Page 238 - Improving Machinery Reliability
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Machinery Reliability Audits and Reviews 209
LE
A
CONTACT POINT
Figure 3-86. Shift in contact point experienced by gear-type coupling.
and a misalignment angle ~1 = 0.057' (approximately 0.001 inhn parallel offset), we
calculate
M, = (193,000) (0.3) = 57,900 lb - in
M, = (193,000) (sin 0.057) = 193 lb - in
MT,,,~! = J(27,878)2 + (57,900 + 193)* = 64,435 lb - in
This moment is fixed relative to the actual angular misalignment a, and is seen by
the shaft as a rotating bending moment at a once-per-revolution frequency.
The contoured diaphragm coupling causes two bending moments:
Moment caused by angular misalignment which results in bending the diaphragm
In this expression, kB equals the angular spring rate of the diaphragm (lb-
iddegree); a is the misalignment angle. This moment acts in the plane of angular
misalignment, as did M, in the gear-coupling analysis.
Moment caused by turning torque through a misalignment angle a. It can be
expressed as
MT = T sin a
The total moment is now
