Will the Mark XVI's modified ETA 2892 movement run slow as the power reserve runs down?

I have a new Mark XVI that runs quite well and accurately when fully wound. However, as the power reserve runs down (e.g., with maybe an hour or two left or less) I notice that the watch begins to run quite slow, losing seconds at a rapid pace.

I haven't estimated exactly how slowly the watch runs at the end of its power cycle but I would guess that it might lose 20-30 seconds per day at this slower rate. When fully wound the time-keeping is close to spot on with an atomic clock -- maybe 1-2 seconds slow per day.

Thanks for your input!

John McLeod

Firstly welcome to the forum and congratulations on your new watch which is automatic as you no doubt know.
As a new watch it will take time to break in, about a month if worn continuously. Wind the crown clock wise for forty winds and it should be approx. fully wound and then wear on wrist and if you are reasonably active it will remain effectively fully wound.
Not sure how you are judging the power reserve though since the watch has no PR display or other indicators. It's not correct to wind this watch five winds when stopped and expect it to run correctly, hope this helps.

A watch will run more accurately with a fully wound mainspring. As it get toward the end of its power reserve it will lose amplitude and be less accurate. Usually, keeping a watch at least half wound is best.

Pray do instruct me on something. How do you keep an automatic half fully wound especially with no PR display??

Bill is 100% right. Even if you do not have a power reserve you can judge an automatic watch given its autonomy. That is, if a watch will run 48 hours from a state of full wind, letting it sit a day (24 hours) will be half wound. Isochronism error does show as the mainspring gets fully unwound, but shows more in, say, a 7 day watch than a "regular" one.

Dis ist not da old internal combustion engine dat requires piston rings to "lap" in to irregular cast iron cylinder walls. If da pivots are of da highest form and da uhren ist properly lubricated, da werks should attain der "settled" rate in da matter of several hours not days. The oft repeating of dis statement does not add credence to it. Da uhrmachermeister scratches at his eyes when he hears dis. sm

As da balancier reaches da "short arcs" da rate increases. If by coincidence, an "event triggered" complication was be actuated at da end of da gangreserve, da instaneous rate could be affected.

sm iiH!

Stiff, re the month break in, I was quoting the service manager of many years experience of the UK importers of a decent Swiss watch company where I worked. He had been in the trade over 35 years so his knowledge base was somewhat fuller than mine.
As for new cars, I still run them in and I was told by two separate sources that the factory issue oil in new cars is not the same as used thereafter by their dealers. It's a different spec. But I am not a watch maker, car mechanic or petro chemical or hydro carbon specialist.

Thanks for all of your input so far. As I mentioned, this Mark XVI is brand new and I've only been wearing it for a couple of weeks. It may take a few more weeks for me to give you a more complete report of its performance.

Since my original post, I have hand-wound the watch a bit more and worn it all day. With a full wind, it's now running spot on to one second fast per day, which is wonderful performance (thank you IWC). Interestingly, it was initially losing one second per day, even with a full wind. So there has been a slight change in its fully wound performance based on my non-scientific observations.

I have yet to wind it fully and let it sit for 40-50 hours. This will be the next step and I'll let you know how it goes.

I did do a bit of research and have discovered that some ETA-based movements will run fast or slow as they're nearing the end of their power reserve. The centering of the hairspring via the etachron adjustment may be one determining factor. But this is beyond my understanding, so I mention this with hesitation.

John

Slow?

Would you care to expand on dis "research"?

sm iiH!

Yes, I'll try to expand on my "research". Here is a link and a quote from a person on the Watchuseek.com Watchmaking forum. Again, I am not qualified to comment on the technical issues involved but include this for those who may find it relevant to the question of why my Mark XVI seems to run slow as the power reserve runs down. I hope this is helpful or, if not, at least interesting!

John

Here's the link:

forums.watchuseek.com/f6/does-2892-movement-run-slower-runs-down-651086.html

... and here's the specific quote from the link:

"IWC Mark XVI uses 2824, not 2892.
The main reason that error related to power reserve is balance amplitude. You will see either faster or slower when power reserve is lower.
1) faster: If hair spring is not set to the center of ETAChron. When balance amplitude is lower, hairspring constantly hits the edge of ETAChron which causes faster.
2) slower: if hair spring is set to the center of ETAChron. Since 2824/2892's ETAChron gap is much smaller than swing amplitude, slower is very rare unless you only wind a few hours of power reserve.
As to Rolex, it uses free-sprung hairspring so amplitude will not change frequency, you normally will not see power reserve releated error very much.
For your case, I recommend manually wind watch fully, and set it on table with face up, compare it with standard time (for example, time.gov) every hour up to 50 hours. And plot the curve using Excel to see how error is related to power reserve. Any way, as a chronometer, you should not see more than 5 seconds in 24 hours."

Can you advise what specific Model# (3255-XX) your new Mark XVI is and da year in which it was produced?

sm iiH!

Stiff,

It's an IW-32555-01 purchased on February 2012. Not sure of the date of manufacture.

John

John --and others,

Please do NOT believe all you read on the Internet, even if it sounds knowledgeable.

