Is hyraulic drive posible?

[PAW]

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]

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. :)
>
>
>
>

[Mark Hickey]

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. :)
>>
>>
>>
>>

[Rob Turk]

"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

[[email protected]]

On Wed, 30 Jun 2004 23:53:15 -0700, "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. :)

So the engine drives a pump and the pump drives a hydraulic motor, and
the motor spins the prop, right? I'm thinking of the homebuilt
designers maxim: "Build it light and simplicate." In addition, you've
got the prop spinning at 3200 rpm which is kind of high and will mean
a smallish, noisy propeller that doesn't produce much low speed
thrust, which means long takeoff runs.

In addition, the weight of the items you mention will likely be higher
because you will need some means of cooling the oil, as it will be
working hard. There will also be the weight of the oil lines.

I'm not an expert but since you asked, here's a guess: Airplane
designers are a particularly ingenious lot. If it were possible to
utilize such a prop drive as you describe, I think someone would
probably have tried it by now. After all, we've had virtually every
other manner of providing thrust including photovoltaic cells coupled
to electric motors.

My guess is that your idea might work, albeit extremely marginally and
heat rejection will be a major issue, as will be efficiency due to all
the pumping losses incurred building pressure and converting the
pressure to rotational thrust. All for, in my opinion, relatively low
propeller thrust.

I'll bet a good mechanical engineer could compute the relative
efficiency of this design vs. a direct drive prop or PSRU driven prop.
That should be relatively painless and you'd know before buying any
pieces if this would be worth it or not.

Corky Scott

[Bob Kuykendall]

Earlier, wrote:

> ...In addition, you've got the prop
> spinning at 3200 rpm...

Well, that's one of the things that makes hydraulic drive sort of
compelling: There are plenty of variable displacement pumps that will
give you infinitely variable ratios. So there's no reason at all why
you would be constrained to 1:1 drive. Or even to any fixed ratio. And
the pumps and motors developed for airline and military aircraft
application offer some pretty good power/weight ratios. We're not
necessarily limited to the cast-iron lumps that Grainger sells for use
in industrial trash-smashers and the like.

> ...There will also be the weight of
> the oil lines...

Well maybe the weight of the oil lines would be compensated by the
absence of shafts, belts, gears, etc...

One possible application might be for driving remotely-mounted
propellers for unconventional configurations, as the OP suggests.
Sure, for your typical aircraft of conventional configuration, direct
drive will probably continue to be best way to go. But perhaps for
retractable-propeller self-launch sailplanes, and other odd layouts,
the advantages of hydraulic drive might outweigh the disadvantages.

Bob K.

[PAW]

"Bob Kuykendall" > wrote in message
om...
> Earlier, wrote:
>
> > ...In addition, you've got the prop
> > spinning at 3200 rpm...
>
> Well, that's one of the things that makes hydraulic drive sort of
> compelling: There are plenty of variable displacement pumps that will
> give you infinitely variable ratios. So there's no reason at all why
> you would be constrained to 1:1 drive. Or even to any fixed ratio. And
> the pumps and motors developed for airline and military aircraft
> application offer some pretty good power/weight ratios. We're not
> necessarily limited to the cast-iron lumps that Grainger sells for use
> in industrial trash-smashers and the like.
>
> > ...There will also be the weight of
> > the oil lines...
>
> Well maybe the weight of the oil lines would be compensated by the
> absence of shafts, belts, gears, etc...
>
> One possible application might be for driving remotely-mounted
> propellers for unconventional configurations, as the OP suggests.
> Sure, for your typical aircraft of conventional configuration, direct
> drive will probably continue to be best way to go. But perhaps for
> retractable-propeller self-launch sailplanes, and other odd layouts,
> the advantages of hydraulic drive might outweigh the disadvantages.
>
> Bob K.

Thanks Bob.

