1/2 VW - 2-Cylinder Aero Engine

[GreenTwin]

We got off-topic in another scale 4-cylinder VW engine build, and started talking about 1/2 2-cylinder VW engines.

I am starting this thread so as to not hijack the original VW 4-cylinder thread.

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[GreenTwin]

There was a show on TV about someone who was in some sort of ultralight competition, and he uses a 1/2 VW engine.
He had problems with it, and could not get it to perform correctly.
I think the fundamentals of a 1/2 VW design are ok, assuming you did your design homework, and could get the crankshaft and timing worked out for a semi-smooth run.
There are many twin designs like that which run well, such as the BMW motorcycle engine, so obviously it can work well.

I noticed a lot of TIG welding on the head.
I would cast a new head and crankcase, and perhaps cast a new crankshaft in ductile iron.
Lost PLA on the cylinders and heads.

I would make it at least 1/2 size, but I guess we better save that discussion for a new thread.

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[GreenTwin]

Tom-AMS posted the following, which brings up many questions.

My company has specialized in both air-cooled VW & Harley engine rebuilding since 1963, we've built many engines for aviation and or industrial applications. (plaines, gen sets, air compressors, natural gas compressors. IIRC, Global Machine Tool sold a 2 cyl VW for aero use; I think Mosler, Inc bought out Global. Others were Hummel Engines, Better Half Engines, Simplex. One unique 1/2 VW engine put out by Lonestar Ultra-Light used the VW crankcase/lower end with Harley TwinCam cylinders and heads. The "all VW" 2 cyl are good for ~40 hp, while the "HD/VW" makes ~73 hp. Cutting and welding the VW vase is not as difficult as it may seem. I did my first one in 1969 - the mag alloy is either AS41 (later cases) or AS26 - both TIG weld easier than welding aluminum, from my experience. There are also aluminum alloy cases (we sell both new alum. & mag cases) however the aluminum case weight about 14 lbs more than the mag alloy case... so not the best choice for aero.
Tom-AMS

How are you getting 40 hp out of two cylinders ?
Better air flow, better carbs, better compression ?
That is a bit of a trick.
Does the engine life have to be derated ?

What about a thrust bearing ?
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[GreenTwin]

ddmckee54 posted these from the other thread.​

I am going to copy these here for the purpose of discussion.
Photos by ddmckee54:

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