Aman Saraf
Second Year
Mechanical
Though the inception of "South-pointing chariot" was done as early as 2600 BC by the Yellow Emperor Huang Di, the first historically confirmed version was created around 200-265 AD.
It was a two-wheeled chariot, pulled by a horse, with a statue of a person riding on it. The statue's arm was extended, pointing south no matter how the chariot moved. The chariot could travel in curves, loops, or any convoluted path, even backward, but that statue stubbornly continued pointing South—but only if the ground surface was flat and level and the wheels didn't slip.
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| Chinese South Pointing Chariot. Model by George H. Lanchester. Science Museum of London. |
Its secret was a geared mechanism inside the enclosed body of the chariot. The differential motion of the wheels drove the gears, which in turn causes the statue to rotate the same angle as the carriage turns, but in the opposite direction.
How did it work?
First of all for understanding the working of the “South-Pointing Chariot” we need to understand the differential gear mechanism, which is explained in the following video
First of all for understanding the working of the “South-Pointing Chariot” we need to understand the differential gear mechanism, which is explained in the following video
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| Differential with bevel gears, using Eitech parts (left), and one with crown and pinion gears, using Meccano parts (right). The gears' grub screws will be removed, since all these gears must rotate freely on their shafts. |
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| Differential, from instruction book of Meccano Standard Mechanisms, 1934, UK Edition. |
CALCULATION RELATED TO SOUTH POINTING CHARIOT
Note: consider the chariot moving forward & turning leftwards.
Note: consider the chariot moving forward & turning leftwards.
Note: All the three gears inside the differential have been taken identical for the ease of calculation. (Radius- r)
Velocity of point P = W1*r
Velocity of point O = Wb*r
Velocity of point Q =W2*r
Now,
Wb*r + Wg*r = W2*r ----------------- eq-1
Wb*r - Wg*r = W1*r------------------------ eq-2
Solving we get
Wb = (W2 + W1) /2
Wg = (W2 -W1) /2
W2>W1 if the chariot is turning towards left.
Consider that angle covered by the chariot in one second is W
Radius of inner circle of the path = ri
Radius of outer circle of the path = ro
Radius of the wheels = R
The distance traversed by the inner wheel in one second = W1*R = W*ri
The distance traversed by the outer wheel in one second = W2*R =W*ro
As previously calculated,
Wb = (W2 + W1) /2
Wg = (W2 -W1) /2
Using these 2 eq & solving the above we get
W = 2RWg/(ro-ri)
W= (ro+ri)Wb/2R
Wg cannot be connected easily with any other gear as it lies inside the differential gearbox, instead it is much easier to connect Wb to other gear to achieve the desired rotation of the beak ( beak always points south) , but the eq. Linking W & Wb has a term (ro+ri), this term is not constant, therefore here we do a small manipulation in the mechanism.
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| Open version of the south-pointing chariot. Mechanism and housing mostly of Erector parts. |
As you can see in the above model one of the wheel connects the differential gear via cross lap pulley (left wheel) this accounts for the opposite rotation of one of the differential gear,
Therefore now with above modification we shall replace W1 by (-W1) & on solving the above eq. Again we get,
W=2RWb/(ro-ri)
Now 2R/(ro-ri) is a constant term therefore ,
W=kWb
Now with specific value of k we can link the Wb gear to the chariot gear to achieve the desired rotation.
nice approach !!
gud one...
:)
Nice post ; once also go through the differential , works on same concept, most of us fail to recognize its vitality in an automobile .
bhai proness... :)
nice!!!!
gud goijn bro
nyc work buddy keep it up
keep it up bro!!!