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The main working parts of any clock and for this particular clock it was important to me that they were varied and a mix of wood and metal parts. The other parts such as the frame, bearings, escapement and overall design are all linked from the main clock index page.
The first primary gear on the second wheel - 10 teeth - actually brass roller tubes rotating on steel pins.
The aim here was to reduce friction to a minimum and to make a rough copy of the John Harrison gear (below).
The only image available online for a search of "John Harrison gear" - this shows wood based rollers.
My gear has 10 teeth, the bobbin is made from 2 parts and of mild steel, the pins in the centre of the rollers are mild steel and soft soldered into the bobbin. A small 8BA grub screw is used to locate this on the second wheel shaft. A total of 23 parts for the one gear.
The plywood gear centre machined with 60 slots using a slitting saw in place of a profile gear cutter. The teeth are 1.5mm thick ebony tiles that were then sanded to a rough shape before being individually glued into the slots.
The gear glued, left to dry thoroughly and then sanded back smooth.
I then placed the gear back onto the mandrel in the lathe and sanded the teeth so that they were all exactly the same length and slightly tapered.
This gear is 114mm in diameter from the tip of the teeth.
I machined the edges of the teeth to give a rounded shape using my small pillar drill and a solid carbide burr.
The piece of thick plywood was clamped to the table to give a raised surface that I could rest the gear on and arranged the burr such that it overlapped the depth of the tooth to be machined.
It is necessary to take this machining steady and to make a number of passes.
Note where you start and always ensure that the cutter rotates in the correct direction versus the gear tooth as it will easily split the wood.
This process creates lots of dust and in this case ebony and so best to wear a mask.
A thin coat of polyurethane varnish before the next stage of machining.
This 600 tooth gear meshes with th 10 teeth brass roller gear shown at the top of this page.
Having just checked the mesh by hand the gears feel really good, time to make the spindle.
The pair of gears running together
The spindle being fitted with No. 1x1/4 inch brass screws
The small Engineer Inc screwdrivers are superb.
The 60 tooth gear with spindle attached.
I machined the holes to lighten the gear overall.
The gear still needs finishing with sandpaper and then a very light polish on the main surfaces.
The main clock index page.
If you have made a similar clock and would like to share your experience we would love to hear from you - ed.