Making Metal Clockworks for Home Machinists. Stan Bray
are happy to indulge.
Before finishing with the history of clocks, it is interesting to think how time itself has changed. Until quite late in the nineteenth century, every town or district kept its own time. Communication between areas was very poor, with limited transportation, and it mattered not what time it was in a town forty or fifty miles away. With the coming of the railways all this changed. A person traveling from say London to Birmingham and then wanting to get a connection to somewhere else needed to know what time that connection would leave in relation to the train on which he or she would arrive. The railways therefore organized their own time, known as Railway Time, which was consistent right throughout the country. Gradually this was adopted throughout the country until everyone used the same. Now time is related directly to the Greenwich Meridian and known as Greenwich Mean Time. Other countries also take their time from the meridian, with allowances made for time zones. As a result, it is possible for anyone, anywhere, to know what time it is in any other part of the world.
The drawing represents an ancient water clock of about 200 BC, said to have been made by Ctesibius of Alexandria, who was a famous inventor. Water passes through the funnel into the reservoir, and in so doing raises the plunger. This incorporates a rack, and a hand with a gear wheel attached rotates to indicate the hours. The carefully regulated water supply is allowed to run for twenty-four hours and then the reservoir is emptied and the cycle repeated.
Chapter 2—The Frame
The frame of a clock will generally be made of two flat plates joined together at or near the corners with pillars. All parts are usually made of brass except in exceptional cases where we might get a steel frame fitted with bushes. The plates are sawn and filed to size, and, after ensuring they are flat and square, they should be held firmly together with clamps, preferably the toolmakers’ type, while two or three small holes are drilled through somewhere near the corners. These holes are to accept pins or rivets that are used to ensure the plates do not separate during operations; once the pins and rivets are in place, the clamps can be removed.
The next task is to mark the position of the pillars that join the plates together and drill the holes for them; we will come to how they can be fitted shortly. Occasionally clock designs do not have this type of plate; instead they are made with strips of brass, more often than not cut into fancy shapes, and instead of four pillars there are only two, one at each end. The principle of joining them together and drilling the pillar holes remains exactly the same, however. As building progresses, other differences will emerge. For example, there will not be a pendulum, so they will not be fitted with a back cock.
Four basic pillars. There are several ways of securing them and, in this instance, locating lugs have been machined on the ends, which are tapped to accept screws.
The Pillars
Generally speaking, the pillars, or spacers as the layman would call them, will consist of brass bars that may or may not be shaped. Shaping is a matter for the individual builder and, in a limited way, is the opportunity for him or her to express him or herself. Fitting the pillars to the frame is done in several ways: some are hollow and a stud is pushed right through and the parts held secure with a nut, or perhaps the ends of the pillars are machined down and threaded to accept a nut. In other cases they are drilled and tapped and screws passed through the frames into them. A third alternative is to machine a step in the pillar ends and pass this through the holes in the frames, which are then secured with a taper pin, fitted in a hole drilled across the step. One thing that is common to all these methods is that, when assembled, the frames must be rigid and square.
The two plates held together with the four pillars and with the barrel fitted for test purposes.
Pillars should generally be made of brass, unless another material is considered more suitable. The securing threads can be external for use with nuts, or internal for screws. The shape is only limited by the constructor’s imagination; some suggestions are shown above.
Setting Out the Train
The most common way of setting out the train is to scribe a straight line lengthwise down the plates and to set the escapement, center or hour wheel, and the great wheel and barrel along this. The third wheel has to be set at one side in order to allow the pinions and wheels to mesh. Just occasionally we come across another design where the escapement and hour wheel are in line and both the third wheel and barrel offset. This is very rare and any details required for such an arrangement would be available from the drawing and any instructions that might go along with it.
Marking Out
Sometimes clock plans will give measurements showing where pivot holes will be placed; if not, it will be necessary to work out spacing for oneself. Start by lightly dot punching a suitable place for the great wheel on the centerline. Use a depthing tool to mark out a position on the line of the minute wheel; this means meshing the great wheel pinion with the minute wheel so they run very smoothly and without any binding. When satisfied with the meshing, use the tool to make a second mark on the line that has been marked on the plate.
A homemade depthing tool with a number of spare spindles. The design of the tool is similar to the commercial models and requires the use of a heavy spring.
Depthing Tool
A depthing tool is something that some people will not have come across before; it is a tool for setting out gears to ensure that they run smoothly. They can be bought, but for normal purposes a homemade device will do just as well, those that are purchased being far more sophisticated than necessary for occasional clockmaking purposes. The tool is simply a means of meshing wheels and pinions, or two wheels, or the escape wheel and pallets, so that a check can be made to ensure they run properly. A professionally made tool will be spring-loaded and fully adjustable, but good results can be obtained from a simple device consisting of two lengths of bar that swivel together with two holes to accept punches. The punches are the same diameter as the wheel arbors, and so the wheel and pinion are simply slipped on and adjusted. If different-sized arbors are likely to be used, fit brass bushes that can be interchangeable. One of the punches is set in the mark already made and the other is lined up on the line on the plate. A slight tap with a small hammer and the correct place for the arbor of the hour wheel is marked. John Wilding, who is one of the finest clockmakers in Britain, recommends a piece of slotted bar for the same purpose, an idea that works very well.
The back cock must be absolutely square, otherwise the pendulum cannot operate properly.
The depthing tool being used to assemble a plexiglass (Perspex) wheel and a pinion. The tool is adjusted until they are running freely and then it is locked in position. The tool is placed on end, and a smart tap with a hammer on each spindle leaves indents at the correct spacing ready for drilling. As well as obtaining the distances for wheels, the tool can also be used to check the working of the escapement.