Brake Motor Max Loading

[dpsmith85]

I am looking into buying a brake motor to support a vertical load. Our current design is a 200 to 1 two stage reduction gear reducer. The torque at the output of the reducer is around 3500in-lbs. I am looking at a leeson brake motor catalog #114167 that's brake can support 72in-lbs of torque. Based on that the calculation be as simple as:
1) 3500in-lbs/.7 = 5000in-lbs <-------I'm increasing the output torque to account for the loss of efficiency of the gearbox
2) 5000in-lbs/200 = 25in-lbs <-------I'm now dividing the torque at the output by the gear ratio to get the input torque at the shaft
Because 25in-lbs is less than the rated 72in-lbs I should be good correct?

I just want to make sure I'm thinking about this correctly

Thanks

 

[Oldhydroman]

If I understand you correctly, the output of your gearbox drives a load which is oriented in such a way that when you turn off the electric motor the load tries to run the motor shaft backwards. If this is so then the "inefficiency" of your gearbox means that your brake doesn't need as much torque to stop the load coming down as your motor needs to drive the load up. The losses in the gearbox help to hold the load up - imagine what would happen if your gearbox was only 1% efficient.

It is sometimes difficult to evaluate gearbox efficiencies because they change with wear, temperature, lubrication, manufacturing tolerances, alignment of drive shafts etc. So assume 100% efficiency for the load holding function and know that this will result in an overestimate of the brake torque you will actually require. I think that means that a brake torque of just 17.5 in-lbs would be sufficient.

If your brake is on the motor then any failure in the drive train or gearbox will cause the load to drop. The closer you can move the brake to the load the more failures you can tolerate - but you will then need your brake to have a higher torque.

DOL

 

[dvd]

What stops the load from moving? The brake, or a programmed deceleration? With a high-torque brake is it possible to have a quicker stopping time that causes a gearbox overload?