Hydraulic power was the only way I could think of to use one engine with
two drives in an in-line thrust design. Some of these motors are very
lightweight (IMO) and,as you said, are not the $150.00 cast-iron jobs from
Graingers. These are $2300.00 each. They're piston motors. They ( Eaton )
carry several that are rated from 2000 RPM, up to 3600 RPM... several models
to choose from. And, they have a ton of torque! :

Phil (on his way to the patent office) :) J/K

[PAW]

"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. :)
> >
> >
> >
> >
>

[Barnyard BOb -]

> Hydraulic power was the only way I could think of to use one engine with
>two drives in an in-line thrust design. Some of these motors are very
>lightweight (IMO) and,as you said, are not the $150.00 cast-iron jobs from
>Graingers. These are $2300.00 each. They're piston motors. They ( Eaton )
>carry several that are rated from 2000 RPM, up to 3600 RPM... several models
>to choose from. And, they have a ton of torque! :
>
>Phil (on his way to the patent office) :) J/K
++++++++++++++++++++++++++++++++++++++

If one gears a clock motor low enuff...
it is said that one could pull the earth off axis.
Hardly a desireable speed for a prop.

There is no free lunch where torque is concerned.
Best be careful what is implied to the uninformed.

http://vettenet.org/torquehp.html
http://www.carcraft.com/techarticles/868/

P.S.
Rotsa' ruck at the U.S. Pat. Off.


Barnyard BOb --

[PAW]

"Barnyard BOb -" > wrote in message
...
>
>
> > Hydraulic power was the only way I could think of to use one engine with
> >two drives in an in-line thrust design. Some of these motors are very
> >lightweight (IMO) and,as you said, are not the $150.00 cast-iron jobs
from
> >Graingers. These are $2300.00 each. They're piston motors. They ( Eaton )
> >carry several that are rated from 2000 RPM, up to 3600 RPM... several
models
> >to choose from. And, they have a ton of torque! :
> >
> >Phil (on his way to the patent office) :) J/K
> ++++++++++++++++++++++++++++++++++++++
>
> If one gears a clock motor low enuff...
> it is said that one could pull the earth off axis.
> Hardly a desireable speed for a prop.
>
> There is no free lunch where torque is concerned.
> Best be careful what is implied to the uninformed.
>
> http://vettenet.org/torquehp.html
> http://www.carcraft.com/techarticles/868/
>
> P.S.
> Rotsa' ruck at the U.S. Pat. Off.
>
>
> Barnyard BOb --

You lost me. :) What gearing are you talking about? These motors would be
direct-drive.

Phil

[Rip]

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. :)
>>>
>>>
>>>
>>>
>>
>
>

[PAW]

"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

[Rip]

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
. ..
>>>
>>>
>>>>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
>
>
>
>
>
>
>
>
>

[Blueskies]

Hydrostatic transmissions (hydraulic pump driving a hydraulic motor) are used all over the place for heavy equipment.
These are best for high torque, relatively low speed operation. A good aerospace quality pump will give you about 90%
efficiency, and the motor will be about 85%. Industrial pumps and motors typically are much less efficient. As someone
else said, the heat rejection will be an issue (we cool our pumps through heat exchangers inside fuel tanks sometimes).
You will be better off using direct drive from a couple of small engines than using a big engine and driving a pump then
driving a motor...

Our smaller pumps can spin up to 13,000 rpm (Apache helicopter) and deliver as much as 85 gpm @ 4500 psi (B2 bomber).
Our motors can deliver full torque at very low speeds (<100 rpm)...

http://www.parker.com/ag/pdf/abexbrochure.pdf

--
Dan D.
http://www.ameritech.net/users/ddevillers/start.html


..
"PAW" > wrote in message ...
> 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. :)
>
>
>
>

[PAW]

"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? :D

[Harry K]

