[QUOTE=alistairsam;766030]Hi,
Even if the load is balanced correctly, won't the moment of inertia be a factor to get it rotating, and won't that increase with the weight of the ota?
yes there is a force involved in putting to motion that is higher than normal running , you would need to know friction of the bearings to be exact (operating temp, adjusted to manufacturers spec and or material etc these can be found on makers sites usually) but I dont think you need to be exact. You can apply a fudge factor to cover all issues, maybe 20% above normal running??
have a look at this
http://bftgu.solarbotics.net/tutorials_mech_torque.html
eg. there would be a significant difference when you try and turn the shaft by hand between a perfectly balanced ota that weighs 10kg and another balanced ota that's say 30kg on the same shaft?
how do you measure that?
torque.....the twisting force, you should consider an overload clutch as well or over engineer the drive to compensate.