1
$\begingroup$

Does protuberance affects dimensions like tooth tip/root height, pitch diameter etc? In my books there is a short sub-chapter about the protuberance but nowhere is said if it affects these basic dimensions for outer-normal gearing: These are my calculations for two gears of outer normal gearing:

enter image description here

So if I was to considier protuberance of the gearing to minimize pitting effect how would this protuberance affect these dimensions i.e. would the formulas and coeficients change if so, then how and to what value? Or am I just simply ignoring the fact that the gearing will be with protuberance and I just simply move on to next step?

$\endgroup$

2 Answers 2

0
$\begingroup$

I'm an electrical engineer, know little about gears and never heard of protuberance before reading your post.

My reading of Hob Basics Part II by Keith Liston suggests to me that protuberance is only relevant to the gear cutting operation and not to the gear meshing in operation. On page 4 of the PDF he states,

... but a protuberance is required for larger numbers of teeth to eliminate contact between the tip of the shaving cutter or grinding wheel and the fillet of the gear tooth.

$\endgroup$
2
  • $\begingroup$ @Puchatex, thanks for accepting my answer but I think you should un-accept for a couple of days to encourage responses from people who actually know something about gears. Then accept the best answer - if you're content that it's right. $\endgroup$
    – Transistor
    May 1, 2022 at 16:09
  • $\begingroup$ Actually your response gave me a hint where to look, the answer to my question was literally in one sentence I have missed. Thanks. $\endgroup$ May 1, 2022 at 18:22
0
$\begingroup$

The author of this question probably meant profile shift (ISO 21771, 4.2.9). While protuberance is generally a parameter in gear machining, the effect of "moving the involute" might appear similar to profie shift. Answering the question: When you design gears with different profile shift coefficient (and/or in combination with pressure angles different from 20°), you may as well choose a tooth tip hight and tooth root height which are off (not h*a = 1). Thus you may gain a lot of freedom designing gears with optimized contact ratio (5.4.7.1), flank- and root-stresses and more leading to better efficiency, lower noise excitation and better power to weight ratio.

However, if you are only just beginning to design gears with different profile shift, you should probably keep the height factors constant to the V-circle. In effect, tip and root diameter should change with profile shift.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.