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Dynamic vehicle analysis

  1. Feb 23, 2009 #1

    Just needed some help with analysis of vehicle loading in dynamic and static conditions.

    Basically what are the axial and radial loads acting on the axle/wheel in static and dynamic conditions? Accompanying formula would be helpful.

    How would i go about finding out the loads under static and dynamic conditions, that would be in acceleration, braking, cornering etc.
    Also vehicle moving on level ground and inclined plans(% grade is known)

    If you guys have any ideas of books i could refer as well as online links it would be helpful

  2. jcsd
  3. Feb 23, 2009 #2
    This is pie in the ski. There isn't a magic formula you just plug into that gives you these kinds of numbers. It will depend on many parameters. The size and weight of the car, the design of the suspension, the road surface, to name a few.

    I would look for a book in vehicle dynamics from SAE and amazon.
  4. Feb 23, 2009 #3
    All parameter are known, i just wanted to know how i would go about calculating the forces.
  5. Feb 23, 2009 #4
    Again, there is no magic equation that tells you this. You want to seriously answer your question you're going to need a PhD in vehicle dynamics. That's basically the magnitude of what you're asking. What I would do if I were you is look for papers from SAE that people have done and just use those values as a zero order approximation of what you would expect to see.
  6. Feb 23, 2009 #5
    I think you are reading too much in to what he wants. I'm pretty sure everything he wants to know can be found from a FBD with some weight transfer thrown in.

    TO OP: Specify more clearly what you want. I'd suggest you read up on a basic mechanics textbook. something like meriam and kraige - statics.
  7. Mar 1, 2009 #6
    Thanks anyway, i had got pretty much what i wanted, but i wanted a second opinion :P
  8. Mar 1, 2009 #7

    Ranger Mike

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    i respectfull beg to differ..
    emperical answers are available, as in all things...in the mean time..

    Pls see ranger mike post Dec29-08, 12:31 PM post on race car physics in general physics forum

    i wil endeavor to get the requested info ref; axle load, etc..but give me a day..its all in the race car trailer
  9. Mar 4, 2009 #8

    Ranger Mike

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    Ok, here is how we determine the proper springs for each corner of the race car. you asked about loads on each wheel..well here is an example of our old door slammer running on a medium banked asphalt track.
    Stock suspension wit solid rear axle.
    We calculated that tit is under 1.3 Gs in the turn..see other post from Ranger Mike on calculating . Gs
    car weighs 2800 lbs. of 35% of weight will transfer under 1.3 G
    and 75% will be on front end due to engine weight and corner loading

    2800 lbs. X .35% = 980 lbs. transferring or loading tires

    75% of 980 lbs. = 720 front end weight
    divided by three to determine wheel rate ( two front springs and sway bar )
    so we need wheel rate of 240

    Wheel rate = (Length of A-arm divided into inside frame mount point to center of spring mounting point) squared

    times spring rate

    now the hard part
    get out the tape measure and measure bottom front A-arm length
    1. inside frame mount point to center of outside ball joint
    2. distance from inside frame mount point to center of spring mounting point

    stock Chevy A-arm is
    16.5 inch inside frame mount point to BJ and 9 inch from inside frame mount point to center of spring pocket
    assume you have a 1000 lbs. spring
    wheel rate = 9 / 16.5 = .54

    .54 x .54 x 1000 = 290 lbs. spring required to handle weight transferred

    I know this may not answer your question completely but there are a lot a of variables..
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