I am a complete beginner to hydraulic systems, and I've wanted to learn more about this area. I'm designing a hydraulic system that involves using hydraulics to push/pull objects using pistons. I have looked at what the basic requirements are for a hydraulic system, but there is one thing that escapes me.

I come from an electronic background, and I noticed that the hydraulic pumps (for example, this one) seem to lack a motor to drive the fluid. Am I wrong? If not, I've been looking everywhere for a motor that can/should be attached to said pump, but I cannot seem to find anywhere that sells them. Is it just a simple DC motor (with correct specs), or should there be a specific motor designed for hydraulic pumps?

Looking around, I came across this, but looking through the specs, I don't see a power requirement, and being used to seeing power consumption in datasheets, I'm not even sure it is a motor!

  • 1
    $\begingroup$ Correct, a gearbox is not a motor. I believe the shaft dimensions on the pump are what determines which motor is compatible, and hydraulic motors are simply motors that supply a high torque at low RPM. But this is not my subfield so I'll leave the answer to someone else. $\endgroup$
    – Air
    Feb 5, 2015 at 17:17

3 Answers 3


You are correct, getting oil pressure will require an electric motor as your source of rotation, potentially a gear box to slow that rotation down, and the pump itself. You'll also need a reservoir to store the non-pressurized oil and probably a filter to keep the oil clean (dirty oil will damage your components.)

If you're new to the world of hydraulics, and want to keep things a little simpler for now, you might want to search for a 'Hydraulic Power Unit' which usually includes all of these components, already connected together. This way you just have a pressure line out, and a return line ('tank line') and don't have to be too concerned with RPM, torque, or any of the rest.

If you want to assemble the whole thing yourself, or no HPU's are available that work for your application, you'll want to find a motor with the same output as your pump's input (In your case a tapered shaft.) In your specific example, if you see their datasheet at http://docs-europe.electrocomponents.com/webdocs/12c4/0900766b812c44d2.pdf you can see that they offer these pumps in a range of different shaft types most of which conform to a standard interface (SAE J744, for example). You'll want to pick a motor with a compatible output shaft. You'll need to make sure that the RPM and Torque of the motor work with your pump and provide enough flow an pressure respectively for your hydraulic application.

Please remember that hydraulics can be very dangerous. There can be significant amounts or stored energy that you can't see. Think of the whole system as a giant line capacitor.

  • $\begingroup$ The line 'make sure RPM and torque work with your pump' is, I think the heart of the matter and could be expanded greatly. +1 for remebering the safety aspect. $\endgroup$
    – mart
    Feb 5, 2015 at 20:22
  • $\begingroup$ Definitely, but that would probably go best in a different question. This one is 'what parts do I need?' Matching an electric motor (and/or gearbox) to any device would take a longer answer than this. $\endgroup$
    – Ethan48
    Feb 5, 2015 at 20:23
  • $\begingroup$ Your right, we need more how to size motor [+gearbox] for <application> questions anyway. $\endgroup$
    – mart
    Feb 5, 2015 at 20:30
  • $\begingroup$ Thanks! This was exactly what I was looking for! I am new to this, but I really want to learn of this. In term of assembling everything individually, I'm still a bit unsure on what kind of motor, but I'll start with HPUs and see where that takes me! $\endgroup$
    – Tom
    Feb 6, 2015 at 9:41
  • $\begingroup$ If you decide to do a separate pump and motor next time, feel free to post a new question about that. Let us know the specific pump or motor you want to use and your requirements for the matching half. For example, what flow and pressure do you require? Or if you need to pick a motor, what power is available and what duty cycle do you need? Best of luck! $\endgroup$
    – Ethan48
    Feb 6, 2015 at 14:46

I would consider looking into BLDCs as motors, if they fit the hydraulic power required for your application, i.e. motor electric power = hydraulic power. I would pick a slightly bigger motor, with maybe 1.2 times the hydraulic power. Also, dependent on the hydraulic system you want to actuate (whether it's parallel or series, just like in electricity) and when it contains valves, you either need volumetric flow rate (increase/decrease motor speed), pressure (increase/decrease motor moment), or a certain combination of both. That is for the gear pump you mention.


to Calculate the Horse Power for the Hydraulic system we Need following data 1) G P M of the Pump ( Vane / gear / piston pump ) 2) Working pressure of the hydraulic oil in P S I

Therefore ; H.p = 0.0005833 x P.S.I x G.P.M


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