"PAW" > wrote in message >...
> "Barnyard BOb -" > wrote in message
> ...
> >
> >
> > > Hydraulic power was the only way I could think of to use one engine with
> > >two drives in an in-line thrust design. Some of these motors are very
> > >lightweight (IMO) and,as you said, are not the $150.00 cast-iron jobs
> from
> > >Graingers. These are $2300.00 each. They're piston motors. They ( Eaton )
> > >carry several that are rated from 2000 RPM, up to 3600 RPM... several
> models
> > >to choose from. And, they have a ton of torque! :
> > >
> > >Phil (on his way to the patent office) :) J/K
> > ++++++++++++++++++++++++++++++++++++++
> >
> > If one gears a clock motor low enuff...
> > it is said that one could pull the earth off axis.
> > Hardly a desireable speed for a prop.
> >
> > There is no free lunch where torque is concerned.
> > Best be careful what is implied to the uninformed.
> >
> > http://vettenet.org/torquehp.html
> > http://www.carcraft.com/techarticles/868/
> >
> > P.S.
> > Rotsa' ruck at the U.S. Pat. Off.
> >
> >
> > Barnyard BOb --
>
> You lost me. :) What gearing are you talking about? These motors would be
> direct-drive.
>
> Phil

I am much of a lurker here but...It seems to me that a lot of the
naysayers are missing the point that you are proposing to drive -two-
props with -one- motor. There should be at least a break even if not
a savings in weight over -two- motors driving two props. I like
considering off the wall projects and have attempted a few myself,
mostly failures.

Harry K

[Orval Fairbairn]

In article >,
"Blueskies" > wrote:

> Hydrostatic transmissions (hydraulic pump driving a hydraulic motor) are used
> all over the place for heavy equipment.
> These are best for high torque, relatively low speed operation. A good
> aerospace quality pump will give you about 90%
> efficiency, and the motor will be about 85%. Industrial pumps and motors
> typically are much less efficient. As someone
> else said, the heat rejection will be an issue (we cool our pumps through
> heat exchangers inside fuel tanks sometimes).
> You will be better off using direct drive from a couple of small engines than
> using a big engine and driving a pump then
> driving a motor...
>
> Our smaller pumps can spin up to 13,000 rpm (Apache helicopter) and deliver
> as much as 85 gpm @ 4500 psi (B2 bomber).
> Our motors can deliver full torque at very low speeds (<100 rpm)...
>
> http://www.parker.com/ag/pdf/abexbrochure.pdf
>
> --
> Dan D.
> http://www.ameritech.net/users/ddevillers/start.html
>
>
> .
> "PAW" > wrote in message
> ...
> > 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. :)




As Dan pointed out above, it is "possible," but not practical, as the
losses alone (pump + motor) reduce your efficiency to (.9 * .85) 76% vs
100% on a direct-drive system. In addition, you have the added weight of
the pump & motor and the added complexity of the overall system. Total
system reliability is the reliability of each component X the
reliability of every other component of that system. If you have three
critical components whose total reliability is .99, the system
reliability is .99*.99*.99 = .97.

[[email protected]]

In article >, "PAW" > wrote:
> This is a BS question, but I'm curious. :)

Not a BS question at all. You definitely could do this. Unfortunately, the
hydraulic route will come at a price of reduced efficiency. You will probably
loose 15-25 percent of your horse power. With this in mind, though, you can
easily pick the proper size pump and motors to get the rpm of the propellers
anywhere you want, with the engine running at what ever rpm it likes. Why
heck, you could even put small motors on the main wheels and use them for
brakes and to run the airplane backwards for parking. That would turn some
heads.

best luck,
tom pettit


>
> 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. :)
>
>
>
>

[Morgans]

"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


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.711 / Virus Database: 467 - Release Date: 6/26/2004

[Jay]

"PAW" > wrote in message >...
> "Bob Kuykendall" > wrote in message
> om...
> Hydraulic power was the only way I could think of to use one engine with
> two drives in an in-line thrust design. Some of these motors are very
> lightweight (IMO) and,as you said, are not the $150.00 cast-iron jobs from
> Graingers. These are $2300.00 each. They're piston motors. They ( Eaton )
> carry several that are rated from 2000 RPM, up to 3600 RPM... several models
> to choose from. And, they have a ton of torque! :
>
> Phil (on his way to the patent office) :) J/K

But what was the original reason you wanted an in-line thrust design?
I've been keen on that layout (in-line) for fail-soft/reliability
benefits. I didn't like the idea of a single point failure in the
most likely place to have a failure (engine) meaning a forced landing.
If you use a single engine to drive 2 props, you don't get that
benefit.

There are some other bene's I could see though such as
1) Engine located at center of gravity perhaps on main spar
carry-through. So you could save some structural weight.

