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Thread: Negative consequences of very large steering work product in a passenger car?

  1. #11
    A few more points. [You can tell it is getting close to competition because I'm getting all pumped...]

    Despite our absurdly high aero loads, I've never really had trouble steering our cars on really SCCA autocross courses. And were talking +- 2.75 g. Obviously it comes down to steering power, not effort. The worst thing in my opinion is the minimum sized slaloms. I believe they are 25ft. If your car is understeering through them it will make for a really long day. The number one thing you can do to help reduce steer effort is to free up the car through slaloms. You want it loose enough that it feels like the car will drive itself through the slaloms. This needs to be balanced with high speed slaloms too, but this is why having adjustable dampers can be a huge help.

    Mike

  2. #12
    Senior Member
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    Adambomb,

    "If we can [have light steering] with a steel frame car with 13" tires and SLA suspension, it should be a piece of cake with a brown go-cart!"

    Yes, I am quite sure that a brown go-kart with the right steer-axis geometry (ie. close to "centrepoint") could have very light manual steering, even with only +/- 45 degrees available at the steering-wheel. After all, normal go-karts with massive Castor + Offset (which demand that the driver physically lifts the inner-rear-wheel at each corner) can manage with this sort of quick steering ratio.

    My main concern is what happens when the aero-undertray is added... I have no doubts that drive-on-the-ceiling, 3G-levels of downforce are possible on the Skid-Pad. But this means that without active-aero (that bleeds off DF) the car will literally have over a TON of downforce at the higher FSAE speeds. So now steering loads may become a problem (though not certain).

    Furthermore, if, say, active-aero is fitted to keep downforce = weight, then the car should now be travelling 40% faster than normally. The slalom cones are now going past rather quickly. With even more downforce (implying 4,5,6+G?? cornering) the slalom becomes a blur.

    Bottom line is that I reckon this high-G performance is possible, but on Autocross style courses things like "steering feel" are not really important. All that the driver needs, and has time for, is to make small, fast, hand movements (eg. see "side-stick" below), and then adjust according to subsequent car behaviour.
    ~~~~~o0o~~~~~

    Mike,

    "-Design steering with highest steer ratio you can get away with...
    -Reduction of friction in steering system very important
    -Structurally stiff suspension important,
    ...
    -Power steering a realistic possibility, ...
    -Higher tire pressures can help with reduction of steer effort."


    I just wanted to restress some of your above points. Any "Steering/Suspension Guys" currently in FSAE should be particularly concerned with reduction of friction, and increase of stiffness.
    ~~~~~o0o~~~~~

    Just as a BTW, my interest in side-stick steering came from an early involvement in "Pedal Car Racing". (<- It seems that this is still happening these days, although in my day (mid-1970s) all the races were 6 hours long! Oh, yes, ... you kids sure have it easy these days... )

    These Pedal Cars originally had normal steering-wheels, but the benefit of quick driver changes soon led to the almost universal adoption of side-stick steering. The cars+driver are significantly lighter than in FSAE, the speeds are similar (often fast, downhill sections, with right-angle corner at bottom), the cornering Gs are less (but enough to quickly shred the skinny tyres), but overall the side-stick steering, with ~90 degrees lock-to-lock (or less), works very well.

    Z

    PS. The Tech Rules in that Pedal Car link would be a good example for a "new, improved" FSAE Rules set.

  3. #13
    There are a interesting article on this available on the FSG website: http://www.formulastudent.de/a...ves-box-of-tricks/1/

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