Torque Distrubtion

[CodeRed7]

Hello, I had a quick question about torque.

I'm using a motor rated for 100 oz-in to drive the gearing system. I have two loads attached to the gearing system, that each require 80 oz-in and 0.7 oz-in to both start rotating and continue to rotate.

My understanding is that the sum of the torques that are actually applied to loads is equal to the output torque of the motor.

My question is will the motor constantly output 100 oz-in of torque? Or will it output something greater than 80.7 oz-in to get it running, and then once running will it output 80.7 oz-in?

 

[desertfox]

Hi CodeRed7

The motor will need to apply a larger torque whilst getting up to speed and then will output a steady torque to match the external loads.

 

[CodeRed7]

Okay that is what I thought, is there anyway to predict that larger torque if I only know the final speed that it reaches?

 

[CodeRed7]

And how would I know how much torque will be applied to each load when the motor outputs a larger torque?

 

[desertfox]

Hi

Well it depends on the rotational inertia of all the components and how fast you want the system to come up to full speed.
Its like sitting in your car and starting off from zero speed up to 40mph, the engine provides sufficient torque to the wheels to get the vehicle started and accelerated up to final speed. Once at final speed on a flat straight road the torque output is constant.
So you need first to work out the inertia's of the rotating parts, decide how long the system comes up to full speed say 5 seconds and from this you can go forward and size your motor.

 

[CodeRed7]

All right perfect I'll work on that, the only issue is determining the inertia of the parts. I have actually already selected the motor, I am more concerned with the torque that each rotating part will experience as I am designing a shrink fit and need to know the amount of torque that the fit can withstand.

 

[tbuelna]

Besides knowing the inertias of all the rotating components between the motor shaft and the load, you'll also need to determine the mechanical losses produced in the drivetrain from things like friction. These mechanical losses usually vary substantially in relation to speed.