Shape of the gear tooth fillet by analytic equation? 3

[PrintScaffold]

Hello everyone!

I wonder if formulas exist to analytically draw the shape of the gear tooth fillet (the same way as with the involute shape of the main part of the tooth itself)? I understand that it is being formed by the hob, and essentially is the product of the relative motion of the hob and wheel itself. Is it possible to express this shape by an equation?

http://www.cadroad.com

 

[3DDave]

Hi Gearcutter - I just looked at the earlier trochoid posting and wanted to see the images you posted links to, but they are no longer on photobucket. I would appreciate if you could repost the pictures. Thanks.

 

[gearguru]

I agree with tbuelna. There is much more in the correct gear profile than the exact involute and trochoid or another root curve.
What we did in UG those years ago was mostly to try what we would be able to calculate/program. It did not have much value - if any at all - for manufacturing those gears. But it was fun to see how fast the UG created pretty gears (helical too) using just our digital input.

 

[tbuelna]

What makes optimizing gear root fillet shapes difficult is that it becomes an iterative process involving a pair of gears, where changes to one gear can affect the mating gear. So you go back and forth between the mating gears tweaking the fillet shapes and re-calculating the stresses until you get an acceptable result for both gears. Ideally, all gears in a drivetrain are optimized for a given system service life. It does no good to have some gears that will last far longer than others based on the lifecycle requirement for the total system.