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May 12, 2015 at 2:31 pm #49587
Greetings all. Have any of you folks ever worked on the Hamilton Model 21 chronometer (I’m guessing that Bob has.)? I have one that the staff somehow broke at the lower pivot. While it is is technically a clock, it shares more in common with watches, but with some differences. It has a helical hairspring that makes use of a different type of collet that seems to call for a special tool. I don’t want to mess up any parts on this thing, as the parts are rather pricey, especially something like the helical spring. The Hamilton manual calls for a “hairspring wedge tool” that looks like a screwdriver, and probably is. The problem is that I’ve ground an old screwdriver tip down pretty small, but it still doesn’t fit well into the collet slot. Levering from the bottom looks dangerous, as there’s a type of hairspring stud that hangs down below the hairspring and sort of inhibits a clear shot for a lever. Does anybody have any ideas, hopefully based on experience with these timepieces? Thanks ahead of time. Cheers.
Brian W. (Apparently ANOTHER Brian W.)May 14, 2015 at 5:51 pm #62767
Sorry. Aside from doing quick daily backups I’ve been away from the forum dealing with some personal issues for a few days. This type of hairspring is best removed with the tool you mention. I used a modified screwdriver when I used to work on these movements. Most screwdrivers have a bit too much angle on them and can be altered by grinding down one side to reduce the angle. This slight taper will enable the blade to be inserted and gently pressed into the slot just enough to expand the collet while holding in place where a screwdriver with a more extreme angle will require more force to open the collet and may tend to slip. I think you can see where slipping could be real bad in this case. Having the Hamilton manual in hand should help you to set the impulse and unlocking jewel back up (very important to get this correct) but if this isn’t covered I may be able to help you with that so please let me know.
Before removing the hairspring do make note of it’s position on the balance so it can be replaced close to it’s original position. Also I’m sure the manual must cover this but just in case, let down ALL power to the train including maintaining power before dealing with anything related to the escapement! Any accidental tripping of the escapement can result in a damaged locking jewel and/or a bent or broken escape wheel tooth/teeth. When setting up the impulse and unlocking jewel do this first manually to make sure everything looks good then add just enough power to give the escape wheel enough torque to give slight impulse. One complete turn may possibly be too much as this is a fusee providing that extra leverage right from the get go in addition to whatever setup power was wound into it, which could deliver close to full torque with just a single turn. I could be wrong about that though as I don’t remember how much torque there actually is after one turn but probably best to creep up on it.
It’s been a couple of days since you posted this so you may have already finished the job but if not then I hope this helps Brian,
BobJune 5, 2015 at 12:43 pm #62768
Thanks for your input and expertise. Obviously, it is I who should apologize for the late response. I ended up putting the job aside until I feel that I can dedicate more time to study and attack with due finesse. I did let down both the mainspring and maintaining power in the fusee before removing the balance. Still, I do see what might be the tiniest of chips out of one of the jewels on the balance. It’s tough to see, as I don’t have a microscope to look at it with, but it does seem like it could be imperfect. It may well have been running that way since I got it professionally serviced many years ago. I can’t know for sure. Heck, I have no idea how the balance staff got broken, as it was always either in the gimbals box or in the aluminum storage box made for it. It’s all a great mystery.
I really think that this is one of those jobs best left to an expert, someone who really knows these clocks. However, that also comes with a $500+ price tag. I may just have to wait until I get more flush with cash, and have fewer other interests to spend what I do have on, before I get it repaired. I may also consider selling it. We’ll see.
Thanks again. My apologies for the “post and dash”. That was very nice of you to offer your advice. I hope that all’s well with you and yours.
Cheers.June 6, 2015 at 9:10 pm #62769david pierceParticipant
I have never even seen one of these timekeepers let alone taken one apart. There is, however, a video on Youtube showing the disassembly and assembly of one of these devices. The video is done by non other than the great and often unappreciated BUNN SPECIAL.
davidJune 8, 2015 at 10:02 am #62770
Thanks for the recommendation of that video. I actually did watch it when I originally removed the balance assembly. Surely it saved me from doing more damage. And yes, BunnSpl is probably under-appreciated for his help with watches, but not for his rather humorous presentation of same. Good info, but you can’t help but chuckle at his edit-free videos.
In order to safely let down the mainspring and maintaining power, I had to use vise-grips on the winding key I had.
These model 21’s are very impressive movements, as they less like a clock than they are like a monstrous pocket-watch. Very precise, and probably very finicky to set up. That’s why I’m avoiding restaffing for now.
MrRSeptember 5, 2017 at 10:50 am #62771
Thanks for your input on this job, Bob. Years later, I finally ended up getting a new staff from larry Crutzinger (Hamiltonparts.com), and am tackling the restaffing job. I have just successfully removed the hairspring, but not until I fought with it for a couple of days. Below is a post that I added to my similar thread on the NAWCC message board. Maybe someone will find it handy. Or perhaps Bob will respond with a warning not to do it this way? Either way, the post describes how I went about it.
