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Thread: Rod end Bearings

  1. #21
    I don't mind that there may be a better way to do the job. Saying that it doesn't work though and is no good is where I have trouble when there are working examples.

    I'm leaning toward rod ends inboard for alignment on my project and ball joints wheelside, but I have Miata uprights and the ball joints for the miata are a pain. The lower is an odd shape for a-arm attachment and the upper is an integral part of the stock a-arm. They're also different size mounts top and bottom in the upright so I can't just buy a handful of lowers to do all four positions. I'm having a hard time finding substitutes because I can't find published dimensions on the taper bores of other makes. Four rod ends might make life easier although I agree that I could maybe do better.

    My car is also not an FSAE, but more like a roadgoing Formula 1000 car. I don't much care if people turn up their noses as long as nothing breaks going into the turn. How I get there I'm not sure, but I thought I'd post something I saw while doing research on the problem.

  2. #22
    I see where Kevin is coming from and I pretty much agree. It also highlights one of the niggling issues I have with the design event, and it has to do with cost. Cost is no object in teh design event. I included some comments regarding the cost of a component in my chat with a judge during the design event and was told flat out that "there is a separate event for cost, we don't consider that here." A-Arms with rod-ends are cheaper, and easier to make and adjust. However, though they can be sized/overbuilt to maintain reliability, they are still more prone to failure than sphericals. The biggest problem though is simply the fact that they are not the lightest solution. The fact that they are unsprung mass compounds the issue.

    Thus, in a pure motorsport, cost-no-object, design event like SAE, the outboard rod-end is a dead-end.

    But for the rest of world, if its crap and it works, its not crap.
    -Steve Yao
    UNM LoboMotorsports '03-'05
    UWashington Formula SAE '06-'08

  3. #23
    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Jersey Tom:
    I'm just sayin.. I wouldn't expect to see that on a production car. I've always seen horizontal or vertical sphericals wheelside on performance cars (outside of fsae).


    Delft 2004

  4. #24
    I'll be damned.
    Colorado FSAE | '05 - '07
    Goodyear Tire & Rubber | '07 - '11
    NASCAR Engineer | '11 - ??

  5. #25
    In my exp. driver ability is in inverse proportion to vehicle cost.
    Is it possible that the designer intended the upright to break away in an impact with a wall, traffic island, etc so that damage to mountings is mimimised?
    The ability to repair the car for another attack on the scenery is much better than taking it home on the trailer.

  6. #26
    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by James Waltman:
    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Jersey Tom:
    I have to admit those are some amateur looking a-arms on the Atom. </div></BLOCKQUOTE>

    Yeah, those Atom guys are hacks. Right, Jack? </div></BLOCKQUOTE>

    you will have to ask the british why rod ends on the corners is good idea...
    College dropout extraordinaire
    (formerly WWU Rev-Hone Racing)

  7. #27
    look at the Atom, not even in double shear!!
    The innocent shall suffer. Bigtime.

    Georgia Southern Alumni

  8. #28
    Rod ends can work JUST FINE if you size them appropriately.

    Everybody always talks about the weight savings of going to sphericals. Well, how much is it? Its negligible if you maintain the replaceablity of the bearing. That means retaining the spherical bearing with a snap ring.

    If your goal is to make design semi's then you better have sphericals...but dont waste the effort unless you at least have an understanding of every system in your car and know why everything is how it is. In all honesty, I think designing your car with the thought of trying to make design semi's is stupid.

    Design your car as YOU think is best! If the judges dont like your rod ends...well I guess you're not going to make design semi's. I guarantee you learned more than someone who designed based on what he/she heard the judges like.
    Rutgers Formula Racing 04,05, 06

  9. #29
    Sphericals are considerably cheaper to implement, at least for us.
    Colorado FSAE | '05 - '07
    Goodyear Tire & Rubber | '07 - '11
    NASCAR Engineer | '11 - ??

  10. #30
    Even if you do go with sphericals, it's no guarantee of design semis. Let's say you can justify the weight savings, and it amounts to something measurable when you consider all your suspension joints, I wouldn't be surprised if a judge asks "What about adjustability?".

    Basically, what you need to do is show a clear progression of your concept of how your way of making a certain component is best to achieve your overall goal.

    For instance, if your overall design goal is "design a car with maximum adjustability so the average weekend autocrosser can tune the car for the track conditions", then do rod-ends everywhere and justify it. If your overall design goal is "max weight savings so that we have X performance characteristics", then go with sphericals and justify that.

    In either case, make sure your design direction is perfectly aligned with your goal. For instance, if you put rod-ends everywhere, but to adjust camber you need to remove the outboard bolt, twist the rod-end a few turns then re-assemble with a new lock nut, this is no good. You'll likely get "well if the goal was adjustability, why do i need to work so hard to change one parameter". Likewise, if you design for max weight savings as a goal, make sure there are no obvious ways that will save more weight over the design you have, or you'll get called on it. If there are, have a damn good reason why you didn't do it.

    At least that's my way of looking at it.

    Matt Gignac
    McGill Racing Team

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