Gents C7 suspension spring and chops problem.

[rogerj]

Work progresses on the complete refurb of a Gents Master Clock. This one was in poor condition when I bought it many years ago - especially the case which had stood in an inch of water at some time so the case has been completely taken apart, reglued and refinished. I've started to re-assemble and have hit my first snag.

The suspension spring is broken with less than 1/8" showing from the pendulum block. I believe this part is called the chops so will use that term. The chops are two equal sized pieces of steel pulled together by a small screw - which I have removed. The blocks will not separated and with the amount of effort that I'm using so far and the broken piece of spring will not pull out and I don't want to risk damaging anything.

Close inspection show what may be the heads of two small pins below the clamping screw. Are they also penetrating the spring? Are both parts of the chops permanently fixed to the invar rod or just one ? Basically how do I get the spring out ? (one side of the chops has a serial number 7078 BTW)

The next problem will be where to get a new suspension spring as it seems to be a type special for the C7 ?
Any help appreciated as I'm not very familiar with clock stuff.....just fascinated..Roger

 

[Rogerstar1]

My suspension spring on a Self Winding Clock Company Master Clock was broken, too. I found a replacement at TimeSavers.com
They have a pretty extensive collection of springs and I hope you can find what you need. Click here:
http://timesavers.com/search.html?q=suspension+spring&go=Search

Buy several if you locate the correct one as the weight of the pendulum can be quite hard on this somewhat delicate part. I've broken a few adjusting the pendulum length.

 

[Rogerstar1]

Here is another relevant thread addressing clock speed and thickness of the suspension spring. I never knew of the correlation, adjusting by pendulum length alone. Click:
https://mb.nawcc.org/showthread.php?26925-suspension-springs-and-clock-speed

 

[rogerj]

Thanks for that information. Among the timesavers suspensions I saw pre-drilled springs for the PO No.36 master clock. Next time I order I'll get a couple of those as spares for my own PO 36 clock.
Unfortunately I can't see the springs listed for the Gents C7. The C7 spring is unusually thick at 15 thou. (.4mm) I've attached a photo. When assembled, there is 19mm exposed between the chops.
At least, since I first posted, I have found that there ARE two pins securing it to the chops (as well as the screw) and have managed, with a borrowed punch, to drive them out.
I have found a 12 thou feeler gauge that might do but don't know how to make the holes with the tools I have.
So still hoping someone can tell me where to buy replacements. The spring shown is broken in 2 places.

 

[Rogerstar1]

I would think 'sistering' two thinner suspension springs one along side of the other to achieve a servicable thickness would work. (Indeed your orginal appears to be two side by side springs in your photogaph) Drilling holes in the precisely right places is a taller order but not impossible. Mark with a pilot indentation using an awl and then, beginning with a tiny drill bit mounted in a drill press SLOWLY begin the process of drilling through and then reaming the correct sized hole. The length of your new suspension spring makes no difference as the overall length of the pendulum is what is critical and may be adjusted by raising or lowering the bob.

CAVEAT: I'm strictly an amateur myself! Listen and follow my advice at your peril.

 

[rogerj]

Well, I now have a replacement suspension spring. Made on the lounge floor with a dremell type tool. After posting my last I found I also had a 15 thou feeeler gauge of exactly the right width.
The chops at the head of the pendulum rod have a fixed 15 thou gap so a thinner spring would need to be shimmed.
There was already a hole at one end of the feeler gauge which was enlarged with small pointy grind stone.
The lower screw hole was first punched with the tip of a masonry nail (on a steel block with a small hole) and the burr at the back ground off. This was repeated from the other side until a small pointed steel reamer could enter and it was then enlarged to fit the screw.
The suspension spring was then assembled into the chops and the pin punch (1.44mm diameter) was used to punch through the spring using the locator pin holes in the chops as a guide. Only a single tap with jewellers size hammer was needed to do this.
The holes were then slightly enlarged with the small pointed reamer.
So I shall be on the lookout for another set of imperial feeler gauges so I can make a spare. An amateur solution but it's done the job. Thanks for you input Rogerstar1. I started out thinking I would have to buy this part but in the absence of a suitable source was encouraged to have a go !
In searching eBay I see that there are plenty of clock mainsprings advertised that are 15 thou thick and I would think are another possible source of suitable spring material.
Roger