Harley motor in a homebuilt?

clare @ snyder.on .ca wrote ...

No, David was right. ...

He sure was. I misread what he meant. Engine RPM vs prop RPM. The error was mine.

Daniel

David

Many years ago, someone told me that motorcycle engines had a lot of
vibration and for that reason were not really reliable for use in a
very light aircraft that their horsepower would pull. Vibrations
caused failures in the structure????

One data point FYI.

Big John


On Fri, 19 Sep 2003 10:06:41 GMT, David Hill
wrote:

I'm working on a replica of a 1924 airplane originally powered by an
Indian Chief motorcycle engine. I've spent a year or two trying to find
a modern engine that somewhat resembles the Indian, and the best I have
come up with is a Harley-Davidson.

Looks like with an 80 cid Evolution engine I can get ~40 hp at ~3400 rpm
(direct drive) or ~60 hp at ~4500 rpm (PSRU setup).

Has anyone here tried this? Or know of anyone who has done this? I'm
looking for caveats, tips, and techniques. Based on experience, not
opinion. Oh, sorry, I forgot where I was. grin

Indian just went belly up re article in todays paper. Stated in 1902
it said.

Big John


On Fri, 19 Sep 2003 10:06:41 GMT, David Hill
wrote:

I'm working on a replica of a 1924 airplane originally powered by an
Indian Chief motorcycle engine. I've spent a year or two trying to find
a modern engine that somewhat resembles the Indian, and the best I have
come up with is a Harley-Davidson.

Looks like with an 80 cid Evolution engine I can get ~40 hp at ~3400 rpm
(direct drive) or ~60 hp at ~4500 rpm (PSRU setup).

Has anyone here tried this? Or know of anyone who has done this? I'm
looking for caveats, tips, and techniques. Based on experience, not
opinion. Oh, sorry, I forgot where I was. grin

This month's Kit Planes talks about a Nieuport replica with a Yamaha
engine as the powerplant. The guy has the engine locked in second
gear to supply his reduction. I saw a site with it a long time ago
but can't find it now. Apparently it has hours on it in the air and
pulls ok. Personally I have no opinion on the feasability but we are
experimenters.

Canuck Bob wrote:
This month's Kit Planes talks about a Nieuport replica with a Yamaha
engine as the powerplant. The guy has the engine locked in second
gear to supply his reduction. I saw a site with it a long time ago
but can't find it now. Apparently it has hours on it in the air and
pulls ok. Personally I have no opinion on the feasability but we are
experimenters.

When I first started looking at using a V-Twin motorcycle engine, my
inclination was to use a Jap V-Twin rather than a Harley, mainly because
in motorcycles the Jap engines are 1) smoother, 2) more reliable, and 3)
more powerful. However, the big drawback is that the transmission is
integral with the engine.

The plus side of that is you already have a well engineered gear
reduction system in place. The minus side is you have a lot of extra
weight that you really don't need. I've talked to folks that used other
Jap engines; they removed as much of the transmission innards as they
could, leaving only what was necessary. This involved some tricky
welding, and still left a lot of metal in place that wasn't really needed.

My inclination changed recently after I dropped by a local Harley shop
and started asking questions.

Turns out the Harley motor is separate from the transmission.

Turns out you can get a new-in-the-crate Evo engine for about $2900.
Comes with dual sprockets standard on the crank (just waiting for a
chain drive PSRU).

Turns out it's a dry sump engine; requires a separate oil tank. Can you
say "lots and lots of oil, and an oil cooler to boot"? That'll help a
lot in regard to engine cooling.

Turns out you can get it either carburated or with electronic fuel
injection. EFI means I can keep the simple single lever control
(throttle only) of the original plane, but be able to operate
efficiently at varying altitudes.

So, the only hard part is designing and building the PSRU. I've seen
the one at http://www.hog-air.com/. From the pictures it looks like it
ties in to the cylinder heads, while the engine mounts are at the base
of the cylinders. It seems this would put a bending stress on the
cylinder bases that they were not designed for. I hope to get a first
hand look at it next month and ask the designer about it.
--
David Hill
david at hillREMOVETHISfamily.org
Sautee-Nacoochee, GA, USA

So, the only hard part is designing and building the PSRU. I've seen
the one at http://www.hog-air.com/. From the pictures it looks like it
ties in to the cylinder heads, while the engine mounts are at the base
of the cylinders. It seems this would put a bending stress on the
cylinder bases that they were not designed for. I hope to get a first
hand look at it next month and ask the designer about it.

Couldn't find any specs on the engine other than the torque at 3000 RPM,
and the Harley web site, like the hog-air web site, was kind of a pain
to navigate.

Any idea if they have the power curve on line?

thanks

Ed Wischmeyer

Ed Wischmeyer wrote:
Couldn't find any specs on the engine other than the torque at 3000 RPM,
and the Harley web site, like the hog-air web site, was kind of a pain
to navigate.

Any idea if they have the power curve on line?

thanks

Ed Wischmeyer

There's a "list of verified horsepower figures for a variety of the Twin
Cam 88 and 95 CID Engines" at
http://www.nightrider.com/biketech/hplist_twin_cam.htm

If you drop down to the first 68 hp motor 88 CID engine listed, you can
click on it and get a dyno chart at
http://www.nightrider.com/biketech/dyno_sheets/max_green_tcdyno.jpg

Just looked up what the Harley website says about torque at 3000 RPM;
they claim peak torque of 85 ft-lbs. The dyno chart referenced shows a
peak torque of about 76, maybe 77 ft-lbs at 4000 RPM. Harley's probably
measuring at the crank; the dyno chart is of measurements taken at the
rear wheel.

hope this helps,
--
David Hill
david at hillREMOVETHISfamily.org
Sautee-Nacoochee, GA, USA