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Cyma R-425 Service "things That Go Bump In The Night"


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Cyma R-425 Service "Things that go bump in the night"

 

Here's something a little different, that I hope you all find enjoyable to follow.  A Bump Automatic by Cyma ... the R-425 Movement.

 

This watch was purchased by my Uncle in Sierra Leone back in the 60's, in his wilder younger years.

 

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The automatic winding feature of this movement using a "Bump" system, which these days is a very rare method of winding the mainspring

 

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As you may have noticed in the first picture of the Dial, the numbers on the Date Wheel have been removed.  Once I pulled off the Dial I could see that the number have peeled off the Date Wheel and adhered to the back of the Dial.  I have no idea how this happened :wacko:  One possible explanation is that the previous person who serviced this watch cleaned the Date Wheel with something that over time loosened the paint and glued it to the back of the Dial ... who knows :blink:

 

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As you can see, whatever they used completely stripped the painted ... absolutely nothing remained on the Date Wheel.

 

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Anyhooooo, on with the disassembly ...

 

The plate that secures the Date Wheel on this movement is a full plate, held by 2 screws.

 

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Once removed we can see the Keyless Work and the Calendar Work.  All very standard looking with no surprises.

 

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Here's a closer reference photo of the Keyless work.

 

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Once the Calendar and Keyless Work was removed I flipped the movement over and removed the Bump Weight.

 

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The Automatic Gear Train Bridge was the next to be removed.

 

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Once the bridge was removed the Automatic Work is revealed.

Notice the fine spring system for the Ratchet Arm of the Automatic Work ... this same spring system is used throughout

 

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I removed the plate that holds the Auto Work revealing the next layer containing the Barrel Bridge and Gear Train Bridge.

 

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The Gear Train is your typical looking train except for the having the Second Wheel come up through the plate and running to a long fine pinion.  Very interesting and you rarely see this type of complexity in your average movement these days.

 

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The shock system for the Balance is one I'm not familiar with and would appreciate some input from the old hands on how to clean and oil this correctly.

And yes, the Balance is 18ct Gold ... very purrety B)

 

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Here are all the parts after cleaning ... LOTS of plates in this movement, they fill half the parts tray :P

 

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Stay tuned for the assembly!!  And I may have a solution for the Date Wheel ... :ph34r:

 

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Hi watch fans!

 

I have an update on the Date Wheel for ya.

Remember how I said I may have a solution; well not really :(

 

Here was my Watch Ninja Secret :ph34r:...  The Date Wheel off an ST96-4 Movement looked to be the same!

 

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Even the gear teeth aligned perfectly. same diameter and pitch

 

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BUT, the devil is in the details ... and upon closer inspection, and the use of a micrometer, the thickness of the ST96-4 wheel is a few thousands thicker.

 

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And the curve on the ST wheel is flater than the R-425 wheel

 

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... this thing is about as useful to me as a parachute in a submarine!  :huh:   Back in the parts bin you go!

 

And so the search continues.

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It,s just shows how easy it is to get caught out with used parts.

For example,fitting a replacement hairspring yesterday,

1. checked the strength (dangles 1/2 inch attached to balance)√

2. found the vibration point√

3. adjusted hairspring so all aligns with reg pins & stud aligns with its hole. √

4. used Mark,s vid to get position of stud before attaching to balance.√

 

All perfect BUT the dam collet on the replacement hairspring was fatter than the original so the hairspring could not run flat. After many adjustments to the hairspring & the stud height it now runs OK but not perfect so I will have to re-visit it yet again.

Blast & Dam & double bum

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Hi Lawson,

 

Can you use the staking tool to give the disk the concavity it needs? and maybe file it down a bit first, in a flat stone? Maybe a stupid question... (filling a parachute with air inside the submarine and hoping it doesn't leak!) 

 

I don't know, just an idea.

 

Cheers,

 

Bob

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