My skeleton clock

[Mark FraserParticipant @markfraser24249]

I’d like to try my hand at the Stevens skeleton clock so beautifully done by Sam Stones. I don’t have access to ME in that era, does anyone have back issues or ?? /thanks / mark in Canada

 

[Mark FraserParticipant @markfraser24249]

I’d like to try my hand at the Stevens skeleton clock so beautifully done by Sam Stones. I don’t have access to ME in that era, does anyone have back issues or ?? /thanks / mark in Canada

 

[Richard ParsonsParticipant @richardparsons61721]

Sam

There are several reasons why a balance wheel (and a pendulum) clock ‘run fast’. Two of them are: –

1. “Over Powering” The power source is in putting too much power into the going train which over speeds the escapement

2. “Too hard a balance spring”. This is what you may have here. Springs can be softened in two ways. One is by making them longer the other is by heating them in an oven.

From your descriptions of winding the springs and the pictures one of your problem is tensioning the wire as it is wound. Have a look at SWAMBO’s sewing machine there you will see two dish shaped plates on a common shaft and pressed together by an adjustable spring. I always use a threaded mandrel and secure the wire under a collar as this does not damage the wire. I set the lathe lead screw gear box to the same TPI (or pitch if you have been metricated). I place in the mandraulic drive (a handle) and wind. When the spring is to length I lock the headstock and put a tool makers clamp onto the loose end cut the wire and proceedwith the heat treatment as required.

Good luck

Dick

[Sam StonesParticipant @samstones42903]

Hi Dick,

Thank you for your comments, and for following the clock’s progress. Once again, your comments fit into the picture perfectly.

Now here’s an update on my headway, and a couple of responses.

The clock may require some more tweaking of the balance wheel weights, but I’m pleased to note that it is running very well indeed.

Since I have no data on the validity of the main-spring/fusee `compensation’, I suspect that there could be `patches’ where the `going’ train is over powered. However, for various reasons, I’m compelled to accept that the main spring is here to stay, and changing the fusee profile is not an option either.

When the clock was running fast (28 minutes for one hour), using wire which was 0.011″ (0.28mm) diameter the balance spring was clearly too stiff. My calculations for moment of inertia showed me that to get the same stiffness which John Stevens’ flat-section spring would exhibit, (ie. 0.02″ x 0.005″), the wire diameter would have to be 0.008″ (0.02mm). As an earlier post of mine indicated, this was claimed by my friendly music-shop owner to be the thinnest steel guitar string.

All further springs were wound using this size wire, after removing the stock completely from the music shop. Many springs failed to meet my requirements. Besides gluing the wire to the mandrel, my final method of tensioning the guitar string was to hang a weight onto the end of a braided nylon thread (the same 80lb fishing line I’ve wrapped around the fusee ), then attaching this to the guitar string. Thus I had constant tension, and the wire could twist freely if this needed to occur.

For more information with lots of friendly responses, please see five other threads via :- http://www.modelengineer.co.uk/forums/searchresults.aspSearch=spring&SearchType=1&t=133

With the best spring that I could produce, (upon reflection, it was perhaps too stiff [not enough turns], my inclination was to add weight to the balance wheel.

 

As you can see here

the balance wheel has tiny screws with large heads. These are positioned around the rim, the intention being that they provide a means for time adjustment. To increase the mass of the balance wheel, I slid and glued a brass bush onto the heads of both of the two main adjustment screws, and began a more serious approach to getting the speed correct. With more mass and tweaking of the screws several times per day, I finally achieved an accuracy within three seconds per hour. It ran for about five weeks, with occasional but not yet a full winding.

I was therefore satisfied that the clock could be pulled apart for a final scrub up.

After more messing about in the garage (I don’t have a workshop), I had also made a better-looking spring which I duly fitted as per `the book’ instead of using sewing needles jammed into place. Sourcing some clock oil from a very friendly antique clock restorer in Melbourne, I set the clock ticking.

With (perhaps) an extra turn of wire on the spring, this time the clock was running too slow, so off came the extra mass from the two main screws. They did look a bit clumsy alongside the existing screws. I had also used shellac for the glue, so applying a little heat to each main screw and the weights came loose.

Now the clock was running too fast, but gradual unscrewing of the main screws has produced an accuracy equal to or even better than the previous results.

Phew!

 

Regards to all,

Sam

Edited By Sam Stones on 16/09/2011 01:08:31

[Richard ParsonsParticipant @richardparsons61721]

Sam Hi

I have been looking in the wrong books. In ‘Oz’ do you have a Public Library Union? Where you go to your local Public Library and ask for a book, if they have not got it they will then pass the request to the union who will find if any library in the union has a copy.

The book I found the solution in is ‘Watch and Clock Making and Repairing by W.J.Gazeley published by Hale ISBN 0-7090-4995-1. I was looking at another book by the same author called ‘Clock and Watch Escapements’.

In the first book Gazeley describes two tools for winding balance springs. These are wound 3 of 4 at a time. Each spring is used to make certain that the other springs are correctly spaced. I will PM you a scan of the pages (copy write and all that ‘rhubarb&#8217.

You wind in three or four wires unless you will be using ‘Over Coils’ when you only use 2 wires. Remember you do not have to use steel you can use bronze or beryllium copper. Wind your springs and when you have enough turns you tighten down the cover plate to hold everything secure. You then have to ‘set’ springs. You put the winder into an inert atmosphere at about 1500°F (815°C) for 5 minutes. If you are using steel you will need to harden and temper them. You then fill the winder drum up with soft soap secure the cover plate and heat it up to red heat. Quench in water with about 1/8” of oil on the top to reduce thermal shock. To temper, put the whole lot in to a pan with brass turnings and cover with more turnings place a of polished steel on the top. Heat slowly until the polisher steel turns light blue. Remove the barrel and quench immediately.

You then have to polish, and flatten your springs

Ho Ho what fun!

Dick

[Sam StonesParticipant @samstones42903]

Hello again Dick,

 

I’ve sent you a PM as requested.

 

Best regards,

 

Sam

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