SharkD <mik### [at] gmailcom> wrote:
> Also, I am having trouble visualizing how the device behaves differently 
> on curved surfaces (i.e. the Earth) as opposed to a flat plane. I wish 
> the article had some diagrams or animations.

  I don't think that the curvature of Earth played a significant role in
the distances involved (probably like a thousand kilometers at most,
relatively close to the equator).

-- 
                                                          - Warp

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SharkD wrote:
> Warp wrote:
>>   A more complicated invention of antiquity is the so-called
>> south-pointing
>> chariot. A Chinese invention which is, basically, a chariot with a figure
>> on top which always points in the same geographical direction
>> regardless of
>> how the chariot is moved and turned. In other words, the figure acts as a
>> non-magnetic compass, obviously very useful for travelling long
>> distances.
>> The invention might be as old as from 2600 BC (although with certainty
>> it's
>> at least from 200 AD).
> 
> It would have to be very heavy, otherwise it might bounce instead of
> roll around corners, and rotation information would then be lost.
> 
> Also, I am having trouble visualizing how the device behaves differently
> on curved surfaces (i.e. the Earth) as opposed to a flat plane. I wish
> the article had some diagrams or animations.
> 
> -Mike

I don't think the the curved surface causes the distance that each wheel
travels to vary. It is more the geometry of the problem. Start at a
point on the equator, with the compass pointing south, and go directly
north till you hit the pole. Turn 90 degrees left, and the compass
should point to your left. Walk to the equator. By now, the compass
would be pointing to the east.

Also it is a good example of how a triangle is not limited to 180
degrees outside of Euclidean geometry.

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Darren New schrieb:
> clipka wrote:
>>> The invention might be as old as from 2600 BC 
> 
>> Quite a remarkable feat even for 3rd century I'd say.
> 
> An even more remarkable feat for being built just days after Noah's 
> flood subsided! ;-)

Yes, that's why I'm rather inclined to believe the 200+some AD assumption.

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Warp schrieb:
> 
>   I don't think that the curvature of Earth played a significant role in
> the distances involved (probably like a thousand kilometers at most,
> relatively close to the equator).

Indeed. I guess they'd have "re-calibrated" the cart daily whenever 
possible. Sunrise or sunset would have been a good opportunity. So the 
device would have had to work for typical distances of, say, some 100 
km: Two days' travel for a human (I don't think a traveling band would 
have had the luxury of a cart ride for all at that time), allowing for 
an occasional day good enough for traveling but too bad to get a vector 
to the morning or evening sun and no chance of asking any locals where 
exactly south might be.

And the precision required would have been quite a deal lower than for, 
say, finding Baker Street 22a after having made so many U-turns - all 
they needed was a rough vector to the next village.

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Quite spectacular looking thingy - but the principle is the same as used 
here:

http://de.wikipedia.org/wiki/Schiffshebewerk_Niederfinow

Have a trough (granted: a rather big one) filled with water and a 
counterweight equal to the weight of trough and water. Ship moves in, 
displaces water in trough equal to ship's own weight, balance achieved.

All needed to lift any weight you want is a big enough trough and some 
electrical power to overcome friction.

About the cables: of minor importance - a cable can break but the Falkirk 
Wheel's supports may break, too. Cables do not tend to break easily, if well 
maintained.

The Wheel is looking much more impressive - but on the other hand it needs a 
lot more space.

"clipka" <ano### [at] anonymousorg> schrieb im Newsbeitrag 
news:4ab4e792@news.povray.org...
>I think this is one of the most ingenious canal lock designs to date:
>
> http://en.wikipedia.org/wiki/Falkirk_Wheel
>
> Virtually all you need to do is overcome some friction (note that the 
> thing does not dip into water at the lower basin, otherwise energy would 
> be needed to displace water in that position). And there's no risk of 
> breaking of any cables or hydraulic pipes.

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TC schrieb:
> Quite spectacular looking thingy - but the principle is the same as used 
> here:
> 
> http://de.wikipedia.org/wiki/Schiffshebewerk_Niederfinow

It appears a good deal more complicated in the actual implementation: 
192 counterweights, double cables for safety, and not to forget the 
additiona worm drives normally running "idle", just in case the second 
set of cables doesn't hold either. All this is done away by the 
exceptionally simple construction of the Wheel.

As an aside, by using another caisson as the counterweight you also get 
effectively twice the capacity for the same total weight.

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Warp wrote:
>   I don't think that the curvature of Earth played a significant role in
> the distances involved 

The article does say something about it working for geodesics, too.

-- 
   Darren New, San Diego CA, USA (PST)
   I ordered stamps from Zazzle that read "Place Stamp Here".

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Well, you are right - the technical execution is more complex.

But then the wheel only seems to be more impressive than the elevator 
because it is better looking, a real beauty ;-)

And the principle is beautiful, too.

Let's compare the technical details:

(Provided the English wikipedia is correct for the Wheel, the German 
wikidepia for the elevator)

                       Wheel / Elevator

Trough capacity:   2 x 250 t / 1 x 2500 t
Lift:                   24 m / 36 m
Build date:             2002 / 1914

Basically the Wheel, impressive as it looks, is quite small compared to the 
rather unspectacular looking elevator. The elevator can lift 10x more 
tonnage. If you take in account that for smaller ships the wheel can bring a 
little ship up and another one down, if there actually >are< two ships there 
at the same time wanting to go into opposite directions, the elevator can 
still shift 5x more tonnage in a single go.

Now, I am no architect, but I guess if you wanted the Falkirk Wheel to shift 
10 times more load, across 1.3 times the distance, the wheel would become 
very heavy indeed. If the troughs were made to hold 2500 t of water the 
supports would have to carry 10x more load. You would have to increase the 
Wheel's diameter to 49 m minimum, and this would add to the forces that 
would have to be absorbed by the Wheel's wings.

A non-rhetoric question:

Has anybody here any idea how much the Wheel's wings or struts would have to 
weigh to replicate the ship elevator's capacity?

"clipka" <ano### [at] anonymousorg> schrieb im Newsbeitrag 
news:4ab65a44$1@news.povray.org...
> TC schrieb:
>> Quite spectacular looking thingy - but the principle is the same as used 
>> here:
>>
>> http://de.wikipedia.org/wiki/Schiffshebewerk_Niederfinow
>
> It appears a good deal more complicated in the actual implementation: 192 
> counterweights, double cables for safety, and not to forget the additiona 
> worm drives normally running "idle", just in case the second set of cables 
> doesn't hold either. All this is done away by the exceptionally simple 
> construction of the Wheel.
>
> As an aside, by using another caisson as the counterweight you also get 
> effectively twice the capacity for the same total weight.

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Warp wrote:
>   A more complicated invention of antiquity is the so-called south-pointing
> chariot. A Chinese invention which is, basically, a chariot with a figure
> on top which always points in the same geographical direction regardless of
> how the chariot is moved and turned. In other words, the figure acts as a
> non-magnetic compass, obviously very useful for travelling long distances.
> The invention might be as old as from 2600 BC (although with certainty it's
> at least from 200 AD).


Easy enough to gum up, though: just knock it over, and it loses its basis.

Impressive, nonetheless :)

...Chambers

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> Indeed. I guess they'd have "re-calibrated" the cart daily whenever 
> possible. Sunrise or sunset would have been a good opportunity. So the 
> device would have had to work for typical distances of, say, some 100 km:

FWIW modern cars today use the same principal.  That's why if you have a car 
with GPS (a built-in one, not an aftermarket one) it still knows which way 
you are facing when driving around underground (eg parking garage or 
tunnel).

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