From an efficiency standpoint I think you're better off turning a
single big prop rather than 2 smaller ones.

[Ralph DuBose]

"PAW" > wrote in message >...
> > wrote in message
> ...
> > In article >, "PAW"
> > wrote:
> > > This is a BS question, but I'm curious. :)
> >
> > Not a BS question at all. You definitely could do this. Unfortunately,
> the
> > hydraulic route will come at a price of reduced efficiency. You will
> probably
> > loose 15-25 percent of your horse power. With this in mind, though, you
> can
> > easily pick the proper size pump and motors to get the rpm of the
> propellers
> > anywhere you want, with the engine running at what ever rpm it likes. Why
> > heck, you could even put small motors on the main wheels and use them for
> > brakes and to run the airplane backwards for parking. That would turn
> some
> > heads.
> >
> > best luck,
> > tom pettit
> >
> >
> > >
> > > 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. :)
> > >
> > >
> > >
> > >
>
> That's a thought.... movement without the props turning. A Mazda 13b turbo
> can do 250-300 hp EASY. Power available for the pumps shouldn't be a
> problem. At least, *I *can't see how it could. :)

There are some commercially built single engined hovercraft that
use hydralic drive systems for the lift-fans. It allows excellent
control of porportionality of the lift function separate from thrust.
The upside is that it gives infinite variabilty and good packageing.
The downside is that appropriate systems are pretty expensive and do
add some weight and waste power but in larger craft this is not
excessive. But keep in mind that the lift function normally requires
around 30% of total power requirements in a large hovercraft and that
thrust is 70% which is of course by direct,mechanical drive so the
power losses from the hydralics are less significant than if used
everywhere.
I design/build racing hovercraft as a hobby and worship at the
church of "Light and Simple." The biggest real improvements have come
from learning how to make better components with composites. I have
tried about a 1000 ideas (and kept a few) but most of the progress has
been from making things lighter and better shaped - same as it ever
was.

[[email protected]]

In article >, "PAW" > wrote:
>

Yeah, but: that reduced efficiency comes at the price of needing a place to
dump the extra heat. A previous poster pointed out rightly that you would
probably need another radiator to get rid of it all. Radiators in general are
one of the worst parasitic drags on an aircraft.

All the same, the ideal is intriguing.

tom pettit

> That's a thought.... movement without the props turning. A Mazda 13b turbo
>can do 250-300 hp EASY. Power available for the pumps shouldn't be a
>problem. At least, *I *can't see how it could. :)
>
>
>

[Capt.Doug]

>"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? :D

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]

"Capt.Doug" > wrote in message
...
> >"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? :D
>
> 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.
>
>


Why 2 propellers? Because the Skymaster was an in-line twin. :) The
mini-master flew on two 65 hp Rotax engines. I was hoping to do the same
'cept with a single 200-250 hp rotary and a pair of 75 hp motors.

Someone else mentioned; If the props weren't turning, you could drive it
with small motors mounted in the wheels. Taxi with no prop blast. :)

[sidk]

One would not simply bolt a prop to a pump shaft... you will need to
add a suitable bearing and hub assembly which will surely weigh some
pounds.

Sid Knox

"PAW" > wrote in message >...
> 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. :)

[PAW]

"sidk" > wrote in message
om...
> One would not simply bolt a prop to a pump shaft... you will need to
> add a suitable bearing and hub assembly which will surely weigh some
> pounds.
>
> Sid Knox



Actually, there are several brands that will handle a thrust load in excess
of 1000 lbs. But, a shaft to handle the loads properly would be the right
way. Not a big deal. The hub should be as light or lighter than any Rotax
PSRU, belt or planetary. I'd hope for 350-400 lbs of thrust per motor. More
would be sweet. Should be easy enough with the right hydraulic motor...
eh??? I'm pulling these numbers out of my ass hoping someone will tell me
where I'm screwing up... other than just telling me via e-mail I'm too lazy
to research it myself. Well, IMO, the USENET *was* a place to research....
at one time, many years ago. :)

Can not a 75 horsepower gas engine be replaced with a hydralic motor of
proper RPM and torque)?