OK, so after finally working up the courage to earnestly try to replace the staff on my Hamilton chronometer, I bought a staff from Larry Crutzinger. For hairspring removal, Larry suggested that I might try to lever the collet up while spreading it at the same time. I couldn’t figure out a way to get under the collet without having too much of a chance to distort the helical hairspring or scratch the balance arm. Then I re-tried something that might be unorthodox, dangerous, or one of those secrets held by the “chronometer-guild”.
I had been supporting the balance wheel on a movement-holder made especially for a Waltham ’92 model (Not the side with nubs.). It supported the rim, and 60% of the arm, very well. Still, I could not get the collet to do anything but spin…no lift. I tried many times, with many differently shaped wedge-tools.
As my next “trick”, I decided to try again by letting physics(?) work more in my favor, that I would turn the balance over and push from the bottom rather than attempt to lift from the top. I was able to get a well-formed-for-the-job screwdriver tip into the outside of the collet. It got a good enough bite that I decided to twist it while I had another brass wedge brought in from the other side and twisted it to lift while I pushed a bit with the top screwdriver. Voila, the balance dropped cleanly and everything appears to be quite undamaged.
I used a wooden 16s movement holder to support the balance during this attempt. It worked fine, but didn’t support the arm of the balance, just the rim. Fortunately, it didn’t take a lot of downward force to get the collet to finally drop.
Again, while this may not be the suggested method, and carried its own risks, I wish I would have tried it sooner, as there may be a scratch or two on the collet that will be seen under magnification. Nothing terrible, but slipping out of the slot is a reality, especially if you don’t have the right tool with the right angle. And seriously, I doubt many have that tool without making one by finding the right angle by trial and error. And you always have to be pushing down, thereby fighting yourself, when you spread the collet from the top.
Your mileage/damage may vary. Cheers.September 7, 2017 at 10:44 am #62772
The chronometer challenge continues. After finally removing the hairspring, I moved on to removing what they call the “unlocking roller”. I first inserted a brass wedge into the side opening of the roller to see if I could get some movement. Once I did, I used a pair of tapered-nose pliers that have non-marring (for the most part) smooth jaws. This worked well to remove the unlocking-roller cleanly.
Now came/comes the removal of the impulse-roller. It’s sort of like a conventional roller, but it has a jewel that sticks out the side of the roller table, rather than down. What this means is that I can’t use the lathe headstock-to-tailstock tug to remove it, as the jewel would be broken off. Conventional roller removers that I have will not accommodate the large size of the balance-arm and roller table on the chronometer. So here I am again, scratching my head to figure out a way to remove the impulse-roller table, all the while trying to adhere to the horologist’s oath of “Do no damage”, but it’s not easy.
The movement holder that the balance is resting on is one that was made especially for working on the Waltham 1892 models. Cheers.
September 7, 2017 at 10:38 pm #62773
Great pics. Thanks for putting them up here.
You’ll need something like a large crows foot to do it safely. Not sure where you can buy one these days but it’s fairly easy to make one.. Take a look at this link Chronometer roller remover tool and it should give you some ideas. I can put a pic up here tomorrow of the one I made many years ago if you would like to see it.
BobSeptember 8, 2017 at 8:23 am #62774
Excellent, Bob, thanks for the image of the tool. Yes, that one looks like it would be “the ticket”. I guess what I ended up doing was much like that. I used a pair of tong/pliers with a locking ring. The design allowed the a tight enough jaw closure so I didn’t need a third hand.
That sort of made a “crow’s foot”, didn’t it? I then set a beautifully machined piece of steel, salvaged from an old timing machine, as an anvil. The foundation needed to be solid to avoid any loss of focused power. Using it atop the movement holder provided enough clearance and it came out after quite a few taps, but came out cleanly. It probably would have taken fewer if I had used something other than wood to elevate the anvil. Thanks again, Bob. One of those “crow’s foot” tools would sure come in handy.
Fortunately, Larry C. provided me with a new hub along with the staff. It does seem like getting that off intact may be difficult. I may try just for the experience. Perhaps I’ll use heat on the hub to see if I can break the bond that has formed after many years. We’ll see. Cheers.
September 8, 2017 at 6:57 pm #62775
Hey you’re welcome Brian. What you came up with was clever though!
Glad it worked for you.
I know you probably already thought of this but for the benefit of others following this thread…watch the heat closely so you don’t change or draw out the temper on that staff.
Good luck on the next step and please let us know how it works out.
BobSeptember 10, 2017 at 6:35 pm #62776
Since I’m not going to be reusing the staff, I’m not to going to concern myself too much with the temper of it. And since I have another hub, I suppose I can just leave this one as a spare. I know that they can be re-pivoted, but I don’t know how to do that. Maybe someday…
I will update this thread if I decide to remove the hub from the staff. Cheers.September 11, 2017 at 10:16 am #62777
Sorry I had it backwards. I was thinking that you needed to either move or remove the new brass balance seat for some reason from the new staff and replace it with the old seat. Got it now! I need to brush up on my reading comprehension skills!
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