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Thread: Steering Rack Location-Opinions Needed Please

  1. #11
    That's interesting. From the data I've seen I'd say that the typical FSAE car has enough compliance to make me worry about how it's going to influence my cars performance, but to each their own.

  2. #12
    Most teams don't have access to a K&C rig so the best thing they can do is shoot for difficult stiffness goals on their uprights, good load paths into the chassis, and avoid these "dallara style" steering rack joints. 90% of the teams use pretty much identical spherical bearings/rod ends and similar sized steel control arms so we're all going to be in the ballpark of each other in terms of compliance.

    That still doesn't really hit the topic at hand though, did you avoid low rear steer on your car because the compliance was so bad you worried about inducing oversteer in every corner?
    Ryan M.

  3. #13
    You'd be surprised at who can get access to a K&C rig.

    I agree with you on the main point of your last post, that there's an upper limit as to what is achievable for the typical team. But from the K&C data that I have on multiple cars(from several teams) I think it's fair enough to say that many teams are either not setting aggressive enough stiffness targets or achieving the targets that they set. There's actually about an order of magnitude difference between a podium finisher and a middle of the pack car.

    Maybe I wasn't clear in my last post. All I'm saying is that if you want to use a low rear steer arrangement, that's perfectly fine as long as you understand the other implications it will have. Even if the compliance doesn't dominate your response (in my case it does not) it is more than likely a non-negligible effect.

  4. #14
    So what precautions would be need to be taken if we decide to go with a low rear steer arrangement? What harmful effects are there that should be tried to be designed around?

  5. #15
    Senior Member
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    The two cv joints need to be at the same in-plane angle along with a phase angle on the shaft for a CV effect. OR, use a Cardan for one joint and a CV joint or an approximate CV joint in the other. These parts are already available for other similar applications. Consider a modified ATV front drive shaft for example...

    Another option to consider is a deliberate mis-phasing of the steering shaft in order to produce a non-linear overall steer ratio. That could mean quick on-center, slow off-center, or just the opposite. The BIG question to answer is which way do you want it. But that's another chapter...

  6. #16
    On a similar topic, where do all of you purchase your steering racks?

  7. #17
    Can't you just flip the pinion/rack arrangement to change the steering direction?
    Wesley
    OU Sooner Racing Team Alum '09

    connecting-rods.blogspot.com

  8. #18
    Yes.
    Ryan M.

  9. #19
    After dropping an extra steering rack that we had laying around our shop into position where it could attach on the front side of the upright, it seems that it gets awfully close to the pedals and would obstruct your ability to drive...after looking through pictures we have from VIR I don't see too many teams going front low, saw a good amount with rear low steering though

  10. #20
    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by LafayetteFSAE:
    Would you be able to tell me the rule # that pertains to the steering rack?

    Also, can you explain more about how our steering inputs aren't linear on last years car?

    Another thing I'm concerned about is if the rack is mounted on the floor and attaches to the back side of the upright(so a standard rack w/out modification would work), how can you get the steering shaft down at such a steep angle, I feel that a single u joint would lock up due to the large angle </div></BLOCKQUOTE>


    I don't mean to be rude but if you don't know about the template rule then you need to re-read your rules. I am not looking up the rule number because its just silly. Its like looking up the restrictor sizes we all know what they are we dont need the rule number. Just search around the forums about the template rule. I think Pat Clark mentions that the rule was created to force a lower placement of the rack. But if you are looking for a rule that states "the rack must be here" there isn't one. You can go with a top mount still but the template rule was created to guide you away from it.

    For the linearity of your steering input. I am a nearly dyslectic powertrain guy so i apologize for my poor job at explaining it. Basically the angle from your rack to you attachment on the upright is causing it. That angle is going to change as you turn the wheel. Which will change the rate of your steering angle input to actual wheel angle. I think thinks a poor explanation i apologize.

    I don't mean to call you baby ugly either. We have done the same, we even did it last year when we were aware of it but it was minimal and couldn't be avoided with the c-factors available. Sure we could of made our own rack but i big portion of FSAE is weighing time to gain and we found it not to be worth it.

    Also they are correct you can flip the rack and that would work. Didn't think about that and because you are on the front side of the upright flipping it wouldn't make the the steering shaft angle isn't going to be any worse then putting it on the backside. Good luck with your small drivers though this might be just as bad in ergonomics as the top mount but then again it could work perfect. I would suggest this if you can pull it off.

    I am sure my roommates/teammates are giggling over the fact that i am commenting on suspensions threads.

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