DESIGN, PRODUCTION AND APPLICATION OF THE HYPOID REAR-AXLE GEAR 260041
After defining hypoid-gears and outlining their action, together with their general characteristics and advantages, the authors compare them specifically with spiral-bevel gears and follow this with a description of how the axis of the pinion is offset from the axis of the gear and how the direction of the offset determines whether the spiral is right-handed or left-handed.
Considering pitch-lines, details of the mesh between a crown-gear and an offset pinion are presented, since this constitutes a special case of hypoid-gearing, and the application of these principles to a pair consisting of a pinion and a tapered gear is discussed. The rate of endwise sliding, the proper ratio of gear-diameters, tooth loads and tooth profiles are other phases treated specifically, and computations of surface stresses by the Hertz formulas, with special reference first to a comparison between helical teeth and straight teeth, and then with reference to hypoid-gears, are outlined.
Following a description of the newest method for the production of hypoid-gears and a statement of the machining operations needed, it is pointed out that the finish-cutting of the pinion is the only major operation which requires machinery different from that used for the production of spiral-bevel gears and pinions.
Outstanding points covered in the discussion include statistics and comment on actual pressures on the teeth of spiral-bevel and hypoid-gears; maximum amount of offset allowable for hypoid-gears; distortion of pinions due to heat-treatment; and additional considerations relating to the respective merits of “overshot” and “undershot” mountings.