Correct method for increasing end-shake.

[nickelsilver]

1 hour ago, Deggsie said:

Yes. You’re right. I just took out the barrel, removed the lid and measured the internal diameter of the AS1187 barrel. It’s 9.25mm. The anodised washer in which the new spring was safely stored has 6.50 stamped into it. Here are the photos I promised:

 

I image it’s feeble compared to the correct spring.

 

By the way, the watch guy has an excellent database for GR (General Ressorts) mainsprings on his web site. It will now hopefully allow me to search eBay for movt numbers other than AS1187/94 to find the same mainspring.

 

https://watchguy.co.uk/cgi-bin/mainsprings

 

Kind regards

Deggsie

 

 

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Yes, Ranfft is awesome but not infallible for some info; just checked my Generale Ressorts book and they say ref. 4502, 1.60x 0.105x 280 8.5.

[Deggsie]

Well the watch guys database turned out to be extremely handy indeed! I filtered all GR4502 springs and noted it is also used in the ST1686 - the very movement I bought in a box of spares a couple of years back. So, I installed the ST1686 main spring into the AS1186 (much longer and now looks proportionately correct) and immediately it ran up with gusto! On the timegrapher, with no regulation Im getting 280degrees amplitude, +7s/day rate and a BE of 1.0ms This is similar in all planes except pendant down. I think after another clean and proper lubrication this will improve. [emoji106][emoji16]

 

 

 

 

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[saswatch88]

8 hours ago, Deggsie said:

Hello saswatch and thank you. Reading your reply gave me a eureka moment. It seems the nos mainspring I purchased was not correctly identified by the eBay seller and is too short as well as too narrow and too thin!

 

The photos below show the mainspring dims as per Ranft and the dims of the mainspring I purchased. Presumably such undersizing would mean the impulse kick to the balance wheel would not be strong enough to achieve correct amplitude?

 

 

Kind regards

Deggsie

 

 

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Look for mainspring that has metric size on package but most should have both Dennison and metric like Samson springs.