Is hyraulic drive posible?

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!

PAW wrote:
This is a BS question, but I'm curious.

I was looking at some hydraulic motors the other day and was wondering if
a pump and motor could be used to drive a prop. A crazy example; two
hydraulic motors and a couple pumps (powered with a mazda 13b maybe ??) to
power something like a Cessna 337 in-line thrust type aircraft.
Understanding weight would be an issue, I'm wondering how it would, or could
,work. I was looking at an Eaton motor that was rated at (up to) 3200 RPM @
about 120 ft. lb of torque. Weight was 20 lbs. They have a pump (48 lbs)
that moves 42 gpm @ 4000 psi.

Is it possible? Single place would be fine.

Rip wrote:

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!

You should patent that idea!

Mark Hickey

PAW wrote:
This is a BS question, but I'm curious.

I was looking at some hydraulic motors the other day and was wondering if
a pump and motor could be used to drive a prop. A crazy example; two
hydraulic motors and a couple pumps (powered with a mazda 13b maybe ??) to
power something like a Cessna 337 in-line thrust type aircraft.
Understanding weight would be an issue, I'm wondering how it would, or could
,work. I was looking at an Eaton motor that was rated at (up to) 3200 RPM @
about 120 ft. lb of torque. Weight was 20 lbs. They have a pump (48 lbs)
that moves 42 gpm @ 4000 psi.

Is it possible? Single place would be fine.

"Mark Hickey" wrote in message
...
Rip wrote:

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!

You should patent that idea!


I'm sure the USPTO will be unable to find any form of prior art and assign
the pattent in a heartbeat...
Rob

"Rip" wrote in message
. ..
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!


And how might you suggest powering two props with *one* engine (when the
props are 12 feet from each other at opposite ends of the aircraft) via your
"less complex" methode of direct drive from the engine. Keep in mind a 13b
spins at 6000 RPM. Opps, gotta add a re-drive (or two). Thank you much for
your brilliant (and sarcastic) less complex answer.


PAW wrote:
This is a BS question, but I'm curious.

I was looking at some hydraulic motors the other day and was wondering
if
a pump and motor could be used to drive a prop. A crazy example; two
hydraulic motors and a couple pumps (powered with a mazda 13b maybe ??)
to
power something like a Cessna 337 in-line thrust type aircraft.
Understanding weight would be an issue, I'm wondering how it would, or
could
,work. I was looking at an Eaton motor that was rated at (up to) 3200
RPM @
about 120 ft. lb of torque. Weight was 20 lbs. They have a pump (48 lbs)
that moves 42 gpm @ 4000 psi.

Is it possible? Single place would be fine.

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
. ..

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!



And how might you suggest powering two props with *one* engine (when the
props are 12 feet from each other at opposite ends of the aircraft) via your
"less complex" methode of direct drive from the engine. Keep in mind a 13b
spins at 6000 RPM. Opps, gotta add a re-drive (or two). Thank you much for
your brilliant (and sarcastic) less complex answer.


PAW wrote:

This is a BS question, but I'm curious.

I was looking at some hydraulic motors the other day and was wondering

if

a pump and motor could be used to drive a prop. A crazy example; two
hydraulic motors and a couple pumps (powered with a mazda 13b maybe ??)

to

power something like a Cessna 337 in-line thrust type aircraft.
Understanding weight would be an issue, I'm wondering how it would, or

could

,work. I was looking at an Eaton motor that was rated at (up to) 3200

RPM @

about 120 ft. lb of torque. Weight was 20 lbs. They have a pump (48 lbs)
that moves 42 gpm @ 4000 psi.

Is it possible? Single place would be fine.

"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
. ..

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

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

"Rip" wrote in message
...
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).




Not a problem. When I say "lightweight" I mean in comparison to most
motors. I see many that are 50-100 (or more) pounds. To me, a hydraulic
motor than weighs in at 20 lbs, spins at the proper speed without a gearbox,
and provide 100+ ft lbs of torque, is lightweight. Eaton *claims* 90%
efficiancy.


And I don't blame you for not getting out of ground effect. What was that
wankle good for... 50 hp?

"PAW" wrote in message And I don't blame you for not getting out of
ground effect. What was that wankle good for... 50 hp?

The hydaulic drive is workable, though you will lose some efficiency.

I'm wondering why you chose to have 2 propellers. They will be less
efficient than a single propeller, unless perhaps you stagger them to make a
contra-rotating prop like many marine drives use.

D.

"PAW" wrote

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

Weight is still going to be the gotcha. Plus, don't forget an extra
radiator for cooling the hydraulic fluid. Hummm. Where do you suppose that
heat energy came from?
--
Jim in NC


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