Pressure Angles

[dlavery]

The best resource that I have ever found for a really good introduction to gear design is the technical section in the Handbook of Gears by Stock Drive Products. You can download the whole thing as PDF files from the SDP web site. As good as the stuff on the Martin site is, they really don't get into the background knowledge you really need to understand what is going on and why the formulae work. The Handbook Of Gears is a bit surprising because it is tucked away inside the SDP catalog. But it is a great reference for understanding both introductory gear theory and application considerations.

There is a whole section (see Section 13) on gear tooth strength and design. Most of their calculations are based on the Lewis formula, or a modified (Barth) Lewis formula. As has been discussed several times on these forums, the Lewis formula calculations are based on industrial duty cycles, and the assumption that the gears will undergo millions of rotations. For almost every FIRST application this will result in a very conservative solution. While these calculations will provide a workable solution, it will be a bit of "overkill" for most FIRST robots (and therefore, lead to a potentially heavier gear system than is really needed, as the recommended gears are larger - and heavier - than need be). Joe Johnson's suggestion of using a beam stress calculation to determine tooth size will provide a very workable answer that will be closer to the optimal solutions for FIRST applications.

-dave

[Joe Johnson]

Originally Posted by dlavery

The best resource that I have ever found for a really good introduction to gear design is the technical section in the Handbook of Gears by Stock Drive Products. ...
-dave

This is very true. For one reason and another, my formal education skipped Gear Design. When I was transfered to a group that eats & sleeps gears, I needed a gear primer ASAP. I read the Stock Drive Products handbook cover to cover. Not only did it allow me to pass as a gear guy, I was quickly regarded by many as the group's go to guy with regard to gear design.

Surely there is a lot to learn beyond the pages of the SDP catalog, but it is a great start. One bit of advice. Learn the ideas, look up the formulas. The other way round will drive you mad in gear design.

Finally, the Lewis formulas are a wonderful tool that is just plain too conservative for intermittent use applications. FYI, I found this old thread and this old thread where I give some details as to making the calculation. In case my recommendation is not convincing enough, even Ol' Man Beatty told me uses the method I described to size gear teeth.

Joe J.

[Smrtman5]

Thanks for the great link to more helpful gear stuff! Im really getting into it. Theres so much to learn, so many diferent aspects and such. But my theory is: if you want to know it, youll learn it.

Originally Posted by Joe Johnson

Learn the ideas, look up the formulas.

And thanks for the good advice! Im def. remembering that one.

Maybe one day ill have my own office and i can cover the walls with posters of various useful formulas lol.


Hmm...but now im starting to think.....what about chain and sprockets?