Green Twin Oscillator Build

[greentwin]

A buddy of mine showed me 3 photos of a steam engine for sale in England a few years ago, and said he wanted to build a few scale models.
I wanted to practice 3D modeling, and so I developed a 3D model for the engine (a twin oscillator) in Solidworks, not really thinking I could actually design an entire engine in SW.
The 3D model turned out so well that we started to discuss a couple of barstock builds, and then said "Why not cast it in aluminum".
The I said "Well why not just cast it in gray iron?".

The problem was, I had never made a complete engine of any type, had limited machining skills, no foundry experience or foundry, and did not even know if melting iron in a backyard setting was even possible, much less safe.

I built a foundry, learned how to melt gray iron and aluminum, learned pattern making and 3D printing, and began to cast parts.
After much experimentation, two flywheels were cast in gray iron, with the remaining parts cast in 356 aluminum.

What a wild journey the build was, but my buddy and I finally pulled of building two scale replicas of the engine in England, and I was able to publish the engine with drawings in Live Steam Magazine.

Some photos and narrative below.
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[greentwin]

This is my furnace.
I often pour at night, so I don't have to work out in the sun.
It is also much easier to see what is going on inside the furnace without the glare of the sun.
The burner uses diesel as fuel, and a Toro leaf blower for combustion air.

Melting iron takes about 1 hour.
You have to wear a lot of leather due to the radiant infrared heat that comes off the furnace, crucible, and molten iron.

The pour temperature is probably in the 2400-2500 F range.

 

[greentwin]

Here are some screencaps of the 3D model that I made.

 

[greentwin]

And the finished 3D model, which I was able to test in a 3D simulated run, to verify the correct function of the parts.
(with screencaps of a few more bits and pieces, and some translucent screencaps)

 

[greentwin]

Lots of mold making and casting.
I was having trouble understanding the iron casting process, and was not getting consistent pours on the smaller parts, and so rather than delaying the project, I cast the base and small parts in 356 aluminum.
It took me quite a few years more to completely master the iron casting process, and quite a few years after the green twin engine was cast.

Everything was "learn-as-you-go", which can make things very tedious.
Learn pattern making, learn mold making, learn how to operate an oil burner and furnace, learn how to machine parts accurately, learn how to assemble a steam engine, etc.

Somehow I was able to get through it all.

 

[greentwin]

After some trial and error, I figured out how to make some nice castings.

 

[greentwin]

I discovered resin-bound sand early in the build, and that made things infinitely easier.
The molds harden, and can then be handled, or even drilled/cut/machined/glued, etc.

Flasks were the "snap flask" type, which means you can remove the wood flask from the sand to prevent damage during the pour.

 

[greentwin]

The machining went pretty well, considering this was my first complete engine to machine.

I had previously practiced machining random steam engine parts, and generally ruined four parts before I mastered machining any one component.
I had a wall of ruined practice parts, but was ready when I started machining this engine, and I really did not make any serious machining mistakes in the process.

Everything got machined, and then painted, and finally assembly.
The colors were custom-mixed in order to try and match the original engine.

 

[greentwin]

I later got to where I could pour consistent clean gray iron.
This is one of my cut ingots, and some smaller ingot slivers that are broken to reveal the section.

 

[greentwin]

And finally the engine was complete.
Rather a long learning journey, but a lot of fun.
I really did not know if I could pull this build off, since just about everything was a new learning experience.

Not too bad for a first engine attempt, in my opinion.

It runs very well in forward or reverse, and will self-start in any position.

Power is delivered to a load via a belt on the flywheel, which extends out the bottom of the base through an opening in the base.

My flywheel is 6" in diameter.
Bore is 1.25", stroke is 2".