what engines are making successful aero engine conversions?

"Stealth Pilot" wrote in message
...
On Fri, 15 May 2009 13:26:27 -0400, Orval Fairbairn
wrote:

In article ,
Stealth Pilot wrote:

(snip)
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.

From what I have heard, the Pobjoy was NO joy to fly! Apparently it was
highly unreliable and would quit at the least desirable times.

The Pobjoy factory was destroyed during a WW-II bombing raid (perhaps by
disgruntled RAF pilots who had flown one?).

(snip)

I was talking with the Shuttleworth Trust guys about their Comper
Swift and its Pobjoy. evidently it has been made from a few different
models and is a nightmare for replacement parts. they have had it
embalmed for 3 years now. they usually rest aircraft for two years at
a time in rotation but the Pobjoy is problem enough that they didnt
take it out of preservation. It leaks oil like the best of british
engines evidently.
but the design of the pobjoy has aspects that are brilliant. picture
90 hp out of a little engine 22 inches in diameter.
it has one often overlooked claim to fame in that it was the first of
the high reving geared reduction engines.

I still maintain that this engine is worthy of a manufacturing revisit
and update for the homebuilder market.

does anyone know whether any of the drawings remain for any of the
pobjoy engines? I'd like to build one.

Short Brothers in Ireland evidently bought out Pobjoy when it went
toes up but I have not been able to find out whether any of the Pobjoy
factory drawings have survived.

Stealth Pilot.

I have heard that the (so called) area rule has a considerable effect on
drag at surprisingly low speeds.

Presuming that is the case, the benefit of the smaller diameter engine might
be trivial, except on a single seater or a tandem two seater, so you might
also consider the Rotec radial.

Peter

On Sat, 16 May 2009 10:58:14 -0400, "Peter Dohm"
wrote:



I have heard that the (so called) area rule has a considerable effect on
drag at surprisingly low speeds.

Presuming that is the case, the benefit of the smaller diameter engine might
be trivial, except on a single seater or a tandem two seater, so you might
also consider the Rotec radial.

Peter



rotec is not in consideration. my target is a light 40 hp engine for
single seat aircraft.

Stealth Pilot wrote:
On Sat, 16 May 2009 10:58:14 -0400, "Peter Dohm"
wrote:


I have heard that the (so called) area rule has a considerable effect on
drag at surprisingly low speeds.

Presuming that is the case, the benefit of the smaller diameter engine might
be trivial, except on a single seater or a tandem two seater, so you might
also consider the Rotec radial.

Peter



rotec is not in consideration. my target is a light 40 hp engine for
single seat aircraft.

Rotax 503, although I doubt that's what you'll want...

"Stealth Pilot" wrote

rotec is not in consideration. my target is a light 40 hp engine for
single seat aircraft.

How about a Harley Davidson motorcycle engine? I see some guy has been
using one for airplane use.

It seems like it would have a lot of things going for it. Air and oil
cooled, power output shaft designed to drive a primary drive belt, just like
could be used to drive a prop. Light and should have plenty of power for
your use. Plenty engines available, different sizes, and good supplies of
aftermarket parts.

The only drawback is the uneven drive pulses, and only two cylinders-at
that. Still, it seems to work for at least one guy.

I saw a three cylinder Harley-like engine on a TV motorcycle show once. I
wonder how that would work.

And, it sounds cool for a bonus!
--
Jim in NC

Morgans wrote:
How about a Harley Davidson motorcycle engine? I see some guy has been
using one for airplane use.

It seems like it would have a lot of things going for it. Air and oil
cooled, power output shaft designed to drive a primary drive belt, just like
could be used to drive a prop. Light and should have plenty of power for
your use. Plenty engines available, different sizes, and good supplies of
aftermarket parts.

The only drawback is the uneven drive pulses, and only two cylinders-at
that. Still, it seems to work for at least one guy.

I saw a three cylinder Harley-like engine on a TV motorcycle show once. I
wonder how that would work.

And, it sounds cool for a bonus!

I don't think a HD engine has sufficient cooling fins on the cylinder
heads to run at a steady power output and not melt. It's the VW problem
all over again. And as has already be discussed, casting cylinder heads
is no easy job.

If someone were to custom build an engine, there are HD parts that would
make the project go a bit quicker. I once sketched up an opposed twin
using parts from the all aluminum head HD engine back in the mid 1980s.
It was a somewhat doable project but I wasn't thinking of it as an
aircraft power plant but rather an modernization of the very rare WWII
military Harley XA.

Tony

On May 16, 11:42*pm, Anthony W wrote:
*It's the VW problem
all over again. *And as has already be discussed, casting cylinder heads
is no easy job.
----------------------------------------------------------------------------------------------------------

Ummm.... well, not necessarily. If we could come up with a
professional pattern for a Lost Foam Casting we can come up with a
single-piece, one-cylinder cylinder head having nearly TWICE the
cooling-fin are of the stock VW cylinder head.

No, not like the Scat head, but similar to it, with regards to one-
head-per-cylinder. What makes it different is that you need TWO
castings... because the Volkswagen's exhaust valves are on the
corners.

