On Wednesday 19 September 2007 16:16, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Sjokomopu fired this volley in
:

I'd like to use a hydraulic engine as a backup propulsion system on my
boat. I need max 50kW at 200rpm.

Does anybody know if I can use a hydraulic radial piston engine as a
hydraulic pump while I am not using it (as an engine, that is) as a
backup for my hydraulics system??

I also worry if I could power such a hydraulic engine with my existing
axial piston pump (powered by a 3cyl diesel) or if that is simply a
question of getting the flow vs. pressure right.

Thx for your input,

Al

We in the U.S. use the term "engine" mostly to describe a prime-mover --
a device which directly converts a fuel to mechanical energy. What you
describe seems to be a "hydraulic motor" -- a device that converts a form
of transmittable energy (hydraulic force) into rotary mechanical energy.

Many hydraulic motors may be used as pumps with no particular
limitations. Some types are not. A radial or axial piston pump/motor is
usually suitable for both types of duty. Variable-displacement pumps are
seldom used as motors, but fixed-displacement types work fine.

LLoyd


Sorry for the confusion. You were right, I was referring to motor in that
case, not engine. So I suppose I will be able to find a motor that can
double as a pump.

Any idea how much power an *unloaded* radial piston pump would use up?
I'm asking because I am wondering if I can leave the motor/pump connected to
the propeller shaft all the time or if I have to devise a physical
connect/disconnect mechanism to reduce overhead.

What is the lowest-loss hydraulic pump type, anyway - anyone???

Al

Francis fired this volley in
:

Any idea how much power an *unloaded* radial piston pump would use up?
I'm asking because I am wondering if I can leave the motor/pump
connected to the propeller shaft all the time or if I have to devise a
physical connect/disconnect mechanism to reduce overhead.

What is the lowest-loss hydraulic pump type, anyway - anyone???

Well, they all have friction losses, and unless of the variable-
displacement variety, they must move fluid even when unloaded. Friction
losses of the fluid circulating also add to the total loss.

But most pumps in the under-20gpm range absorb only a small fraction of a
horsepower at "idle". Stiction torque at startup is fairly high, but
idling torque is low.

LLoyd

Francis fired this volley in
:

What is the lowest-loss hydraulic pump type, anyway - anyone???

Al

Sorry... another poster might know.

LLoyd