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Advice on Carbon to Alloy Mainspring Replacement


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I'm working on a lovely Smiths Empire watch with the 'RY' movement (https://17jewels.info/movements/s/smiths/smiths-ry-empire/)...
The mainspring is broken and I thought to replace with an alloy. I've been fortunate to this point to not have to rely on the raw calculating but I can't find a reference for this caliber from Dr Ranfft or the other usual subjects...

The calculators @  https://www.vintagewatchstraps.com/mainsprings.php return some interesting results, as the barrel of this movement is relatively large and the old spring is quite thick. From my calipers I came up with D 15.7 arbor 4.1 thickness .17 height 1.27. Unfortunately neither the alloy charts nor Cousins show any close replacements. I only found one close listing on the defunct http://www.obsoletewatchandclockparts.com/770-mainspring.htm that used to stock and sell Smiths parts...

I'm in new territory so guidance is appreciated...

IMG_0820.jpeg

Edited by rehajm
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1 hour ago, rehajm said:

I'm working on a lovely Smiths Empire watch with the 'RY' movement (https://17jewels.info/movements/s/smiths/smiths-ry-empire/)...
The mainspring is broken and I thought to replace with an alloy. I've been fortunate to this point to not have to rely on the raw calculating but I can't find a reference for this caliber from Dr Ranfft or the other usual subjects...

The calculators @  https://www.vintagewatchstraps.com/mainsprings.php return some interesting results, as the barrel of this movement is relatively large and the old spring is quite thick. From my calipers I came up with D 15.7 arbor 4.1 thickness .17 height 1.27. Unfortunately neither the alloy charts nor Cousins show any close replacements. I only found one close listing on the defunct http://www.obsoletewatchandclockparts.com/770-mainspring.htm that used to stock and sell Smiths parts...

I'm in new territory so guidance is appreciated...

IMG_0820.jpeg

Wow that was a read on therories of spring sizes. Which one did you use . Barrel diameter, arbor diameter,  rule if thirds , rule of half reamaining spring space etc etc. 

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The Generale Ressorts book shows a 13"' (ligne) Smiths movement, which this one is, as using a spring 1.60 x 0.135 x 660 in a ring 14.5mm diameter. 0.17 seems really thick for a 13"' movement, but it is a pin lever (and not a very tall spring), and GR does have some errors in the book. It's not uncommon to find springs far off the original size that have been used in the past to get the watch going, which might explain the height difference.

 

For a spring that should work according to your measurements Cousins has GR ref 3398 1.30 x 0.17 x 520 x15, which should be fine (and cheap at 7 pounds).

 

 

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1 hour ago, Neverenoughwatches said:

Wow that was a read on therories of spring sizes. Which one did you use . Barrel diameter, arbor diameter,  rule if thirds , rule of half reamaining spring space etc etc. 

Haha...uh, yes? (haha)...then I considered torching and folding over the end of the broken spring 😅...

59 minutes ago, nickelsilver said:

The Generale Ressorts book shows a 13"' (ligne) Smiths movement, which this one is, as using a spring 1.60 x 0.135 x 660 in a ring 14.5mm diameter. 0.17 seems really thick for a 13"' movement, but it is a pin lever (and not a very tall spring), and GR does have some errors in the book. It's not uncommon to find springs far off the original size that have been used in the past to get the watch going, which might explain the height difference.

 

For a spring that should work according to your measurements Cousins has GR ref 3398 1.30 x 0.17 x 520 x15, which should be fine (and cheap at 7 pounds).

 

 

Thank you so much for your assistance. I was uncertain if a taller spring would be appropriate to consider. I did wonder if the spring was a service replacement. Based on the amount of whale oil in the keyless works this watch surely visited the repair shop. I have the oil cleaned up but never did find the harpoon...

...interesting to me is it's quite a large barrel, and the existing spring, even when broken, made this an ambitious movement...

IMG_0813.jpeg

1 hour ago, nickelsilver said:

The Generale Ressorts book shows a 13"' (ligne) Smiths movement, which this one is, as using a spring 1.60 x 0.135 x 660 in a ring 14.5mm diameter. 0.17 seems really thick for a 13"' movement, but it is a pin lever (and not a very tall spring), and GR does have some errors in the book. It's not uncommon to find springs far off the original size that have been used in the past to get the watch going, which might explain the height difference.

