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Minute Recording Jumper Repair

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I thought I'd break this out as a separate narrative from the Pierce Navigator repair I posted here.  Anyone who has done an old chronograph repair is aware of how delicate part 8270 (minute recording jumper) is.  The Pierce 134 movement is put together quite a bit differently from your normal chronograph in that it has a vertical clutch arrangement as opposed to the laterally engaged coupling clutch found in the more common Venus and Valjoux chronograph movements.  As a result of this uniqueness many parts, while functionally the same, are designed in a wholly different way.

The Pierce minute recording jumper (pawl) is different from the typical jumper piece in that it is not a spring, but rather a pivoting lever which is held in tension by the thinest of wires.


The wire needs to be manipulated in to put the jumper under just enough tension to hold the minute register wheel static until activated by the intermediate wheel.  Too much tension will cause the watch to stop when the elapsed minutes are recorded, and too little tension will allow the minute register wheel to spin freely.

Unfortunately it is not uncommon for the wire providing tension to fail after manipulation.  Here I have a jumper in which the wire has broken and the jewel (well, actually it's just a cut piece of steel) has come lose.


Initially I though it would be a simple fix to replace the broken wire.  I used some 18 gauge electrical wire which was composed of several strands of thinner copper wire.  Stripping the insulation off, I took a single strand of the copper wire and assumed it would suffice.  Under the microscope it was evident that this approach wouldn't work.  Even the smallest copper wire I could find was several times thicker than the wire I needed.

Using the bench micrometer I measured the thickness of the broken wire at 0.05mm.  To give an idea of how thin this is, I snapped a picture under the microscope of the wire next to a human hair.  The wire is on top, the hair on the bottom.


Armed with hard data I was ready to take a second shot at the challenge.  Using the internets I found a company in the UK which could supply nickel wire in the same thickness.  I placed an order, then added a couple spools of varying thickness just in case (and to make the product to shipping cost ratio a bit more reasonable).

The wire arrived in due course and was exactly as described.



I began my repair by knocking out the brass pin which secured the old broken wire to the pawl.  A sewing needled was used to knock the pin out.


The "jewel" was then replaced using a bit of shellac and a alcohol lamp.


Now it was time to replace the spring wire.  I cut a length from the spool and threaded it through the eye piece on the jumper.  Naturally this was done under a microscope.


A replacement pin was inserted to hold the wire in place and the excess was trimmed off using the scissors on my Swiss army knife (they seemed to be the perfect tool for this job).

As you can see had two jumpers to repair:


I'm very pleased to have been able to repair these parts as they can be quite expensive when purchased second hand; from personal experience I've seen the Valjoux and Venus jumpers cost between $30 and $120 USD which is quite a lot for a little bit of steel.  Pierce parts can be hard to come by also.  I currently have two Pierces in varying stages of repair so the jumpers will come in handy.

On a side note I don't vape so I have no idea why tiny nickel wire is necessary for smokeless smoking. :blink:

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  • 2 weeks later...

Howdy, Ry!

I just loved your blow-by-blow of this repair.  What ingenuity to come up with the solution like you did.  I think pinning with the brass was a good idea... the shellac might have worked, but the replacement pin, I think, adds just a bit more security, owing to the pressure it would be under.  

Great job and I thoroughly enjoyed the walk-through.  :thumbsu:


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