Re: Green Twin Oscillator Cast/Build
« Reply #12 on: July 27, 2013, 05:39:37 PM »
Another attempt at the base.

Not a bad attempt, but poured too slow with too small a sprue, and aluminum too cold.

The finish was better on the bottom.

Was still trying to zero in on pour temps, gating/risering, and numerous other things.

Offline tekfab

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Re: Green Twin Oscillator Cast/Build
« Reply #13 on: July 27, 2013, 05:41:25 PM »
Sorry to interrupt, what size of delevan nozzle did you use ?

Mike

PS Good stuff !

MetalCaster

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Re: Green Twin Oscillator Cast/Build
« Reply #14 on: July 27, 2013, 05:44:41 PM »
This is a third attempt at pouring the base.

My Petrobond was getting a bit dry, so I mulled some 30 weight non-detergent oil into it (too much oil), and started getting erosion as the sand/oil mix failed.

This casting is probably usable, but I will save it and try to improve upon it.


MetalCaster

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Re: Green Twin Oscillator Cast/Build
« Reply #15 on: July 27, 2013, 05:51:30 PM »
I used the largest size, which is 1 gal/hr, but don't be fooled, with 15 or 20 psi for atomization, and 5psi on the fuel tank, you can move 4 gal/hr or more.

I will post my sketches on the siphon-nozzle burner,  use at your own risk.
I assume no responsibility for anyone's use or misuse of this information.

MetalCaster

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Re: Green Twin Oscillator Cast/Build
« Reply #16 on: July 27, 2013, 05:57:36 PM »
And one more page for the siphon burner, and some photos of the setup.

Sorry for the general messyness of my shop/driveway/equipment, etc, you will never see RobWilson-like quality in my equipment or setups, but hopefully I can make up for that in what I make (attempt to make).

The burner below is my first attempt with a welding tip nozzle, made in a single afternoon.

For me, it makes little sense to build a lot of quality into a piece of equipment that is experimental in nature, and has a high chance of not working.
Hopefully I can slow down and put a little more quality into the equipment once I get the basics figured out.
« Last Edit: July 27, 2013, 06:29:36 PM by MetalCaster »

MetalCaster

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Re: Green Twin Oscillator Cast/Build
« Reply #17 on: July 27, 2013, 06:03:17 PM »
This is the Delavan siphon-nozzle burner used with a pressurized fuel tank (5 psi using an aquarium pump for safety and to prevent overpressure on the fuel tank, it does not take much pressure on the fuel tank at all, but too much will result in disaster).

It starts on propane outside the furnace, and then you can change it to diesel in a few seconds.

I simplified the tubulator (spin vane) upon a recommendation from someone on another forum, and used a simple sheet metal unit.

The first photos are starting the burner on propane out of the furnace (a test in the shop;  don't try this in your shop for carbon monoxide and other hazardous reasons).

Note:  The Delavan nozzle has an o-ring inside of it, and this item is cooled by the fuel flowing through the nozzle, as well as by the combustion air flow, but you should turn off the burner and pull it away from the furnace immediately after you turn it off to avoid overheating and ruining the o-ring.
« Last Edit: July 27, 2013, 08:52:00 PM by MetalCaster »

MetalCaster

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Re: Green Twin Oscillator Cast/Build
« Reply #18 on: July 27, 2013, 06:14:00 PM »
And the Delavan burner up to speed.

Video here:

(How about that beer gut, and I don't even drink beer; can't due to celiacs).
In the video, the burner has been started with propane only, no combustion air, then a little bit of diesel is turned on, then a little bit of compressed atomization air, then immediately turn off the propane and leave it off, then turn on more compressed air, then more diesel. and finally full compressed air.

You will have to play aournd with this sequence and perhaps get the furnace hot on just diesel and some compressed air before you turn on your combustion air blower (I use a pour-man's blower, which is the output of my shop vac).

Under no circumstances should you ever use the propane other than for a minute or so during the initial start.
I am guessing you could make this a propane-only burner, but I have not looked at that yet, and don't like the vapor-pressure cold propane tank problems that generally are caused by high propane flow.

The 5psi pressure on the fuel tank makes the burner output constant regardless of fuel tank position, elevation, or fuel level changes in the tank.
So the burner is operated at a slight (5psi) fuel pressure, not really a siphon pressure.
The burner works fine as a siphon unit only with the exception of irregular output as the fuel level drops in the tank.

MetalCaster

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Re: Green Twin Oscillator Cast/Build
« Reply #19 on: July 27, 2013, 06:17:28 PM »
I had seen others melt cast iron online, and they make it look so simple.
The first time I tested my new siphon burner with my furnace, I was sure it would work well.