 

For a spring that should work according to your measurements Cousins has GR ref 3398 1.30 x 0.17 x 520 x15, which should be fine (and cheap at 7 pounds).

 

 

...and since you were kind enough to supply the GR reference I did circle back to the Cousins GR online copy (I don't have access to the book..) I see the 4585 in the size you mentioned but I was uncertain since Smith had both the LY and RY Empire (and the PY, which is pocket watch?)...it also quite different in size from what I had...

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2 hours ago, nickelsilver said:

The Generale Ressorts book shows a 13"' (ligne) Smiths movement, which this one is, as using a spring 1.60 x 0.135 x 660 in a ring 14.5mm diameter. 0.17 seems really thick for a 13"' movement, but it is a pin lever (and not a very tall spring), and GR does have some errors in the book. It's not uncommon to find springs far off the original size that have been used in the past to get the watch going, which might explain the height difference.

 

For a spring that should work according to your measurements Cousins has GR ref 3398 1.30 x 0.17 x 520 x15, which should be fine (and cheap at 7 pounds).

 

 

Thanks for the 👉 to this useful document Nickelsilver 

1 hour ago, rehajm said:

Haha...uh, yes? (haha)...then I considered torching and folding over the end of the broken spring 😅...

Thank you so much for your assistance. I was uncertain if a taller spring would be appropriate to consider. I did wonder if the spring was a service replacement. Based on the amount of whale oil in the keyless works this watch surely visited the repair shop. I have the oil cleaned up but never did find the harpoon...

...interesting to me is it's quite a large barrel, and the existing spring, even when broken, made this an ambitious movement...

IMG_0813.jpeg

...and since you were kind enough to supply the GR reference I did circle back to the Cousins GR online copy (I don't have access to the book..) I see the 4585 in the size you mentioned but I was uncertain since Smith had both the LY and RY Empire (and the PY, which is pocket watch?)...it also quite different in size from what I had...

The ly is 8 3/4"'  i think of this as the lady's( LY) .Also TY 10 1/2 "' the RY had 2 versions of the 13"' caliber 144 and 649 Empire the 649 is shock protected

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30 minutes ago, praezis said:

This is a Roskopf type movement. They need extra long springs that are hard to get today. The usual mainspring calculation does not work here.

Frank

...so if using rule of thirds or rule of half in my example returns something in the 500-530 range are you suggesting it should be longer?

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2 hours ago, rehajm said:

...so if using rule of thirds or rule of half in my example returns something in the 500-530 range are you suggesting it should be longer?

The GR catalogue is stating 660mm which seems rather long compared to the other calibers, py has a 17.5mm barrel and only a 500mm spring. Though looking at the thickness it seems quite thin for the size of barrel so maybe correct length. 

2 hours ago, rehajm said:

...so if using rule of thirds or rule of half in my example returns something in the 500-530 range are you suggesting it should be longer?

Have you calc'd the sizes through each  theory ?

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10 minutes ago, Neverenoughwatches said:

The GR catalogue is stating 660mm which seems rather long compared to the other calibers, py has a 17.5mm barrel and only a 500mm spring. Though looking at the thickness it seems quite thin for the size of barrel so maybe correct length.

Yes...and consistent with praezis comment regarding the long springs of Roskopf type movements...

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After a bit of the Parrot Sketch with Cousins website the GS recommended 1.60 x 0.135 x 660 x 14.5 size appears in my shopping cart. I figured Cousins of all should have parts for these Smiths and of course they have many of them once I found where to look...

Three days to the US, then assembly.  I shall update the results...

Edited by rehajm
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5 hours ago, rehajm said:

After a bit of the Parrot Sketch with Cousins website the GS recommended 1.60 x 0.135 x 660 x 14.5 size appears in my shopping cart. I figured Cousins of all should have parts for these Smiths and of course they have many of them once I found where to look...

Three days to the US, then assembly.  I shall update the results...

Heeelllo POLY  🦜  😅

Edited by Neverenoughwatches
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On 12/6/2022 at 6:13 AM, rehajm said:

I'm in new territory so guidance is appreciated...

