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 as target:

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 further ?
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 made.
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 Solutions

The original solution of Mr. Partridge himself: Five gears

(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