Yes, I realize it takes more power, and depending on the quality and proper
sizing of the pump/motors, piping etc. etc., it's still less efficiant than
a direct drive. One place it would save weight is in the PSRU. I'd use a
Mazda 13b, no matter what (after years with them , I am convinced of their
reliability). PSRU are not light units themselves... EASY outweighting some
of the hydraulic motors I've seen. So, maybe the 250 lbs of weight that
would have went into a second engine could be swaped for the weight in
fluid,pumps ,motors add supporting cast members. :)

I'll get it sorted out. :)

>
> "PAW" > wrote in message
>...
> > 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. :)

[ChuckSlusarczyk]

In article >, Richard Riley says...


>:That's my dad's quote. He told me there is no limit to what a man can
>:do. I'm from Thailand, but I tell my employees (mostly latinos) the
>:same thing, "Este es Estados Unidos, todos es possible".
>
>HA! A latino friend of mine says the same thing to his (all latino)
>employees - but he says "Este es *United States,* totos es possible."

My Polish Grandfather ...in fact everybody in the Polish ghetto where I grew up
used to say "we're in America now learn to talk english". That's why everything
was possible,we all learned english as the common language and we all became
Americans. Not so anymore.

Chuck( I never saw a voting ballot in Polish)S

[Richard Lamb]

PAW wrote:
>
> "sidk" > wrote in message
> om...
> > One would not simply bolt a prop to a pump shaft... you will need to
> > add a suitable bearing and hub assembly which will surely weigh some
> > pounds.
> >
> > Sid Knox
>
> Actually, there are several brands that will handle a thrust load in excess
> of 1000 lbs. But, a shaft to handle the loads properly would be the right
> way. Not a big deal. The hub should be as light or lighter than any Rotax
> PSRU, belt or planetary. I'd hope for 350-400 lbs of thrust per motor. More
> would be sweet. Should be easy enough with the right hydraulic motor...
> eh??? I'm pulling these numbers out of my ass hoping someone will tell me
> where I'm screwing up... other than just telling me via e-mail I'm too lazy
> to research it myself. Well, IMO, the USENET *was* a place to research....
> at one time, many years ago. :)
>
> Can not a 75 horsepower gas engine be replaced with a hydralic motor of
> proper RPM and torque)?
>
> Yes, I realize it takes more power, and depending on the quality and proper
> sizing of the pump/motors, piping etc. etc., it's still less efficiant than
> a direct drive. One place it would save weight is in the PSRU. I'd use a
> Mazda 13b, no matter what (after years with them , I am convinced of their
> reliability). PSRU are not light units themselves... EASY outweighting some
> of the hydraulic motors I've seen. So, maybe the 250 lbs of weight that
> would have went into a second engine could be swaped for the weight in
> fluid,pumps ,motors add supporting cast members. :)
>
> I'll get it sorted out. :)
>

Not very likely, PAW.

What you are describing is now a 500 pound motor/drive with LESS
usable power than the single engine set up.

It might work ok in a boat.
But not in an airplane.

Sorry,

Richard

[Andy Asberry]

On Fri, 02 Jul 2004 09:06:23 -0400, GeorgeB > wrote:

>On Thu, 1 Jul 2004 14:35:53 -0700, "PAW" > wrote:
>
>>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.
>
>An issue is that a hydraulic drive is less efficient than direct,
>belt, or gear. There will be the additional weight of the pump and
>motor. There are 2 additional points of failure, the pump and motor.
>If you elect to drive the motors in series, the first in the string
>will run "slightly" faster than the 2nd (assuming a case drain) if
>they are otherwise identical. You have fluid lines to concern
>yourself with. The first, if in series, MAY not like having its
>outlet at "half" system pressure. Maintaining positive suction head
>will require consideration.
>
>I design and provide technical support for electrohydraulic systems
>for a living, and this is not a place that I owuld recommend their
>use.
>
>George

Maybe you can answer a question I've had for sometime. What is the
relative efficiency of hydraulics, belts, gears and chain drive?
You've given the hydraulic answer. Care to take a stab at the others,
please?