The main advantage here is the high precision you can get using Lost
Foam Casting. Plus, there's no need for any DRAFT in the pattern.
That means you can produce up to ten fins per inch (!) from a
casting. But you're looking at a minimum run of about 5000 units to
get the price down to where it's affordable.... and it STILL doesn't
address the main issue, which is the fact we are running out of VW
engines. But if we DID have such heads we could assemble a 140cid
engine capable of delivering an honest 65 hp.

-R.S.Hoover

Bob wrote:
On May 16, 11:42 pm, Anthony W wrote:
It's the VW problem
all over again. And as has already be discussed, casting cylinder heads
is no easy job.
----------------------------------------------------------------------------------------------------------

Ummm.... well, not necessarily. If we could come up with a
professional pattern for a Lost Foam Casting we can come up with a
single-piece, one-cylinder cylinder head having nearly TWICE the
cooling-fin are of the stock VW cylinder head.

No, not like the Scat head, but similar to it, with regards to one-
head-per-cylinder. What makes it different is that you need TWO
castings... because the Volkswagen's exhaust valves are on the
corners.

The main advantage here is the high precision you can get using Lost
Foam Casting. Plus, there's no need for any DRAFT in the pattern.
That means you can produce up to ten fins per inch (!) from a
casting. But you're looking at a minimum run of about 5000 units to
get the price down to where it's affordable.... and it STILL doesn't
address the main issue, which is the fact we are running out of VW
engines. But if we DID have such heads we could assemble a 140cid
engine capable of delivering an honest 65 hp.

-R.S.Hoover

I don't know what it cost this guy to have his engine parts cast but the
article is certainly enjoyable to read...
http://www.flashbackfab.com/pages/excel00.html

I wasn't thinking of continuing to use VW engines, I was talking about
making a boxer twin out of Harley-Davidson engine parts. The 80cid
engine of about 1984 on would be the one I was thinking about but the
newer 88cid engine would be worth looking at too.

when I was first thinking about this project I had the opportunity to
pick up a damaged BMW R90 engine and my crazy idea was to start with the
Beemer crank and built something custom from there. However that was
long ago and I don't have the resources now that I did back then...

Tony

"Morgans" wrote in message
...

"Stealth Pilot" wrote

rotec is not in consideration. my target is a light 40 hp engine for
single seat aircraft.

How about a Harley Davidson motorcycle engine? I see some guy has been
using one for airplane use.

It seems like it would have a lot of things going for it. Air and oil
cooled, power output shaft designed to drive a primary drive belt, just
like could be used to drive a prop. Light and should have plenty of power
for your use. Plenty engines available, different sizes, and good
supplies of aftermarket parts.

The only drawback is the uneven drive pulses, and only two cylinders-at
that. Still, it seems to work for at least one guy.

I saw a three cylinder Harley-like engine on a TV motorcycle show once. I
wonder how that would work.

And, it sounds cool for a bonus!
--
Jim in NC

IIRC, the then current Harley was a recommended powerplant for some ot the
Mignet "Flying-Flea" aircraft of the period c1970.

Peter

Peter Dohm wrote:
"Stealth Pilot" wrote in message
...
On Fri, 15 May 2009 13:26:27 -0400, Orval Fairbairn
wrote:

In article ,
Stealth Pilot wrote:

(snip)
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.
From what I have heard, the Pobjoy was NO joy to fly! Apparently it was
highly unreliable and would quit at the least desirable times.

The Pobjoy factory was destroyed during a WW-II bombing raid (perhaps by
disgruntled RAF pilots who had flown one?).

(snip)
I was talking with the Shuttleworth Trust guys about their Comper
Swift and its Pobjoy. evidently it has been made from a few different
models and is a nightmare for replacement parts. they have had it
embalmed for 3 years now. they usually rest aircraft for two years at
a time in rotation but the Pobjoy is problem enough that they didnt
take it out of preservation. It leaks oil like the best of british
engines evidently.
but the design of the pobjoy has aspects that are brilliant. picture
90 hp out of a little engine 22 inches in diameter.
it has one often overlooked claim to fame in that it was the first of
the high reving geared reduction engines.

I still maintain that this engine is worthy of a manufacturing revisit
and update for the homebuilder market.

does anyone know whether any of the drawings remain for any of the
pobjoy engines? I'd like to build one.

Short Brothers in Ireland evidently bought out Pobjoy when it went
toes up but I have not been able to find out whether any of the Pobjoy
factory drawings have survived.

Stealth Pilot.

I have heard that the (so called) area rule has a considerable effect on
drag at surprisingly low speeds.

Presuming that is the case, the benefit of the smaller diameter engine might
be trivial, except on a single seater or a tandem two seater, so you might
also consider the Rotec radial.

Peter




Interesting point, Peter.

The skinny tandem Piper Cub, for instance, has much higher equevilant
flat plate area than a fat side by side Taylorcraft.

Years ago there was an article in Kitplanes about someone trying to
use a Honda Goldwing engine. Did that ever come to fruition?