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Thread: Tie rod connected to jacking point

  1. #1

    Tie rod connected to jacking point

    I would like to ask what do you think about our solution for tie rod handle- whether it meets the rules or not.
    We want to mount our at the ends of the jacking point. JP is connected to the frame by two tubes on each side (A and B). As you can see, tube A is not "properly triangulated", but it is not the primary structure. Our analysis shows also, that tubes A and B can be smaller than 1"" O.D.
    Generally, I don't see anything contrary to the rules, but as we know- this is always the judge who tells whether it is ok or not.

    Best regards

    Bez tytułu.jpg

  2. #2
    One of the main concerns for the inner tie rod point is to be mounted on a stiff place on the frame, especially for the rear axle where any toe compliance will be detrimental to car performance. Now, your structure looks sufficiently rigid to me and no, I don't think you'll have any problem with the rules. However you ought to perform your own analysis and calculate the expected deformations(pro tip: include the bushings or "tie rod handles" in it).

  3. #3
    Rules should be fine. It's up to you to figure out if it's structurally fine. What are your tie rod loads? Do you know both your mechanical trail and your pneumatic trail? What's your target max deflection?
    Any views or opinions expressed by me may in no way reflect those of Kettering University, it's students and administrators, or our sponsors.

  4. #4
    Senior Member
    Join Date
    Mar 2005
    Modena, Italy
    The thing to remember in the toe compliance story on a racecar is that, regardless of the name, the toe link is no more important at controlling toe compliance than the either the control arms or the upright.

    Your layout looks to have a very vertical "kingpin axis" roughly lined up with the wheel centre (longitudinally at least). In this case the toe link could very well be seeing a tiny force compared to the control arms which would make the structure of its attachment point and the link itself less critical in the toe compliance story.

    However, the lateral leg of of the lower arm looks like it would be taking the majority of the cornering force so it will contribute to the majority of the cornering toe compliance. So if you want to control lateral compliance steer - concentrate on the lower control arms.

    The third main contributor is the stiffness of the upright in bending. The fact that toe link attaches largely in a plane with the lower arm means that the bending compliance of the upright won't impose much of a toe angle so you'd only really need to keep an eye on the relative stiffness' of the attachment points.

    In short, you need to know the distribution of the link forces before you can make any judgements on the toe compliance. Don't concentrate only on the toe link either. It's called the toe link only because it sets the static toe.

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