•
Idler sheave
—a sheave designed to regulate the tension of the
belt, control the path of the belt, reduce belt vibration, and provide
takeup if the sheaves move with respect to each other. It is not part
of the power train.
•
Belt pitch length
—the length of a V-belt along its neutral axis.
•
Neutral axis
—a line located about two-thirds of the distance from
the bottom (narrow part) to the top (wide part) of a V-belt.
•
Sheave pitch diameter
—the diameter of the circle formed by the
neutral axis of a belt as it runs around the sheave. In a V-belt
sheave, the pitch diameter is always less than the outside diameter
of a sheave.
•
Arc of contact
—the length of the arc (measured in degrees) of the
circle where a belt makes contact with the sheave. Reducing this
arc reduces the belt’s ability to transmit power.
•
Center distance
—the distance from the center of the driver
sheave to the center of the driven sheave. V-belts work best when
the center distance is about equal to or slightly less than the sum of
the sheave diameters.
•
Speed ratio
—the speed (measured in rpm) of the high-speed shaft
divided by the speed of the low-speed shaft. This ratio equals the
ratio of the pitch diameter of the low-speed sheave to the pitch
diameter of the high-speed sheave.
V-Belts
1.04
V-belt drives are the most widely used belt drives in industrial
plants. Originally, only one or two simple belts of this type were
manufactured. Today there are many kinds of V-belts available.
4
1
/
2
in.
5
/
16 in.
13
/
32 in.
21
/
32
in.
17
/
32
in.
7
/
8
in.
1
1
/
4
in.
3
/
4
in.
1
1
/
2
in.
29
/
32
in.
A
B
C
D
E
Fig. 1-1.
Conventional V-belts