# Hydraulic motor selection

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1. Nov 16, 2014

### mister student

Hello
I need guidance on selection of a hydraulic motor.
Motor would be used to drive the wheel of a vehicle. Motor needs to generate a torque of 18.3Nm in order to overcome static friction and move the vehicle. And the motor needs to be small enough to be coupled with the tire (see the picture)

From where should i start?
And can a single hydraulic pump be used to drive 2 identical hydraulic motors?

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2. Nov 16, 2014

### Danger

3. Nov 16, 2014

### jack action

Here's another one: http://www.hydraproducts.co.uk/hydraulic-calculators.aspx

You also need to know the desired rpm and power outputs as well to identify the pump/motor you need.

Basically (in SI units):

pressure X displacement = torque
torque X rpm = power
displacement X rpm = flow rate
pressure X flow rate = power

And yes, you can drive 2 motors with one pump.

4. Nov 17, 2014

### mister student

I've checked out the links you provided.
I've been browsing manufacturers of hydraulic motors and checking out their data sheets to see their rpm and torque ratings.
the problem is that in all the data sheets I've seen they did not mention the stating torque which is the torque required to start turning a load. They give the running torque.
In my application the most important thing that i need is a starting torque of 18.3Nm. Running torque is the late story when the motor has gained certain rpm. I dont need a torque of 18.3Nm when motor is in running condition with some hundred rpm. I need the 18.3Nm torque when the vehicle is stationary and the motor is struggling to turn my wheels.
Is there any specific formula to calculate the starting torque from the running torque?
Or if you know any catalogues or manufacturer websites that would give this information kindly inform me.

Last edited: Nov 17, 2014
5. Nov 17, 2014

### jack action

At one point, you will have to talk with the manufacturers, as this will depends on the construction of the motor. For example, this hydraulic motor built especially for high starting torque claims 90% of running value.

6. Nov 18, 2014

### mister student

Yes...i also found in some websites that generally the starting torque of gear and vane hydraulic motors would be around 70 percent of their continues torque rating