I have a 992 that has been serviced and runs great in all positions but loses about 3 minutes per day. What do I look for next. Possible weak mainspring? It seems to pick up the pace a little when it is held up aginst the stop fully wound. Gently not too hard. What do you all think?

Aaron Bereiter
NAWCC# 156432
Very Proud IHC Charter #55
We rise highest when we stoop to help others.

Seems like it looses the most time overnight. I wind it fully in the morning about 6:00 am.
Just a observation I thought might help to figure this one out.

Aaron Bereiter
NAWCC# 156432
Very Proud IHC Charter #55
We rise highest when we stoop to help others.

You described the two classic examples of a tired mainspring.

When you said..."It seems to pick up the pace a little when it is held up aginst the stop fully wound. Gently not too hard"...That's the weak mainspring, my advice would be to replace it.

When you say..."Seems like it looses the most time overnight. I wind it fully in the morning about 6:00 AM"... that is further evidence.

A mainspring has least power toward the end of its wind. When it is already weak it is even more apparent.

You're well on the way, Aaron!

Lindell

Aaron,

I would go with Lindell's post and change the mainspring. If, however, you change the mainspring and find it's still losing time you may want to adjust the balance.

If you've ruled out all other possible causes for the watch running slow (including poise) you can make a minor adjustment to the balance as follows:

1. Set the regulator to the center position and time the watch for at least two days, winding the watch at the same time each day. Let's also assume it's now running about 4-5 minutes slow each day.

2. Remove the balance and check if the mean timing screws are turned out any. If so, turn each one in no more than a quarter turn each. Recheck the timing. If it still runs slow, try another quarter turn each. If it still runs slow and the mean timing screws or the screws immediately adjacent to the mean timing screws are now screwed home, you will need to remove some weight.

3. Using a screw undercutter, remove the identical amount of material from two opposing balance screws (try undercutting the screws immediately adjacent to the mean timing screws). Remove only a tiny-tiny amount.

4. Recheck your timing. Let's assume you removed a little too much and the watch now runs one minute fast per day.

5. Unscrew each mean timing screw no more than a quarter turn each. Let's assume the watch now runs 10 seconds slow per day.

6. With the regulator already setting at the mid position, you can now fine tune the watch toward the "F" position. In a perfect world, the balance should be adjusted to keep near perfect time with the regulator at the mid position. This allows a full range of future adjustments from "F" to "S".

Some may prefer to undercut the mean timing screws but I've found that removing and installing these screws will eventually cause them to back out during operation. It is important that these screws maintain good thread friction. Also, never undercut or adjust the screws near the balance cut end. This will interfere with timing during temperature changes.

Hope this helps you a little!

John D. Duvall
Rosamond, CA.
NAWCC Member 0144772
NAWCC IHC Happy Camper 192

Thanks Lindell and John. The mainspring is on the way and I'll keep you all updated.

Aaron Bereiter
NAWCC# 156432
Very Proud IHC Charter #55
We rise highest when we stoop to help others.

One more thing. Can anyone tell me if the mainspring for a 992b will work in a 992. The supply house calls them the same. I know where to get nos 992b springs and would rather run a original part than a aftermarket "will fit" part.
Thanks,

Aaron Bereiter
NAWCC# 156432
Very Proud IHC Charter #55
We rise highest when we stoop to help others.

I can't recall for sure if 992 and 992B models use the same mainspring, but I don't think they do. I'm at home right now, and my reference books are at the shop, so I can't readily check at the moment (perhaps someone else will look this up and report the results -- hint - hint ).

In any event, it's very unlikely that a "set" (weak) mainspring would cause a timing error of several minutes per day in a railroad watch. Railroad watches such as the 992 are adjusted for isochronism, which means they should keep relatively consistent rates regardless of the condition of wind (fully wound or after 24 hours running). Essentially, a "set" mainspring will provide diminished power immediately, instead of after 24 hours running, but it shouldn't make a huge difference in a watch that's adjusted for isochronism ("iso" means "same," "chron" means "time," "ism" means "having the quality of").

NEVER, EVER ALTER THE WEIGHT OF THE MEANTIME SCREWS!!! Those are very important, and altering their weight will alter the effect they have. Think of it this way: if one screw weighs 4mg, but the opposite one weighs only 2mg, when they're both turned equal amounts, the net effect will be different. Turning the 4mg screw 1 turn, would be roughly equal to turning the 2mg screw 2 turns.

Also, don't use the meantime screws for correcting poise errors. The meantime screws should (ideally) be set so they're screwed roughly half-way in, which allows for maximum adjustment potential (just like setting the regulator in the middle of the scale). When poising is required, it should be accomplished by adding and/or removing weight from the wheel in the necessary positions. Personally, I've found that poise errors can often be greatly improved by switching screws from one side of the wheel to the other. In other words, if the balance is heavy at one particular screw, switch that screw with the one on the exact opposite side, and vice versa. It doesn't always work, but when it does, it saves additional trouble.

