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Can I sub T end for unavailable DB? (Vostok 2809)


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Hi Everyone,

I'm looking for help in replacing a mainspring, if possible.  I have a Vostok 2809.  The end has a little cross grove with an additional piece of metal attached to it.  I believe it's what Cousins calls a DB end, but nothing in the width, strength or length is available.  They have plenty of T end mainsprings in stock however for cheap.

The barrel ID is 12mm, and the available inner height is 1.6mm. I calculated a strength of 0.138 or so. 

Thanks in advance for any tips, including leaving it alone.  🙂

 

 

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Hi @AndyGSi - Thank you so much for  that, searching was really hard for me.  I managed to find a stronger DB end of 0.15 as a reasonable substitute. 

I think it's a DB instead of DBH, but not sure if there's a practical difference.  I've taken apart a donor mainspring barrel and this is what I've found:

Donor mainspring Width: 1.88mm, thickness: 0.13 mm

Barrel Inner depth: 2.25mm

Barrel ID: 12mm

Lid thickness: 0.56mm

If I do the math for the width correctly (2.25 - (0.56+0.1)) = 2.25 - 0.66 = 1.59

What do you think??

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@AndyGSi Also curious what to expect substituting what may be a 70 year old mainspring for a brand new one. 

Doing a little more testing, the watch slows down and gets up to 270 degrees of amplitude when on a full wind. Teeters out in a few minutes after that though.  Sorry, still need to do the free oscillation testing, just want to let her run a couple of days before I feel like i know where she's at, then I'll do more.

A little more info:  The lid is hollow.  That is, there is a lip at the edge approximately 0.2mm.  So do I count the lid thickness as 0.56, or 0.36? If 0.36 then I still don't get to 2mm but 1.79mm, still shy of 2.

 

Edited by NigelTufnel
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32 minutes ago, NigelTufnel said:

I managed to find a stronger DB end of 0.15 as a reasonable substitute. 

You may find that the 0.15 is too powerful.

Can you post photos of the barrel and lid as I would have expected the
Zenith 135 spring to be something that's wouldn't change on the Vostok.

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@AndyGSi Apologies for the lack of focus, but you can see the insides of both along with the end of the mainspring.  For the record, this is the donor, which is just like the one ticking right now, so I've not bothered to clean it.  I did NOT leave the other one in this shape!:

image.png.3f14e53220afcdd00267b349046a5070.png

Edited by NigelTufnel
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What I see is that the donor spring width is almost 1.9. The original will be the same. This only means that the measurements are nod that correct. And yes, the lid thickness is the smallest thickness, not with the lip. If the amplitude varies, then check what I have written about the 3rd wheel in previous message.

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1 hour ago, NigelTufnel said:

I'm using 44.  I've read somewhere 44 to 46 was the correct amount.  It's not too bad, but the speed is too high to regulate.

Yes 44 is correct.

45 minutes ago, NigelTufnel said:

Folks, turns out my digital calipers have too much play in the depth rod.  Can anyone recommend calipers or a micrometer with small enough feeler/depth gauge to work in a 12 mm barrel?

I've got this. You can zero it with the thickness of the base and then just measure the overall to give the internal.

https://www.amazon.co.uk/gp/product/B07K2VC3KR/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

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3 minutes ago, AndyGSi said:

Yes 44 is correct.

I've got this. You can zero it with the thickness of the base and then just measure the overall to give the internal.

https://www.amazon.co.uk/gp/product/B07K2VC3KR/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

That looks pretty but no idea how to measure inside the barrel with those big anvil faces. 

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7 minutes ago, NigelTufnel said:

That looks pretty but no idea how to measure inside the barrel with those big anvil faces. 

I can't remember the size and it's at work but the part that moves is small enough to easily fit inside a 12mm barrel.

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2 hours ago, mikepilk said:

I use cheap calipers like this. They are accurate enough for most uses. When I check against my micrometer, they are pretty close.

 

image.png.151cf532a84867e752057e6e85261dbe.png

The problem with these is trying to use the depth gauge when it waggles about on something that's only a few mm.

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