HUB SIZING
Fenner Drives Keyless Bushings transmit torque and other loads by means of mechanical interference
generated by pressure exerted on both the shaft and mounted component hub. Therefore, consideration
must be given to the amount of hub material (wall thickness) required to prevent permanent expansion (i.e.,
yielding).
The following information is provided to assist you in determining the required hub diameter DN for any
keyless bushing application.
Following standard industry practice, the criterion σti < Sy is used to determine DN as follows:
DN = D [{Sy + (Ph × C)} / { Sy - (Ph × C)}]0.5
where:
D = hub bore diameter (from product specifications)
Ph = contact pressure applied to hub bore (from product specifications)
Sy = yield strength of hub material and
C = Stress Reduction Factor which assumes the value of 1.0, 0.8 or 0.6 depending upon the relationship of
your actual hub width Hw to the contact length L of the keyless bushing selected. Use the illustrations on
the right to determine C for your application.
i = inside of cylinder
o = outside of cylinder
ν = Poisson’s ratio ,for steel: 0.29
E = modulus of elasticity, for steel: 3.0 × 10 7 psi (2.07 × 105 N/mm2)
P= pressure
τ = torsional hub stress
Q = (di/do)2