Page 83 - Electric Drives and Electromechanical Systems

76 Electric Drives and Electromechanical Systems

FIG. 3.2 A gear train using compound gears; gear 1 is on the input shaft, gears 2 and 3 are compound gears on
shaft A; gears 4 and 5 are compound gears on shaft B and the gear 6 is mounted on the output shaft.
Product of the teeth numbers on the driven gears
n ¼ (3.6)
Product of the teeth numbers on the driver gears
The advantage of a compound train over a simple gear train, is that a much larger
speed reduction from the first shaft to the last shaft can be obtained with smaller gears. If
a simple gear train is used to give a large speed reduction, the final gear may have a
significant diameter compared to the input gear.
In practice the actual gear train can consist of either spur, or helical gear wheels. A
spur gear (see Fig. 3.3A) is normally employed within conventional gear trains and has
the advantage of producing minimal axial forces which reduce problems connected with

FIG. 3.3 Conventional gears. (A) Spur gear train. (B) A helical gear.