Page 67 - Gear Technology Solutions

contact direction. This ideal condition can only be achieved with correct
amounts of crowning, adjusted to the operating displacements. It is interesting
to mention that a hypoid gearset with crowning will fulfill the first and third fun-
damental gearing law even in case of gearbox inaccuracies.

Figure 16: TCA of hypoid set from Figure 11 with added crowning
and shaft displacement

4.8 Transmission Orientations

Hypoid gearsets are used as final drive gears in cars and trucks. Hypoid gears
are not used as simple reducers, but their purpose is to redirect rotation and
torque by a certain angle, commonly 90°. In case of hypoids, the second pur-
pose of lowering the center of gravity of a vehicle body has become very im-
portant in the automotive and truck industry. The redirection of rotation and
torque has to be done at the driving axle of a vehicle. The engine orientation of
vehicles with a rear wheel drive is longitudinal. Because engines of cars and
trucks are commonly in the front, a longitudinal oriented propeller shaft trans-
mits the engine rotation to the rear drive axle as shown in Figure 17. The
transmission, which is located between engine and propeller shaft, needs to
have a gear shaft orientation identical to the direction of the engine crank
shaft. The hypoid gearset redirects rotation and torque and provides the final

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