[GeorgeB]

On Thu, 08 Jul 2004 02:52:48 GMT, Andy Asberry
> wrote:

>>I design and provide technical support for electrohydraulic systems
>>for a living, and this is not a place that I owuld recommend their
>>use.
>>
>>George
>
>Maybe you can answer a question I've had for sometime. What is the
>relative efficiency of hydraulics, belts, gears and chain drive?
>You've given the hydraulic answer. Care to take a stab at the others,
>please?

STAB, yes ... feelings based on things I have seen and heard ... NO
HARD FACTS to back this up. (I looked and failed to find support)

hydraulics TOTAL ... ~80%
v belt, 90-95%
tooth belt, 92-97%
spur/bevel gear, 96-98%
worm gear, 25-80%
chain. 96-98%

lesser ratios (nearer 1:1) are more efficient.

[bryan chaisone]

Isn't this country wonderful. I've been here since nine and I can
really appreciate it.

Bryan "The Monk" Chaisone

ChuckSlusarczyk > wrote in message >...
> In article >, Richard Riley says...
>
>
> >:That's my dad's quote. He told me there is no limit to what a man can
> >:do. I'm from Thailand, but I tell my employees (mostly latinos) the
> >:same thing, "Este es Estados Unidos, todos es possible".
> >
> >HA! A latino friend of mine says the same thing to his (all latino)
> >employees - but he says "Este es *United States,* totos es possible."
>
> My Polish Grandfather ...in fact everybody in the Polish ghetto where I grew up
> used to say "we're in America now learn to talk english". That's why everything
> was possible,we all learned english as the common language and we all became
> Americans. Not so anymore.
>
> Chuck( I never saw a voting ballot in Polish)S

[Russell Kent]

Andy Asberry wrote:
> Maybe you can answer a question I've had for sometime. What is the
> relative efficiency of hydraulics, belts, gears and chain drive?
> You've given the hydraulic answer. Care to take a stab at the others,
> please?

Andy,
One thing to keep in mind with every power transmission apparatus is:
Every watt of power that goes into it comes out either as power at the
working end, or heat somewhere along the way. So the more heat the
apparatus sheds (as a percentage of input power), the less efficient it is.

Russell Kent

[Fred the Red Shirt]

GeorgeB > wrote in message >...
> On Thu, 08 Jul 2004 02:52:48 GMT, Andy Asberry
> > wrote:
>
> >>I design and provide technical support for electrohydraulic systems
> >>for a living, and this is not a place that I owuld recommend their
> >>use.
> >>
> >>George
> >
> >Maybe you can answer a question I've had for sometime. What is the
> >relative efficiency of hydraulics, belts, gears and chain drive?
> >You've given the hydraulic answer. Care to take a stab at the others,
> >please?
>
> STAB, yes ... feelings based on things I have seen and heard ... NO
> HARD FACTS to back this up. (I looked and failed to find support)
>
> hydraulics TOTAL ... ~80%
> v belt, 90-95%
> tooth belt, 92-97%
> spur/bevel gear, 96-98%
> worm gear, 25-80%
> chain. 96-98%
>
> lesser ratios (nearer 1:1) are more efficient.

Based on what I recall from my mechanical engineering days
spur gears will be the most efficient. This is because
spur gear teeth have a curvature called an involute which
permits rolling contact between the tooth surfaces. Still,
I think 95% is about the best you get with spur gears, I
wonder if I can still find my old texts...

Bevel gears have some sliding contact between the teeth and
so more friction less efficiency than spur gears. But they
have more surface in contact between meshing teath so they
can handle larger loads for their size. Typical worm drives
with a small worm and a large worm gear for a large speed
reduction and large torque gain will be the least efficient,
down around 5%, IIRC.

V-belts are probably the trickiest to optimize. Too little
tension and energy is lost in slippage, too much and energy
is lost in elastic deformation of the belt. Cog belts allow
you to reduce the tension on the belt without slippage.

The other drive mechanisms tend to have their highest efficiency
with a slightly 'sloppy fit' that minimizes elastic deformation
but also introduces other problems like backlash, vibration and
so on.

