Is hyraulic drive posible?

"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.

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.

"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.

"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?

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.

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.

"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.

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

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

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?

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.