Dual Spring National Time Recorder Clocking in clock – why two springs? Explained.

I teceivef an email asking about the architecture of an easy dual Spring National Time Recorder with an integrated clocking in mechanism. As I was writing the response I thought “thisight interest others….” So. Here is my response.

Dear Malcom,

I think I know the unit you are talking about. Both springs drive the clock and the stamping mech which I found odd but seemed to be the case as there was a single con rod gearing to two wheels either side. I think the springs wind in opposite directions so they can use the same wheel set up to reach this gear that looks like a chuck key end. (they are loop end springs as I remember).I really should be able to recall the name of this conical gear.

At any rate, it’s quite a handy feature as if you disconnect the universal joint on this gear both springs power the clock as the power has to go somewhere and there is no differential joint or slip clutch to stop the power reaching the escapement.

The point here is that main springs on these clocks are massive and hard to source, so the ability to use two half worn springs to drive only the clock means you can get another 20 years of time keeping, albeit without clocking in and out of the house every morning.

You might have a different config as I’ve seen a few and the later ones drive off electric motors, however, if you’ve got the one I think you have, then the above is worth knowing. It’s also quite nice that all your doing is a disconnection as opposed to a modification, so the history of the clock remains intact.

I’ll probabay stick this up as s blog post if you don’t mind; others may find it useful and it saves me explaining it again. These national time recorders are a little bit of our industrial history and I think they shine a light on what it was like to go to work at the silk mills here in Braintree for instance. Pretty much the same as today except now you need tons of planet polluting tech to tell your boss what time you arrived.

Good luck with it and keep on clocking. Apologies for any spelling errors – I’m doing this from my phone watching TV.


Justin Holt
Braintree Clock Repairs
07462 269529