Strain gauge in rotating shaft
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  1. #1
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    Default Strain gauge in rotating shaft

    I would like to measure the thrust on a rotating shaft (and ideally the torque also). How do I do that? (obviously you can't just put strain gauge in the shaft because it needs wires, unless there are wireless gauges maybe.

    The only thing I could think of would be to add a ring to the shaft and add a thrust bearing to the ring. Since the back of the thrust bearing is stationary you could attach the strain gauge to that.

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    Quote Originally Posted by jscpm View Post
    I would like to measure the thrust on a rotating shaft (and ideally the torque also). How do I do that? (obviously you can't just put strain gauge in the shaft because it needs wires, unless there are wireless gauges maybe.

    The only thing I could think of would be to add a ring to the shaft and add a thrust bearing to the ring. Since the back of the thrust bearing is stationary you could attach the strain gauge to that.
    That sort of thing can be done, we used to run a torque sensor on each drive shaft on the Indy Cars I used to work on. basically it was a strain gauge glued to the surface of the drive shaft and a little battery powered transmitter that spins with the drive shaft. We would run one on each side and compare the data from each side to make sure the differential was working properly. The transmitters sent the data to a receiver on the gearbox, then on to the data logger or to the telemetry as required. The stuff we were running was by PI Research. Be sure you are sitting down when you look at their price list.

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    there’s ways of also doing it inductively both to power it and read it at the same time. None of its cheap or simple, equally most of it will need some kind of installed calibration, you need 2 channels to do thrust and torque separately.

    Torques oftern far easier to approximate by setting up the drive such that the torque causes a reaction on a stationary load cell. Axial thrust is also easily mesured at the stationary bearing that absorbs that thrust by simply mounting it to load cell.

    If you want good accuracy, you need as smooth a vibration free drive as possible too.

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    You might be in the wrong sub forum. I'd imagine anyone working with and monitoring turbines could answer.

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    To know how to use strain gauge first step is to measure deformations using a resistive strain gauge one should rely on the phenomenon of resistance change of the conductor, which affects its shape. Examination of the element in terms of vibrations should start from correctly bonding the strain gauge to the tested surface. The tested element influences the strain gauge, whose resistance values change under the influence of the size change.
    Last edited by The real Leigh; 04-13-2019 at 09:20 PM. Reason: link removed

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    Yes you can put strain gauges on a rotating shaft. The guys at the place where I co-opted put 20 30 gauges on some fan blades. They would spin it up to full speed and collect data until it made a mess. They had some sort of rotary union never got to look at it very close.

    Shoot did not see the post was a few years old sorry.

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    OK, #5 is a classic SPAM, so where's Digger Doug when we need him?

    He's not the hero we deserve, but he's all that's left...

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    The classic way to measure rotational torque is (was?) a calibrated torsion bar driving the device and a differential gearing (between the two ends of the bar) coupled to a indicator showing the amount of twist on the torsion bar(the angle between the two ends of the bar). I still have, and using, one of those indicators. It comes with a number of calibrated torsion bars for a wide range of torque. Strain gauges can be used directly on the shaft with a rotating circular antenna and a stationary pickup loop around it.


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