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##### Asked by: Heide Weyhreter

business and finance mechanical and industrial engineering industry# How do you calculate gears?

**gear**by the number of teeth on the "drive"

**gear**foreachinterlocking set of

**gears**to

**calculate**theintermediate

**gear**ratios. In our example, theintermediate

**gear**ratios are 20/7 = 2.9 and 30/20 =1.5.

Likewise, how do you calculate the number of teeth in a gear?

The ratio of a given pair of spur **gears**is**calculated** by dividing the **number of teeth** onthedriven **gear**, by the **number of teeth** on thedrive**gear**.

**Module**" is the unit of size that indicateshowbig or small a

**gear**is. It is the ratio of thereferencediameter of the

**gear**divided by the number ofteeth. Assumethat there are two friction pulleys in contact whosediameters areequal to the reference diameters.

Similarly one may ask, how do you calculate gear reduction?

The “**reduction**” or **gear**ratiois **calculated** by dividing the number of teeth on thelarge**gear** by the number of teeth on the small **gear**.Forexample, if an electric motor drives a 13-tooth pinion**gear**that meshes with a 65-tooth **gear**, a**reduction** of 5:1is achieved (65 / 13 = 5).

When you hear people refer to numbers like 3.08, 3.73,or**4.10**, they're talking about the **ratio** ofthering-and-pinion **gears** in the rear axle—hence,thenumbers are more accurately 3.08:1, 3.73:1, or **4.10**:1.Thatalso **means** that for every one turn of the ring**gear**,the pinion will turn 4.11 times.