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Thread: Hub Splines - Aluminum?

  1. #1
    For our vehicle I'm looking into different hub designs.

    The idea is to manufacture a tripod housing/stub axle out of aluminum and connect it to the hub(rotor) part that the brakedisc and wheel is bolted on to.

    Local problems like the tripod eating away in the aluminum tripod housing can be helped with steel inserts.
    Are there other teams out there that have used aluminum stub axles with splines or other interfaces?

  2. #2
    Could you do it? Sure, in theory. Particularly if you take an aluminum part and have it properly toleranced, hard coated, cleaned, and well taken care of... can do a lot of things.

    Now think about all who is going to be banging and wrenching on this car. How well is it maintained? What's the general attention to detail?

    The position you most certainly don't to be in, is having an aluminum wheel galled and stuck on an aluminum hub, and pretty much no way of getting it off. Bending and yielding 1/2" bolts trying to craft up wheel pullers. At 2am. With a track day the next morning.

    Ask me how I know...

    Valid exercise worth considering. It's one I went through... ultimately decided to go away from the billet aluminum hubs we had been doing for several years and go with a billet steel design - which was smaller, equal weight or lighter, cheaper, easier to manufacture, AND more durable / reliable!

  3. #3
    Senior Member
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    Muldert,

    In general, I agree with exFSAE that steel is better.

    However, as an educational exercise you might want to look up the tripod CVs used on early Citroen DSs (~1960). These had aluminium housings with C-shaped steel liners for the rollers. They are generally considered superior (longer lasting, etc.) to the later all-steel tripod housings. These would be too big for FSAE, and were inboard so no wheel bearings, etc., but are interesting from the "what actually works" point of view.

    Z

  4. #4
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    On Z's example:

    That is exactly the style of the hubs that UNSW@ADFA uses. Al hubs with wirecut C shaped hardened steel inserts that are press fit into machined holes for the tripod to run in. That hub has been running for almost three years now over 4 competitions and there has not been a problem with them.

    If you have a look through the FSAE-A photos from 2009 onwards you should be able to see some examples of our setup.
    Matthew Chapman

    ADFA Racing
    UNSW@ADFA
    2006-2011

  5. #5
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    Our team is running aluminum hubs with steel inserts for years. Works fine. The first car with this design was the 08 car and they still work.
    The problem is how to manufacture the steel inserts. But I won't tell you all the secrets .
    Rennteam Uni Stuttgart
    2008: Seat and Bodywork
    2009: Team captain

    GreenTeam Uni Stuttgart
    2010: Seat and Bodywork / Lamination whore

    Formula Student Austria
    2012: Operative Team

  6. #6
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    Cole,

    UWA ran Al hubs with steel inserts as discussed while I was a student there. They can be quite difficult to machine, but I wouldn't bother machining them now. Try and find a local source that has EDM capabilities. That way you can have the steel inserts cut from incredibly hard steel with no more difficulty than any other type of conductive material. Also not very expensive.

    Kev

  7. #7
    Thanks everybody for the quick replies!

    Im not that worried about the tri-pod housings.
    Steel inserts inspired by the taylor racing tri-pod housings: http://www.taylor-race.com/images/ATP2BANNER.JPG. These will suffice imho.

    We have the opportunity to produce everything out of 7075 and also the proper facilities.
    What worries me is; the splines and the thread of the stub axle in Al. I can hardly find info on splined axles in Al.

    It's interesting that the replies are so varied on this subject.

  8. #8


    Not strictly the same as what you asked, but i believe wisconsin use ali stubs between the dif and their tripods (which mesh with a housing which is iternal to their halfshafts, which also look to be ali. not sure if there are steel inserts in there but i imagine so?)

    I believe they're faily approachable.
    Electronics Warwick Racing 11' Alumni

  9. #9
    Those axles are actually a prototype of carbon fiber axles that we are producing now. The aluminum splines have worked with no failures to date. That being said, they must be closely inspected after any long period of driving just to make sure no major deformations have occurred.

    I would like to note something that we discovered in running these axles with then UW team. If you can see in that pic, the actual CV joints in the carbon tubes were aluminum at this point. Even with hard coat anodizing and using 7075, the balls from the CV's ended up deforming the aluminum quite a bit in a fairly short time. Therefore we have switched to steel CV housings. We did try using steel inserts on these CV's but had a lot of trouble getting them to stay in. Another interesting concept we tried was using ceramic tracks in aluminum housings, but finish machining them was pretty much impossible with CNC's we have in our shop.
    Dan Lentsch
    RCV Performance Products
    815-312-5705
    RCVFSAE@gmail.com

  10. #10
    Originally posted by exFSAE:
    Could you do it? Sure, in theory. Particularly if you take an aluminum part and have it properly toleranced, hard coated, cleaned, and well taken care of... can do a lot of things.

    Now think about all who is going to be banging and wrenching on this car. How well is it maintained? What's the general attention to detail?

    Ask me how I know...

    Valid exercise worth considering. It's one I went through... ultimately decided to go away from the billet aluminum hubs we had been doing for several years and go with a billet steel design - which was smaller, equal weight or lighter, cheaper, easier to manufacture, AND more durable / reliable!
    exFSAE,

    Currently we have a steel stub/CV with a polygon connection to an Al hub. And the stub runs through the hub and a castle nut keeps them together. I want to switch to a steel hub, so it is more durable, and either have a polygon or maybe a sinusoidal spline connection to the stub. But I'm not sure how to keep them together while keeping about the same weight and was wondering how you did that?

    The position you most certainly don't to be in, is having an aluminum wheel galled and stuck on an aluminum hub, and pretty much no way of getting it off. Bending and yielding 1/2" bolts trying to craft up wheel pullers. At 2am. With a track day the next morning.

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