When weight is removed from one or more balance screws to correct poise errors, the net result is an overall reduction in the mass of the balance wheel. Obviously, that will increase the rate of oscillation, and will necessitate additional changes (meantime screws loosened, timing washers added, etc.). If it becomes necessary to alter the poise significantly, it's best to remove 1/2 the required amount from one side of the wheel (by undercutting one or more screws), and adding 1/2 to the opposite side (by installing a timing washer). Doing that will maintain the correct overall mass and moment of inertia of the balance.

With all that said, however, for a railroad watch to suddenly produce a rate that's two or three minutes per day slow after servicing, tends to indicate that something in the watch has changed. Obviously, the watch kept good time originally, and if everything in it is returned to its original condition, it should do so again.

One really simple problem that can result in a slow rate after service is failure to tighten the hairspring stud. Other relatively simple problems can include bent regulator pins, and/or balance screws that have worked loose. Check the regulator pins to see that they're straight, parallel, and that the space between the pins and the spring is minimal. Also, check the balance screws and be sure that all of them (except the meantime screws) are snug -- not "tight," but snug.

If all that turns out OK, it's possible that someone in the past did something to the watch which resulted in a gaining error, and made adjustments to slow the rate accordingly. The recent service may have merely corrected the previous problem, in which event it will also be necessary to reverse the previous modifications.

Happy adjusting!

------------------

Steve Maddox
President, NAWCC Chapter #62
North Little Rock, Arkansas

Everyone, I did notice that the hairspring was difficult to remove from the regulator pins. I removed the balance and recleaned it. All four meantime screws are set the same, probably a few turns out. All balance screws are snug. I opened the regulator pins a little and reinstalled the balance/ cock assy and, its back running and we'll see whats happening now. Thanks and still waiting on the mainspring.

Aaron Bereiter
NAWCC# 156432
Very Proud IHC Charter #55
We rise highest when we stoop to help others.

Perhaps I wasnt' clear in my message above (or maybe I just assumed too much).

The space between the regulator pins and the hairspring should be MINIMAL.

Opening up the regulator pins will make a watch run slower -- particularly in the vertical positions and when the balance arcs are low. It's a legitimate positional and isochronal adjustment for watches with flat hairsprings, but for watches with overcoil (Breguet-type) hairsprings, changing the shape of the overcoil is more technically correct.

--------------------------

SM

Thanks Steve. I moved them very little. They are not quite parallel to each other on the tight side. And were still the same. The watch has lost ten seconds in the last hour.
How long should it run before I begin timing it?

Aaron Bereiter
NAWCC# 156432
Very Proud IHC Charter #55
We rise highest when we stoop to help others.

Update, It lost 1 1/2 min overnite. Still the same rate as before. Next the mainspring because it is the next thing I can do.

Aaron Bereiter
NAWCC# 156432
Very Proud IHC Charter #55
We rise highest when we stoop to help others.

Well, I got mu mainspring and its wrong! Can someone please point me in the right direction of a mainspring. Help. The end of the new spring is not correct to fit in the slot in the barrel or the cap.

Aaron Bereiter
NAWCC# 156432
Very Proud IHC Charter #55
We rise highest when we stoop to help others.

Aaron,

Replacing the mainspring certainly shouldn't hurt (I typically do that as a matter of routine), but I seriously doubt that it's the whole problem.

Of course, without actually observing the movement, I'd hate to say for sure, but I expect you'll end up having to remove a little weight from the balance.

BTW -- What sort of balance work have you done on this particular watch up to this point?

-------------------

SM

Steve, Thanks for the help. Nothing has been done to the balance. I got this watch and it wouldnt keep time. I cleaned and oiled it and it was better. But not much. All the numbers match and nothing looks to have been changed. Please read my previous post reguarding the mainspring. I am not set up to do any balance work and just reciently learned to clean and oil. I am learning this as I go. Nothing was dammaged durring the overhaul.
Steve, are you interested in straightening this out for me? It will be a while before I am set up and able to work on the ballance due to other projects and school. Let me know and thanks,

Aaron Bereiter
NAWCC# 156432
Very Proud IHC Charter #55
We rise highest when we stoop to help others.

[This message was edited by abereiter on February 20, 2003 at 19:40.]

Steve,

I don't think I would ever try to make weight changes to these screws, but for the sake of discussion and my own understanding, what would be the harm so long as the same amount was removed from each screw? I'm assuming, of course, that the screws are the same weight to begin with.

Regards,
Mike

Mike -- Removing weight from the meantime screws will reduce their mass, which in turn, will reduce their potential to adjust the rate. Essentially, the bigger the meantime screws, the more effective they are.

Aaron -- Since the watch didn't keep good time to begin with, there's no telling what someone may have done to it in the past. It may have had the hairspring replaced, or anything else.

I've responded to your e-mail, and as I indicated, I'll be more than happy to help you in any way I can, but as you're trying to learn how to work on watches, it seems to me that this is as good an opportunity as any to do some balance work.

If you're uncomfortable about anything, you can always try it first on a loose balance, but unless you get really wild and crazy, I doubt you'll have any problems.

------------------

SM

Thanks alot Steve. I'll see what I can do and keep you updated.

