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Motorcycle vs Car Physics

Discussion in 'Other Off Topic Forum' started by ferrari_kid, Mar 18, 2004.

  1. ferrari_kid

    ferrari_kid Formula Junior

    Jul 5, 2003
    768
    A question for all of you engineering mechanical types out there. Why is it that a motorcycle can take a turn of say, radius 100m, faster than a car can take the same turn? I brought it up with my physics teacher and he went off topic and we discussed why a motorcycle must lean to turn. It was interesting none the less, but didn't answer my question. I assume that it had a lot to do with what was discussed though. We touched on the subject with the torque being created while in a turn and the shorter wheel base of the motorcycle being able to make a sharper turn, but the forces involved weren't clear. Is there someone who could enlighten me?
     
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  3. ATBNM3

    ATBNM3 Formula 3

    Nov 17, 2003
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    Don Jackson II
    Motorcycles have faster acceleration and deceleration cars have faster corner speed.
     
  4. FrostCS

    FrostCS Karting

    Mar 3, 2004
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    Christopher
    Well, I am not exactly an engineer. But I will try to explain to the best of my abilities.
    Generally, a car has 4 factors that relate to the turning radius of the vehicle. Wheelbase, Track, Camber, and Steering angle. (I am not counting weight or body roll for this example, because it's just to be descriptive)

    The longer the wheelbase, the larger the turn, since the turning angle itself will be wider (basically think of making a side of a triangle longer), so the shorter, the sharper the angle.
    Next is the track, the wider the track of the car, the more room it will take to turn, but the more stable it will be in the turn since the center of gravity is lower.
    Third we have Camber, which is the angle of the wheel to the ground, changing the camber on the car will have opposing effects on the turning radius (ie what you do to the front will have opposite effect on the rear). I beleive it was more negative camber on front added oversteer, and positive on back added understeer or vice versa, someone correct me if I am wrong there.
    Last, is steering angle itself, or the angle of the wheels along the ground (direction), which in itself is pretty self explainatory.


    For motorcycles, We can immediately get rid of two of these, camber, and track. Since There is no "fixed" of either of these, the rider leans to change the center of gravity (tighter lean, lower center of gravity, quicker turning). Leaning also changes the Camber, effecting differently as the rider distributes his weight to the back, or the front.
    Wheelbase is still an issue, which is why you see drag bikes, with long swingarms (adds stability, and you lose turning radius).
    Then steering angle again, which is well, self explainitory.
    I hope that helped. (Yea.. I'm a slow typer with bad grammar.)
    CS
     
  5. teak360

    teak360 F1 Veteran
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    Nov 3, 2003
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    The best handling bikes on the market today will get there a$$e$$ handed to them by any decent handling car in a turn. Step up to a Grand Prix bike and a Ferrari F1 car on your huge 100 m radius and the F1 car would absolutely run over the bike if it didn't get out of the way.
     
  6. ATBNM3

    ATBNM3 Formula 3

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    Don Jackson II
    That's my thinking.
     
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  8. ferrari_kid

    ferrari_kid Formula Junior

    Jul 5, 2003
    768
    It came up when looking at the Suzuka track in Japan and the huge 130R turn. I wanted to know how fast MotoGP bikes could take it, knowing it would be slower than an F1 car anyway. I know F1 cars can beat motorcycle on the track, but they are more extreme versions of a car.
     
  9. ART360

    ART360 Guest

    Even though the motorcycles accelerate harder, and brake about the same, the cars seem to turn quicker lap times. An example: Infenion raceway: lap record, AMA Superbike: Matt Maldin: 1:36.2, best cart time 1:33.

    Speaks volumes. Having said that, I'll take the bike ride every time. Your not looking at a video game, make a mistake, take an ambulance ride. Most of the car drivers that I know think motorcycle racers are crazy. Maybe their right.

    Art
     
  10. Texas Forever

    Texas Forever Four Time F1 World Champ
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    Apr 28, 2003
    44,427
    Texas!
    Several points:

    1. Except at very slow speeds, you don't "turn" a motorcycle. You corner by countersteering. To go left, you push on the left grip, this turns the wheel slightly to the right, the motorcycle starts falling, and the rest is history...

    Countersteering is something that even very few bikers understand. But, those who know, also know that countersteering is the perhaps one number safety skill to learn when riding a bike. I have seen guys "hop" their bike sideways at 90+ mph to avoid debris by countersteering.

    2. There is no way that a motorcycle can out brake out or out "G" a modern car. Two oval tires with a patch of maybe 4" compared to four tires with a patch of 16". Ain't gonna happen.

    3. That said, the dumbest move on a motorcycle is to, "lay 'er down." Stupid, stupid, stupid. Even though it is a very small contact patch, modern motorcycles can grip like nobody's business. I always tell people that if you come into a corner too hot, DO NOT STAND THE BIKE UP! This will make the bike go straight, which in a corner is not a good thing. Lean, mo fo, lean.

    Just remember, the shiny side goes up, and the rubber side goes down.

    Dr "Skinny-Tire Biker" Tax


     
  11. teak360

    teak360 F1 Veteran
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    Very few people understand this and it is a very interesting phemomena. The most interesting part is that at low speeds you do the opposite, so in theory there should be a speed in between where you do neither to turn......hmmmm.
     
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  13. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    6,999
    I doubt that it can.

    However, make it 10 meters and the bike can beat the car. At 10 meters the width of the car makes the arc through the corner sharper and thus the car takes the corner with a 12 meter radius while the bike can use a 14 meter radius.
     
  14. ART360

    ART360 Guest

    Dale:

    Laying a bike down is stupid. Dr. Hurt from LA did some studies: .8 G when on the ground. .95 while braking. If you are going to run into something, you'll be going slower if your on the brakes. Most of the time when someone "lays a bike down" they've locked up the front wheel or rear wheel, and fell down on their own, they don't want to admit to that, and they claim it was intentional.

    Art
     
  15. Texas Forever

    Texas Forever Four Time F1 World Champ
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    Apr 28, 2003
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    Texas!
    Back when I used to have the patience to listen to the "Born-Again" Harley types (you known, the guy who rode a Honda 90 during high school and then buys a 800 pound Harley when he turns 50), I used to hear this all the time, i.e., I laid 'er down to avoid crashing. I guess enough beer can make anything sound intelligent. (We have the whole sub culture of doctors, lawyers, and Indian Chiefs in Texas who buy a big Harley and ride from ice house to ice house on the weekend drinking beer at each stop. These are the same guys who don't use the front brake because they're scared of flipping the bike...)

    I used to try to explaing the laws of phyics to them. Didn't work. I used to explain what happens when a sliding bike catches rubber. (It flips up into the air and typically comes down on the rider sliding on the ground.)

    I finally learned my lesson. Namely, I stay as far away from these accidents waiting to happen as I can. I know that this is evolution at work, but I don't want to see the results.

    Dr "When I ride alone, I prefer to ride by myself" Tax




     
  16. teak360

    teak360 F1 Veteran
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    Nov 3, 2003
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    I've heard guys say this too. On big street bikes you can actually lock-up the front tire for an instant at high speed and hear the tire screach. It is very controllable. I used to do this on my Vmax just to show people it could be done.
     

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