Spline Strength

[Dbolejack]

I need to calculate the torque capacity of a spline. I am looking at a 30 degree involute. What are the formulas to calculate the torque capacity of a spline?

 

[desertfox]

Hi Dbolejack

Try the machinery's handbook.

regards

desertfox

 

[CoryPad]

As a first approximation, you can use a simple formula for this by using the material's shear strength and the spline geometry:

T = n [·] [τ] [·] w [·] l [·] d/2

where

T = torque
n = number of teeth
[τ] = material shear strength
w = tooth width
l = tooth length
d = pitch diameter



Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[tbuelna]

Dbolejack,

Designing a spline is not as simple as it seems. As CoryPad says, you can look at shear through the teeth to get a very rough estimate of where a spline may ultimately fail. But that may not be a good spline design for your application.

The additional factors you must consider are what type of life do you require? Are the loads reversing? Is the spline lubricated? Does the spline experience axial movement or misalignment? Is the load distributed evenly along the length of the spline's engagement? What tolerance class of spline is economical for you to utilize?

All of these variables will have an impact on the material and heat treat selection, as well as any load factors you may need to apply to your analysis to guarantee satisfactory performance from your spline.