We live in a small village and the local church has a tall spire with a tower clock movement. Some while ago my friend Dave and I were invited to have look at the workings of the clock which was quite interesting. The clock is still hand wound twice per week and it does not have any added technology to maintain the time keeping accuracy. This was some time ago and I thought nothing more of it.
I am a member of the British Horological Institute (BHI) and attend the local meetings once per month. Earlier this year the subject for the monthly lecture was the Tower Clocks of Cooke of York. This was particularly poignant for me having spent my early years growing up in the York area. To my surprise that evening I discovered that the clock here in the village was a Cooke clock. For those interested the presenter of the talk, Darlah Thomas together with her husband have produced a book on the Cooke family containing a listing and description of the known Cooke clock installations and indeed the optical devices the company produced. It is a splendid volume worthy of any coffee table collection.
So back to the story …. the village clock, a Cooke clock and I was living in its shadow.
At the meeting I met David Pawley who spends his life maintaining tower clock movements throughout the south of England. You can read his website Tower Time here. I mentioned where I lived and he asked if I would mind helping him with some maintenance on the village clock here in my village. He had been waiting for the striking mechanism to wind down so the weights were fully dropped and the time was rife to lubricate and check the strike pulley system. We spent a pleasant morning doing the necessary work and I enjoyed the experience.
During the activity David asked if I could further help him to remove the dials from another tower clock in the local area. The tower was on a farm estate and of wooden construction. The woodwork was in need of repair which necessitated a temporary removal of the dials and motion work. Dave (my friend) and myself duly turned up on the day to help David Pawley and had yet another interesting time working on and removing the items in question.
What impresses me is that these clocks have run for years and years. The technology available when they were designed and built was basic yet here are movements that keep to seconds accuracy after all these years.
I would not be offending David Pawley if I say he is not young and I would compliment him by saying that he carries an enormous accumulation of knowledge and skills. One day his knowledge and skills will pass into history and I do not see a new generation filling that gap. There are a lot of tower clocks in the UK and I can’t see a new generation coming forward to fill the need for maintenance.
I just dared to hit run on my first attempt at Mill Turning. I need to qualify this in that the first run I was cutting air above the set up. It looked OK so I put the real material in the spindle and I got a turned part as designed in Fusion 360. I didn’t part it off and you can see the result below.
Mill Turning is where you place the material you want to shape (usually a rod of some kind) in the mill spindle instead of a milling tool. The tools are mounted on the milling table (see above in the vice) and are completely stationary but move via the actions of the table in the X axis and the spindle in Z. The software is conned into thinking the material is really a milling tool and that the tools are the material.
It has taken me the best part of a week to work out how to model this in Fusion 360 and I have been helped enormously by watching Jason Hughes on YouTube. It involves allocating a different Work Coordinate for the location of each tool.
If I can get this more streamlined and get some better lathe tooling in place to support it, then I will be able to turn clock pillars. This was the last stumbling block in moving to CNC assisted clockmaking.
Tonight I am a very happy bunny. A glass or two of Merlot with dinner perhaps ?
After completing the write up on the Sherline CNC Indexer for use on the Myford for clock wheel cutting, I realised that an important part of the process was the cutting mechanism itself.
I had adapted the Sherline headstock motor and spindle assembly to mount on the Myford vertical slide to act as a secondary cutting source. I use this for cutting clock teeth and for drilling holes ‘off centre’ to the lathe axis for such processes as arbor mounting holes.
I am now running Version 21 of Gearwheel Designer and it gets better all the time.
I decided to make a ratchet wheel as my next test. This highlighted the need to think about the process order on the mill. Below is the design image in Gearwheel Designer.
My CNC sequence was as follows : –
Cut the square brass blank a little oversize and draw a diagonals on it to show the nominal centre (Manual operation).
Drill four holes in the corners outside of the working area of the cutting and use these holes to fasten down the blank to the milling table (which I had protected with a piece of MDF). (Manual operation)
With a drill bit as appropriate, drill radial holes in the centre of the spoke petals and also the centre hole.
Fasten the petals down to the MDF using these radial holes.
Cut the gash outline of the wheel.
Remove the four corner screws and remove the liberated brass outside the gash cut.
Cut the rough pass on the teeth.
Cut the fine cut on the teeth.
Fasten down the periphery of the wheel with small clamps.
Gash cut the spokes to leave the petals free from the blank.
Remove the screws holding the petals and remove the brass liberated.
Run the final cut on the spokes.
Job done apart from a light sanding to remove any small burrs.
Some more images follow : –
The purists will now tell me how it isn’t a proper wheel because the crossing interfaces to the rim have radius rather than a sharp corner.
Well a file will soon fix that …. and I can tell them how I watched another three episodes of House of Cards while this wheel was being cut.