Richard,
Which Hirth box are you using on the one-rotor?
As far as Rotax boxes go, I believe the A through C boxes are
basically the same except for rmounting flange -- and the C box has
a starter. But I think structurally they are the same.
You can pick up a fairly good A box for maybe $200.
The Rotax box seems to work well on 100 hp Subarus and Suzukis, but
these are four-cylinder engines with more power pulses per rev. I
would be more worried about a one-rotor, because of the single power
pulse per engine shaft revolution -- like a 2-cylinder piston engine.
I think belt is a good cheap solution for a one-rotor. If you are
handly, you might even whip one up yourself...
Regards,
Gordon.
Donald, a small correction: the A and B boxes are similar, the B having
more mounting points than the A. The C and E are similar, the E having
the starter. The A and B boxes can only handle half the prop inertia of
the C and E.
(FWIW)
Paul, on all the other engine forums I belong to the view is that
TORQUE is what an engine is looking for, that HP. sells the engine, but
torque turns the prop. Yet you say that the plane flies on horsepower,
and that the rotary has very little torque. Agreed, the equation says
that hp. is a direct function of torque and rpm, but surely the torque
is what powers the props to speak, and that torque determines the amount
of pitch one can run on the prop? ( I am excluding applied
torque associated with reduction ).
Please explain, or correct me if I have the whole idea wrong.
Regards,
--
Erik Snyman
Messina
South Africa.
Here is a little article on the subject by my late great rocket
scientist friend Vance Jaqua. PL
TORQUE "LET'S TORQUE ABOUT HORSEPOWER"
It seems that wherever you go, people seem overly obsessed by
torque. "Yeah
that engine may have a lot of horsepower, but it really takes torque
to turn
that prop", just as if we were talking about two unrelated
characteristics
of the engine. Yes! It does take torque to turn that prop, but
torque alone
Big snip............
resonance rpm ranges. Super charging, and high energy fuel and oxidizer
additions increase power all over the range, with real potential for
total
"meltdown".
CONCLUSION
It pretty much boils down to the fact that that it is not enough to
"torque
the torque" you have to work the work!
Vance Jaqua
Erik, here is a little quiz you can ask people that have
a problem understanding engine torque and HP.
I have two engines. One is a 200 HP V6 at 4500 RPM.
The other is a 200 HP rotary at 7000 RPM.
The V6 has a 1.66:1 PSRU.
1)What is the torque at the prop?
2)What is the torque of the engine at 4500 RPM?
The rotary has a 2.59:1 PSRU.
3)What is the torque at the prop?
4)What is the torque of the engine at 7000 RPM?
Extremely well explained. Thank you.
--
Erik Snyman
Messina
South Africa.
---------------------------------------
Erik, here is a little quiz you can ask people that have
a problem understanding engine torque and HP on the groups.
I have two engines. One is a 200 HP V6 at 4500 RPM.
The other is a 200 HP rotary at 7000 RPM.
The V6 has a 1.66:1 PSRU.
1)What is the torque of the engine at 4500 RPM?
2)What is the torque at the prop?
The rotary has a 2.59:1 PSRU.
3)What is the torque of the engine at 7000 RPM?
4)What is the torque at the prop?
A question for the advanced students only. Both props are 80%
efficient.
5) What is the V6 engine thrust at 150 MPH?
6) What is the rotary engine thrust at 150 MPH?
If one answers 1 through 4 correctly one gets a B.
If one answers 5 and 6 correctly one gets an A :).
Paul Lamar ...No rotor no motor.
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