## Talking down torque. Motor required to raise and drop a hen house door.

I must have been asleep in physics when we did torque (well it was a while ago, before I discovered beer) and am re-visiting the subject afresh. I am trying to choose a motor to lift a pop-hole door to a hen house. The motors I'm looking at have a torque rating from 400 to 1000 gf.cm, which I gather to be gram force cm. I'm just not to sure on the significance. My plan is to have a string attached to the door and a motor to wind it up about a foot. If the door weighs 500g, what motor should I go for?

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 Torque = radius * Force. Force should be the weight of you door. (500 grams *9.81(gravity)) radius comes from whatever sprocket or shaft or gear mechanism you have connected to your motor. so if you had a sprocket on your motor that had a 10mm sprocket, you would create/require this much torque: T=r*F T= 10mm*(500g*9.81m/s/s) T=10mm*(.5kgs*9.81m/s/s) T= 10mm*(4.905Newtons) T=.010meters * 4.905 Newtons T= .04905 Nm T= .04905 Nm =500.1727 gramforce centimeter (gfcm) conversion is 10197.2 gfcm for 1 Nm
 Thanks. So are the units of gfcm as straight-forward as: a motor rated at 500 gfcm can lift a 500g mass with a maximum spindle/spool radius of 1cm and therefore the same motor could lift a 250g mass with a 2cm radius spool?

## Talking down torque. Motor required to raise and drop a hen house door.

here's a page with some great info:

http://www.clear.rice.edu/elec201/Book/motors.html

One interesting note: