How do I install this mainspring?

[Bopmd]

Hello,

I was cleaning my Longines sport chief and after reassembly it worked very well untill I wound it up fully. I believe the issue is that I did not install the mainspring correctly. Where does this banana shaped piece go and what is it's purpose? 

Thank you very much in advance

[watchweasol]

Hi  The "banana" piece is the broken tongue from the outer end of the mainspring which attaches its self to the barrel wall when the spring is installed. Automatics have a much longer piece which acts as  a brake and slips as thw watch winds up non automatics employ a spring like yours.  see the following Image attached 

[JohnR725]

If you look at the picture posted above it's a T end mainspring. The problem with any of the unusual shaped mainsprings are that you can't just push it in it has to be in the right place otherwise it will never magically go into the right place all by itself. Ideally for T end it would be nice if you had a mainspring winder. You'd wind it all most all the way into the winder you'd leave a little bit out. Then you slip the little bit out and the winder into the barrel so your barrel for the winder has to be little smaller than usual. Rotated around until the tea party is over the slot or hold that it goes into push it into place and then use something to hold it in place. Like push on it with the end year tweezers the biggest screwdriver you have it just has to be held in place when you push the mainspring out otherwise it's not going to be there when the mainspring comes out. Once the mainspring is out any fantasy thought of rotating it to get it to go where it's supposed to be is a very very limited. So basically it has to be where it's supposed to be when it's inserted.

If you hand wanting it in you do have to make sure it's in the slot before your wind the rest of the spring otherwise the same problem cannot be rotated to get it in place is too much pressure on the barrel wall.

[Bopmd]

12 hours ago, JohnR725 said:

If you look at the picture posted above it's a T end mainspring. The problem with any of the unusual shaped mainsprings are that you can't just push it in it has to be in the right place otherwise it will never magically go into the right place all by itself. Ideally for T end it would be nice if you had a mainspring winder. You'd wind it all most all the way into the winder you'd leave a little bit out. Then you slip the little bit out and the winder into the barrel so your barrel for the winder has to be little smaller than usual. Rotated around until the tea party is over the slot or hold that it goes into push it into place and then use something to hold it in place. Like push on it with the end year tweezers the biggest screwdriver you have it just has to be held in place when you push the mainspring out otherwise it's not going to be there when the mainspring comes out. Once the mainspring is out any fantasy thought of rotating it to get it to go where it's supposed to be is a very very limited. So basically it has to be where it's supposed to be when it's inserted.

If you hand wanting it in you do have to make sure it's in the slot before your wind the rest of the spring otherwise the same problem cannot be rotated to get it in place is too much pressure on the barrel wall.

Ok, thank you. I did get it in the notches in the barrel, but I just wasn't sure what do with the broken piece. Watch works perfectly now without the piece. I would probably be smart to get a new spring, but I'm on a budget :)

[rodabod]

Worth pointing out that to substitute using a T-end mainspring, sometimes a short section of T-end is used with a conventional resilient hooking spring which works as an alternative. More often seen as a repair job on older watches. Some barrels which have cut-outs for a T-end will also have a suitable notch to allow a resilient hooking to work as well - such as those found on 40’s and 50’s JLCs.