Balance Indications

TM55-4920-201-14

1-32. Balance Indications. (See figure 1-28).

one aide of the bushing than on the opposite side),

Because of the length cd the arbor assembly (from

as shown in view B. If the assembly is out of

balance to its maximum allowable balance

the flexible suspension element to the indicator

tolerance, one edge of the black disc will be exactly

disc), arbor tilt produces a magnified displacement

even (tangent! with one edge of the indicator

of the top end of the arbor with relation to the

bushing, as shown in view C. If the assembly is out

vertical line of suspension. The resulting ec-

centricity between the black indicator disc, which

of balance beyond its allowable balance tolerance,

moves with the tilt of the arbor, and the indicator

an edge of the black indicator disc will pass under

the edge of the indicator bushing, as shown in view

bushing, which remains in the line of suspension,

reveals the direction and degree of unbalance.

1-33. If an assembly has been properly mounted

NOTE

and the specified sensitivity setting for that

I f the assembly being balanced is

assembly has been observed in accordance with

positioned too high on the balancing arbor,

section IV, operation instructions, an assembly

the system become, unstable, like an in-

perfectly balanced will be indicated by the indicator

verted pendulum. When this condition is

bushing being concentric (perfectly centered)

present, the arbor will remain tilted in

within the back indicator disc, as shown in view A.

whatever direction it is manually pushed.

If the assembly is slightly out of balance, but within

Even though an assembly is in perfect

allowable balance tolerance, the black indicator

balance, no balance indication can be

disc will be slightly eccentric with the indicator

achieved while this condition exists.

bushing (more of the black disc will be visible on

1-38