What Do You Think Of This Mainspring?

[Ray]

I recently cleaned and oiled the Seiko 7002 I got off eBay. I had it running for a few minutes and it keeps stopping. I removed the balance and moved the pallets by hand and there seems to be very little power there. I've uploaded a photo of the mainspring, does it look ok? If so maybe it is slipping and I need more braking grease? This is my first attempt at troubleshooting, just trying to think it through logically.

[WillFly]

To me it looks as though it's lost its spring. There's a noticeable kink in it - around 7 o'clock in the large loop on the left - and that may be indicative of the state of the spring. might be worth in investing in a new one - they're not particularly expensive.

[Geo]

The only thing that I can see wrong with it is the slight kink that Will mentioned. Apart from that it looks healthy enough to me having the "S" shape that it should have. Would I lubricate and re-fit, probably as the kink appears that it could be straightened easily. I can't argue with the suggestion of replacement on grounds of cost and the fact that you have gone this far, especially if it is for a customer.

[Marc]

The kink that Will has pointed out would be enough for me to want to replace the spring as it is a potential breaking point; however, I don't think that he spring is "set". The main coils look well spaced and it has a healthy reverse coil on it, so I would be surprised if it's not providing enough power. Also, I believe that a lack of braking grease is likely to result in the mainspring failing to slip rather than slipping too early. The way that braking grease works is that is holds against the shearing force between the bridle and the barrel wall, allowing the spring to be wound up, until the shear force reaches a certain strength, and then it allows the spring to slip. As it slips the shear force reduces to below the braking limit and the bridle once again grabs the barrel wall. I could be completely wrong on that though :-)

Try winding the mainspring by hand (use a screw driver in the ratchet wheel screw on your Seiko as I don't think it has manual winding) and see if you can feel when it slips. If you can get just a couple of turns on it then that should be enough power to run for considerably more that just a few minutes.

 

When you reassembled the movement after cleaning it did you test the free running of the train without the pallet in place? A puff of air on the escape wheel should be enough to spin the whole train easily, and a couple of clicks of power on the mainspring (again use a screw driver to turn the ratchet wheel) should spin the train first of all the right way, cause the train to overshoot the springs fully unwound position, and then recoil in the opposite direction for a couple of turns of the escape wheel (or more).

 

If the train won't spin with a puff of air or there is no recoil then you need to strip the train back and reassemble one wheel at a time, each time testing the freedom of the train for power loss until you find the problem, which could be anything from a bent pivot, broken jewel, incorrect end or side shake, damaged wheel or pinion teeth, etc, so it is important to always thoroughly inspect every part after cleaning and before installing it.

 

If everything in the train is free enough to see recoil from a couple of clicks on the ratchet wheel then reinstall the pallets and put about half a turn of power on the ratchet wheel. Now by just very gently nudging the pallet fork from side to side with the tip of a clean oiler you should see the pallet fork snap smartly across to the opposite banking pin. Also, if you stop nudging the pallet fork just before it snaps across and take the oiler away, the pallet should return to the banking pin you were nudging it away from (this is called draw).

 

If it doesn't snap across or draw back then carefully inspect the pallet stones for any chipping or damage, and the pallet arbor pivots and jewels.

 

If it does snap across nicely and draw back properly, then the issue is likely in the balance assembly.

 

I hope this helps.

[Ray]

Thanks for the quick response and all the suggestions guys, I recently completed the timezone courses but this is the first watch I've bought which has a fault (I was hoping it just needed a clean). I wound the barrel manually last night using a screwdriver and nudged the pallets and they definitely weren't snapping across as expected. I'll strip it down tonight and test how free the train is without the pallets in although I did that at the time and thought it seemed ok, I'll check to see if it's recoiling.

[clockboy]

I had a similar fault with a Seiko and found the spring barrel cover was scored & was catching the spring. I skimmed a tiny amount away off on my lathe & it  worked a treat. Not a recommend repair but with no replacement part available I had no alternative.  

If the barrel cover is OK I would change the spring & use braking grease in the barrel rim.

 

 

PS Have an unusual large pocket watch in for repair approx. 26 Ligne. When time will do a post (watch this space)

Edited January 28, 2015 by clockboy

[Ray]

Thanks clockboy, something else for me to check later. Sounds good, I'll keep an eye out for your post.

[bobm12]

I believe that's a Seiko mainspring (7S26 et al) and the kink you see is the place where it touches the tail as it is winded on the barrel. I'd say it is good to go. I usually clean it with lighter fluid, then lightly rub/film with moebius barrel oil and smear the actual barrel with the Seiko S4 oil. That's all it take. Just be careful not to break it when inserting it back in the barrel.

 

Cheers,

 

Bob

[Ray]

I disassembled the watch and discovered I hadn't quite pushed the canon pinion all the way on, pleased I realised that before removing the mainspring from the barrel (the photo above was took during disassembly before I cleaned everything). It's been running now for over two hours so hopefully that's it. I'm going to leave it overnight before finishing assembly, maybe I'll let it fully run down to test the power reserve on the spring.

[Geo]

That's good that you've found the problem and sorted it. If it's been going for over two hours I'm sure you've cracked it. :)

[bobm12]

Hi Ray, I believe It should be between 36 and 43 hours on a healthy mainspring for those movements!

[Ray]

Cheers Bob, thanks for the info

[Ray]

Got the watch all back together and it's been running well for over 24 hours. The plan was to put it back on eBay to make a small profit to buy another watch to work on. Going to keep it tho, it'll make a good waterproof beater watch for kayaking and jet skiing on holidays etc.