Tug of War - a review .......................................................................... by Paul Joachim
The WLMS Tug of War Challenge
Members of the WLMS have been thinking about livening up their meetings a bit. One outcome of this was the setting of challenges between members. The first such challenge was issued to Roger Poulet by Paul Joachim - that he could not build an "N" gauge 2-rail electrified powered locomotive in Meccano. Roger met the challenge triumphantly - but that is another story.
Chris Bourne then challenged Paul Joachim to a tug-of-war. The machine was to be built entirely of Meccano parts and was to be powered by a single, post-war, No 1 Clockwork motor. Once the machines had been wound up and released, the driver was not allowed to touch them. Otherwise anything goes!
At the club meeting on 10th of March three entries to the challenge appeared, and a fourth - breaking the rules by using electric power - also was offered.
Paul Joachim offered "The Brute"
Chris Bourne offered "Chain Gang"
John Turnbull gave us "Cat Track"
and Ray Atkins produced an electrically powered robot equipped with a huge flywheel and anti-overturning device.
"The Brute" was designed after much discussion on "Spanner". It is based around the internally geared wide-tyred road wheels from the Action series sets. Four of these wheels and tyres are set up on stub axles and driven through their rims by 19-tooth pinions. The hubs are strengthened with metal 57 tooth gear wheels and six hole bush wheels locked into the hubs with bolts. The front axle is arranged with a simple pivoted centre suspension controlled by eight of the Meccano compression spring sets. The rear axle is rigid with the chassis. Both axles are driven by cardan shaft through bevel gears. A ratchet is arranged to prevent back-driving of the transmission, so The Brute has to be hauled bodily against the friction of its tyres in order to lose the tug of war. Finally, drive is taken from the clockwork motor, not through its conventional output shaft, but by spur gear direct from the spring shaft - thus providing a very slow, powerful drive that is impossible to back-drive. On one winding the machine will travel just ten inches if left free. The vehicle is heavily laden with spare parts to maximise adhesion...
"Chain Gang" used similar squashy soft Meccano tyres, but did not have any form of suspension, so immediately there was a potential loss of grip if the surface was at all uneven. Both axles were driven through their bosses by sprocket chain from a common layshaft driven at considerable spur gear reduction from the motor output shaft. The chassis was well weighted, but perhaps half the weight of "The Brute". A novel idea was a spring loaded suspension link on the drawbar that converted some of the pull in the tug of war rope to add load to the front axle, so the harder the pull, the better the adhesion on the front tyres.
John Turnbull's "Cat Track" used the Meccano Caterpillar Track system for adhesion and drove the front axle with modest reduction from the output shaft of the clockwork motor. Very little additional weight was added to the chassis, so although the machine was quite fast, it was let down by poor adhesion.
Ray Atkins' robot was also equipped with squashy Meccano tyres and well weighted down. The traction power was provided by a battery powered M0MkII motor and the machine's functions were IR controlled through the Meccano IR pack.
The first heat was between "The Brute" and "Chain Gang". Three marks, a few inches apart, were drawn on the floor of the Johnson Hall. The members assembled to witness the epic struggle, and young Lydia Goodman issued the countdown: "three, two, one, go!"
We had been worried that these two machines would just lock into a dead heat. However, after a bit of growling, "The Brute" steadily pulled "Chain Gang" backwards, "Chain Gang's" wheels slipping helplessly on the polished floor. The second heat established "Chain Gang" as easily superior to "Cat Track".
Finally, "The Brute" took on Ray's electric robot. Despite the advantage of electric power, "The Brute" just hauled the electric machine helplessly backwards, back-driving its transmission!
So Paul Joachim, Chris Bourne and John Turnbull, in that order, take the honours for the tug of war challenge.
The next one? Well, Chris has already challenged Paul to a return match. This time the aim is to produce a No 1 Clockwork motor powered machine that will walk across the hall (about 20 feet) unaided. All Meccano, one winding and the fastest walker wins. The designers are already at work...
Anyone else out there playing similar games with Meccano?