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Timex Self-Wind – the poor man’s Pellaton

November 15 2010 at 9:02 PM
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Chascomm  (Login Chascomm_)
Chinese Watch Guru
from IP address 151.130.37.18

 
This post is not actually about an Asian watch, but I’m justifying posting here because it all came about as a result of my exploration of the conceptual thread connecting the IWC Pellaton auto-winding system to the Seiko Magic Lever:
http://www.network54.com/Forum/642233/message/1287629174/For+fans+of+the+Magic-Lever+auto-winding+system

Along the way I discovered the unusual Timex Self-Wind system. I became curious to examine this device for myself. Ancre-Steam generously provided me with a sacrificial victim.

And here it is; a Timex calibre M31 Self-Wind, designed in the USA and made in Dundee, Scotland. This particular example was made in 1968

[linked image]

It’s a typically clean 1960s Timex style. Easy to read, compact, and doing a reasonable job of disguising the bulk of an automatic movement. Curiously no country-of-origin is specified on the dial.

The caseback, in typical fashion of the time claims the watch to be ‘Water Proof’.

[linked image]

Inside the back is the first piece of evidence that we are dealing with a Dundee-made watch.

[linked image]

Incidentally, while we’re talking origins, I’ve read that the one part of the Scottish Timexes that was always bought in from elsewhere was the dial.

[linked image]

Now, down to the nitty-gritty…

Here is our first view of the movement with the back off. Not much to look at is it?

[linked image]

That huge rotor blocks our view of everything. At least it has a couple of large apertures to access the screws securing the rotor mount.

And this is the dismounted rotor:

[linked image]

As you can see, the mounting plate lies flat upon the movement top plate. Technically it would have been feasible to build the rotor pivot into the top plate, but that plate is just a piece of stamped sheet metal, and it is shared with all the hand-winding versions. So instead, to keep things simple, the rotor is permanently fixed to the mounting plate. I have been professionally advised that this is the fatal flaw of these movements as once the rotor gets a bit of free-play due to wear, there is nothing to tighten up. In the next picture you will see three blued-steel studs embedded in the top-plate which help protect the rotor when taking a hard knock.

Anyway, the really interesting feature of the rotor is the eccentric portion of its axle, clearly visible in the photo above. Essentially it is a cam of circular profile, which engages this fascinating assemblage:

[linked image]

Functionally this is identical to Albert Pellaton’s patent so I can only guess that Timex was standing poised to leap in when the patent lapsed. The rotor cam moves the cam-feeler (those big antlers) in an arc from side to side, which draws the spring-loaded pawl fingers back and forth along the pawl wheel. One of the fingers pulls the wheel in one direction and glides over the wheel in the other. The other finger pushes the wheel on one direction and glides in the other. Thus bi-directional winding is achieved. The spring-loading is biased in one direction, so care must be taken in handling when the rotor is not there to hold it all together. The device has a tendency to go ‘sproing!’ and tangle up.

Here’s a close-up of the assemblage, showing the guides on the pawl-wheel to prevent vertical slippage of the pawl fingers. Also you can see the cam-feeler angled upwards to clear the rotor mounting plate.

[linked image]

All things considered though, Timex did a reasonable job of keeping the additional thickness to a minimum. Which was rather important considering the height of the base movement.

[linked image]

In case the engineers amongst you were thinking that the mounting of the pawl wheel directly on the mainspring barrel would result in an impossibly high torque-load, all is not as it seems. It’s time to turn the movement over.

Here is the dial side of the main plate, with the hour wheel and minute pinion removed for the sake of clarity:

[linked image]

The most eye-catching feature is the epicyclic gearset coaxial with the barrel. Hand-winding rotates the annular gear, the pinion in the centre connects through the middle of the barrel to the auto-winding pawl-wheel. Both of these engage the orbiting pair of wheels which turn the wheel on which they are mounted, winding the barrel arbor. This system ensures effective decoupling of the two winding systems.

So there you have it; the secrets of the Timex Self-Wind revealed. I hope you enjoyed the journey. I know I did.

Stay tuned for my report on cleaning and reassembling the watch. Hopefully it will look this way once again AND be ticking.

[linked image]

 
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