Hydraulic Pump/Motor: Can it Work as a Motor?

[1nv3n73r]

hey people. literally just joined, hehehe
my question is, can a hydraulic pump be used as a hydraulic motor. i have an idea and want to have it operating using hydraulics rather than having shafts and gearboxes to transfere to work.
any comments welcome, good or bad, but i prefere good...hehehe

 

[jack action]

From Wikipedia:

Conceptually, a hydraulic motor should be interchangeable with a hydraulic pump because it performs the opposite function - similar to the way a DC electric motor is theoretically interchangeable with a DC electrical generator. However, most hydraulic pumps cannot be used as hydraulic motors because they cannot be backdriven. Also, a hydraulic motor is usually designed for working pressure at both sides of the motor.

 

[1nv3n73r]

Thanks Jack action.
There is information there that I didn't know about.

 

[Randy Beikmann]

What you are describing is a hydro-static transmission. The pump and motor can each be designed to be pump/motors, but they aren't necessarily that way, as jack action said.

 

[Baluncore]

can a hydraulic pump be used as a hydraulic motor.

Conceptually simple, but there are many traps for the beginner. Pumps will often have a big inlet because only atmospheric pressure is available to push oil into the pump chamber, it can have a smaller outlet.

Pumps are usually designed to rotate in one particular direction. A hydraulic pump is designed to have a low and a high pressure side with seals to prevent it sucking air on the inlet side or weeping oil on the high pressure side.

A hydraulic motor may be designed for bi-directional operation. It can be operated with positive pressure on both ports. Bidirectional motors will have a third connection to drain fluid to the reservoir tank that leaks past the internal seals.

Hydraulic motors and pumps might get to 90% efficiency. A pump driving a motor will therefore have 90% * 90% = 81% efficiency. You will need to pay for that 19% inefficiency, you will also need an oil cooler to remove the 19% waste heat. A manual change gearbox will be closer to 98% efficient.