Gears

  Alasdair Massie

Gears – such an important part of everyday life…involved in many machines.

At their simplest, they increase/decrease torque or speed or change direction of motion.

I think every school building should have a gear wall so students can experiment and get their hands on gears. If you have a laser cutter or 3D printer, you can make your own. There are a couple of nice sites to explore gear design :

a) Gear Generator is awesome for designing and combining and animating gears—but there is a cost to download files.

b) Evolvent Design lets you design and download svg or dxf. They also teach a little about the number

c) Barry S has created a cuttle.xyz file to generate gears. You can download an svg

d) Wood Gears allows you to design and print out on paper…like to cut out by hand

e) Engineers Edge lets you design and download svg or dxf — they also teach a little about the numbers

f) Jerome Leary webpage lets you design and download a dxf

There is a neat website that lets you draw with your finger/mouse a “circle” and a gear show up http://www.gearsket.ch/

 

There is one very important thing about all the numbers associated with gears.  If you want the gears to mesh, the Module has to be the same. It is associated with the linear density of the teeth, so the size of the teeth. The angle also has to be the same if they allow you to input that.
I have most often seen 20 degrees.
Number of teeth is always one of the input variables.
If you need to know how big your gear will be, it is approximately the Module times the Number of Teeth. Approximately because that diameter is actually about halfway up/down the teeth, at the mesh point of another gear

My Module 2.5, 40 tooth gear is about 100 mm in diameter (actual d = 105 mm)
My Module 2.5, 20 tooth gear is about 50 mm in diameter (actual d = 55 mm)

So figure out a way to mount some gears…like a peg board wall , and make some gears.