Will the gear tooth break?

[Matt Adams]

Originally Posted by Joe Johnson

Pcircular = 2 Pi/P = .31"
Circular Tooth Thickness = Pcircular/2 = .16
Tooth Height = 2.25/P = .11

This can be approximated as a beam
L = .11 in
H = Circ Tooth Thickness = .16 in (this is conservative but a first order approx)
T = .375 in
F = 164 lbsf
I = (1/12) T * H^3 = (1/12) * (.375) * (.16)^3 = .000128 in^4
c = H/2 = .08

Joe J.

I confess I double checked your circular tooth thickness. Perhaps we're just using different terminology, but if you mean the thickness of the gear tooth on the circular pitch, I think the formulas are different.

I have:
pCircular * Pdiametral = pi

and
Circular tooth thickness:
t = pi / (2 * P) or 1.5708 / P

So I get a tooth height (thickness) of (1.57 / 20) = 0.07854 in. or exactly half of what you found.

Calcs:
I = (1/12) T * H^3 = (1/12) * (.375) * (.07854)^3 = 0.0000151 in^4
c = H/2 = .0392

Hence, the stresses are substantialy higher.

I know that there's lot of terminology floating around, are we just using a differnent lingo?

Matt