3 wheeled vehicle

Discussion in 'Physics' started by strantor, May 25, 2012.

  1. strantor

    Thread Starter AAC Fanatic!

    Oct 3, 2010
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    I've seen some 3 wheeled vehicles on battle bots a long time ago, and some 3 wheeled line following robots. They type I am interested in, do not have a steering mechanism. They steer like a tank or a bulldozer or ZTR lawn mower. 2 parallel wheels have independent drive mechanisms and the 3rd wheels is a caster. Turning is accomplished by commanding a higher speed to one drive wheel than the other, or applying brakes to one drive wheel and not the other. they can literally turn on a dime, in place. I have never seen a high speed vehicle that employs this method (have you? links or leads if so, please?:)). When I picture a vehicle like this operating at high speed, the picture is very cloudy. I don't know how it would behave. I'm looking for examples of this if they exist (I haven't been able to find any) or even just your speculation of how it would behave. Imagine a ZTR lawn mower going 100mph. I picture 2 wheels in front, with one following caster in the rear - would be safer, more stable at high speed and less likely to tip in cornering than a tricycle design.
    I am guessing, that the longer and narrower the vehicle is, the less likely it would be to make unintentional drastic turns at high speed, but the more difficulty it would have making tight turns at low speed and vise versa. I presume there would be some optimal ratio of length to width. It's unclear to me whether it would be able to turn at all at high speed.
    This isn't an automotive thread, just a physics curiosity of mine.
     
  2. Markd77

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  3. strantor

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  4. nerdegutta

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  5. MrChips

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    How about this one?

    [​IMG]

    [​IMG]
     
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  6. BMorse

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    Most of my robots have this particular drive design since it is easier for them to maneuver in tight spaces.....
     
  7. strantor

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    how fast does your fastest robot go? And do you notice any change in maneuvering characteristics at higher speeds?
     
  8. bertus

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  9. atferrari

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    Understand that for stability, if that is your concern, there is a point related to the ratio between widht and height ( logical, after all).
     
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  10. TomRich

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    Jun 1, 2012
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    Basically they have some benefits that also include the potential for smaller size, making transportation cheaper (petrol price is ridiculous), simpler and even more fuel-efficient. Many of them fill the gap between car and motorcycle, that is light and maneuverable like a motorcycle, yet with a car's seating and protection benefits. They also boast improved aerodynamics because of their inherently triangular shape, yet with one fewer wheel, some designs are not quite as stable and therefore are more prone to tipping over than conventional, four-wheeled cars. Which leads me to believe that they will be a real road hazard! Happy to try it and test drive it not sure if I would buy!
     
  11. StudyingEE

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    Dec 3, 2011
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    For something that operates the way you are describing, the closest real object I can think of is a modern era military tank where the tracks/turning are done at high speed by varying the speed of each track. The coast wheel in the rear of the tri-wheel design you are describing makes the vehicle unsatable at high speed unless you have an auto-correct for the distribution of the weight of the vehicle on the three wheels.
     
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  12. strantor

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    Thanks, I really hadn't thought about that. Imagine how disasterous it would be if it started doing the shopping cart wobble @80mph!
    Right, I had thought of a tank, but I think the tanks has more going for it, in the amount of traction. When I mentioned I was not sure if it would turn at all in high speed, it's because of traction. I can imagine braking on one side of the 3-wheeler, trying to get it to turn, to the point of locking up the wheel and smoking it, and the 3 wheeler still wants to go in a straight line (or a very wide arc) - the tank on the other hand has gobs of traction, so its probably not an issue. But, like I said I have no idea if that's actually how it would behave; I've never seen anything like to to base the assumption on, just a gut feeling.
     
  13. Sparky49

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