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    Re: Lost people DO follow circles, says research
    From: George Huxtable
    Date: 2009 Aug 22, 14:20 +0100

    This notion has generated much attention, under the name of "South pointing
    chariot", as can be seen by googling that term. A lot of nonsense has been
    talked about it.
    It appears to have been a Chinese invention, a sort of Executive Toy, to
    look impressive at military parades. It attached a form of differential gear
    between the two wheels, to integrate the difference between their numbers of
    turns, and rotate a pointer accordingly, to point in a constant direction. .
    As for "aiding travellers crossing the Gobi desert", that's complete
    nonsense. It demands exact equality beteen the dimensions of the wheels. If
    their radii differ by only 1 part in 1000, then after just a mile of travel,
    the pointer will have rotated through all the points of the compass. Each
    time one wheel, more than the other, sinks into a sandy surface, a
    corresponding offset error occurs in the perceived direction.
    It's a nice story, but completely impractical. The sort of thing that builds
    up into a popular legend.
    As for travellers failing to walk in a straight line if they are deprived of
    any sensory feedback of direction, why should occasion any surprise?
    contact George Huxtable, at  george@hux.me.uk
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    ----- Original Message -----
    From: "Philip Lange" 
    Sent: Saturday, August 22, 2009 11:56 AM
    Subject: [NavList 9598] Re: Lost people DO follow circles, says research
    | Perhaps this may be of help?
    |        Source: History of Tribology by Duncan Dowson
    |        In History of Tribology Dowson shows a picture of a Chinese cart
    |        or chariot with a wooden figure on top.  The figure was connect
    |        to a set of gears so that it always pointed in a constant
    |        direction.  This cart aided Chinese travelers crossing the Gobi
    |        desert where it was difficult to avoid becoming lost.
    | Found on: http://tribologynews.wordpress.com//category/history/
    | Philip
    | On Fri, 2009-08-21 at 20:17 -0700, James N Wilson wrote:
    | > This somehow reminds me of learning some years ago about an ancient
    | > method to maintain orientation while crossing the Gobi desert.
    | > Primitive
    | > bevel gears were somehow used on a cart to maintain the orientation of
    | > a
    | > statue on a vertical axis. As long as both wheels rotated the same
    | > amount, the statue pointed straight ahead. But if one rotated more
    | > than
    | > the other, the statue pointed in a different direction, indicating
    | > that
    | > the cart had turned.
    | >
    | > Alas, I can't find anything about this now, and my old references have
    | > been lost. But it is interesting, even if I can't now figure out how
    | > it
    | > was done. I do remember that it was ingeniously simple.
    | >
    | > I'm remembering a bit more. This was offered to me as the first use of
    | > the bevel gear principle, and it was before the internet, so what I
    | > saw
    | > was hard copy. I wish I had it now.
    | >
    | > Jim Wilson
    | > ___________________________
    | |
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