STANDARD HANDBOOK OF MACHINE DESIGN
requirement, overloads, shaft dislocations, temperatures, and other environmental conditions).
• Economy: Those flexible-connector drives suitable under performance criteria are further investigated with respect to their applicability from the economic point of view. The economy of flexible drives is influenced by the following factors:
Production cost of the flexible connector
Subsequent design expenses required because of the selection made (e.g., pul
ley costs, costs of larger bearings to take up the required initial tensioning
force, costs of lubrication facilities and seals required, of special installation
arrangements, and of tensioning devices)
Transportation and installation costs, mainly dependent on the space require
ment and the weight of the drive
Operation and maintenance costs
Failure risk as well as costs of repair and subsequent costs
The relative importance of these factors varies with the machines used, and the costs of the flexible connector as the drive element are the least important. A drive unit will prevail wherever its special technical properties ensure the most economical drive.
To facilitate the selection of suitable flexible connectors, Table 31.5 compares the most important operating characteristics of flexible connectors and remarks on investment costs as well as maintenance and installation.
Figure 31.33 shows the results of a comparison of costs, when different flexible connectors are used, for a system consisting of two pulleys, the flexible connector, and the driven shaft, including the required roller bearings. The costs were determined following calculations for the drive with the power transmission capacity, the center distance, and the speed of the driving pulley given.
Figure 31.34 shows the specific power transmission capacity of different flexible-connector drives as a function of velocity. This specific power transmission capacity indicates the rating of the flexible connector and thus the space required. The higher the specific power transmission capacity of the flexible connector, the smaller the space required for the installation of the drive.