Gearbox

[bobdahaxor]

Mr. Andy Baker or anyone else who is skilled in gearboxes...

Why do you use 14.5 for your pressure angle instead of 20? I find that a lot more gears use 20 and I want to build a gearbox. Is there any reason to not go with 20 or any reason to go with 14?

[Travis Covington]

Mr. Andy Baker or anyone else who is skilled in gearboxes...

Why do you use 14.5 for your pressure angle instead of 20? I find that a lot more gears use 20 and I want to build a gearbox. Is there any reason to not go with 20 or any reason to go with 14?

I can't speak for why andy uses 14.5 degree gears, but in general 20 deg gears can handle slightly more torque/load but require a little more precision to do so without increased friction or binding. 14.5 degree gears run a little smoother and are a tad more forgiving, but can't handle as much torque/load. (were not talking a huge increase in capacity with the same face widths though)

A quote from The Boston Gear Theory Overview

"While 20° PA is generally recognized as having higher load carrying capacity, 14-1/2°PA gears have extensive use. The lower pressure angle results in less change in backlash due to center distance variation and concentricity errors. It also provides a higher contact ratio and consequent smoother, quieter operation provided that undercut of teeth is not present."

http://bostongear.com/pdf/gear_theory.pdf

Very useful info in there...