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Knight Rider Mythbusters

  1. Jan 1, 2009 #1
    I've seen the episode and understand what is going on....

    What do you suppose would happen with a front wheel drive car? Would it be the same effect?

    I am guessing 4 wheel drive might throw a bit of a monkey wrench into things right? Wouldn't that keep the wheels from any free spinning?
     
  2. jcsd
  3. Jan 1, 2009 #2

    mgb_phys

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    good.

    The mini is front wheel drive, the principle doesn't change - momentum is more important than wheel speed.

    4x4 have a differential to allow front/rear wheels to rotate at different speeds.
    A particularly poor 4x4 drive might be a problem.
     
  4. Jan 1, 2009 #3
    I have a suspicion that there was another episode that I may have missed...with a Mini cooper doing the same thing? I'll have to keep an eye out for that.

    The diff in the 4x4 is what I thought might cause a problem.

    Thanks,
     
  5. Jan 2, 2009 #4

    Ranger Mike

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    a differential is a mechanical device used to transmit engine rotation , having passed through a transmission ( various gearing to multiply engine torque) via a drive shaft
    to the drive wheel of a vehicle. Open Diffs are a series of gears that permit the right rear wheel to drive the car and the left read wheel to rotate in the opposite direction. This is why only one tire leaves a ' patch of rubber' when yo udo a burn out.
    if yo uever yjacked up the rear end of one of these cars and turned one rear wheel, the other wheel will rotate in the opposite direction...

    A limited differental has clutches tha tlock up both wheels when going in a staight line..GM called it Positraction, Chrysler called it Sure grip..etc..the clutches are required so they can unlock the inside wheel when making a turn permitting the outside wheel to drive aroubnd the corner. If you ran a spool ( no diff gears , both axels locked in drive mode) you would spin the car out going around the turn. A 4 x 4 is simply two differentials..one in front and one in the back,,both driven by drive shaft from a transmission via transfer case.. that when actuated will provide drive to all 4 wheels..in my opinion, doubles the weight , parasitic drag and kills MPG, a ral bear to work on and ...a must for soccer moms afraid of that really bad snow storm that happens once every 10 years...oooooo!!!

    i did not see the movie so can not comment on question.
     
  6. Jan 2, 2009 #5
    I knew about the one wheel spinning in the opposite direction when the vehicle is jacked up, but didn't know what it was called, or what the reasoning was. Thanks for the explanation.

    The movie that we were talking about is a mythbusters episode in which they try and do the classic Knight Rider thing when they drive into a moving big rig.



    Thanks again.
     
    Last edited by a moderator: Sep 25, 2014
  7. Jan 2, 2009 #6

    Ranger Mike

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    Happy New year
    IMHO same thing with front wheel car..in fact..it is easier to pull a chain then push it, which makes front wheel drive so much easier to drive...regardless ofRWD or FWD..once the drive wheels transition from road to ramp, you got it made as long as you got sufficent traction...
     
  8. Mar 15, 2010 #7
    i wanna ask this. How come the car doesn't stall, (even not a little insatability movement occurs) because it's in high gear and going with 5 mph when it enters the truck, they didn't mention that they press clutch and put the gear in neutral. What do you say?
     
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