Crowned Spline Drive 1

[59standard]

I am considering crowned splines for a drive system with a fixed angular offset in the range 2-5 degrees (depending on other design factors). I'm aware that crowning is more often used for tolerance/deflection induced misalignments on nominally in-line shafts, but the package space we have is extremely tight and precludes UJ's , CV joints etc. Lubrication will be fully immersed oil bath.
My questions are:
-Are crowned splines covered in any of the ANSI or DIN standards or others out there ?
-Is there any published data on crowned spline stress calculation, FE analysis, and/or test experience ?
The only reference I have so far is the formula in Machinery's handbook, but I would like something a bit more up to date to cross reference.

 

[tbuelna]

59standard,

Can't provide any good text references, but....

A crowned (external) spline can be analyzed for torque capacity similar to any other spline, except that the tooth contact is more of a point load condition rather than the conformal contact of a straight spline. The individual tooth contact condition can be considered a sphere on a concave surface, with the sphere having the crown radius and the concave surface having the tooth profile radius at the pitch line.

The contact condition will be partially boundary and partially hydrodynamic during operation if the spline is in an oil bath. The relative shaft angular motion at the spline interface can actually be beneficial with your crowned spline, since it helps to encourage a hydrodynamic oil film at the contact zone.

A case hardened spline tooth would be very beneficial with your crowned spline, since contact stress is much more of an issue than tooth root shear strength will be. A non-linear FEA contact analysis can be done fairly easily on a sector of the crowned spline joint. The teeth should load share fairly well with a good quality spline.

Good luck.
Terry

 

[gearcutter]

This a response I gave to a similar post last year:

Crowned Spline Couplings or Gear Couplings or Gearflex Couplings or Muff Couplings or Barrelled Spline Couplings, they are all the same thing, are quite common in the steel making and mining industries or anywhere else requiring the transmission of high torque between non-aligned shafts. Just about any steel rolling mill line will have these couplings at every stand. Any motor/gearbox interface I've ever seen in the Longwall Mining industry will use these couplings. I've seen transmissions as large as 2500KW using them.

Amongst all the flexible type couplings available, they are unique as they have the ability to transmit the greatest loads and be the most reliable.

Contrary to popular belief; it is the backlash between mating members that allows for the misalignment and not the tooth profile as some gear couplings are not crowned.

I have seen these couplings run successfully with as much as 5 degrees axial misalignment.

If you take the time to look, there is a wealth of information on the internet which I've found over the years.

Books to get hold of are:
Couplings And Joints (design, selection, application) - J. Mancuso (Marcel Dekker, 1995)
Flexible Couplings (their design, selection and use) – Michael M. Calistrat (Caroline Publishing, 1994)

Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

http://www.aussieweb.com.au/email.aspx?id=1194181