Calculate torque of a motor from straight bar load cell

[PaulB]

TL;DR

I have a motor sitting on a calibrated bar strain gauge. The shaft of radius R is grounded to a wall. When the motor spins, a force F is measured on the strain gauge. The motor body is coupled to a square body with sides of length 4R

How do I calculate the torque of the motor?

 

[Swamp Thing]

When the motor spins...

I assume there is a slipping clutch somewhere?

 

[Baluncore]

What is the strain gauge attached to, apart from the body of the motor?

 

[PaulB]

Yes, it is attached as a cantilever beam, a distance D away. The strain gauge has been calibrated in this position, so we can ignore the moment caused by D.

 

[sophiecentaur]

I assume there is a slipping clutch somewhere?

Or is this the starting torque of a stalled motor?

 

[PaulB]

Or is this the starting torque of a stalled motor?

Starting torque of a stalled motor.

 

[sophiecentaur]

Starting torque of a stalled motor.

The summary tells us the motor spins.(?)

 

[PaulB]

The summary tells us the motor spins.(?)

Correction: the motor is powered, but stalled against the wall exerting its stall-torque.

 

[Baluncore]

Yes, it is attached as a cantilever beam, a distance D away. The strain gauge has been calibrated in this position, so we can ignore the moment caused by D.

We are not mind readers. Where is the point D on the diagram ?
How far is D from the axis of the motor ?