hydraulic pump&motor selection 2

[cosgriff]

My company is having me research the feasibility of using a hydraulic system on a new product, but I do not have much background in the field. My problem is this:

Our machine has four shafts (ABC&D), which must all run at the same speed. Sometimes, all four will have power applied to them, but often only AB or CD will be powered. We are looking at running hydraulic pumps off of these shafts, which will need to handle up to 500hp (total) at up to 2500RPM.

Is it possible to place one device on a shaft to act as both a pump and motor? Will this be reasonably efficient? If so, what would the proper term for the device be, and where could I begin searching for one to use on our prototype?

Thanks!
ecosgriff

 

[EdDanzer]

Pump/motor systems are somewhat new technology. Most motors can work as a pump but are not as efficient as a pump. Without more information about what you are going to use the pump flow for and how much motor power is required there is no way to provide much information.

 

[cosgriff]

The pump flow will be used to drive several(?) motors. The power input into shafts ABC&D is expected to vary anywhere from 50hp-500hp (maybe more...), and we would like to reproduce as much of that power as possible with the motors.

Our other option right now would be to mechanically couple the input shafts to the devices we would power with the hydraulic motors. This may be more efficient, but it would be valuable to have modular systems.

So, if a motor can be used as a pump, would it be feasible to have one large pump and one smaller motor on each shaft? It won't take much hydraulic power to turn the shafts when they aren't under external power.

Thanks for the post EdDanzer!
cosgriff

 

[hydromech]

Axial piston hydraulic motors can work as pumps as long as they are boosted...that is they don't have a high negative pressure on the inlet.

If they struggle to fill, they are very noisey and the resulting cavitation kills the pump/motor very quickly.

Radial piston and gerotor type motors I am not so sure about.

Either way, 125 HP will require a big pump/motor and at 2500 RPM there will be a lot of oil moving around.


When they are being used as pumps, what will you do with the oil? You will have 500 HP to get rid of...and lots of energy too!

Regards

Adrian

 

[kcj]

I am not clear. CAn you explain application more:

Q
Our machine has four shafts (ABC&D)
Sometimes, all four will have power applied to them,
often only AB or CD will be powered.
looking at running hydraulic pumps off of these shaftsQ


So, when you say power applied to them, meaning these hydraulic devices turn the shafts, which turns the machine?
And only need to drive certain shafts at certain times?

Or that the machine turns the shafts, which drives the pumps? and that certain shafts may not rotate at times to drive the pumps?


There are overrunning clutches to mechanically isolate drives, in/out clutches and splines, motors that can freewheel in certain conditions, etc. Many options, I just don't understand the application.

500 hp, 125 per pump/motor, is easy. No worries there. There are significant 'accessory' type issues of charge, flushing, cooling, filtration, spike protection, etc etc that complicate things a lot from just basic
'pump/motor/hose', but these are all normal practices in the hst applications.

Some tradeoffs between mechanical drives and hydrostatic are: energy efficiency vs. simplicity vs. cost vs. controlability vs. flexibility vs. stall or overload ability. Depending on which is most important to your product, the favored answers can change a lot.

Sounds interesting, more info please.
kcj

 

[EdDanzer]

Cosgriff,

You sill did not define what was being done with enough detail. If you are trying to regenerate energy this complicates the system especially if there is a wide range of power fluctuations. Each shafts input and output torque and rpm range is the least information required to provide more information. If you do not feel comfortable providing this information on this website, go to

http://www.danzcoinc.com

and contact me directly.

 

[cosgriff]

HydroMech,
Thanks, I'll do some research on Axial-piston motors. The excess hp will be used to drive several motors on the subsystems.

kcj,
"Or that the machine turns the shafts, which drives the pumps? and that certain shafts may not rotate at times to drive the pumps"

Exactly... but all the shafts must run at the same speed, even when the machine is not applying power to them. When the machine is not applying power, I would like the hydraulic system to apply that power instead (although it shouldn't require much), with the excess power going into the subsystem motors.

Thanks everyone for all the help!!
-cosgriff

 

[MikeHalloran]

You can buy gearboxes that bolt right up to Diesel flywheel flanges, and have up to four shaft outputs to drive hydraulic pumps. You could just substitute clutches for the pumps, and drive your four shafts without wasting a lot of power and money on hydraulics.



Mike Halloran
Pembroke Pines, FL, USA

 

[automatic2]

you could mount variable displacement or pressure compensated pumps on each shaft. The unused pumps would zero thier output, negating drag on the prime mover.

 

[maxcanada]

Use variable displacement piston pump is good idea.
Changing the swash plate angle from positive to negative will change the pump mode to motor mode while the shaft rotation direction does not need to be reversed.

 

[Newmanite]

Hi all this is my first post so please bear with my ignorance.
A pressure compensated flow controlled pump system sounds like the obvious go but how much thought have you gone into control circuits between independant shaft drives? Logic systems such as pilot operated slip in cartridge valves or just by load sensing to the pump?
I am not an engineer but am keen to absorb knowledge in this field and add where I can

 

[juzboarder]

Try

http://www.apexhydraulics.co.uk

for professional advice. They helped me with a similar problem.