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Spline Shaft Extreme Wear Help????

Spline Shaft Extreme Wear Help????

Spline Shaft Extreme Wear Help????

Look at the attached picture and notice that the retaining ring is still on the spline shaft. This spline shaft couples a torque convertor/motor into the top of a gear reducer. Sitting in the top of the gear box it is flush to the bottom. However, when assembling the torque convertor/motor assembly on top of this spline shaft there is roughly ½” of play upward that this spline can navigate towards. The retaining ring per the manufacturer of this equipment is supposed to prevent this spline shaft from coming into contact with the bolt that is securing the torque convertor to the bottom of the electric motor. How in the world can this spline shaft be forced upward to cause this much damage in only 3 months roughly with the retaining ring still in place? We have spoken to the manufacturer who is in Italy and did not get much help. They actually suggested we turn over this spline shaft and insert it in upside down which we were originally told by them to never do this. I guess my real question is how or what is causing this shaft to navigate up in the first place and then to cause so much damage to this spline?
Any help or advise would be appreciated at this time or feel free to send me to someone else you may know who might be able to help.

RE: Spline Shaft Extreme Wear Help????

Possibilities include:
1) Static Torque in excess of rating
2) Design does not meet torque requirements
3) Shaft misalignment
4) Dynamic torque (torsional vibrations)
Two or more of these issues could act together.


RE: Spline Shaft Extreme Wear Help????

A sketch of the assembly to which you are referring would be most helpful.

RE: Spline Shaft Extreme Wear Help????

Without a sketch we have to imagine your arrangement. It looks tome like a pretty severe misalignment of the the components so the spline shaft was wobbling with lots of sliding occurring on every revolution. A little dirt would help to accelerate wear. The misalignment would push the shaft axially.

RE: Spline Shaft Extreme Wear Help????

As others noted, a sketch of the installation would be most helpful.

With only the benefit of the photo provided, here's a couple observations:

- While external retaining rings are often used to provide axial constraint of splined quill shafts, the retaining ring is typically installed in a close-fitting groove machined into the spline teeth. It appears there may have been such a groove on this shaft at one time, but the location where it should be has been severely worn away. Strangely, while the shaft material at this location is severely worn, the retaining ring seems largely unaffected.

- If you look at the spline teeth below the retaining ring, it is obvious the mating internal spline only engaged about half the face width. Given the extreme amount of material loss evident on the lower section of these spline teeth, there may have been a lubrication deficiency, or the material used did not have sufficient bearing strength capability for the operating conditions.

RE: Spline Shaft Extreme Wear Help????

Miss-alignment would allow an axial force that could result in your gear moving up or down during operation.

The wear looks to be caused by the retaining ring itself. Check the hardness of the gear compared to the retaining ring I wouldn't be surprised if it was either much softer and/or more brittle. Did the gear get properly heat treated or did it experience a temperature that could have altered its properties (annealed)? The image also indicates that the retaining ring did not spin with the gear but was stationary.

As long as the machine is running the axial force would be maintained and the ring would slowly cut the grove wider resulting in your picture.

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