--

FF

[Fred the Red Shirt]

(Harry K) wrote in message >...
>
> I am much of a lurker here but...It seems to me that a lot of the
> naysayers are missing the point that you are proposing to drive -two-
> props with -one- motor. There should be at least a break even if not
> a savings in weight over -two- motors driving two props. I like
> considering off the wall projects and have attempted a few myself,
> mostly failures.
>

Actually, I'd charaterize it as driving two props with three motors.
Two hydraulic motors direct driving the props and one motor driving
the hydraulics.

I think a mechanical drive, like the chain drive the Wright Bros used,
would be more efficient.

--

FF

[Matt Whiting]

Fred the Red Shirt wrote:

> GeorgeB > wrote in message >...
>
>>On Thu, 08 Jul 2004 02:52:48 GMT, Andy Asberry
> wrote:
>>
>>
>>>>I design and provide technical support for electrohydraulic systems
>>>>for a living, and this is not a place that I owuld recommend their
>>>>use.
>>>>
>>>>George
>>>
>>>Maybe you can answer a question I've had for sometime. What is the
>>>relative efficiency of hydraulics, belts, gears and chain drive?
>>>You've given the hydraulic answer. Care to take a stab at the others,
>>>please?
>>
>>STAB, yes ... feelings based on things I have seen and heard ... NO
>>HARD FACTS to back this up. (I looked and failed to find support)
>>
>>hydraulics TOTAL ... ~80%
>>v belt, 90-95%
>>tooth belt, 92-97%
>>spur/bevel gear, 96-98%
>>worm gear, 25-80%
>>chain. 96-98%
>>
>>lesser ratios (nearer 1:1) are more efficient.
>
>
> Based on what I recall from my mechanical engineering days
> spur gears will be the most efficient. This is because
> spur gear teeth have a curvature called an involute which
> permits rolling contact between the tooth surfaces. Still,
> I think 95% is about the best you get with spur gears, I
> wonder if I can still find my old texts...
>
> Bevel gears have some sliding contact between the teeth and
> so more friction less efficiency than spur gears. But they
> have more surface in contact between meshing teath so they
> can handle larger loads for their size. Typical worm drives
> with a small worm and a large worm gear for a large speed
> reduction and large torque gain will be the least efficient,
> down around 5%, IIRC.

You are saying that 95% of the power is lost in the gear set? I find
that really hard to believe. If you put 100 HP in and lost 95HP in the
gears, that amount of heat would likely melt them down in short order.


Matt

[Andy Asberry]

On Thu, 08 Jul 2004 14:38:45 -0400, GeorgeB > wrote:

>On Thu, 08 Jul 2004 02:52:48 GMT, Andy Asberry
> wrote:
>
>>>I design and provide technical support for electrohydraulic systems
>>>for a living, and this is not a place that I owuld recommend their
>>>use.
>>>
>>>George
>>
>>Maybe you can answer a question I've had for sometime. What is the
>>relative efficiency of hydraulics, belts, gears and chain drive?
>>You've given the hydraulic answer. Care to take a stab at the others,
>>please?
>
>STAB, yes ... feelings based on things I have seen and heard ... NO
>HARD FACTS to back this up. (I looked and failed to find support)
>
>hydraulics TOTAL ... ~80%
>v belt, 90-95%
>tooth belt, 92-97%
>spur/bevel gear, 96-98%
>worm gear, 25-80%
>chain. 96-98%
>
>lesser ratios (nearer 1:1) are more efficient.
Thanks.

[Fred the Red Shirt]

Matt Whiting > wrote in message >...
>
> > Typical worm drives
> > with a small worm and a large worm gear for a large speed
> > reduction and large torque gain will be the least efficient,
> > down around 5%, IIRC.
>
> You are saying that 95% of the power is lost in the gear set? I find
> that really hard to believe. If you put 100 HP in and lost 95HP in the
> gears, that amount of heat would likely melt them down in short order.
>

Yes, it would. I suggest that you avoid worm drives for transmissions
that handle 100 hp continuous duty. Worm drives are used where you
need a huge torque increase and can afford a huge power loss better
than you can afford the space complexity and expense of a planetary
gearbox or a battery (Damn it's late at night what do you call these?)
of spur gears.

