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Robot Steeringy — Parallax Forums

Robot Steeringy

FRC2370FRC2370 Posts: 128
edited 2012-12-13 11:29 in Robotics
New 'bot will feature a legitimate steering system with a wheel (in the midst of fabricating a polycarbonate, Formula 1 style wheel). My question is, which steering system is easier to fabricate:

A pitman arm kind of thing
Pitman arm.jpg


Or a full Rack & Pinion (without the hydraulic power steering aid - robots only 110 pounds :P )
Rack-Pinion.jpg


The steering shaft needs to be 3/4", round tube metal (for quick-release hub, wires, etc). And i have no way of easily getting it welded :P keep that in mind
Pitman arm.jpg
700 x 525 - 36K
Rack-Pinion.jpg
400 x 300 - 24K

Comments

  • graffixgraffix Posts: 389
    edited 2012-12-11 00:12
    I would take the pitman. I think its easier to make and the system could take more abuse. IMHO. Thats a close call. It would be nice to here what others would say.
  • kwinnkwinn Posts: 8,697
    edited 2012-12-11 17:55
    When I was racing go-carts they all used the pitman type of steering. It was mechanically simple, very durable, and when properly designed turned the wheels so that their angle was a close match to their turning radius (inner wheel angle was greater than the outer).
  • FRC2370FRC2370 Posts: 128
    edited 2012-12-11 20:53
    So go with the pitman steering? And how does one fabricate this? (aluminum? Steel? copper?) and easiest way of assembly since i don't have wielding equipment at all available, nor do I know how to :P
  • kwinnkwinn Posts: 8,697
    edited 2012-12-12 12:37
    Yes, I would suggest going with the pitman steering. I have attached a rough sketch of how it was done on the go-carts. You may be able to make most of it using steel brackets from a hardware store.

    I am not sure if a 90 degree bracket is ideal but it is a good place to start. The size of the bracket needs to be determined, and will depend on the wheel steering arm size.
    Steering mechanism.png
    541 x 250 - 7K
  • FRC2370FRC2370 Posts: 128
    edited 2012-12-12 15:55
    This is without doubt build-able. The steering wheel is getting built this very moment. So materials needed? (sizes, lengths, radius?)
  • kwinnkwinn Posts: 8,697
    edited 2012-12-12 19:44
    FRC2370 wrote: »
    This is without doubt build-able. The steering wheel is getting built this very moment. So materials needed? (sizes, lengths, radius?)

    That would depend on several things such as the wheel base of the robot, the orientation of the steering mechanism, the minimum turning radius you want, the wheel assemblies you are going to use, etc. Even knowing all that, there would still be some experimentation required on your part. You should post a diagram of the robot chassis with dimensions along with any parts you intend to use in it's construction.
  • FRC2370FRC2370 Posts: 128
    edited 2012-12-12 20:50
    I'm in the midst of doing a Sketch up model at the moment. I'll convert it to a .dxf and post it when its finished here ??
  • kwinnkwinn Posts: 8,697
    edited 2012-12-13 11:29
    FRC2370 wrote: »
    I'm in the midst of doing a Sketch up model at the moment. I'll convert it to a .dxf and post it when its finished here ??

    A dxf is ok, but almost everyone has a pdf reader so I would suggest that format.

    For figuring out the optimal steering geometry I would suggest using a plywood disk instead of the angle bracket and wood for the steering arms. Once you have determined the dimensions required you can make the metal parts. Another option to consider is the use of a bicycle sprocket instead of an angle bracket.
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