I'm a student, trying to work a Holzer table for a crankshaft to derive critical speeds from theory, to check on observations. In the table examples I have seen, rotational stiffness is quoted in Newton-meters/radian. I've derived that stiffness using Ker Wilson's formulae for Le/DE^4, and the expression Stiffness = Pi/32 x (1/(Le/De^4) x Shear modulus.

I'm using a value for shear modulus of the material (steel) of 76 GigaPascals, Newtons/square meter. The result should be in Newton-meters/radian. But the stiffnesses I get differ from those I see used in examples, by orders of magnitude!

Am I using the correct value and unit for shear modulus? Thanks, John