Elgin's mainsprings don't have a conventional "T" end but instead use a "T" riveted to the end of the spring near the hook hole. It is referred to as a "double braced" mainspring.

The mainspring barrels on many older Elgin 6s and 16s mainspring barrels have only one slot for the mainspring "T" and it is located in the barrel cover, not the barrel itself. When installing a new #817 mainspring, you must file off half of the "T" before putting it into the barrel. This is normally enough capture if the cover fits correctly and the barrel hook is not worn.

However, on a 16s Elgin conversion movement I'm repairing, the mainspring would slip nearing a full wind. To remedy this, a slot was cut into the barrel (see slide) so that a full "T" spring could be used along with a little help from the barrel hook. The later model Elgin's had slots in both the barrel and cover. Other models may have had this same design but most that I've seen have been either 6s or 16s.

I've never been a fan of Elgin's mainspring barrel and spring design. They are one of the most difficult springs to install and IMHO, poorly engineered.

John D. Duvall
Vice President, Education

I have been having enough problems installing a T-end mainspring on an 18s Dueber Grand and the barrel and cover both have slots. Wish someone could tell me how to keep the T tab in the barrel slot while I eject the spring from the winder. I use a Watch-Craft winder (2 cranks and 6 holders with the button ejectors on the ends). With the 18s spring it is a major chore just getting enough pressure to release the spring. Without fail the tab never remains in the slot. I retried so many times that I broke the spring at the center hole ( Spent 2-3 hours redrilling and filing a new innermost hole! ). The only way I finally got it in place was by attaching a pin vise to the arbor and winding by hand until it slipped some, then again, mm by mm, then too far and around again! Finally got it in and the spring winds and holds fine but still have to replace the roller jewel before I have the pleasure of seeing it run.

Kenny

Kenny,

1. Try to push the mainspring about half way out of the winding barrel. This may allow you to start the "T" end into the spring barrel before plunging the spring in.

If that fails,

2. Try lubricating the inside wall and floor of the barrel with mainspring grease. After installing the mainspring, you should be able to slip the mainspring around with your thumb pressed hard against spring.

John D. Duvall
Vice President, Education

Thanks for the advice, John. I use white vaseline as a mainspring lubricant. Maybe I didn`t use quite enough around the barrel edge. Didn`t want to make it too sloppy. I did find that it works a little better if you leave an inch or so of the mainspring extended from the winder and wind this in the barrel before placing the winder head in. It`s still a hit and miss proposition, however. I believe the problem is not being able to hold the barrel and winder firm and steady due to the force needed to extract the spring. If there was a way to clamp the two together securely I think the tab would stay in place.
Oh well, persistance prevails! Anyone who spends 2+ hours fixing a hole in a $4 mainspring is persistant..........or cheap?



Kenny

Kenny,

You might try lubing the walls of the winder barrel. It could help you in pushing the mainspring out.

I've had no luck in winding the mainspring into a winder barrel that is small enough to allow the last inch of mainspring to remain outside and still fit all of that into the movement barrel, i.e., Elgin double braced springs

I've had my best luck with lubing the walls of the watch spring barrel and plunging the mainspring in with spring "T" end just ahead of the hole/slot. If I'm lucky, the "T" end will uncoil slightly and find the slot. If not, I turn the spring with my thumb a little at a time until the "T" is aligned with the barrel slot and then apply force down on the exposed "T" to seat it in place. With Elgin’s, the hole at the end of the spring will usually catch the barrel hook and you can here the spring click into position.

John D. Duvall
Vice President, Education

I have been filing down the little tab on the spring when I replace one in a 18s Elgin. How did you cut the slot,and finish it. Your idea makes slipping of the spring a lot less likely,if at all.



Frank

Frank Juchniewicz

I, and many other collectors and restorers, follow the advice that you should not modify the watch to fit the part -- you should modify the part to fit the watch. Modifying the barrel may be practical for a common, non-collectible watch, especially when it allows it to accomodate the mainsprings that are available today. However, a collectible watch should be left as it was made. This is important for historical research where someone may be trying to document production changes of a particular model.

[For similar reasons I discourage swapping of entire balance wheel assemblies, rather than replacing a balance staff, just because it is easier].

Frank,

I would only recommend this mod/repair if the barrel hook is badly worn causing the mainspring to slip. I drilled out a tiny series of holes next to each other and then filed and trued the slot.


Jerry,

Should I have tossed the barrel in the trash and put the movement back in the drawer? Maybe use a barrel (with different serial number) from another watch? The hook was worn down from previous slipping making the barrel unusable. Even bending a tongue at the end of the spring would not work.

I agree with you 100% about not swapping assemblies such as balances, etc. I agree with you about not modifying the watch to fit the part. That would be botchery.

