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CMC Meeting, July 07

The next meeting of the Christchurch Meccano Club is on Friday 3rd August.

The challenge

This challenge was: "Build a Meccano model, powered only by a Meccano No.1 clockwork motor, designed to travel as quickly as possible from a standing start along a straight course of around 10 metres."

A fantastic response, with eight entries for the race along with a few other 'weird' entries that were not serious racers.  There are two distinct camps – one was the very simple kind with the driven wheels either directly on the motor output shaft or mounted through the motor and connected by a single gearing down, and the other type of entry was a much more complex vehicle with many gears and some form of automatic gearchange to give the best balance between acceleration and top speed. 

The eight entries were first drawn by lot into four races of two cars, each race being the best of three runs.  The four entries that were knocked out in this way were:

Grace's entry Grace entered a straightforward motor driving 2'' wheels with tyres geared down by 3:1 from the output shaft.  Probably not geared low enough for the large wheels, or perhaps with a less powerful motor (the 1a), this didn't have the speed to keep up with Peter's challenge.

Joy's entry Joy's entry used a nickel-plated motor, driving modern (1990's) Meccano rubber push-fit wheels directly on the driveshaft.  Although it went well, it couldn't cope with the transition to carpet and stopped before the end of the race on both runs, allowing Charles' entry through. Drive was directly from the output shaft of the motor, to 1990's Meccano push-fit rubber tyres.

Hugh's three-wheeler Hugh's entry fell comfortably into the over-engineered category, with three large wheels and a three-speed automatic gearbox using two adjacent worm gears to drag the intermediate shaft across to change gears.  First gear wasn't low enough for the wheel size, though, and it lost out to Robert's entry in the deciding race.

Cameron's entry Cameron's entry was very similar in design to Joy's, and made a better show of handling the carpet.  However, it uses a 1a rather than No.1 motor, and didn't have enough power.  A close race saw it lose out to Neil's design. Drive was, like Joy's entry, directly to the rubber wheels from the output shaft of the motor.  This gives a good top speed but not enough acceleration from the start.

Now we're down to four entries, and the semifinals.  The two losing models in the semifinals were:

Neil's entry Neil's long and thin entry was driven by a 3" sprocket wheel mounted on the motor winding shaft, driving a ¾'' sprocket on the rear axle with a 3'' wheel and tyre.  It went well, and had a trick pawl and ratchet final drive (to allow the vehicle to continue after the motor stopped), but wasn't fast enough to keep up with Robert's entry.  Neil's entry was the most successful to use the smaller 1a motor. Robert went through to the final, and is shown in the picture below lining up on the left.

Charles' entry Again in the 'simple' category, Charles' entry combined the 1990's tyres with a 25:60 gear pair spanning the space (1 hole down and 2 holes back) between the driveshaft and the lowest hole.  Acceleration was excellent, but this was probably geared down too far and was overtaken after about halfway by Peter's entry.

Robert and Peter lining up for the final We don't have a close-up of Peter's entry, but it can be seen here on the right at the start of the first race in the finals.  Drive is geared down to 3" wheels and tyres, and was a good balance between acceleration and top speed.  The finals went both ways, and so at one-all the deciding race was run...

Robert's entry ...and in a very close race indeed, the two racers crossed over and Robert's just reached the line first, by a fraction of a length as Peter's entry started to overtake.  Robert's entry is very similar to the two much less successful versions by Cameron and Joy, but perhaps his choice of motor made all the difference. Are the red motors really that much more powerful than the others? Something to test in the future, but it certainly appears that the larger No.1 motors are more powerful than the smaller 1a versions.

Models on display

There were a few more racers present – but not serious entries.  Peter's alternative entry was the best finished and looked the most like a race car, but far too heavy to get going at all well. 
I'm not at all sure this one deserves a picture at all, but at least it worked.  Once it got going (which took a fair while), momentum kept it going rather well, and presumably there would have been little chance for any competitor getting in its way.  No chance of that though – all the other models were well in front by the time this got going.

The final drive is by sprocket chain on the far side of the model.  On the other hand, this is the first time anyone has used a GRB in an entry to one of our Christchurch Meccano Club challenges, so I suppose it almost deserves a mention for that alone.

To the right is a close-up of the gearbox on Hugh's racer.  The worm arrangement on the right-hand side drags the forward axle to the side, changing gears from 15:60 to 19:57 and 25:50.  Although this worked, the lower gear was not low enough and the gap between gear ratios probably not large enough.  Given the huge 5½'' circular girders used as wheels, it needed a much lower gear to get started.

The above picture is a scan from the 1968 Meccano trade catalogue, showing display model 68/1 "Mechanisms Board (small)".  To the right is a recreation of this board, using ½'' MDF sprayed medium red, and restored medium red/green parts.  It is stand-alone and driven by a 12V motor with a small lead-acid battery mounted behind the display, including switch and charging socket. 

Business

The Club has obtained a reasonably large amount of Meccano documentation, and proposes to have this available to club members through a library system.  Grace was voted in as the club's librarian, and we hope to have a full catalogue of the paperwork available by the next meeting.  There are a small number of valuable old manuals which are to be put up for sale to raise club funds, and the remainder consists of Meccano manuals, modelplans, and what appears to be copies or originals of every Meccano-related page in every Meccano magazine right from issue number 1. 

This would be a fantastic resource to have on the internet, although it will be a lot of work.  Many years ago, there was an organised scanning of Meccano magazines that were supposedly going to be available on a non-profit basis, but all that remains of the substantial amount of work put in by many meccanomen is a collection of CDs of low-quality scans and limited viewing software, now sold commercially at a very high cost.  It would be worthwhile to scan all the Meccano-related pages at a much higher quality and make them available to everyone.

The CMC Challenge – "Something useful"

Almost all Meccano models are just that – models.  They are similar to real objects, but only replicas of them.  The challenge this month is to build something that is not a model, but instead a real, useful object.  It may be stationary or motorised, performing a function in itself or it might be a tool to assist with a job.

The Competition

At the CMC meeting in August, all club members present will vote for their favourite construction, and the one with the most votes will win.  In the event of a tie, the most senior disinterested club member will have the casting vote.

Definition of ‘Meccano model’

As usual, you can use any Meccano part ever made and sold as Meccano, or any reproduction part that is structurally identical to a Meccano part.  Parts may not be cut or deformed such that they cannot be used for their intended function again.  You can cut a 2 down into a 2a (it becomes a reproduction part), but not down to a 5” long strip (which has no Meccano equivalent). 

Cord, driving bands, and springs may be of any type.  Motors must be genuine Meccano.  Non-Meccano washers may be used in your model solely to protect the paintwork (these don’t count as a part).