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

[NigelTufnel]

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. 

 

 

[AndyGSi]

The 2809 is based on a Zenith 135 which has a spring size as below.

Are you sure the barrel is only 1.6mm?

[NigelTufnel]

Removing dube.

Edited September 12, 2024 by NigelTufnel
Dupe

[NigelTufnel]

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??

[NigelTufnel]

@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 September 12, 2024 by NigelTufnel

[NigelTufnel]

I messed up.  I did not find a DB substitute.  << sigh >>

[AndyGSi]

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.

[NigelTufnel]

@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!:

Edited September 12, 2024 by NigelTufnel

[nevenbekriev]

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.

[NigelTufnel]

@nevenbekriev Really a good catch.  The digital caliper's depth gauge is not aligning correctly with the pincers.  I need to zero them out separately. 

[nevenbekriev]

PS If the amplitude gets to 270, then no point to change the spring and no need to do the free oscillations test - it will only show the balance is OK.

[AndyGSi]

I think you need to check the measurements again as the 1.9mm is heading towards the 2.0mm of the Zenith 135.

28 minutes ago, nevenbekriev said:

PS If the amplitude gets to 270, then no point to change the spring

@NigelTufnel If it teeters out after a few minutes what does it drop too?

[NigelTufnel]

@AndyGSiI did a full wind this morning, 3 hours later its' +32s/d at 221 amplitude.  Yesterday it pretty much held this all day.

[AndyGSi]

56 minutes ago, NigelTufnel said:

@AndyGSiI did a full wind this morning, 3 hours later its' +32s/d at 221 amplitude.  Yesterday it pretty much held this all day.

They don's sound that bad for an old spring.

What lift angle are you using?

[mikepilk]

Hard to find data on these movements. No reference to mainspring in the GR database, Cousins or Jules Borel. Must be a reference somewhere

[NigelTufnel]

5 minutes ago, AndyGSi said:

They don's sound that bad for an old spring.

What lift angle are you using?

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.

[NigelTufnel]

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?

[tomh207]

Mitutoya have a very good reputation but they can be expensive. Machinists sometimes refer to the calliper as the “guessometer”

 

Tom

[NigelTufnel]

I see many affordable units, but the small dimensions of this barrel make me worry I'll end up with something too large to use here.

[AndyGSi]

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

[NigelTufnel]

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. 

[AndyGSi]

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.

[AndyGSi]

So the head is 6mm Diameter

 

[mikepilk]

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

 

[AndyGSi]

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.

 

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