Gearing is one of the most important components between prime movers and driven units. If gearing is not selected properly, it can cause many problems. Gearing transmits great power at high rotational speeds. Recent advances in turbomachinery technology, especially in turbines, compressors, couplings, and bearings, have required gearing to withstand high external forces. To design problem-free equipment, it is important to consider the effect of the external system on gearing. Thus, all the factors that influence design, application, and operation of gear drives, should be considered in the design phase.

Since problems encountered with gears are complex, it is unfair to blame them on the gear manufacturers alone. The gear supplier is much less informed about the package than any other group. Problems should be handled as a team effort between manufacturers and users. One factor causing problems is that the system is not timed in terms of spring constants and masses. The gear is usually the only item required to operate with metal parts in such close contact with other components. This setup can result in early failure. Gearing is also subjected to cyclic loading varying from 0 to 55,000 cycles per minute.

With current materials and heat-treating techniques, the use of high hardness gearing with tooth loads of 1500 2000 pounds per inch of face at pitchline velocities of 20,000 30,000 feet per minute is not at all uncommon. In turbine-driven test equipment gear drives have been built with pitchline velocities as high as 55,000 feet per minute and...