Driveline Spline Alignment Methods

[AHilditch]

Hi there,

I have currently run into some issues with completely destroying male drive shaft splines and causing driveline failure. There was tooth shearing on the male spline and obvious wear on the female. After analyzing our spline design, it was determined that a better spline material and hardening will be used in the redesign. Though material was a factor in the failure, misalignment of the splines was the leading culprit. So now I am looking for methods of spline alignment, but I am unsure of my options. I am throwing around the idea of alignment pins of some kind, but I am very unfamiliar with this situation. I would appreciate any and all that can at least point me in the right direction!

Thank you!
Ahilditch

 

[MiketheEngineer]

Universal Joints??

 

[AHilditch]

yes, universal joints.

 

[tbuelna]

AHilditch,

You didn't describe the particulars of your spline joint geometry. Some splines, such as side fit splines, are not designed to provide radial positioning. The only types of splines that would provide accurate radial positioning are root fit or major diameter fit splines.

Tooth shear failures or flank fretting failures can be caused by many things, including misalignment, lack of load sharing between teeth due to index errors, edge loading due to lead errors or torsional wind-up, etc.

When adding alignment features to your spline joint, whether it's using root/major diameter fits or adding pilot diameters, make sure that your spline is not geometrically overconstrained. Another thing to check is the L/D aspect ratio of your spline tooth engagement. If the engaged L/D is over 1.0 and the torsional stiffness of the shafts is low, you may need to use some lead correction to compensate for torsional wind-up.

Good luck.
Terry

 

[AHilditch]

Terry,

I'm sorry for the lack of information, I am new to the intricacies of splines and am not sure what info I need. I'm working on bettering my knowledge base.

Your post it very helpful and it's giving me terms to start reading up on. I have a Side fit, pitch diameter spline joint. I am weighing the benefits of changing to a Major Diameter fit.

Thank you for your help.

 

[flash3780]

RWD Automobile driveshafts use at least two universal joints to compensate for the misalignment of the front and rear splines. On especially long driveshafts, a third universal joint and a central carrier bearing is used.

FWD vehicles often use CV-axles with Rzeppa joints (or similar) on the outermost joint to smoothly transfer power to the splines in the wheel bearing/hub assembly dispite the larger angular misalignments that FWD axles tend to experience.

Depending on your specific application, McMaster-Carr might have some off-the-shelf universal joint assemblies that suit you. Good luck.

//signed//
Christopher K. Hubley
Mechanical Engineer
Sunpower Incorporated
Athens, Ohio
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