**Simple Gear Selection Procedure**

The Lewis formula, in the form given by can be used in a provisional spur gear selection procedure for a given transmission power, input, and output speeds. The procedure is outlined as follows:

- Select the number of teeth for the pinion and the gear to give the required gear ratio. Note that the minimum number of teeth permissible when using a pressure angle of 20
is 18.*°* - Use either the standard teeth numbers or as listed in a stock gear catalog.
- Select a material. This will be limited to those listed in the stock gear catalogs.
- Select a module, m from standard or as listed in a stock gear catalog
- Calculate the pitch diameter, d = mN.
- Calculate the pitch line velocity,
- Calculate the dynamic factor,
- Calculate the transmitted load, W
_{t}= Power/V. - Calculate an acceptable face width using the Lewis formula in the form

**References:**

CHILDS, PETER R. N. *MECHANICAL DESIGN ENGINEERING HANDBOOK*. BUTTERWORTH-HEINEMANN LTD, 2014.