36HP VW Engine

(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

Claton,
These engines were used in light homebuilts before the 1300cc and up engines
were available. I am talking light weight single seaters. i.e., Tipsey
Nipper.
I built a 1200 cc VW which I think is a 36 horsepower. I happened to have
two of these in my backyard so I just wanted to see if one could be
converted after an A&P advised me to use one on my small Supercat airplane.
I don't remember the year of the engine. It has oversized jugs making it a
1385cc. Jugs went from 77 to 83mm. Stock crank is 61mm opposed to a 69mm for
a 1600cc. It is installed on the Supercat homebuilt but has not been flown.
Test runs indicated 3250 rpms using a 54X24 wideblade Tennesee prop, which
is too big for the engine. Old modifications back in the 60s for a 1200cc
engine included installing Corvair cylinders which increased the
displacement some more. (lot of machine work)
Great Plains Aircraft does not carry a full line of replacement parts for a
36 horse engine. Cylinders, pistons, rods, and heads from a 1600 won't fit.
Not very many of the parts are interchangable. Crank and rod bearings will
fit. Cam will fit. Flywheel endpiece is different. A 1600cc flywheel won't
seal at the case because the rear of the crank is different. Heads are
different - smaller valves - single port. Rods are shorter therefore the
case is narrower. I liked to have never found four rebuilt rods for my
rebuild. No cam bearings are used in the 36 horse engine. The only place I
know to get a rebuild kit is J. C Whitney. It cost more than a 1600 kit. The
larger jugs came from Larry's Offroad Supply. He just happened to have a
set. I would use a 1600 if I were to do it over. But I sucessfully converted
the engine. I did use a Great Plains hub. See some pics at
http://www.geocities.com/tomlc1/Volks.html
and at http://www.geocities.com/tomlc1/volks2.html
Tom Cummings
"Claton Cadmus" wrote in message
om...
(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

Claton, First buy a copy of "Hot VW's " magazine at the drug store.
Next look for a rebuildable "core" dualport engine built after '68
expect to pay $100.00..... you can build one up for about 500- 800
bucks, (there's a little machine work to do if you want to use big bore
cylinders.) Expect 55 honest horsepower if you build an 1835 version.
The VW aftermarket parts sources are enormous! Have fun!
.........Marvin www.flysquirrel.net

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