Michael Tomlinson is one of the clock makers in the club. Here he describes how clockmakers use a depthing tool with a photo of one
he has recently completed.
Clock wheels are not usually made to exact dimensions from a drawing (a somewhat strange concept for a steam model engineer used to building precisely "to drawing" ).
Instead wheels are made first then the accurate distance between the pair of axles is established using the depthing tool.
Two axles on which newly made wheels are to mesh and revolve are mounted in parallel between pairs of pivots on the depthing tool then, using an screw adjustment to
move axels closer or further apart, spun until the sweetest running position is found. The distance between axels is then transferred to the clock plates using points like a
pair of dividers. Each successive meshing pair of clock wheels in the gear train is treated in the same way.
John Bolter is another of our clock makers.
French Great Wheel Skeleton Clock
This clock was made from a kit supplied by Classic Clock Kits and came fully machined, fully assembled but unfinished. The procedure for dismantling it (letting down the mainspring can
be very hazardous), finishing and reassembling was described in the Model Engineer, Volume 195. The work was mainly filing up and polishing together with some minor adjustments,
as some of the clearances were a little tight.
The clock is driven by a powerful spring housed in the barrel at the base and drives the Great Wheel via a wire cable and a fusee which compensates for the decreasing force of the spring
as it runs down. The wheel turns once in 24 hours, the second wheel (behind the dial) turns once an hour and drives the escapement wheel and pendulum.
The clock keeps reasonably good time, which is improving as it 'runs in', and it goes for 15 days. In some ways, the most interesting part of the work was making the case as this was
not part of the kit and no drawings were supplied.
And now for something a little different:
Though not built by a TSMEE member (!), I was facinated by the following story.
While the quality and workmanship is obvious it is amazing to think this ancient computer/clock was invented and built so long ago.
Please follow the links below to watch 2 videos about the Antikythera mechanism. It was discovered in 1900 AD in a shipwreck off the Greek islands,
the Antikythera Mechanism contains over 30 geared wheels and dials and the remains are covered in astronomical inscriptions.
It dates from around the end of the 2nd century B.C. and is the most sophisticated mechanism known from the ancient world.
Antikythera Mechanism - Part 1 http://www.youtube.com/watch?v=DiQSHiAYt98
Antikythera Mechanism - Part 2 http://www.youtube.com/watch?v=znM0-arQvHc