# Trying to find the appropriate motor for a sliding door

1. Feb 18, 2012

### CuriousNotion

My assignment is to create a sliding door with working motor,mechanical and structure calculations. However I keep having trouble when finding the appropriate motor for the sliding door movement. The doors are both 80kg (Which is 784 Newtons). The entire weight is taken is supported by the track with steel wheels that is connected to a steel rail (to prevent the pulling of the driving belt, altogether it is 1568 Newtons for the doors). this the rolling co-efficient of the steel wheels to steel rails is around 0.001.

So the force needed for the belt to pull the door is

F.c = (1568 x 0.001)=1.5696N

The diameter of the belt pulley is 3 cm so the torque needed is

Torque=force x radius = 1.5696 x 0.03 =0.047088 (N/m)Newton-metres.

Nearly all the motors I have found are over 1 (N/m) of torque but very high rpm (which I need to convert to a lower rpm which , if achieved by gear ratios ,increases the torque further. What should I do? Are my calculations wrong. is the rolling coefficient unrealisic? and is all is correct is okay to ignore a torque that is far more than that required?

2. Feb 18, 2012

### aaronfranz

Ignoring the torque problem will be fine as long as the new calculated torque isn't strong enough to hurt somebody.