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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?

George.

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" 
To: 
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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