SAE joint selection graph

GRAPH F

prop-page7-1

CRITICAL SPEEDS

All cardan shafts have a critical speed at which they become rotationally unstable.

Therefore the following calculations have to be applied to ensure safe operation of the system.

METRIC

ηMAX = 1.21x108 x√D2 + d2
L2
η = CRITICAL R.P.M.
D = TUBE OUTSIDE DIA (mm)
d = TUBE INSIDE DIA (mm)
L = JOINT CENTRES LENGTH (mm)

IMPERIAL

ηMAX = 4.8x106 x √D2 + d2
L2
η = CRITICAL R.P.M.
D = TUBE OUTSIDE DIA (INS)
d = TUBE INSIDE DIA (INS)
L = JOINT CENTRES LENGTH (INS)

The max safe operating speed should include a safety factor as below.

AUTOMOTIVE APPLICATIONS

Max safe R.P.M. = η MAX x 0.7

INDUSTRIAL APPLICATIONS

Max safe R.P.M. = η MAX x 0.65

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