Rotational Capacity
A Smalley Retaining Ring, operating on a rotating shaft, can be limited by centrifugal forces. Failure may occur when these centrifugal forces are great enough to lift the ring from the groove. The formula below calculates the RPM at which the force holding the ring tight on the groove (cling) becomes zero.
Maximum RPM
Formula
Table 3
where:
N = Maximum allowable rpm (rpm)
E = Modulus of elasticity (psi)
I = Moment of inertia = (t x b3)/12 (in4)
9 = Gravitational acceleration (in/sec2),386.4 in/sec2
V = Cling/2 = (DG - DI ) /2 (in)
DG= Groove diameter (in)
DI = Free inside diameter (in)
Y = Multiple turn factor, Table 3.
n = Number of turns
γ = Material density (Ibs/in3), (assume .283 Ibs/in3)
A = Cross sectional area = (t x b) - (.12)t2(in2)
t = Material thickness (in)
b = Radial wall (in)
RM= Mean free radius = (DI + b)/2 (in)
Example: WSM-150
V= (DG-DI) 2=(1.406-1.390) /2=.008 in.'
I=(t x b3) 12 = (.024 x .1183) /12 = 3.29 x 10-6 in.4
A = (t x b) - (.12)t2 = (.024 x .118) - .12(.024)2= .00276 in.2
RM= (DI + b) /2 = (1.390 + .118) /2 = .754 in.
N = 6,539 rpm