I don't see where you measured the original spring? Another way to do this rather than calculations is just measure whatever he took out of the barrel. It's not always the right spring but usually if it fits in the barrel at least that gives you a starting point.

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40 minutes ago, JohnR725 said:

I don't see where you measured the original spring? Another way to do this rather than calculations is just measure whatever he took out of the barrel. It's not always the right spring but usually if it fits in the barrel at least that gives you a starting point.

He measured it all except the length (which is hard for a pro unless they have a way to visualize the length of a small diameter spiral). Calipers (even micrometers) can diverge from actual thickness by 0.01mm easily which can be the difference between 220 amplitude horizontal or rebanking. But either someone put in a spankingly too short in height spring previously or the cap won't go on.

 

Vertical micrometers are very handy for figuring out spring heights, hand micrometers less so due to the diameter of the spindle.

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1 hour ago, JohnR725 said:

I don't see where you measured the original spring? Another way to do this rather than calculations is just measure whatever he took out of the barrel. It's not always the right spring but usually if it fits in the barrel at least that gives you a starting point.

Hello and thank you! I didn't share this photo previously but even with my modest skills I could tell my goal should be to find a more appropriate spring...the length didn't seem relevant

IMG_0819.jpeg

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6 minutes ago, rehajm said:

hank you! I didn't share this photo previously

Is an unfortunate classic problem of bonsai's mainsprings and what we find in the barrel.

1 hour ago, JohnR725 said:

It's not always the right spring but usually if it fits in the barrel at least that gives you a starting point

It's also why I said this sometimes they will shove very inappropriate things in the barrel it might still set I had a watch that was hopelessly the width was way too narrow but they shall did in because they managed to get the hook on the protruding in that shouldn't have been there in the first place which ultimately got ground off and it proper T spring of the right type was fitted after a very very long search.

38 minutes ago, nickelsilver said:

He measured it all except the length

I didn't see that as I saw all the references to doing calculations. I usually find for length you can grab the spring and just wretched out and be really careful not to let go because that can be painful. Then definitely a micrometer is better than of the near caliper. Then of course variations between the different Metals Can cause problems with amplitude not just variations in the thickness.

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34 minutes ago, nickelsilver said:

He measured it all except the length (which is hard for a pro unless they have a way to visualize the length of a small diameter spiral). Calipers (even micrometers) can diverge from actual thickness by 0.01mm easily which can be the difference between 220 amplitude horizontal or rebanking. But either someone put in a spankingly too short in height spring previously or the cap won't go on.

 

Vertical micrometers are very handy for figuring out spring heights, hand micrometers less so due to the diameter of the spindle.

Just for an idea to measure the length, a bit time consuming and fiddly but i would think reasonably accurate. Place a sheet of perspex or glass over the spring, then use a piece of fine string ( maybe cotton )to follow the shape. Cut or mark the string when finished laying it out, pull the string out and measure 🤷‍♂️.

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7 minutes ago, JohnR725 said:

It's also why I said this sometimes they will shove very inappropriate things in the barrel it might still set

...and to that point this was a relatively ambitious runner even with the broken spring. Though an economical movement, every part of it is quite beefy and I suspect it ran and maintained decent accuracy for a long time.

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4 minutes ago, rehajm said:

...and to that point this was a relatively ambitious runner even with the broken spring. Though an economical movement, every part of it is quite beefy and I suspect it ran and maintained decent accuracy for a long time.

Let us know how it goes, i have a few smiths inc. Empires to get through, TY  10.5 "'.  They were pretty cheap at the time, they've done well to get this old. The Cheltenham factory models 12"' were far better quality and very different in design. Astral, Imperial, De-luxe, National, Everest.

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5 minutes ago, Neverenoughwatches said:

Let us know how it goes, i have a few smiths inc. Empires to get through, TY  10.5 "'.  They were pretty cheap at the time, they've done well to get this old. The Cheltenham factory models 12"' were far better quality and very different in design. Astral, Imperial, De-luxe, National, Everest.

Thank you- definitely I shall. As with sneezes I tend to do watches in threes- there is a second Smiths Empire in my post box as I write and a Smiths military arrived fresh from the Alnwick auctions yesterday. I'll need your assistance!

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I've used a mainspring calculator which in an excel spreadsheet. I'll see if I can post it.