The barrel in itself is not a watch or an assembly. It is a part. Once the spring, arbor and cover are installed, it now becomes an assembly. I could have replaced the assembly but instead chose to repair/modify the "part".

Even Elgin saw fit to add this slot in later barrel designs!

John D. Duvall
Vice President, Education

Jery, Steve
I can see both views of this dilemma. I would have to make a judgement on a case to case basis. Thanks for the input.

Frank

Frank Juchniewicz

John, there is no need to toss out the movement or original barrel. My 1904 Elgin material catalog indicates that even at this date replacement mainsprings for this model were only available with both projections of the brace. However, the instructions on the page state "When barrels are not intended for the present style of brace, by breaking off one projection the springs are as originally made". In the case of a worn hook I would restore the hook rather than cut an extra slot in the barrel. Looking at an example in my parts drawer it is evident that the hook is set into the barrel. It appears to be threaded in, so I would unscrew the worn hook and fashion a new one out of threaded brass rod. I think this would be only a little more work than cutting a new slot and would retain the originality of the design.

Maybe I am more of a purist, but I would not modify (or replace) a barrel (especially one serialy numbered) to fit the spring any more than I would modify a balance wheel to fit a more readily available modern staff.

Frank writes: "Jerry, Steve.............."

Hey wait -- I haven't replied yet!

I can see both sides too, although there is an easier and probably better way of addressing the problem, particularly from a "conservator's" point of view, and it works equally well with springs that don't have any sort of brace at all.

When a barrel hook is worn and rounded, as depicted in cross sectional view at figure "A" below, a graver or similar implement can be used to undercut the hook as shown in figure "B," thereby removing the small amount of material shown in red. Obviously, such a modification is minor, it cannot be detected from the outside of the barrel, and it will greatly reduce the chances of a spring slipping over the hook.

An additional help is to "undercut" the trailing edge of the hole in the mainspring so that it can better engage the hook. A cross sectional view of the hole through the end of the mainspring is depicted in figure "C" below. A needle file is used to angle the trailing side of the hole to a sharper edge, thereby removing the material shown in red.

I perform both of those minor modifications frequently, and I've never had any sort of resulting trouble.

====================

Steve Maddox
Past President, Chapter #62
North Little Rock, Arkansas
IHC Charter Member 49

Something else worth knowing is.............

The mechanics of how a spring works when wound and unwound.

In the sketch below, cross sectional views are shown of mainsprings (in blue) and barrel walls (in black). I know that barrel walls are actually curved, but it was easier to draw them as straight lines, and the same principles apply.

When an ordinary spring is unwound, the end rests against the barrel wall and hook as depicted in figure "A." When that same spring is wound, the unattached end rises away from the barrel wall, and if the end behind the hook is too long, it will pry the spring up and off the hook as shown in figure "B."

By shortening the excess material at the end of the spring beyond the hole, and the entire mechanics of the spring can be changed. When such alterations are performed, the unwound spring fits the barrel wall essentially the same as before, as shown in figure "C," but when wound, the unattached end is prevented from causing the hole to rise as much from its resting position, as shown in figure "D." Of course, providing a slight inward slant to the inside of the hole in the spring also helps, as indicated above.

In figures "A" and "B," as well as figures "C" and "D," a movement of 15 degrees was applied, but as can be plainly seen, the "rise" from the hook in "D" is greatly reduced.

====================

SM

Jerry,

Thanks! You are correct about the hook. The barrel is actually an assembly. It does appear to have been threaded from the outside in, trimmed and then finished with the outer circumference of the barrel. To restore this setup would be very difficult at best (for me at least).

This same barrel is used on other, older 3/4 plate models and is visible. The mainspring bridge for convertibles cover the complete barrel assembly so the slot is not readily noticeable. However, this does not lesson your point about originality.

Steve,

Thanks for the diagrams. The hook was so worn on this barrel from previous slippage, there wasn't much left to cut. Just repositioning the spring in the barrel may have ground down whatever edge I could have achieved. The riveted brace is down steam of the hole so when the spring is in the barrel, the added width of the brace away from the hole hinders the contact of the hole with the hook. Cutting the mainspring at the brace and fashioning a tongue-end may have worked with an undercut. I tested an old mainspring using this method but did not undercut below the hook into the wall of the barrel. Every now and then I find an old Swiss spring wound into an Elgin barrel with a tongue end. Someone had installed a mainspring they had in stock in lieu of an Elgin spring.

John D. Duvall
Vice President, Education

And Frank writes again ( Jerry and JOHN........).

Somehow, I new Steve would would showup (pays to be prepared)on this thread

Thanks John.

This is a very informative thread,as I'm sure somewhere down the road I will run into the problem that John spoke of.


Frank

Frank Juchniewicz