36HP VW Engine

On 22 Oct 2003 17:23:37 -0700, (Claton Cadmus) wrote:

(Corky Scott) wrote in message ...

Claton, are you just stepping into this world for the first time
without knowing what history has gone by about this engine as used for
an aircraft engine?

Thanks, Corky Scott

Yes, if I knew the history of the engine as it pertains to homebuilt
aircraft I wouldn't need to ask the question. I do know that the
horespower rating on an engine is not at important as it's torque.

Do you have anything constructive to add?

Claton

Sorry Claton, I wanted to find out where you were in understanding
what it takes to make an airworthy engine out of the VW.

My understanding is that the engine cannot be used as is. I don't
know how you intended to use it, whether you wanted to simply bolt a
prop to it or use a Prop Speed Reduction Unit. The crankshaft has
been proven not strong enough to handle the prop loads when used as a
direct drive engine. The crank snaps off at the prop, eventually.

The 36 horsepower you mention is what the engine makes at full rated
rpm. If there is a prop bolted to the engine, the engine cannot turn
full rated rpm because the prop will be spinning too fast: the prop
tips approach or even exceed the speed of sound. When the tips get
going that fast, they have the very same reaction to sonic speed that
ordinary wings do, they produce massive amounts of drag.

Since the engine has to rev up to make it's 36 horsepower, you have to
cut down the prop to allow it to do this. The reduced disc size of
the prop makes it very inefficient in terms of producing thrust.

Then there are issues with the case, which has proven weak too.

There are several companies that produce airworthy versions of the
venerable VW engine, but there are very few original parts left. The
case is stronger, the cylinders are aftermarket racing jugs, the
valves are bigger, the cam is different, and of course, the crankshaft
is forged and machined to withstand prop loads.

I didn't know if you understood all that, which is why I asked.

My apologies if the question upset you.

Corky Scott