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Involute Gears

What Are Involute Gears?

According to wikipedia, involute gears are the most commonly used system of gearing today. They are named as they are because the profile of the tooth follows the curve of an involute of a circle.

Involute gears are useful because they transfer energy between cogs with a constant velocity throughout the meshing, and because they increase tolerance in gear spacing.

This youtube video gives a clear and simple explanation of the failings of square-tooth gears compared to involute gears as well as some miscellaneous gear fundamentals.

How do I guess all of the numbers for my involute gear??

Don't guess the numbers for your involute gear, take a look at some resources others have put together to document formulas and methods of construction.

This engineers edge page has a great set of depictions of the various characteristics of an involute gear and their associated formulae.

There are a good handful of youtube videos describing construction processes which can be used to create involute gears. I found this video relatively clear and used it for inspiration in my own crude OpenSCAD library.

Where is that crude OpenSCAD library?

The involute gear library can be found in the Jb7AtHms git repo for Halifax Makerspace Content. All of the values in the file should look familiar to you if you were looking at the engineers edge formula page mentioned above. The library exploits the fact that the line of action is always tangential to the base circle, the same fact exploited in construction video above. The use of a simple cylinder boolean summation means that the profile shape is mathematically correct and easy to construct, but very inefficient in terms of use of vertices.

If you take a look around in that repo you will also find a composed assembly of these involute gears, both in blender format, and in a ready-to-print STL.


involute_gears.txt · Last modified: 2019/06/18 18:38 by jedsall