The Meccano Magazine Contest
Back in the seventies Mr. Alan Partridge started a series of contests,
for example in January 1977 for the most elementary differential, claiming
that four toothed parts are enough:
One year later, in January 1978, the South Pointing Chariot was choosen
In the M.M. for January 1977 (writes Alan Partridge), pages 30 and 31,
Terry Morris gave us an excellent
account of the co-called Chinese Self-seeking Chariot. I do not wish at
this stage to enter into the controversy as to whether or not it was in
fact an ancient Chinese invention, but I must say that it is a very entertaining
device. In letters in the last M.M., page 67, two writers refer to the
article by Frank Cousins in M.M. September 1955,
pages 498/499, and Dr. Keith Cameron claims that no one has followed exactly
the design by Mr. George Lanchester which appears in Mr. Cousins' article.
So that everyone will start level, fig. 1 shows Mr. Cousins' sketch
redrawn. The vertical central shafts carry wheels which appear to function
both as spur gears and as bevels or contrates ! No wonder the design has
not been copied exactly ! If each of these is made from a Meccano Gear
and a Concrate bolted together as done by Mr.
Oliver, M.M. January 1957, page 36, a total of eleven gears is needed.
Terry Morris used only 10 gears, but could the number be reduced still
Clearly we could omit one Pinion from the differential in either
version, or we might use one of the differentials I described on page 70
of the last M.M. However, further economies are possible. Indeed, I'm not
saying whether or not any differential is needed at all, but if it is,
it is not in the internal details of this that the chief saving is to be
The exact object of this month's problem, then, is this: design
a chariot or hand cart running on two equal wheels. The line joining the
centres of the wheels is to be at right angles to the plane of rotation
of each wheel (this is to distinguish a chariot from a bicycle). The body
of the chariot is to carry a horizontal pointer rotating about a vertical
axis. The two wheels and the pointer are to be connected by gearing in
such a way that, however the chariot is moved, with its wheels remaining
in rolling contact with a smooth horizontal surface, the pointer continues
to point in the same direction. The smallest possible number of toothed
parts is to be used and, as usual, the mechanism is to consist of standard
Meccano Parts without mutilation and non-conventional alignments, with
no cord or belt drive or other frictional device.
Solutions to the problem should be addressed to Chariot Competition,
Meccano Magazine, Binns Road, Liverpool L13 1DA. The designer who we feel
produces the best solution will receive a token prize in the form of a
Crane Kit motor.
||The original solution of Mr. Partridge himself: Five
(Click on the picture left for some more details)
|By substituting two gears with a chain of universal joints Prof. Sleeswyk
proposed this solution: Three gears
Note that the pointer still rotates the wrong way round - small problem
||More universal joints, and we are down to Two:
Mr. Noel C. Ta'Bois was the first to put this idea into a working model,
thus securing capturing the prize.
Look at the scissors-like contraption coupled with excentrics to transport
the left hand roadwheel's rotation to the top of the machine !
(click for a more detailed picture)
|But, why universal joints at all ? Building on oscillating coupling
rods we get down to Two gears as well, which are necessary
only to get "round the corner" to the pointer. Sr. R.G. Torrent entered
this idea, but failed to implement it.
Explanation: If both halfshafts in the picture to the left rotate at
the same speed, but in opposite direction, the "cross" in the middle will
move up and down while swinging round the vertical axis. If the speeds
differ, the "box" guiding the up and down movement will have to rotate.
For the chariot you will need two of these assemblies - one to reverse
the rotation of one roadwheel ("box" fixed to frame !) and one with rotatable
box as depicted to extract the motion for the pointer (vertical axis to
the upper right).
||At this point Mr. Partridge regretted the wording of the contest (see
above): Had he written ".. are to be connected with a minimum of gears
.." the solution would have been NONE.
Adding excentrics and universal joints to the design sketched above
("fixed box" is at the left hand side) the "corner" is mastered with no
teeth at all !
Source: The Meccano Magazine, January 1977 and 1978