Spline Misalignment

[bcats4life]

I am working on a linkage system that has a relatively large amount of misalignment during operation due to thermals.

I am planning to use a spline shaft in this linkage system. Does anyone know how much misalignment involute crowned splines can withstand (I'm sure there are variables that go into this)? Any references that you have would also be very useful.

I believe that involute crowned splines allow the most amount of misalignment, please correct me if I am wrong.

Thank you!

 

[tbuelna]

bcats4life,

The misalignment capability of a crowned spline depends upon the crown radius, spline fit class, length of the splined shaft, and spline axial engagement length. Its angular misalignment capability may be a fraction of a degree or several degrees.

A crowned spline will also have significantly reduced torque capacity, due to its localized contact area. Also, a crowned spline must have the proper rotational degrees of freedom at the opposite end of its shaft.

Sometimes, crowned spline joints are given a small degree of intentional mis-alignment. This causes a "wiping" motion at the contact point which helps to normalize wear.

Hope that helps.
Terry

 

[bcats4life]

Thanks Terry.
Do you know of any books or other references (potentially a website) that describe how to calculate the amount of misalignment a crown spline can withstand?

 

[bcats4life]

Does anyone have information on the design of crown splines and the amount of misalignment they can withstand. I am designing a system that likely will need to withstand a total of 8 degrees misalignment and am unsure if a crown spline would be applicable. I have been unsuccessful in finding a website or book that goes into this detail. Any help would be appreciated.

Thanks!

 

[MikeHalloran]

The level of relative silence here suggests two things:

1. In general, crowned splines are not a good idea, because of the limitations that have already been mentioned, and probably a few more. They're rare enough that no one sells them from stock, so there's no cash flow for spoonfeeding you with a website or a niche market book.

2. You haven't told us diddly squat about your system, so we can't offer help on your particular application.



Mike Halloran
Pembroke Pines, FL, USA

 

[gearcutter]

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

 

[tbuelna]

MikeHalloran,

There's no problem with crowned splines, as long as they are designed and operated correctly.

The output shafts of turboshaft engines commonly use crowned splines to allow for small mounting misalignments between the engine and gearbox. These are very high performance and critical applications.

I have also seen crowned splines used in the actuation system for the Space Shuttle payload bay door drive system. The crowned drive shaft splines are necessary to accommodate the high thermal distortions the shuttle structure experiences in orbit.

Having said that, I don't think a crowned spline should be considered for the shaft mis-alignments of 8 degrees that bcats4life requires. Something like a universal joint or CV joint would be more appropriate.

Regards,
Terry