Before deciding what pneumatic motor to buy, you need to know what level of torque is required for what you need the motor to do. Many customers talk about the required power, strength or force of a motor, but this shouldn’t be confused with the torque.

To select the right motor, you need to know the torque and the revolution speed, and the combination of these two will determine the motor’s power.

But which torque?

It’s important to be clear about when you want to use this torque.

Is it the starting torque?

For example, to operate a crane lifting heavy objects or materials, you need the crane to be able to weight-bear as soon as the motor is switched on, therefore the starting torque is critical. This can be the most difficult torque to assess because it depends to a certain extent on the position of the blades in the rotor when you start up the motor, and this position, inevitably, will be different every time.

Or is it the stall torque that you want to control?

If you need the motor to cut out when a specified torque is reached, then it’s the stall torque that’s relevant. This is significant, for example, if the mechanism is used for opening a heavy door and you want it to stop once the door is closed, or perhaps more importantly if someone is in danger of getting caught in the door!

Or it could be the nominal torque (the torque required during the running of the motor) that is important for your application.

This can be the easiest torque to work out as for a given air supply (pressure and flow), the speed of the motor will depend on the torque required. hence, by measuring the speed, you can deduct the torque. That said, it can also be tricky for the user to judge – for instance when drilling a hole into wood or metal, the strength and thickness of the material will play a part.

If in doubt…

It isn’t always possible to evaluate the required torque without being able to see how the pneumatic motor works in relation to your equipment and how you use it.

Here at Modec, we use the information provided by customers to suggest the motor we think has the closest characteristics to meet their requirements. We are then happy to lend this motor to the customer for trials in situ so that together we can fine-tune the gearbox reduction ratio according to the torque to reach the exact specification.

Results

So, in short, get the right torque and you’ll get the right motor. Get the right motor and it’s job done!