Rusty,

I've just been thinking about that fellow's contention that a single rotor
needs a redrive as strong as a two-rotor, because the power pulse of a
single is just as strong.

As far as I can see, this cannot be valid. If I'm thinking this through
correctly, each rotor will make three power pulses for each revolution of
the rotor, or one revolution of the e-shaft.

Even if two rotors were running out of phase, there would still be two power
strokes for each revolution of the e-shaft on a two-rotor, versus a single
power pulse per rev on a single. Your redrive would need to handle only half
the power.

Tracy's gearboxes are excellent by all accounts, but why use something so
heavy if it's not necessary? (Even so you overall weight of 220 lbs is
excellent for a 100hp engine).

Also, in terms of packaging, on a high-wing pusher like the Kolb, an upright
belt drive would put your thrust line at wing level where it needs to be,
while the engine could be down low, near the plane's vertical center of
gravity (like on the Challenger, which uses such a tall belt drive with the
Rotax 2-stroke).

I am interested in exploring just such an application with a high-wing
pusher design that I am developing. I've been looking at poly-v belts, which
you see driving the engine accessories on newer autos -- but there are
poly-v belts that will handle upwards of 500hp. You also see them on some
two-stroke UL engines.

The advantage of the poly-v over a cogged (synchronous) belt is that they
naturally dampen torsional spikes, by means of slippage. Another plus is
that the pulleys can be considerably lighter.

Regards,

Gordon.

PS: Regardsing the issue of hot exhaust on rotaries, this makes them ideally
suited to turbocharging.


"Bellsouth News Server" wrote in message
...
Hi Gordon,

I'm starting out with one of Tracy's RD1C drives, which is 2.85:1, and
good for way more power than I'll make wiht the single rotor.
Unfortunately, it's about 45 lbs stock. Speaking with Tracy, there's
probably about 5 lbs of weight that can be removed without losing any
strength, and perhaps more if you're willing to sacrifice strength in the
drive. That wouldn't be a problem for the single rotor, but if you ever
wanted to use it on a two rotor, it would be.

Richard Sohn has a running 12A single rotor now, and he's using a Hirth
G-40 gearbox. At last report, his total engine weight was 170 lbs, which
is pretty great. He's custom made many of the parts on his engine to save
weight, and might produce them if it all works out well. He's currently
on a slow, and careful development and test program, and eventually plans
to put the engine in his Avid, which I believe is flying with a Subaru.
It will be interesting to see how the Hirth box works out, but I'm not
sure how much lighter it really is in the long run. I've asked Richard
for the total weight, but since so much of the adaptation is dependent on
his custom end housings, he hasn't been able to come up with a number. My
guess is something around 30 lbs total for the drive.

I asked about belt drives, and found that someone was making one for the
single rotor that David Atkins is selling. So far, I haven't heard any
reports of how that worked, if it even got finished. One other fellow who
makes belt drives told me that he refused to make such a drive for Atkins,
because it wouldn't be strong enough. His point was that the single rotor
is still full sized, and gives the same strength power pulses as the two
rotor does. Because of this, he felt the drive has to be as strong as the
two rotor drive. This does make sense to me, but I'm sure there has to be
a way to reduce the weight further.

FWIW, my plan was to bolt together off the shelf parts, and see what it
weighs. The Kolb Slingshot that I'll be using initially will handle the
weight, when flown as a single place, and with a BRS chute to balance the
CG. Once I get a worst case weight, then I'll start working on reducing
it.

Cheers,
Rusty (hiding rotary info in the light twin thread)


What gearbox are you using? It seems like overkill to put one of Tracy's
boxes -- or something similar -- on a single rotor.

I would think a belt drive might be engineered that would be considerably
lighter -- expecially if you use the poly-v belts.