I am looking for some advice re HTF/APF on a particular gearbox in my workplace.
The input gear has 20 teeth and the output 100, giving a common factor of 20 (20 assembly phases). The attached image details all the relevant frequencies for fault finding, given in Hz unless otherwise stated.
My understanding is that it is desirable to design gear combinations which have a GCF of 1, such as 92/35 teeth. As mentioned above, the GCF in the gears I'm looking at is 20. Does this imply that every 20 teeth on the 100 tooth gear could be exposed to greater wear? And would the wear on the 20 tooth gear be even? Or would a single tooth potentially be exposed to greater wear?
The other interesting thing this combination raises is that APF will always be the same frequency as input speed, and HTF will always be the same frequency as the output speed. This could make fault finding for faults specific to these frequencies more difficult, I assume.
Anyway, on topic again. Last year I had reason to believe that the gears were worn and potentially a tooth was chipped. A visual inspection was carried out and damage was found to teeth on the input shaft. I received no feedback regarding the output shaft although I suspected it would show damage also. The input shaft only was replaced at a shutdown due to time constraints - the output shaft is much more difficult to replace due to the arrangement of this gearbox. Readings obtained after start-up still indicated the same issues, so I am awaiting the output shaft being changed also.
My question is, assuming that what I said above is correct - that every 20th tooth is exposed to greater wear, is it possible that a different 'set' of teeth are now being worn given that the input shaft has been changed? For example, with the old shaft the same teeth were meshing every 5 rotations potentially causing excess wear. One new gear has been introduced, would the wear continue on the original set of 5 teeth on the output gear, or could it theoretically wear a different set of 5 teeth?
Finally, would it be worthwhile looking into changing the configuration of these gearboxes to prevent this setup? For what it's worth, there are several gearboxes on-site that have this configuration and this is the only one which has shown these issues.
Hopefully this all makes sense, thanks for any help you can offer.