race calendar

A Calendar of Meccano Races and Contests being held around the world. To include such events as 'Walking'; 'Tug o' War'; 'Climbing' and 'Robot Wars'. For Contact; Time; Venue; Rules and other matters follow the link to the club web site.

The winning model at the MSS 22nd May 2004 Menstrie Falling Weight Contest

by Chris Shute, Meccano Society of Scotland

I acknowledge with thanks the Photos of Chris Chute's model by Tim Edwards.

Also the write-up (below) by the winning model builder Chris Chute on the design asnd construction features.

For more detsails and photographs of the event see the MSS website and newsletter


Chassis and Tower

A pair of 12.1/2" Angle Girders with a pair of 9" Angle Girders form a hollow T shape, each spaced 3" apart. The lower end of the tower is a 1Girder attached by a Flat Trunnion to a 3.1/2" x 2.1/2" Flanged Plate, the weight catching tray. A Trunnion above joins the Girder to the chassis cross-member, via spacers, so that the catching tray can eventually be adjusted to clear the ground by less than 1/16" maximising the possible drop distance. Five 5.1/2" Strips, some via Brackets, suspend and brace this structure, also steadying the tower. A 24.1/2" Girder extends the tower upwards. Being attached by Fishplates, the final height can be finely set to the maximum 36" allowed by the competition. A 3" Pulley is journalled in the top hole and a 3.1/2" Strip stood-off by twin pairs of spacers. A large pulley suffers less friction at its bearings and keeps the weight clear of the tower, which leans back by 1" at the top. A pair of curved Flexible Plates is used to direct the weight between the chassis members near the end of its drop.


The road wheel axles do not pass through holes in the usual way. Instead, pairs of Faceplates at each corner are overlapped by 1/2", spaced by washers to prevent fouling. At the front, Faceplate pairs are independently journalled in 3.1/2" pairs each side, to overcome any minor discrepancies among Faceplates and axle surfaces. At the rear, Faceplates are fixed to either ends of the same rods passing through the lugs of 3.1/2" x 1/2" Double Angle Strips. One of the rear road wheels can rotate freely on its axle rod. All axle rods are first cleaned with fine steel wool, and then rubbed with a metal polish. Faceplates are selected for minimal wobble. They should spin very freely before meeting the road wheels.

Road Wheels

These are 7.1/2" Circular Strips fixed by 7.1/2" Strips to Bush Wheels or Double Arm Cranks at their centres. The weight of the vehicle is supported through the Faceplate edges onto the polished axles linking the wheels. Arched pairs of Curved Stepped Strips carry the axle when the vehicle is lifted from the floor, but must not touch it during normal travel, of course.


Ideally we need the vehicle to free wheel after the weight has fully dropped. To achieve this, a small bowline knot is tied with Meccano cord around the driving axle. It cannot grip. However, a small Drive Band is held nearby on the axle, trapped beneath a Spring Clip. The tip of the Drive Band is slid under the bowline loop so that when the cord is wound tight, it will compress the rubber, gripping the axle. Sufficient cord is provided so that when the weight has fully descended, the few remaining turns of cord will be unwound under the travelling momentum of the vehicle. The Drive Band will then withdraw from under the cord loop, thus preventing any rewinding of the weight.


For maximum drop, we need a short fat weight rather than a tall thin one. Ideally we want it to fall unimpeded by other parts of the vehicle. I chose to cast my own lead weight, reminded by an article by the late Bert Love in an old Meccano Magazine. This can be hazardous and should not be attempted without adult supervision. The mould was a small terracotta plant pot. Inside the pot, under a long bolt’s head, I fitted a washer, a couple of nuts and a large washer, and on the outside, another large washer fixed with a nut. I melted just less than a pound of lead in a tin can over a camping gas stove in my well-ventilated workshop. Wear goggles and thick gloves, just in case impurities cause splashing.With the plant pot stacked on two bricks so that the bolt shank could hang downwards, I carefully poured the molten lead into the pot and left it overnight. In the morning, I removed the outer nut and washer and the new lead weight, being conical, slid from the pot. I added a Wheel disc, a couple of washers, and a 1/2" Bracket to the exposed thread of the bolt, now trapped securely in the lead. I filed the Bracket into a hook and bent it so that when suspended, the weight would hang vertically.


Our combination of weight, cord, axle, bearings and road wheels will only just work on the average smooth floor. Once rolling, however, the machine has plenty of momentum. In order to get extra power at the start of a run, the weight can be raised up around the outside of the tower Pulley, so long as is doesn't put the structure over the 36" limit. This manoeuvre will almost double the power available from the weight, since it forces the lead weight's centre of gravity almost twice as far as normal from the centre of the Pulley, until the weight has fallen a little and hangs in the usual way. The theoretical driven distance possible from a machine such as this may be simply calculated as follows:

Distance = Weight drop distance x (Road Wheel diameter / Winding axle diameter)

I have ignored the fact that the cord may become wound around itself and therefore increase the diameter of the winding axle. In our recent competition, this machine travelled 37 feet 4 inches on an 8" drop. The Road Wheel/Winding axle ratio is 195/4.1 (if you work in millimetres!) so the 8" drop becomes magnified by a factor of 47.56, sending the vehicle 31 feet 8 inches. The remaining six feet (approximately) was done freewheeling after the weight had dropped. The competition had to reduce the weight drops to 8" because our 39 foot hall wouldn't cope with any of the six competitors running on a full drop. A full drop for my machine would be about 34" so theoretically, a distance of 142 feet may be possible on a longer smooth floor.

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