# Calculate torque of a motor from straight bar load cell

• I
• PaulB
In summary, the conversation discusses a motor that is powered and stalled against a wall, exerting its stall-torque. The motor is attached to a strain gauge as a cantilever beam, with the gauge being calibrated at a distance D from the motor's axis. The conversation also includes questions about the position of point D on the diagram and its distance from the motor's axis.

#### PaulB

TL;DR Summary
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?

PaulB said:
When the motor spins...
I assume there is a slipping clutch somewhere?

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

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.

Swamp Thing said:
I assume there is a slipping clutch somewhere?
Or is this the starting torque of a stalled motor?

sophiecentaur said:
Or is this the starting torque of a stalled motor?
Starting torque of a stalled motor.

PaulB said:
Starting torque of a stalled motor.
The summary tells us the motor spins.(?)

sophiecentaur said:
The summary tells us the motor spins.(?)
Correction: the motor is powered, but stalled against the wall exerting its stall-torque.

PaulB said:
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 ?