Typical worm drives are very low speed, or have a very short duty
cycle. In most of the systems I have seen the worm only turns
at a fraction of an rpm in continuous duty (IIRC 1/15 rpm is common
for the worm in a telescope clock drive with a worm wheel with 96 teeth).
When slewing the telescope they may turn several rpm but only for
a minute or so. If those worms were run continuously at a few
hundred rpm they would certainly coke out the grease in a couple
of minutes.

There are some big-assed worm drives that do things like rotate the
turrets on cranes fairly quickly but they operate intermittently
and that HUGE worm wheel soaks up and dissipates a lot of heat.

I am less than 100% certain of the 5% figure, but will stick by it for
now.

--

FF

[Fred the Red Shirt]

"Russell Kent" > wrote in message >...
> Andy Asberry wrote:
> > Maybe you can answer a question I've had for sometime. What is the
> > relative efficiency of hydraulics, belts, gears and chain drive?
> > You've given the hydraulic answer. Care to take a stab at the others,
> > please?
>
> Andy,
> One thing to keep in mind with every power transmission apparatus is:
> Every watt of power that goes into it comes out either as power at the
> working end, or heat somewhere along the way. So the more heat the
> apparatus sheds (as a percentage of input power), the less efficient it is.
>

Tis true of all devices which is why all electrical resistance heaters
have the same efficiency--the 'waste' heat is indistinguishible from
the 'product' heat.

--

FF

[Fred the Red Shirt]

Matt Whiting > wrote in message >...
> Fred the Red Shirt wrote:
>
> > GeorgeB > wrote in message >...
> >
> >>On Thu, 08 Jul 2004 02:52:48 GMT, Andy Asberry
> > wrote:
> >>
> >>
> >>>>I design and provide technical support for electrohydraulic systems
> >>>>for a living, and this is not a place that I owuld recommend their
> >>>>use.
> >>>>
> >>>>George
> >>>
> >>>Maybe you can answer a question I've had for sometime. What is the
> >>>relative efficiency of hydraulics, belts, gears and chain drive?
> >>>You've given the hydraulic answer. Care to take a stab at the others,
> >>>please?
> >>
> >>STAB, yes ... feelings based on things I have seen and heard ... NO
> >>HARD FACTS to back this up. (I looked and failed to find support)
> >>
> >>hydraulics TOTAL ... ~80%
> >>v belt, 90-95%
> >>tooth belt, 92-97%
> >>spur/bevel gear, 96-98%
> >>worm gear, 25-80%
> >>chain. 96-98%
> >>
> >>lesser ratios (nearer 1:1) are more efficient.
> >
> >
> > Based on what I recall from my mechanical engineering days
> > spur gears will be the most efficient. This is because
> > spur gear teeth have a curvature called an involute which
> > permits rolling contact between the tooth surfaces. Still,
> > I think 95% is about the best you get with spur gears, I
> > wonder if I can still find my old texts...
> >
> > Bevel gears have some sliding contact between the teeth and
> > so more friction less efficiency than spur gears. But they
> > have more surface in contact between meshing teath so they
> > can handle larger loads for their size. Typical worm drives
> > with a small worm and a large worm gear for a large speed
> > reduction and large torque gain will be the least efficient,
> > down around 5%, IIRC.
>
> You are saying that 95% of the power is lost in the gear set? I find
> that really hard to believe. If you put 100 HP in and lost 95HP in the
> gears, that amount of heat would likely melt them down in short order.
>
>
> Matt

Ah, here's a page that compares some worm drives to geared
transmissions, the highest they show is for a measely 60:1
speed reduction. But t looks like a 96:1 worm drive would
typically be not a lot better than 50% efficient. So it seems
I was off by about a factor of 10 - 12 on the efficiency, but
only a factor of 2 on the waste heat so you still better not
run 100 hp through one it unless it is actively cooled or uses
huge gears.

http://www.falkcorp.com/tech-info/wormgear.asp

Not something you'd use to drive a propeller, in any case.

--

FF