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Thread: Leaf Springs

  1. #1

    Leaf Springs

    I know you're all recoiling in disgust at the title of this thread, but I digress.

    So I've been called out before for my pie in the sky thinking on these forums a few times. My opinions on how a FSAE car should be built range from the extreme Keep It Simple, Stupid to the opposite extremely labor intensive and expensive, usually to problems that don't actually end up existing. This is on the extreme KISS side.

    My idea is instead of using shocks and springs, what about pushrod actuated leaf springs. I'm not trying to come off as a complete idiot, but Corvettes use leaf springs, and so do the blade runners in the Paralympics. Since a lot of teams have their suspension mounted inboard, sort of near the centerline of the car; why not have carbon fiber blades in there, weighing less and taking up less space? If you had a football shape or an elliptical shape mounted longitudinally, it would take up almost no room and weigh nothing.

    I'm sure there are a lot of kinematics I don't understand that will affect all of this, but leaf springs worked well for Ben-Hurr and Bullitt. Also, while it would be less tunable,the tuning would be built in, yet they would not be hard to manufacture, and with how simple I'm imagining this setup, replacing the blades for tuning purposes wouldn't be a huge loss.

    And to all those guys who love the brown cart ideas, what's simpler than leaf springs?

  2. #2
    Senior Member
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    Well I am not recoiling. Nice pun, by the way.
    A leaf spring combines springing medium with wheel constraint in one direction - one part, two functions. Nice principle.
    I'm not so sure about pushrod actuation. Why complicate things?
    Keep on imagining, keep on creating, keep up the good work!
    Cheers,
    Geoff
    Geoff Pearson

    RMIT FSAE 02-04
    Monash FSAE 05
    RMIT FSAE 06-07

    Design it. Build it. Break it.

  3. #3
    I just said pushrod for packaging reasons. Unless you did it with pushrods or like a Corvette, it would look weird have them over the wishbones.

    Also, I wasn't even thinking of the pun.

  4. #4
    I believe that UWA's lower flexures as used on 2008-2009 (don't really remember the year) were the best way to combine springing (except in roll-mode) with wheel constraint. Think of a transverse composite leafspring replacing springs and lower a-arms...

  5. #5
    Quote Originally Posted by mech5496 View Post
    I believe that UWA's lower flexures as used on 2008-2009 (don't really remember the year) were the best way to combine springing (except in roll-mode) with wheel constraint. Think of a transverse composite leafspring replacing springs and lower a-arms...
    GM ran this setup for decades on the rear suspension of the Corvette.

  6. #6
    Quote Originally Posted by Zac C View Post
    GM ran this setup for decades on the rear suspension of the Corvette.

    Bill Cobb may chime in about this, but I was partially led to believe that this was to help keep the trunk space large enough to be useful, like, bag of golf clubs useful.

    It definitely does have potential in an FSAE car though, it could probably be implemented very well.
    _______________________________________

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  7. #7
    Google "Smokey Yunick Capsule Car". It was a car that Smokey built for Indy in the sixties. It used a transverse leafspring as the front upper A-arms.

  8. #8
    Quote Originally Posted by Drew Price View Post
    Bill Cobb may chime in about this, but I was partially led to believe that this was to help keep the trunk space large enough to be useful, like, bag of golf clubs useful.

    It definitely does have potential in an FSAE car though, it could probably be implemented very well.
    Corvettes didn't really have a trunk between 1963 and 1997. There's just some space behind the seats where you can stash things. Using a leaf spring vs a traditional lower control arm doesn't free up that much more real estate. It makes packaging a full size spare a bit easier, but I would think you could the same thing with dual a-arms (see 1984 corvette).

  9. #9
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    Quote Originally Posted by Zac C View Post
    Corvettes ...
    The original Corvette independent rear suspension uses the halfshafts (fixed length on left and right sides) as the upper control arms. The transverse leaf spring was connected to the hubs through tension links on each end of the spring. I believe the wikipedia article is correct, http://en.wikipedia.org/wiki/Corvette_leaf_spring
    > In the C2 and subsequent generations, a leaf spring is mounted transversely in the chassis and used in conjunction with several independent suspension designs. Common to these post-C1 Corvettes, the leaf acts only as a spring, and not a suspension arm or a link. Because it is not required to stabilize the wheels, the leaf functions in much the same manner as a coil spring.

    There are suspensions where a transverse leaf spring is used as a control arm, check the photo in the middle of this article,
    http://www.velocetoday.com/mike-hawt...se-mccluggage/
    Caption under the photo is, "Again at Charterhall in Scotland, Mike wins the Formula Libre event with his Cooper-Bristol ahead of Denis Poore's Alfa Romeo."

  10. #10
    I like the idea of using a leafspring in place of the lower A-Arms both front and rear, as long as there are no camber compliance issues. It seems much more integrated, using one part for two jobs, both locating the wheels and for springing. If I were to do it though, I would do it pretty much like UWA's lower 1-piece cf "flexures"....

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