Which I can't, but it looks like this...

image.thumb.png.9d989c29409e0344c15ee71d6d907950.png

If anyone wants this, I can put it in the cloud and give you a link to download it. It's really useful and got me out of a few scrapes not knowing the spring size, as one wasn't present. The last one I used this with was a 100 year old trench watch which I calculated the spring from the arbor and barrel dimensions and got 290 to 300 degrees out of it. What a result! So, this does work well. I find coming down half to one strength when converting from blue steel to alloy mainspring helps from experience. It certainly isn't a direct swap size for size.

Edited by Jon
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9 hours ago, rehajm said:

Thank you- definitely I shall. As with sneezes I tend to do watches in threes- there is a second Smiths Empire in my post box as I write and a Smiths military arrived fresh from the Alnwick auctions yesterday. I'll need your assistance!

Oooooo please can i have at the military, a W10 ? Just had a look Alnwick, a bit far from me but next time I'm up in Newcastle I will drop in.

8 hours ago, Jon said:

anyone wants this, I can put it in the cloud and give you a link to download it. It's really useful and got me out of a few scrapes not knowing the spring size, as one wasn't present. The last one I used this with was a 100 year old trench watch

Absolutely Jon , that would be great and appreciated by all members. Thank you.

Edited by Neverenoughwatches
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13 hours ago, Jon said:

I've used a mainspring calculator which in an excel spreadsheet. I'll see if I can post it.

Which I can't, but it looks like this...

image.thumb.png.9d989c29409e0344c15ee71d6d907950.png

If anyone wants this, I can put it in the cloud and give you a link to download it. It's really useful and got me out of a few scrapes not knowing the spring size, as one wasn't present. The last one I used this with was a 100 year old trench watch which I calculated the spring from the arbor and barrel dimensions and got 290 to 300 degrees out of it. What a result! So, this does work well. I find coming down half to one strength when converting from blue steel to alloy mainspring helps from experience. It certainly isn't a direct swap size for size.

Brilliant Jon! Thank you for sharing…

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12 hours ago, Neverenoughwatches said:

Oooooo please can i have at the military, a W10 ? Just had a look Alnwick, a bit far from me but next time I'm up in Newcastle I will drop in.

Haha, yes, perhaps. I have my hands full with two Empires. The one in this post should be fine once the new spring arrives. The other is a second sweep and non runner. Of course someone thought a quart of oil would do the trick. I spent most of today cleaning it up but there was nothing obvious for why it wasn't running. The balance is free and the mainspring is steel but lovely. I'm a bit worried as some of the pivot holes look oval but will have to do some test fitting to see what's what...

Oh, here's a pic of the W10 for you. The dial looks great- I believe the mess is all on the crystal...

IMG_0836.jpeg

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18 minutes ago, rehajm said:

Haha, yes, perhaps. I have my hands full with two Empires. The one in this post should be fine once the new spring arrives. The other is a second sweep and non runner. Of course someone thought a quart of oil would do the trick. I spent most of today cleaning it up but there was nothing obvious for why it wasn't running. The balance is free and the mainspring is steel but lovely. I'm a bit worried as some of the pivot holes look oval but will have to do some test fitting to see what's what...

Oh, here's a pic of the W10 for you. The dial looks great- I believe the mess is all on the crystal...

IMG_0836.jpeg

Er mate. Do you know what this is worth ? Have the back off , it needs a look inside, hopefully its original and genuine and not been redialled. The last mech watch to be issued to the British army. Crap i am so jealous, but very pleased for you 👍

1 minute ago, Neverenoughwatches said:

Er mate. Do you know what this is worth ? Have the back off , it needs a look inside, hopefully its original and genuine and not been redialled. The last mech watch to be issued to the British army. Crap i am so jealous, but very pleased for you 👍

Looks pretty kosher to me 👍

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52 minutes ago, Neverenoughwatches said:

Er mate. Do you know what this is worth ? Have the back off , it needs a look inside, hopefully its original and genuine and not been redialled. The last mech watch to be issued to the British army. Crap i am so jealous, but very pleased for you 👍

Looks pretty kosher to me 👍

I don’t know what it’s worth but I know what I paid 😜. Thanks- it may have to wait a while- my parts trays are full at the moment…

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