IWC uses a variation of the 2892. It has NEVER used an ETA 2824. In fact the A2 variations in the 2892 were based on IWC enhancements in the early 1990s.

Isochronism error causes a change in rate at the end of the spring winding MORE than balance positioning. All rate changes are reflected by amplitude, and what you quoted is unrelated to ischronism. Free sprung balances are nice (IWC uses them on its in-house movements now) but do not directly affect isochronism.

By the way the 5 seconds quoted is not chronometer standards nor IWC's standards.

Herr Friedberg is of course correct in these statements. [stiff was going to make these points but in a little more subtle fashion.] stiff is frustrated by da perpetuation of da "horological myth". When da Company has used ebauche fourniture they have added great value by substituting and modifying key components to increase all aspects of performance and hence value to da purchaser. [Da scenario dat you reported whereby da regulating pins would be offset in order to eliminate da effects of da lower amplitude would almost certainly result in da additional induced positional error.] Da freesprung balances are extremely effective in minimizing position rate deltas. And Contrôle Officiel Suisse des Chronomètres standards are da matter of record.

Danke.

sm

Thank you Stiff and Michael for the corrections and additional information. I have much to learn about watches, in general, and about this beautiful new Mark XVI, in particular.

In addition to wearing the watch consistently now for several days, I have also wound it fully once each day for the past three days. I know this is not necessary for good performance but it has been interesting to track the timekeeping over this short period. For the past three days, it has gained about one second per day.

In contrast, when I first received the watch only two weeks ago (February 7th), I wound it fully and wore it 6-7 hours per day without further hand winding. It was losing about one second per day (unscientific "testing" I know).

Then I noticed, as I let the power reserve wind down, that it began to lose seconds at a more rapid rate. This resulted in my initial post on this forum. Going forward, I will continue to wear the watch but reduce the hand-winding. I suspect that the watch will perform very well.

In closing, I would like to better understand isochronism and its expected effect on a watch such as the Mark XVI. Is it more typical for an IWC-modified 2892 movement to lose seconds as the power reserve runs down or is it more typical to gain seconds?

Thanks to all!
John

In order to speak with any authority to your "observations", it would be necessary for stiff to know:

1. dat da werks ist fully wound
2. when da initial rate was measured
3. when successive samples were taken
4. dat da uhren was static fur da entire period of observation
5. what standard position da uhren was in
6. dat da "timing machine" utilized for da samples was properly calibrated and operated

sm iiH!

Stiff,

Those are all good questions. I can't answer them all yet except for the fact that I don't even own a timing maching! I simply time the watch against the atomic clock -- which is know is limited and somewhat laborious.

The watch seems to be running quite well when fully wound or close to fully wound. My only question at this point is whether it is common for a modified ETA 2892 to run slow as the power reserve runs down. I'm going to let mine run down over the next few days to confirm that it is, in fact, doing this, but this was my prior observation.

I hesitate to mention this (Stiff and Michael) because it's more unverified information from the Internet that I do not have the knowledge to evaluate. However, one fellow (a watch repair person in northern California) sent me an email in response to one of my posts elsewhere that a 2892 movement will typically run faster as the power reserve runs down and that if the movement slows down significantly, it may be an indication of a broken mainspring. So now I have something new to worry about! The Internet is a helpful but dangerous place, I know.

I have copied his specific remarks below. If you, Michael, or others can comment that would be appreciated. Again, I present this information without any ability to evaluate its accuracy or merit but with the hope of better understanding how my movement should respond to a low power reserve:

"Most automatic movements run a little fast when the mainspring runs down. The reason is clear, when the spring is fully wound, the last coil of spring are not as flexible as the rest of the spring, due to the hook and double layers of coil, the power is weak, once the spring released to 2-3 turns, the first part of the spring has a more straight curve then the rest of the coil, so it will gain a little power, while the spring go all the way from inside coil to outside coil, the inner most spring is bent to the cuvest shape, so is strongest position to pull the barrel. You probably has a broken mainspring, it is not unusual for ETA 2892/ 2824."

John --you're way over-worrying and over-analyzing. There are 86,400 seconds in a day if I've done my math right. Having a few seconds difference is statistically insignificant. The person who "electronically" analysed your watch and told you you have a broken spring is almost certainly incorrect --the differences would be much greater. More likely it could be due to too much or too little oil --by a miniscule amount.

If you're worried, simply have your watch physically checked by a competent repair person.

Thanks Michael. I suspect you're right and that I am simply worrying too much. It's a truly beautiful watch and I should enjoy it!

I did speak with the watch repair person on the telephone just now. He agrees that the mainspring is probably fine and that I am worrying too much, adding that new ETA-based movements require a few days (or more) of break-in to really gauge their performance. This is due to a number of factors, including lubrication distribution and a powder that may be applied at the factory to prevent rust.

I will wear the watch and enjoy it. Please know that I appreciate all of your input.

John

Welcome to the forum John. Its great to see your analytical passion and your enjoyment of your splendid watch will be enhanced when you relax. Some of us here have been through a similar phase in buying our first automatic watch.