Accuracy question--3130 mvmt

[horophile1]

Greetings, all!
I have not posted for a while, but been quite busy in recent weeks/months. Thought I would pop back in to get insight on a recent observation with my 116000 OP (concentric dial, M serial, 2007/2008).

Generally, when worn regularly, every day (working in an office, 9 hrs+ per day; I do move about quite a bit during the day), the accuracy is quite nice (since I bought the watch 4 months ago, using the WatchCheck app, I generally get anywhere from average +1s to usually +2s per day). However, during a recent weekend without wearing the watch much at all, I noticed that it had slowed to about (instantaneous rate) of -10s to -12s/d. Again, this was with no wind/wear.

My inkling is that this was probably due to low power reserve, so I decided to perform a test: a) to do a periodic check of the power reserve capacity, and b) to see if I could pinpoint when the watch slows. On Friday, 10/6, at 15:17, I gave the watch full wind (40+ turns--didn`t require this much to wind fully, but I just wanted to assure that the PR was indeed full) and placed it on the dresser, dial up (at this time, the watch was at -0.3s, instantaneous rate of +0.4 s/d).

Unfortunately, I didn't get a chance to measure the rate often during the last two days. I checked the rate again, on 10/7, at 07:56 (16.5 hours into the test): +0.6s, inst rate of +1.4 s/d (watch therefore still gaining time at this point--performing in its perfectly normal range). I checked again on 10/8, at 08:47 (41.5 hours into test): -11.4s, inst. rate of -11.6 s/d (interestingly, despite the loss, the average/isochronous rate per WatchCheck is still -0.9 s/d). [I'll likely have to perform this test again to see at which point between 16.5 hours and 41.5 hours the watch began losing time.]

So, the power reserve itself doesn't seem to be of issue (still running now, 42.5 hours into test; I wasn't really concerned about this aspect anyway). During normal time on wrist, with occasional winding to top off the PR, there is obviously no concern at +1 to +2 s/d. My question is really this: is it normal for the movement to lose 10-12 seconds within, say, the last 8-10 hours of PR? (Again, I really do not know at which point the watch began to slow.. stay tuned for another test. Also, I am waiting to see if the watch will speed up during its final hours of PR--which is apparently a common occurrence.) Does my description above seem to be cause for any concern at this point? Perhaps most people's consensus would be, hey, as long as it's working fine during regular use, with great accuracy, why worry? I guess I just really wish to know whether the above is, say, an early warning sign indicating service?

Any input or tips would be fantastic! And, despite the above, it's a fantastic piece that I still thoroughly enjoy.

[Tools]

All mechanical movements will follow a curve in performance from fully wound to unwound, as the tension/torque of the mainspring is constantly changing.

It cannot maintain the same precision during the last ~8 hours of wind as it did during it's engineered/designed optimum power range.

[horophile1]

Originally Posted by Tools

All mechanical movements will follow a curve in performance from fully wound to unwound, as the tension/torque of the mainspring is constantly changing.

It cannot maintain the same precision during the last ~8 hours of wind as it did during it's engineered/designed optimum power range.

Thanks! That's a bit what I suspected. I just didn't know how slow was normal within that range, or even if Rolex engineered them so weLL as to maintain the accuracy :until nearly the end of PR. In other words, keep 'em wound! :-)