Quote:
|
Originally Posted by Stu Bloom
Woah Greg, hold on a minute ...
The maximum torque required will be at the point where the force normal to the arm is maximum, which would be in the horizontal position. Max torque required for this application will be the 5lbs X arm length <edit>PLUS the mass of the arm multiplied by the distance from its cg to the pivot point</edit>.
Also Erik, you should make sure your motor has enough power for the speed that you desire. If you multuply the max torque number from above (in foot-pounds) by the maximum angular speed that you desire (in radians/sec) <edit>then divide by 550</edit> you will get the power required in horsepower.
Of course these torque and hp numbers would be the minimum required motor ratings assuming perfect (frictionless) conditions so I would suggest to also increase these numbers by a significant safety factor, maybe 50% (multiply by 1.5).
Hope this information is helpful.
|
I generally design so that the max torque on the motor is 25% of stall torque. If the motor has a fairly stright torque vs RPM curve, it should be turning about 75% of free speed. In this condition, it is turning plenty fast enough for adequate cooling and the motor isn't working too hard. Also if there is a hang up, the motor starts producing more power to break through. If you're running anywhere close to max torque then there is no power left to give.
Make life as easy on your motors as you can. Electric motors like to run at high rpm and light load.
ChrisH