Torque Measurement
Torque Measurement
(OP)
I have a problem with measuring torque on a rotating shaft. The shaft is connected on one end to a Hydraulic Motor rotating at 40 rpm with the output driving a "Feed Roller" through a gear and chain system.
I need to measure the output torque of the motor while the machine is in operation.
I need to measure the output torque of the motor while the machine is in operation.





RE: Torque Measurement
You can place a pickup on each end of shaft on the OD and measure the phase shift as the machine gets loaded. The shaft twist due to torque may be hard to calculate depending on arraingment. You might be better off to reduce the pressure until it stalls for a start point if you don't need to be real accurate.
If you have a coupling with an elastomer element you can place a pickup on each side. Might not be accurate though.
You can mount a idler sprocket with a load cell on the tension side of your chain and measure chain pull.
With all of these you may need average the feedback to null the cogging of the system.
After you do your calculations check them with a torque wrench or a scale and lever arm to get a known.
Barry1961
RE: Torque Measurement
Precise measurement of torque is obviously not an easy task.
RE: Torque Measurement
RE: Torque Measurement
Strain gauge the driveshaft and use a wireless transmitter to transmit the signal.
Buy a torque sensor and install it.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Torque Measurement
Try Lebow model 1700. Look at http://lebow.com/pfull.htm#Torque
I've used their torque transducers many times. Always been happy.
Ed
PS, Not cheap
RE: Torque Measurement
Hp= (GPM x psi)/1714.
There are some ifs and buts that you need to watch for, though (backpressure, flow over the relief, other flow consumers, etc). Your schematic will help some, inspection of the system may help, too.
After that - it is simple:
Torque (lb in) = (hp x 63,025)/ RPM
RE: Torque Measurement
RE: Torque Measurement
If you have any shaft deflection or mis-alignment you are in for trouble if you rigid mount it.
If you do rigid a mount it make sure the mounting bracket is self aligning during the assembly process. If it is not perfect something will give, which most of the times means the shaft will walk.
Barry1961