The only way to calculate the moment accuratly would be to mesure the static hold moment. To measure the moment when the motor is turning would require some sort of brake to stall the motor to it`s breaking point. This is quite overkill for steppers. But the static moment could be calculated quite easy by the "bucket" metod. Tourqe=F*L. So if the motor shaft is 4.75mm in D, that makes the radie is 0.00237meters. The F would be the mass you can put into the bucket including the buckets own mass in kilograms before the motor slips. The total weight would then be the mass * 9.81 (earths gravity).
Motor hold tourqe=(mass*9.81)*0.00237m. The hold tourqe is then exspressed in Newton Meters.
Jon |