It is unfortunate that many of the available data on belting are from sources in which
they are presented in a very simplistic manner. These sources use a variety of charts,
nomographs, and tables to enable someone who knows nothing about belting to apply
them. Little, if any, computation is needed for such a person to obtain valid results. Since
a basic understanding of the process, in many cases, is lacking, there is no way this
person can vary the steps in the process to obtain a better design.
Incorporating the available belt-drive data into a form that provides a good understanding
of belt mechanics involves certain adjustments in the data. Because of this, the
results from the analysis presented here will not correspond exactly with those of the
sources from which they were obtained.
A moderate variety of belt materials, with some of their properties, are listed in
Table 17–2. These are sufficient for solving a large variety of design and analysis problems.
The design equation to be used is Eq. ( j).
The values given in Table 17–2 for the allowable belt tension are based on a belt
speed of 600 ft/min. For higher speeds, use Fig. 17–9 to obtain Cv values for leather
belts. For polyamide and urethane belts, use Cv = 1.0.
The service factors Ks for V-belt drives, given in Table 17–15 in Sec. 17–3, are also
recommended here for flat- and round-belt drives.
Minimum pulley sizes for the various belts are listed in Tables 17–2 and 17–3. The
pulley correction factor accounts for the amount of bending or flexing of the belt and
how this affects the life of the belt. For this reason it is dependent on the size and material
of the belt used. See Table 17–4. Use Cp = 1.0 for urethane belts.
Flat-belt pulleys should be crowned to keep belts from running off the pulleys. If
only one pulley is crowned, it should be the larger one. Both pulleys must be crowned
whenever the pulley axes are not in a horizontal position. Use Table 17–5 for the crown
height.