Page 189 - Root Cause Failure Analysis

Gearboxes/Reducers 177

HUB ON HUB ION
LFFT SI DE RIGHTSIDE
Figure 147 The helix angle of the teeth must be the same no matter from which side the
gear is viewed (Neale 1993).

Herringbone
The double-helical gear, also referred to as the herringbone gear (Figure 14-S), is
used for transmitting power between parallel shafts. It was developed to overcome the
disadvantage of the high-end thrust present with single-helical gears.

The herringbone gear consists of two sets of gear teeth on the same gear, one right
hand and one left hand. Having both hands of gear teeth causes the thrust of one set to
cancel out the thrust of the other. Therefore, another advantage of this gear type is
quiet, smooth operation at higher speeds.

Bevel
Bevel gears are used most frequently for 90" drives, but other angles can be accom-
modated. The most typical application is driving a vertical pump with a horizontal
driver.

Figure 14-8 Herringbone gear (Neale 1993).