Small 4 stroke engine?

On Mon, 06 Jun 2005 22:05:00 -0700, Richard Riley
wrote:

I'm looking for an engine that may not exist. If anyone has a notion
of what it might be, I'd be grateful.

It's for a 103 legal ultralight.

60 lbs or so all up, including re-drive and cooling
35-40 hp.
4 stroke.
More reliable than a 2 stroke Rotax

Any ideas?

Half-VW?

Ron Wanttaja

Richard Riley wrote:
I'm looking for an engine that may not exist. If anyone has a notion
of what it might be, I'd be grateful.

It's for a 103 legal ultralight.

60 lbs or so all up, including re-drive and cooling
35-40 hp.
4 stroke.
More reliable than a 2 stroke Rotax

Any ideas?

I don't know if it's an exact match but the Briggs & Stratton V-twin is
close. They're very detuned in stock condition but the cart racers have
pumped them up considerably with little effort.

Tony

Richard Riley wrote:
On Tue, 07 Jun 2005 05:36:33 GMT, Anthony W
wrote:

:Richard Riley wrote:
:
:I don't know if it's an exact match but the Briggs & Stratton V-twin is
:close. They're very detuned in stock condition but the cart racers have
umped them up considerably with little effort.

Seems unlikely it can be pumped up THAT much - the 31 hp B&S I find on
the web is 125 lbs. The 60 lb engine is only 9 hp. But I'll look at
them.

Have you considered a motorcycle engine? A modern 600cc liquid cooled
engine puts out around 90 peek BHP and probably a 50 or 60 BHP for
sustained output. I don't remember what they weigh but I had a Honda
600cc engine a couple years ago and I was able to move it around without
much effort.

Tony

Richard Riley wrote:
On Tue, 07 Jun 2005 07:17:44 GMT, Anthony W
wrote:

:Richard Riley wrote:
: On Tue, 07 Jun 2005 05:36:33 GMT, Anthony W
: wrote:
:
: :Richard Riley wrote:
: :
: :I don't know if it's an exact match but the Briggs & Stratton V-twin is
: :close. They're very detuned in stock condition but the cart racers have
: umped them up considerably with little effort.
:
: Seems unlikely it can be pumped up THAT much - the 31 hp B&S I find on
: the web is 125 lbs. The 60 lb engine is only 9 hp. But I'll look at
: them.
:
:Have you considered a motorcycle engine? A modern 600cc liquid cooled
:engine puts out around 90 peek BHP and probably a 50 or 60 BHP for
:sustained output. I don't remember what they weigh but I had a Honda
:600cc engine a couple years ago and I was able to move it around without
:much effort.

I've considered them, they seem like a good possibility. The only
problem is I can find weights on the web for the bikes overall, but
not the engines alone. Something smaller than that would be fine - 20
hp sustained, 50 peak would be a blast.

Be carefull with many of the V twins. Not sure if the unbalenced
firing is good for an aircraft. Most of the inline engines are tilted
and the case is set up for an attached transmission on its side. A
flat twin might be the easiest to convert. Or maybe one of the early
smaller Gold Wing engines.

I think they are getting around 30 HP from basically a bored and
stroked 5 HP lawnmower engine in the Jr. dragraces. Don't know if they
are using gas though.

"Sport Pilot" wrote in message
oups.com...
I think they are getting around 30 HP from basically a bored and
stroked 5 HP lawnmower engine in the Jr. dragraces. Don't know if they
are using gas though.


They use an alcohol blend. I don't think they (the motors) live very long
either.

On Mon, 06 Jun 2005 22:05:00 -0700, Richard Riley
wrote:

I'm looking for an engine that may not exist. If anyone has a notion
of what it might be, I'd be grateful.

It's for a 103 legal ultralight.

60 lbs or so all up, including re-drive and cooling
35-40 hp.
4 stroke.
More reliable than a 2 stroke Rotax

Any ideas?

Colin Chapman of Lotus fame was a pilot and into Ultralights. He had
his engine group design a small four stroke intended for this type of
flying that had an interesting prop drive: They simply beefed up the
camshaft and bolted the prop to it. Since all camshafts spin at 1/2
crankshaft speed, they had themselves a PSRU without all the belts or
gears.

Alas, with the death of Chapman, the engine died with him, or shortly
thereafter.

Finding a decent, reliable small fourstroke engine has been going on
for a long long time. Motorcycle engines are intriguing, but attain
their high output via extremely high rpms. In addition, nearly all of
them come with the transmission case cast along with the engine
crankcase. You don't need the transmission, unless you want to use it
as the PSRU, and then you don't need all the gears which add to the
weight you have to carry. People have tried to use the transmissions
as PSRU's with mixed success.

For one thing, the transmissions aren't designed to spin a prop so
some kind of beefed up power takeoff has to be added and it just
becomes a bit of an engineering nightmare. It might actually be
easier to have one of the local machine shops machine a case out of a
block of aluminum using their computerized milling machines.

It's the old story of liability issues, plus the relatively limited
market for such an engine. But I watched Jesse James order a couple
of cylinderheads for a custom chopper he was building, and the camera
guys went to the machine shop where this CNC milling machine cut the
cylinders out of a block of aluminum. If they can do that, they can
cut out a crankcase, it should be a more simple job.

Or, go whole hog and recreate an Offenhauser engine in miniature; no
cylinderhead so no cylinderhead gasket to worry about. Valve jobs are
a bitch though...

Corky Scott

Richard Riley wrote:
I'm looking for an engine that may not exist. If anyone has a notion
of what it might be, I'd be grateful.

It's for a 103 legal ultralight.

60 lbs or so all up, including re-drive and cooling
35-40 hp.
4 stroke.
More reliable than a 2 stroke Rotax

Any ideas?


The Mid-West GAE 50 R for Ultra (Micro)Lights, Homebuilt or
Kit-Planes:
72 lbs / 50HP
http://www.tiho-hannover.de/bmt/bmt/...kel/ggkart.htm
Kumaros
It's all Greek to me

Richard Riley wrote:
On Tue, 07 Jun 2005 07:17:44 GMT, Anthony W
wrote:


:Have you considered a motorcycle engine? A modern 600cc liquid cooled
:engine puts out around 90 peek BHP and probably a 50 or 60 BHP for
:sustained output. ...

I've considered them, they seem like a good possibility. The only
problem is I can find weights on the web for the bikes overall, but
not the engines alone. ...

The Kawasaki 340 and 440 are in use in Ultralights but I think
they are two-stroke.

--

FF

The requirement stated by the original poster was more reliable than a
Rotax. Are we all that sure that a motorcycle engine or a overstressed
lawnmower engine will be even as reliable? Rotax's are pretty damn reliable
if maintained properly.