Phil, sorry for the tongue-in-cheek answers. It's just that there is
very little new under the sun. In my admittedly misguided youth, I built
a one man helicopter, with the tail rotor driven exactly as you suggest
(variable speed hydraulic motor driven by a pump from the main engine, a
wankel from a snowmobile). I never had the balls to take the contraption
out of ground effect, but it did work. Hydraulics can be very efficient
at transporting considerable amounts of power from one end of a tube to
the other, but as others have pointed out, tend to be very heavy.
"Lightweight" is a relative term when speaking of industrial machines
(look at all of the effort involved in certifying aviation diesels, as
one example).



PAW wrote:
"Rip" wrote in message
...

No problem! And I'll also suggest looking up the Aerocobra. WWII fighter
with the engine behind the pilot, machine gun firing through the center
of a tractor propeller. Aren't drive shafts wonderful!

PAW wrote:

"Rip" wrote in message
om...


Sure, why not? Or you could use the engine to drive a generator which
would then drive electric motors to spin the props. Or you could do away
with the added weight and complexity and drive the props right from the
engine!





Yes, drive shafts are wonderful. I just don't like the idea of a shaft
running through where I'm trying to sit.


Here's the problem (IMO) with your response; I was asking about using
hydraulic motors. Several took my 3200 RPM speed as set in stone. I was
ONLY pointing out the fact Eaton has a full line of *lightweight piston
motors* that will handle speeds *UP TO* 3600 RPM at some decent torque
figures. A Mazda 13b is more than capable of producing the horsepower (plus
it's a lightweight water cooled engine) to provide the flow and PSI for
these little motors.

Anyhow, thanks for the "input". I'll stick with asking the engineers at
Eaton my questions because I'm obviously getting nowhere here. For the two
gents that provided information (Corky and Bob), Thank you.

Phil