Subject:
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RE: Rack and Pinion Steering
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 3 Nov 1999 21:03:13 GMT
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Viewed:
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580 times
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Robert wrote:
> I think you should look at a design in which each steering wheel's pivot axis
> is NOT in the same plane as the steering wheel's axle. Specifically, each
> wheel's axle should be behind its pivot axis, where "behind" is referenced in
> terms of the intended direction of motion.
>
> A caster is a good example of such a wheel design -- it requires no special
> effort to make it "point" straight ahead. As long as the thing to which the
> caster is attached is being pushed forwards, the caster automatically swivels
> into alignment.
>
> Automobiles and bicycles also implement a type of "passive centering" in which,
> when you let go of the steering wheel, the forward motion of the car pushes the
> wheels towards center. The bicycle's design relies entirely on weight (downward
> force) and is notable because the pivot axis is not vertical. Automobile
> designs are much more complicated (particularly when the steering wheels are
> also drive wheels) and are probably not worth the effort.
<plant tongue in cheek>
Bicycles also implement an "active buck" mode of Darwinian selection. If
you ride your bicycle in hands-off mode and tilt the bicycle slightly by
shifting your centre of gravity, the wheel will turn. Outside of the range of
"slightly", which is different on every bike and complicated by spring shocks,
you get a radically modified behaviour.
The front forks will quickly spin and put the wheel at 90 deg to the intended
direction of travel. At this point, the front wheel will either stay intact
but stop, throwing the rider forward, or "taco" and crumple, pitching the rider
forward and down.
Either failure mode is undesirable, and in extreme cases the "Darwin Effect"
takes hold and removes the rider from the gene pool. The riders able to adapt
to the effect wear helmets and try to keep their hands on the control points.
</plant tongue in cheek>
We have had a really big snowstorm, and I'm getting a bit punchy. Everything
is starting to be an opportunity to be funny (or at least try)
Cheers,
Ralph Hempel - P.Eng
--------------------------------------------------------
Check out pbFORTH for LEGO Mindstorms at:
<http://www.hempeldesigngroup.com/lego/pbFORTH>
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Reply to: rhempel at bmts dot com
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Message has 1 Reply:
 | | Re: Rack and Pinion Steering
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| Ralph Hempel <rhempel@bmts.com> wrote in message news:000001bf263e$d7...@pro150... (...) axis (...) in (...) special (...) the (...) swivels (...) which, (...) pushes the (...) (downward (...) are (...) of (...) shocks, (...) intended (...) rider (...) (25 years ago, 4-Nov-99, to lugnet.robotics)
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Message is in Reply To:
| | Re: Rack and Pinion Steering
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| (...) I think you should look at a design in which each steering wheel's pivot axis is NOT in the same plane as the steering wheel's axle. Specifically, each wheel's axle should be behind its pivot axis, where "behind" is referenced in terms of the (...) (25 years ago, 3-Nov-99, to lugnet.robotics)
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