Help me identify the correct mainspring for Bunn Special?

[JohnC]

Hi all,

Wondering if some knowledgeable person can help me out with a mainspring code for a model 9 Bunn Special, going barrel. My local supply house has suggested one, but I want to double check. The spring I have now is not Illinois from what I can tell, as it does not match any 16 size Illinois mainspring in PWDB.

Thanks,

John

 

[mikepilk]

Might be something here -

Fom Swigart

From Marshall :

[JohnC]

Thanks @mikepilk. I measure my barrel at 0.76 inches, which makes it "large." From picture 1, that puts me at 47320/21/22.

From PWDB:

https://pocketwatchdatabase.com/search/result/illinois/4006134/parts/Springs

1770 spring matches the dimensions given for 47321.

One hiccup. 47321 is a double brace hole, so unless I am mistaken (always possible) it should hook onto the barrel wall as well as having a T through top and bottom? However my barrel has no trace of a hook.

 

 

Edited April 26, 2022 by JohnC

[JohnR725]

15 hours ago, JohnC said:

The spring I have now is not Illinois from what I can tell, as it does not match any 16 size Illinois mainspring in PWDB.

it would help to have dimensions of the old spring?

I snipped out some images one out of the 1923 Illinois parts catalog. Then off a mainspring list I had the other mainspring list I had was confusing because it insists the same part numbers are T brace. But the pictures maybe that would be okay as it's not a T brace with whole I think it's just a T brace and as long as the TV fits into the slot that's okay.  Then once I confirm your dimensions are on the right track to look like on one of my list is another company that has a  TN spring of the right dimensions but I want to make sure the dimensions are right before I give it to you.

Then the problem with the pocketwatch database is it actually less three different springs because of course there's variations. Then of course there's the minor problem of the pocketwatch database isn't always correct.

 

 

 

[JohnC]

Thanks @JohnR725. Existing mainspring is T-end (no hole), 2.80mm high by 0.18mm thick. Right now I'm leaning toward 1770, also known as 47321.