Aaron Bereiter
NAWCC# 156432
Chapter 185 Charter #55
Chapter 185 Finance VP
We rise highest when we stoop to help others.

Hey guys, I just got a catalog from LaRose. Which mainspring is right for my 992?
Thanks,

Aaron Bereiter
NAWCC# 156432
Chapter 185 Charter #55
Chapter 185 Finance VP
We rise highest when we stoop to help others.

Somebody has got to know.

Aaron Bereiter
NAWCC# 156432
Chapter 185 Charter #55
Chapter 185 Finance VP
We rise highest when we stoop to help others.

Aaron,last week I reiecved amainspring from LaRose for a 992 (s/n 2373442),it seems to work fine although the "ears" on the outer coil weren't as long as the ones on the broken spring.Their stock number was 039337-003,and described as" mainspring Hamilton 16 size,19x5x21 1/4."I was worried about the strength of the small ears, but I installed it anyway and we'll see how long it lasts.The foil that the spring was in reads: MS-JA207 BESTFIT 317/HAM 16s GENUINE HAM 16S.(Wow,looks like I lost my "new registration" status but I'm still definately a newbie...and enjoying the heck out of it!)

Dale, Thanks for the reply. I had exactly the same problem only opisite. The ears on the replacement spring were too big for the hole. I'll try the same spring you got and see what happens. Thanks,

Aaron Bereiter
NAWCC# 156432
Chapter 185 Charter #55
Chapter 185 Finance VP
We rise highest when we stoop to help others.

Aaron,

Do you have the Illustrated Manual of American Watch Movements by The E. & J. Swigart Co.? It sometimes leaves a little to be desired, but I've found it useful to see the complete list of spring strengths for each movement. I take that list and compare it to the LaRose list to find out which one I need.

However, I have found it useful to keep a variety of strengths on hand, especially when you're talking about the white springs, which are stronger than the same size blue spring.

Regards,
Mike

Well, two mainsprings later its up and running again. I'll see how it does in 24 hrs. Thanks again for the help.

Aaron Bereiter
NAWCC# 156432
Chapter 185 Charter #55
Chapter 185 Finance VP

We rise highest when we stoop to help others.

Still the same. The watch lost two minutes overnite.

Aaron Bereiter
NAWCC# 156432
Chapter 185 Charter #55
Chapter 185 Finance VP

We rise highest when we stoop to help others.

Aaron,

Is it loosing time consistantly in all positions? If we can find an error in a particular position we can perhaps better understand the dynamic. (Chapter 14 in de Carle).

A couple of minutes in 24 should be fixable.

Mike Miller
NAWCC Member# 154831
NAWCC-IHC Charter Member# 27

Poorly done hairspring replacement could be a possibility. Maybe improperly vibrated, incorrectly colletted or studded. Lot's of possibilities. It could also indicate some damage to the hairspring. A general weakening from slight rusting. I also wonder about folks who reset the roller jewel without removing the hairspring. The heat from melting the shelac can effect the temper of the hairspring. Also improperly formed overcoil can effect isochronism adjustments.

Normally there is a repeatable pattern to the poor timekeeping that will lead to a root cause. It might take a few days to pin the problem down. But if we can keep Aaron off of his mortocycle for a while he aught to be able to get this one back to standards

Mike Miller
NAWCC Member# 154831
NAWCC-IHC Charter Member# 27

Well, it seems to run good just slow if there is such a thing. It loses the same rate in all positions. It did before the mainspring and still does. The hairspring looks good with no corrosion or marks of any kind. It seems to breathe well and the coils open and close evenly. The meantime screws are probably only a couple of turns out so could this indicate that someone has been monkeying with it before? I dont know what to do.

Aaron Bereiter
NAWCC# 156432
Chapter 185 Charter #55
Chapter 185 Finance VP

We rise highest when we stoop to help others.

Aaron,
This may be obvious, but are there any timing washers under any of the balance screws? If there are, removing them (in opposing pairs) may solve the problem. If not, and the watch is keeping the same rate in different positions, try turning each of the four meantime screws "in" 1/2 turn each. Make sure that the balance is NOT in the watch when you adjust meantime screws, that is a quick way to snap a balance pivot. With all of us "looking over your shoulder" you'll either get the problem solved quickly of go crazy with all the advice. Keep us posted.

Ed Ueberall
NAWCC #49688
IHC #34
http://members.aol.com/stdwatch/

Ed,
I did as you suggested and we'll see how it doing in the morning.

Thanks guys, I'm getting a real education here and thats what its all about.
Thanks again,

Greg, Thats how I ended up with this project. But, it will run like it should. Again.

Aaron Bereiter
NAWCC# 156432
Chapter 185 Charter #55
Chapter 185 Finance VP

We rise highest when we stoop to help others.

4 Hours later and its perfect to the second. I'm excited and had to tell someone. We'll see how it does over 24 hrs.
Jenny dosent get excited about this stuff. 3 minutes a day was ok with her and she couldnt understand my wanting to get it going.


Aaron Bereiter
NAWCC# 156432
Chapter 185 Charter #55
Chapter 185 Finance VP

We rise highest when we stoop to help others.