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 23:20:11 GMT
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Original-From:
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The WordMeister <dwilcox@{spamcake}wordsmithdigital.com>
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Viewed:
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676 times
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Great engineering humor. Thanks. Now, does this mean that when my first-ever
RIS creation shook itself to pieces in <10 seconds I was actually utilizing
evolutionary robotics?
I never grew out of the "It's snowing!" excitement either. Of course, now I
have even better reasons for loving snow--my self-imposed mandate to take
the boys sledding at every opportunity. :) But we've got another month or
two before the blessed stuff starts falling here in southern New England.
--Doug Wilcox
-----Original Message-----
From: Ralph Hempel <rhempel@bmts.com>
To: lego-robotics@crynwr.com <lego-robotics@crynwr.com>
Date: Wednesday, November 03, 1999 4:04 PM
Subject: RE: Rack and Pinion Steering
> 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>
> --------------------------------------------------------
> Reply to: rhempel at bmts dot com
> --------------------------------------------------------
>
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