Meccano Society of Scotland
The Challenge this year was to construct a bulldozer, length less than 12 1/2", breadth less than 6", weight less than 1.5kg, and powered by a No.1 Clockwork motor. Pairs of contestants were faced off on a line and the fully wound motors started simultaneously. When both motors had run down, the model that had crossed the line was deemed to have won. Every contestant played against every other contestant and a league table of results was drawn up on the basis of 3 points for a win, 1 for a draw. Click here for the detailed rules
There were seven entrants in all, including a proxy entry from David Lawrence which had crossed the Atlantic in order to take part and was operated by Alan MacDonald as Proxy Mechanic. All but two entries opted for tyred wheels, mostly small wheels (<1 1/2" diameter). One entry had a single driving wheel made from a 3 1/2" Sprocket wheel and one utilised Meccano caterpillar tracks.
Before the start all entries were weighted and measured. The weighing was carried out on a pair of ordinary kitchen scales and all met the published criterion being in the 1.4 - 1.5kg range. Size measurement was carried out using a gauge made of Meccano which had a rectangular aperture slightly bigger than the 12 1/2" x 6" published length and breadth. Thus a 12 1/2" Angle Girder would pass through lengthwise, even although it is in practice sometimes slightly over that length.
The 6" breadth criterion proved to be quite challenging to meet and at least one contestant had to do some last minute re-design as a 5 1/2" Double Angle Strip with a 6" Rod journalled in the bent ends and two Bush Wheels affixed outside the ends (no washers) failed. David Lawrence's entry failed this criterion as it had rods sticking out on each side beyond the 6" limit.
The site of all the contests was a varnished wooden board and several close contests occurred with at least two where an apparently winning entry was pushed back late in the run and eventually lost.
The winning entry had a Worm Wheel driving a 2 1/2" Gear Wheel, the shaft of which also bore a 1/2" Pinion which drove a 3 1/2" Gear Wheel on the shaft bearing the driving wheels. These were 3" Pulleys with French tyres. The tyres were softer than those on the 2" Pulleys used as the driving wheels on Bill Jack's model and it seems to have been the combination of the softer tyres, a comparatively unused motor and the very high reduction ratio which combined to give this model its success. It also seems that a small number of large wheels with a large reduction ratio was a more successful formula that a large number of smaller wheels.
The results are shown in the table below which includes the Lawrence model.
An unofficial challenge match took place in private after the main event. The owners of the machine activated by a 3" Sprocket Wheel (Alan Blair) and Douglas Carson, whose model had been activated by caterpillar tracks, both maintained that at least part of their failure in the main event was due to the smooth hard surface of the board on which the contest took place. Each of these machines was pitted against the winning entry outside the hall, firstly on an asphalt pavement surface, and then on a hard dirt surface. Both were overcome again by the winning entry.