Starting torque is usually a key requirement for air motors used in operating equipment to lift heavy loads. If the starting torque isn’t sufficient, the crane will not be able to lift the load.

That said, the weight of the loads can vary and you don’t want the crane to suddenly winch lighter loads dangerously into the air. So, finding the required starting torque can often be anything but straightforward !

Lifting a heavy load

The starting torque depends on the position of the rotor blades when the motor previously stopped. As the position is unlikely ever to be the same, an alternative method has to be found to ensure a constant starting torque. The trick is to make sure the rotor (inside the motor’s pneumatic part)  can start without a load, effectively turning freely, and then once it has completed a few revolutions and picked up some speed, it engages with the gearbox (positioned in front of the motor) to take the load.

At Modec, we have developed a centrifugal clutch mechanism that is placed between the pneumatic part of the motor and the gearbox. Certain elements of the mechanism expand to engage with the gearbox when the blades begin to rotate. With this system, the starting torque is achieved when the clutch engages with the gearbox, so the position of the blades no longer matters and the starting torque is consistent.

Controlling the lift action

Equally important for the crane / hoist operator is the ability to slow down or stop the process during the lift action, without fear of dropping or damaging the load.

For this, it is simply a question of incorporating a braking system (available in the Modec range). You can also control the air motor exhaust flow to adjust the speed to the desired level.

And the problems you had previously for finding a starting torque adapted for your equipment and application are now a thing of the past!