Following is a report on the R&D findings regarding remediation of high-value, high-demand spiral bevel gears for the UH–60 helicopter tail rotor drivetrain. As spiral bevel gears for the UH–60 helicopter are in generally High-Demand due to the needs of new aircraft production and the overhaul and repair of aircraft returning from service, acquisition of new spiral bevel gears in support
of R&D activities is very challenging. To compensate, an assessment was done of a then-emerging superfinishing method—i.e., the micromachining process (MPP)—as a potential repair technique for spiral bevel gears, as well as a way to enhance their performance and durability. The results are described in this paper.
An experimental and theoretical analysis of worm gear sets with contact patterns of differing sizes, position and flank type for new approaches to calculation of pitting resistance.
By increasing the number of gears and the transmission-ratio spread, the engine will run with better fuel
efficiency and without loss of driving
dynamics. Transmission efficiency
itself can be improved by: using fuelefficient transmission oil; optimizing the lubrication systems and pumps; improving shifting strategies and optimizing gearings; and optimizing bearings and seals/gaskets.
Gearbox performance, reliability, total cost of ownership (energy cost), overall impact on the environment, and anticipation of additional future regulations are top-of-mind issues in the industry. Optimization of the bearing set can significantly improve gearbox performance.
Gear tooth wear and micropitting are very difficult phenomena to predict
analytically. The failure mode of micropitting is closely correlated to the lambda ratio. Micropitting can be the limiting design parameter
for long-term durability. Also, the failure mode of micropitting can progress to wear or macropitting, and then go on to manifest more severe failure modes, such as bending. The results of a gearbox test and manufacturing process development program will be presented to evaluate super-finishing and its impact on micropitting.
Except for higher-end gear applications
found in automotive and aerospace transmissions, for example,
high-performance, sintered-steel
gears match wrought-steel gears in strength and geometrical quality. The enhanced P/M performance is due largely to advances in powder metallurgy over last two decades, such as selective surface densification, new materials and
lubricants for high density and
warm-die pressing. This paper is a
review of the results of a decade of
research and development of high- performance, sintered-steel gear prototypes.