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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Thu, 4 Nov 1999 21:30:44 GMT
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Viewed:
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673 times
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Ralph Hempel <rhempel@bmts.com> wrote in message
news:000001bf263e$d7634be0$0500000a@pro150...
> 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.
This undesirable result can also be obtained by "cross-braking," or attempting
to apply the left brake with the right hand. Fortunately for me, sometimes
the "less-fit" do survive.
-John Van
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Message is in Reply To:
 | | RE: Rack and Pinion Steering
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| (...) <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 (...) (25 years ago, 3-Nov-99, to lugnet.robotics)
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