what engines are making successful aero engine conversions?

On Thu, 14 May 2009 13:34:22 -0700 (PDT), wrote:

Dear Stealth (and the Group)

We may be looking it this the wrong 'way 'round.

snip

The point of all this is that the lack of Volkswagens or other air-
cooled engines should not be taken as an automatic out. If push comes
to shove I could always convert a stray Holden, offering it up to
something like a Pietenpohl.

-R.S.Hoover

hoover you are proof positive that old dogs can learn new tricks!
I note the use of the word Holden :-) and punch that upturned thumb to
the sky thinking yesss hoover you are a champion :-) :-)

this is a subject pregnant with information shall we say but in
looking at the converted aero engine, or more specifically the
dismantled VW engine on my workbench, a weighup shows that the
chankshaft is the heaviest part in the engine.
making it lighter isnt an option by which I mean making the existing
crankshaft less substantial.
so one weight reduction option is to make it shorter, which leads to
looking again at the pobjoy geared radial made back in 1934. I've
always believed that a modern technology revisit to this design would
pay dividends. at 23inches diameter and delivering 90hp it has to be a
winner.

the great bugbear of the radial of course is the increased drag of the
flat round radial engine when compared to the flat four engine or
inline engine or even v12 layout. ...so history tells us.

I read this today in Bill Gunstons book "Development of Piston Aero
Engines"...

"Nowhere was the process [of drag reduction] more effective than in
the case of radial engines, where instead of offering an ungainly
shape - called by aerodynamicists a "bluff body"- they were enclosed
in a tight cowling in such a way that overall drag was often zero,
thrust from the heated cooling air more than countering drag from
other causes."

I was gobsmacked. NO cooling drag from a tightly cowled radial engine!
(The Hawker Fury was offered as an example)
Cooling drag in a Wittman W8 Tailwind was measured by Raspet to be 10%
of total drag at speeds over 120mph (104 and a bit knots)
I've never ever heard of a flat 4 having no cooling drag.

far from being a hackneyed subject the challenge of locating or
designing and building a 40hp aero engine presents some amazingly
fertile challenges.

one of the real plusses in this quest is that your approach is totally
different from mine and yet both are totally valid paths to follow.
Remember George Graham using a mazda rotary in second gear? That was
another path. he proved the concept but the gearbox failing just
pointed to a more substantial gearbox being needed.
I suppose the real challenge is not to be enthused by the
possibilities but to get machining and put examples in the air.

we arent done yet bob.

Stealth Pilot