After 3 hours of red hot but very solid cast iron (not the slightest hint of liquid iron) wasting 4 gallons of diesel fuel, and endless fiddling about with adjustments, I was cursing the casting gods and Rob Wilson (not necessarily in that order) for getting me into such a mess.  (Sorry Rob, I take it all back now that things are working).
My wife politely excused herself to go run some much needed "errands", code name "he is pissed, I better slip out for a bit".

In one final act of desperation, I turned on 100% oil, compressed air, combustion air, and sealed the burner tube to the furnace entry hole.
I fully expected the burner to extinguish itself with so much input, but low and behold, the cast iron began to melt very quickly.
The neighbors wondered what all the shouting was all about, but the first cast iron melt is a big deal (Routine for some perhaps, but a very big deal for me anyway).
I had the high-five myself since the wife was away shopping. (Edit, my wife reminded me that she was actually there, so I guess my memory is not so good).

So I poured the flywheel using Petrobond for the mould.
Little did I know that Petrobond does not really like cast iron temperatures, and so some of the mould failed, but the pour was successful enough to verify that I could melt and pour iron.

I used big honking weights on top the flask to keep the mould from rupturing.
I need to add a band around the top of my furnace to keep the refractory from cracking, that furnace was made from a cut-up 55 gallon drum what was welded back together Frankenstein-style, with more than a few gaffs and pitfalls in the construction prcess.  It does work though; maybe the next furnace will be pretty.

In the last photo with the furnace lid open, the burner is running flat out, and without a hint of smoke, so the combustion is very complete.

MetalCaster

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Re: Green Twin Oscillator Cast/Build
« Reply #20 on: July 27, 2013, 06:27:26 PM »
A seemingly maze of hoses for the burner, but well worth the trouble to get such performance.

MetalCaster

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Re: Green Twin Oscillator Cast/Build
« Reply #21 on: July 27, 2013, 06:33:07 PM »
This cast iron pour was the flywheel for the green twin.

The sprue, runners, gates, etc. are very sloppy and not necessarily the way they should be optimally, but I did not expect a successful pour anyway, it was all just to see if I could actually melt gray cast iron.

The surface finish varied a bit from top to bottom, not sure what that was about, and I can't remember which surface was better, maybe it is apparent in the photos.

MetalCaster

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Re: Green Twin Oscillator Cast/Build
« Reply #22 on: July 27, 2013, 06:34:57 PM »
And here is the machined rim face.

Not too bad other than the sand inclusions on the back, which I think is a problem that can easily be resolved by not using Petrobond.

And better than I thought I would get for a first attempt at iron.

No hard spots, surface easily cut with carbide bit, no hard inclusions.
The 100 dollar question will be "can I repeat this?".

MetalCaster

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Re: Green Twin Oscillator Cast/Build
« Reply #23 on: July 27, 2013, 06:42:14 PM »
The local metal museum uses both water and resin-based self-hardening sand systems, with a manufactured fine round grain sand.

I decided to try the manufactured sand and the resin system.  The resin system has fumes that you do not want to breathe for any reason.

So this is as far as I got, and I can't even remember how long ago this was, perhaps a year or more, when the big work project started and the green twin project came to a screeching halt.

Hopefully we can get this project underway very soon, and stop taking about casting, and actually cast some metal.

Below is the river sand available in abundance around here, and the lighter colored manufactured sand.
The fine sand and binder system will require careful venting, since the permeability of the sand/binder mix will be low.
The local metal museum used this sand and binder with great success, so I have full confidence in it once I get through the learning curve.

MetalCaster

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Re: Green Twin Oscillator Cast/Build
« Reply #24 on: July 27, 2013, 06:50:17 PM »
And a cupolet cast iron pour at the local metal museum a few weeks ago.

The iron was really flying, it was very interesting to watch.
They have guys working there who use to work in foundries, and I pick those guys brains every chance I get, its an invaluable resource.

Videos here:






They poured several hundred pounds of cast iron the other day at the museum.
All using old radiator material.
No sign of gassing in any of the castings.

They do use an additive, but that is to add fluidity to the pour, since all their work is ornamental in nature.
I need machinability above all else, so I don't use any additive, but I did not have any problems with fluidity.

I think the ladels they are are insulating, since they seemed to stand around using the aditive, stirring, and skimming for a long time before pouring, and still the metal pours like ice tea.

Well, until I can get out and cast again, that is all I have for now.
Happy casting folks.