Torque Measurement 1

[vsquared]

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.

 

[Barry1961]

You can mount the hydraulic motor with a torque arm and place a load cell where the torque arm mounts to the frame.

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

 

[alpharam]

I've seen an arrangement for measuring torque on car flywheel. It involves sensors coupled with clutch pins and a complicated electro-mechanical design, which seems to be know-how.
Precise measurement of torque is obviously not an easy task.

 

[aviat]

If you know the efficiency of the motor you should be able to put a flow meter and pressure guage in the inlet to the motor and from hydraulic formulas determine torque.

 

[GregLocock]

Put a load cell under each foot of the gearbox and/or the motor.

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.

 

[fangas]

Hi V,

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

 

[MilanK]

All of the above suggestions will work. If you do not need the result 'really' accurate, maybe all it takes is to know the flow and pressure that you need to do what you are doing.
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

 

[nolan51]

Does anyone have experience with installing torque arm gear reducers using a rigid bracket to restrain the rotation of the reducer instead of a threaded rod type torque arm? We have had to do this in several installations and are wondering about the reliability of this type of installation. I know that screw conveyor drives, using the same gear boxes bolt directly to the conveyor flange to restrain the rotation with no problem.

 

[Barry1961]

Nolan, this should be a new thread.

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