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Mechanism for steering

  1. Jul 12, 2008 #1
    hello all
    i'm creating a prototype for a 3 wheeled car ( 2 wheels at the back & 1 wheel in the front ) motor with the 2 wheels in the back
    i want to test its stability so i want it to move in a straight line then take a curve
    can someone suggest a simple mechanism for the steering (from the single wheel in the front) ???
     
  2. jcsd
  3. Jul 12, 2008 #2
    If you only have a single drive(single drive to both wheels), you need to tilt the axis of the front wheel, like a bike.

    If you have separate drives for both rear wheels, just use a castor at front, and control the speed of both motors for steering.
     
  4. Jul 12, 2008 #3
    for the first suggestion : will i need to do it manually ? is there any mechanism that can make it move in a straight line then take a curve (tilt the axis) ??

    thanks for help ^_^
     
  5. Jul 12, 2008 #4
    Actually it would be quite easy to do. I'm assuming you have access to motors. a small motor with a sprocket on the drive shaft and a chain attached to a sprocket on the wheels shaft and you could have it steer either direction you wanted. (this requires some programming if you want to control steering)

    The other option is to rig it with a string to a fixed point, when the string goes taught itll jerk the wheel in one direction. but then it'll go in a circle around this fixed po9int until you shut it off or you run out of string!
     
  6. Jul 13, 2008 #5
    What else??
    you cane make a link attached to the shaft of the front wheel, now pull it back to steer one way, push it to steer the other way.

    I didn't get you clearly bear, wont it make it a one way process??

    Anyways, 230, one more idea, mount your front wheel on a shaft, and tie a string to its both ends(wheel is in the middle), now pull this string from one side to steer, & pull from the other side to steer other. Pretty stupid, huh?? You need two exactly same motors(small ones) with each string wrapping over each shaft. Rotate the motors in opposite directions, so while you pull one side, other side will be unwrapping & vice versa.
    Actually, this is how B737 steers, with hydraulic actuators in place of strings.
     
  7. Jul 13, 2008 #6
    To Ank

    Well the second way would, but if he is just testing stability in the process of turning, it would work. The first way is similar to your B737 idea but it only requires the programing and control of one motor. They use hydrolics on planes because you can get more force and they use a hydrolic system to control the flight elements. It would be simpler and more efficent to use one motor with a chain and sprockets.

    I suggested the rope and fixed point because i wasn't aware of any programming skills or circuitry skills which will be required if he is going to want to control the motor apart from on and off. If 230 could let us know of his capabilities and budget we could give more suitable ideas.
     
  8. Jul 14, 2008 #7
    i think the idea of 2 motors at the back is better & easy so i'll use it
     
  9. Jul 14, 2008 #8
    Oh yes, right bear, using a sprocket makes it equivalent to a link.
     
  10. Jul 14, 2008 #9
    Is this for some robotics contest?? If yes, differential drive is your best bet, while for bigger systems, this type of steering is a wastage of energy.
    Best of luck.
     
  11. Jul 14, 2008 #10
    Actually it reuires much more complex programing then using a single motor and chain.
    For that style you have to program the motors to run in opposite and be synchronized.
    It will require programming for two motors. Since it has two motors it is also more expensive.

    My idea requires the programming of one motor either clockwise or counter clockwise.
    It also allows for mechanical advantage so you can use a smaller motor. With ank's concept you cannot change the diameter of the drive shaft or the driven and so if you motor is not strong enough you need a new motor instead of a larger sprocket.
     
  12. Jul 14, 2008 #11
    why not just put the two wheels up front
    and use one in the back
    if you must have three wheels
    like the old morgan trikes
     
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