I have pretty good experience using incremental encoders to measure transmission errors in gearboxes. Although the data processing task is somewhat intricate with gear boxes owing the “not 1:1” transmission ratio, it is still manageable.
I would like to extend the technique to large turbosets by placing rotary encoders at both ends of the shaft line (a intrinsically 1:1 gear transmission without GMF but well torsion vibrations), an easy data acq and processing task .
Problem comes from the high level of thermal differential expansion on such machines as turbosets.
I am looking for brackets to mount encoders
sufficiently stiff angularly not to induce spurious signals in encoders
sufficiently flexible axially to accept the diff expansion without damaging the encoder.
Are any of you knowing where I could find proven commercial solutions for such brackets.
Ah, I forgot to say that diff expansion may rise to 1”.
Gerard

Gerard,

Very interesting test! Here are a few suggestions:

Encoder mounting methods to accomodate large shaft axial movement:
1) https://sdp-si.com/eStore/Direct.asp?CP=Index.htm Bearings-> Linear-> Frelon lined
Mount encoder shaft rigid to main shaft and torsionally restrain encoder case with one or more rods with linear bearings to allow encoder case to float axially and be restrained torsionally
Rigid Support with linear bearings:
2) https://sdp-si.com/eStore/Direct.asp?CP=Index.htm Splines-> Internal & External
Mount encoder case on rigid support and use spline shaft as coupling to main shaft to allow shaft axial movement (assumes negligible torsional movement/looseness)
3) Other encoder methods include making printed encoder target disk or stripes (longer than shaft movement) and using a laser optical sensor.

Walt (w_f_strong at msn dot com)

Walt,
Thanks for your help.
I'll try to figure out how this can help me.
your answer seems right on target.
I gort a phone call from s.o. in Belgium to enquire about my needs. The world is small and news travel fast.
Have a good day.