BOSTON?/span> MINIATURE HTD TIMING BELTDRIVES
BASIC CONSTRUCTION
Timing belts are essentially flat belts with the addition of evenly spaced teeth along the surface that contacts toothed pulleys. Power is transmitted smoothly and without slippage. Pulley pitch diameters are larger than their outside diameters and the belt pitch lines lie within the flat portion. Tension members are molded in the flat portion to serve as load-carrying elements. Miniature HTD timing belts have deep curvilinear tooth forms, as contrasted to trapezoidal for conventional timing belts. Greater strength, lower tooth pressures and decreased stress concentration result in superior performance.
SELECTION
The following general guidelines apply to selection of minia- ture HTDtiming belts and pulleys:
Design with ample reserve horsepower capacity and apply the proper service factors. The belt must have six or more teeth in engagement with the smaller pulley to carry rated Horsepower. Avoid small pulley diameters where practical to assure satisfactory belt life. Belt speed should not exceed 6500 feet per minute. At least one pulley in the drive should be flanged. For vertical shafts or where center distance exceeds eight times the smaller pulley diameter, both pulleys should be flanged.
Horsepower Rating Tables provide ratings for operation no more than ten hours per day under uniform loading. Selection procedure is as follows:
1.Select Service Factor from chart below.
2.Determine Design Horsepower. Design Horsepower = Application Horsepower x Service Factor.
3.Select small pulley and belt size from the rating tables, choosing a combination whose rating does not exceed the Design Horsepower.
4.For speed increasing applications an additional amount must be added to the Service Factor.
5.For speeds, higher than shown in rating Tables, con- sult factory.