SEED Guides Belt Drive Performance < >
3.4 Nominal speed ratio
The speed ratio is a function of the pulley sizes. The minimum
recommended pulley size for a given section depends on the
flexibility of the belt and the mass/unit length. Pulleys are normally manufactured in standard sizes so the
choice of the driving pulley should be the smallest standard size
which is recommended for the chosen belt section such that the
ratio obtained is near to the required value when matched with a
larger standard size pulley. Pulley sizes are normally based on a pitch diameter, which may
be less than the outside diameter. Minimum pulley diameters
recommended for a range of belt types are as follows: