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"Lock-Down" Project - 1890's Waltham Pocket Watch (Part 6)

  • by Darren Thomson
  • 28 May, 2020

Part 6 - Installing the Pallet Fork

With the train of wheels now installed and working, we can turn our attention to the Pallet Fork and its bridge and screws. Here they are..
The Pallet Fork is the thing that you hear "ticking" in a mechanical timepiece. It, essentially, manages the complex interaction between an Escape Wheel (seen in the last blog) and the Balance Wheel. The Pallet Forks' job is multi-faceted. It regulates the movement of the Escape Wheel by locking and releasing it and it also gives input to the Balance Wheel to encourage it to continue swinging back and forth. This whole interaction is still baffling to me, to be honest. It's one of those engineering things that gets harder to understand the more you know about it.

Anyhow, first thing to do is carefully position the Pallet Fork into it's jewelled hole in the main plate..
Once in place, we can install the bridge over the top to secure everything. Before screwing the bridge down, we need to be very careful to ensure that the fork is properly aligned with the Escape Wheel and that it is sitting nicely in both of it's jewelled holes. The fork itself is about the size of a fingernail and very suseptible to breakage.
Once the bridge is on it's time to test the function of the Pallet Fork. We do this by winding some power into the Mainspring. Oh.. by the way, I found a bunch of old pocket watch keys in my spares drawer..
Having wound the watch up, listening carefully for any potential damage in the mainspring, we can gently "nudge" the pallet fork back and forth. If the fork is operating correctly (and the gear train is delivering power to the Escape Wheel) we should see it "tick" into its new position and "tock" back again.
Of course, this "nudging" of the Pallet Fork would normally be the job of the Balance Wheel.. That comes next..

Onwards..
by Darren Thomson 15 June 2020
As can be seen here, this old watch's case has seen better days. On the upside, it is made of solid Sterling silver and experience tells me that I might be surprised at how nice I can get this looking with a little time on the polishing machine.

... And, sure enough, 20 minutes of careful polishing accomplished this..
by Darren Thomson 8 June 2020
After some serious rooting about in my various parts drawers.. I found a bag..
by Darren Thomson 4 June 2020
We are almost ready to put the dial and hands onto the pocket watch but before that can happen we need to clean the dial and install the "Motion Works". 

Examining the back of the dial reminds us, once again, of the general quality of components used here.
by Darren Thomson 1 June 2020
All of the major functioning parts of this pocket watch's movement are now in place and functional. It's time to see if the old girl has life in her. The project pretty much ends here if there is a major issue with the balance or the mainspring (still un-inspected internally for reasons stated back in part 3). There is almost no chance of finding replacement parts for this piece so it could get consigned back to the spares drawer if this doesn't go well..

A careful wind of the mainspring (feels solid and free-moving - click is working well). And....
by Darren Thomson 24 May 2020
For me, this is the most interesting part of the build, certainly from a mechanical perspective. This is where we get to see how the power delivered from the mainspring travels through a train of wheels to deliver suitable energy to the balance.

Here are the components at play for this stage..
by Darren Thomson 23 May 2020
With the barrel and winding system now in place, we would normally secure them with a bridge. In this case, though, it looks like the main bridge has to go on after the rest of the gear train is assembled. So, for now will just make sure that the centre wheel is properly secured into the bridge and test fit the whole thing.

Having inspected the main bridge and centre wheel.. I've found out where that little pinion gear referenced in part 3 lives..
by Darren Thomson 20 May 2020
Now that we have everything clean and checked over, its time to starting putting the 130 year-old movement back together again. Honestly, anything could happen here and, on a job like this one, I won't even bother to start thinking about the watches' case, dial and so on until I know that I can get the movement ticking again. The good news is, it wont take long. An old pocket watch like this is quite a simple mechanism in comparison to modern wrist watches. For one thing, we have less parts to worry about (no calendar, no "keyless works", no automatic winding mechanism...).

We'll start, as with most watches, with the barrel which houses the mainspring and the associated "click" mechanism (the ratchet that stops the barrel and mainspring from un-winding under tension and the thing that you hear when you wind a watch). Here are the components for this part of the build..
by Darren Thomson 18 May 2020
One benefit of buying a "bag of bits" is that I can skip the initial strip down of the watch. Of course, the downside here is that I really don't know if anything is missing or broken. So, the first thing to do is clean everything up and get 100 years worth of grime off of the components and then inspect everything carefully.. In particular the hairspring, gear teeth, mainspring & jewel settings..

The hairspring is by far the most sensitive watch part. This one looks very dirty but it has a good spiral shape to it, with no parts of that spiral touching other parts of it (which is a common cause of "fast running"). The Waltham spring also has a "Breguet Overcoil" design. This is a specific hairspring design invented by Abraham-Louis Breguet (important watch dude) waaaaay back in the 1700's and, essentially, allows for better performance of the hairspring through varying mainspring tensions (watches tend to slow down as a mainspring loses power and go faster when it is fully wound).

I'm going to clean this movement using my ultra-sonic cleaner and, to do that, I like to mount the balance and hairspring in the main plate to keep it safe during cleaning..
by Darren Thomson 15 May 2020
Well, my last little side-project got completed and we are still in "semi" lockdown in the UK so I thought i'd turn my attention to something else that I've been meaning to get to in the workshop.

As a watchmaker, one thing that you will certainly accumulate in time is PARTS. They come from watches that never got repaired, over-ordering when you only need one of something and a seller will only sell you 10 and, frankly.....Well, I don't know where many of them come from... but come they do. Here's a sneaky peak at ONE of my many "parts drawers".. 
by Darren Thomson 11 May 2020
In the final part of this blog series, we'll complete the watch restoration by casing the watch, re-checking the performance of the movement and putting a strap on. 

Casing the movement can be tricky and normally does not go according to plan first time out. A few things to watch out for here include, movement rings not fitting snugly into the case (so the watch moves around inside its case which is not good), hands touching the inside of the glass (this will stop the watch), automatic rotors touching the inside of the case back (so the watch doesn't wind properly) and winding stems to aligning properly. 
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