Clock building in Meccano is an exciting and challenging pass-time. The traditional clock maker over the past 500 years has practiced his craft with files, drills and small specialised machines for making gears and shafts. There is no need for any of that when using Meccano. Meccano provides all the materials for building quite complicated clock mechanisms, without the need for any special machinery and no need for a workshop. The parts are already there pre-formed, ready to use. The result is a clock that in no way is inferior to more traditional methods of clock building. On the contrary, Meccano can be extremely accurate and can include extremely accurate ratios that duplicate the motion of the sun and planets to a high degree of accuracy.
Clock making appears to hold a fascination all of its own, particularly among model engineers. There is something absolutely fascinating about clock making that seems to draw one towards it. In this respect, they are not models at all, but the real thing. Their sole function is to tell the time, and if they fail to do this, are absolutely useless. Indeed there are many much easier ways to tell the time, for example with the simple electronic wrist watch. The building of a mechanical clock becomes a thing of beauty and ingenuity and a joy to behold.
The Meccano clockmaker will want to review the extensive literature on the subject, and it helps greatly to visit a library where books on clocks might be read, or to obtain their own. In addition there are important museums, which specialize in clocks. Clocks are often to be found at Meccano exhibitions, and it helps greatly to be able to examine how they are built, and what their important features are.
Although a clock might look very complicated with masses of gears, it is basically very simple. There is a framework, which usually amounts to a front and back plate joined together by four or more pillars or spacers in such a way that the plates are rigidly held apart from each other. The plates provide bearings for the various shafts, called spindles, and there is a usually some sort of power supply. This could be a weight, a spring or an electric motor. A clock always has some form of escapement which is devoted to the speed at which the clock works. The name is given to this device because this is the point where the power of the clock is prevented from escaping and is converted from rotary motion to reciprocal motion. The teeth of the escape wheel drive some form of oscillator and a tooth is trapped for a period of time depending on the frequency of the oscillator. The tooth is unlocked when the oscillator is at a suitable position on the return vibration. Without the escapement, the gear train would just unwind at no given speed and the clock would be of no use. There are many types of escapement, and to reproduce them is one of the joys of clock-making.
There are usually two gear trains - the Going Train between the power source and the escapement, and this might consist of four gear wheels and three pinions. As every clock must show the minutes and hours, there must be a 60:1 reduction between the two, and both shafts must turn the same way. Â This is the MotionWork, which is linked to the going train at some suitable point.
Finally, clockmakers like to present their work in an attractive manner, and so an ornamental clock case is desirable. This can be a framework with glass sides, or a glass dome, and it helps to have a pleasant looking plinth on which to stand the clock.
The result is a masterpiece of sensible construction, which owes more to the model engineer and the clockmaker than to Meccano. It is Meccano, which makes the whole process that much simpler however, and is a first class way to enjoy this wonderful challenge and enthralling pass-time.
To succeed with Meccano clock building, a few essential rules must be observed.
1. The amount of play of the axle rods in their holes must be reduced. This can be achieved by securing fish plates by their elongated holes to an adjacent hole, and then adjusting them. This applies particularly to the escapement wheel rod. There must be end play on each axle rod, i.e. you must be able to move each rod endways in its bearing holes.
2. For particularly free axle running, us pivot bolts and pivot rods, carefully adjusted.
3. All axle rods, which pass through bearing should be highly polished as should also the gears and their teeth. Rods must be absolutely straight, and should be rolled on glass as a straightness rest.
4. Frames must be rigid and parallel to each other. Pillars can be made using couplings or hollow tubing through which a suitable length of screwed rod can be passed.
5. It is not really necessary to double or even triple bearing surfaces with added plates or strips in order to give a widened bearing surface. The main requirement of clock trains is complete freedom. The old clockmaker's adage 'if it rattle it'll run' is very true. Backlash is not a problem because the drive is continually in one direction.
6. Clockwork requires step up gearing, with a consequent loss of power. Mechanisms must be tested for completely free running. There must be absolute freedom of the train. The test that clockmakers apply is called the freewheeling test. With the train in place but minus the pallets, pressure is applied with the thumb to the centre wheel. The train should immediately start to rotate, and when you release the pressure, the train should continue to rotate coasting gradually to a halt. If this condition is not fulfilled there is no point in proceeding further with the construction until the fault is found. If the test fails, the offending part will have to located, cleaned and re-adjusted as required. Failure at this stage will result in a clock that has a nasty habit of stopping just as visitors are admiring it!
7. Escape wheels should be as light as possible (low inertia) and their pivots should be small.
8. Gear teeth, and especially those of the escape wheel must be concentric with the centre hole. A slight wobble is acceptable.
9. A pendulum suspension spring can be made from feeler gauge. A piece can be cut with scissors 1 1/2" long. it can be clamped between pairs of 1" corner brackets. No more than 1/2" of spring should be exposed between the clamps.
10. While the length of a pendulum is critical to time keeping accuracy, there is no rule as to the weight of the pendulum bob itself.
11. All pivots should be lightly oiled as well as the pallet faces. Normally, the gearing in clocks is not lubricated, but there is no reason why the teeth should not also be lightly oiled. Ensure that the clock is covered to prevent dust from accumulating.