[julesd68]

Some thoughts on my experience of the Miyota 9015 in my new watch.

Official accuracy figures on all movements are based on timings taken when the watch is fully wound is my understanding. I often see people on forums quoting what seem to me amazing daily accuracy figures but you never know if the watch is on a winder overnight to keep the power reserve topped up for the most accurate performance. Do most people use a winder?

The reason I'm asking is that after I gave my watch its first full wind it showed pinpoint accuracy for two days and then as the power reserve started draining it lost a few more seconds every day, especially overnight. I always go out for a good walk each day but I guess I'm not active enough throughout the day to keep the power reserve juiced up. Also I wonder if the 9015 is not particularly efficient at winding on the wrist.

I've been leaving it dial up over night to try and get it to gain a few secs but no luck so far. Next time I will try dial down. I'm hoping the movement might settle and improve over the next few weeks of course. Has that happened for any of you?

Perhaps the only way to ensure consistent daily accuracy is to buy a winder?

 

[MX793]

Try resting it in different positions. Dial up/down are usually the fastest, but may not always be.

You could try leaving it on a winder overnight, or supplement with a few turns of the crown if you think you aren't active enough to keep it wound.

 

[ffritz]

The reason I'm asking is that after I gave my watch its first full wind it showed pinpoint accuracy for two days and then as the power reserve started draining it lost a few more seconds every day, especially overnight. I always go out for a good walk each day but I guess I'm not active enough throughout the day to keep the power reserve juiced up. Also I wonder if the 9015 is not particularly efficient at winding on the wrist.

How do you know the power reserve started draining? A normal office job activity should be more than enough to keep your watch fully wound during the day, and it would only lose 25% of its stored power over night. So it should be operating at 75-100% main spring torque as long as you wear it daily. This shouldn't affect accuracy at all.

Some fluctuations of the beat rate are just perfectly normal for unadjusted movements like the 9015. It's not an indicator that its power is running low. If you wear it daily for 8h or so, there should be no need to hand wind it at all.

 

[julesd68]

You are correct - I can't say for a fact that the power reserve is draining but I am assuming it is due to the fact that the watch is progressively losing more seconds each day. Also, the watch was most accurate for the first two days where it must have been close to full power.

 

[MX793]

How do you know the power reserve started draining? A normal office job activity should be more than enough to keep your watch fully wound during the day, and it would only lose 25% of its stored power over night. So it should be operating at 75-100% main spring torque as long as you wear it daily. This shouldn't affect accuracy at all.

Some fluctuations of the beat rate are just perfectly normal for unadjusted movements like the 9015. It's not an indicator that its power is running low. If you wear it daily for 8h or so, there should be no need to hand wind it at all.

I work an office job and if I take my watch off at the end of the day and let it run to a stop, I never get the full PR from the time I take it off on any watch I've owned. I get somewhere between 20 and 25 hours from my ETA/Sellita movements after a work day (wearing the watch 14 hours or more).

It's not just amount of movement, it's amount of arm movement and how that arm moves that generates rotor motion. I frequently carry notebooks and papers under my non-dominant arm when moving about the office, so not much arm movement to wind the watch as I walk about. I also apparently don't do much winding while walking in general, as I've done numerous trials of this (and typically walk several miles a day after work). Sitting and typing certainly doesn't generate much rotor movement.

 

[MX793]

You are correct - I can't say for a fact that the power reserve is draining but I am assuming it is due to the fact that the watch is progressively losing more seconds each day. Also, the watch was most accurate for the first two days where it must have been close to full power.

When you say "progressively losing more seconds each day", do you mean the rate is slowing each day, or that it loses the same number each day?

Changing rate means that after day 1, it's 2 seconds behind (-2 spd). After day 2, it's 6 seconds behind (-4 spd). After day 3 it's 12 seconds behind (- 6 spd).

Constant rate means after day 1 it's 2 seconds behind. After day 2 it's 4. After day 3 it's 6... Loses 2 more seconds every day.

In my experience, if/when a new movement breaks in, it tends to slow down a bit over the first few days or even weeks of use. So if it was fast on day 1, it gets a bit more accurate. If it was already dead-on or slow, it gets less accurate.

 

[julesd68]

Well I'm not working at all at the moment. So the only proper wrist action my watches get is when I go out for my two daily walks and moving around at home.

In terms of losing time, it has behaved like this - the first figure is what it has lost in 24 hours and the second is the running total. So since last Friday the accuracy has been dissapointing.

Tue +0/+0
Wed +1 /+1
Thus -1/ 0
Fri -6 / -6
Sat -10 /-16
Sun -12 / -28
Mon - 16/-44

 

[julesd68]

Curiously my Tissot Powermatic 80 is very consistent and doesn't behave at all like the Miyota but it does have more than double the power reserve which may or may not be a factor.

Possibly the 9015 doesn't wind as efficiently on the wrist?

 

[MX793]

Curiously my Tissot Powermatic 80 is very consistent and doesn't behave at all like the Miyota but it does have more than double the power reserve which may or may not be a factor.

Possibly the 9015 doesn't wind as efficiently on the wrist?

Anecdotally, I've heard the Miyotas are more efficient than ETA or Sellita. Less dead space in the rotor swing.

Try giving the crown a few turns every day to keep it topped off, either when you put the watch on in the morning or take it off at night. That should help reveal if it's isochronism induced accuracy loss or something else.

 

[julesd68]

I think it is most likely the effects of isochronism at play here. I found this article interesting -

Watch-geeks and the Zen of Accuracy

On accuracy Despite the fact that most watch collectors understand a mechanical watch is inherently less accurate than a quartz watch, the hobby tends to attract people with a certain penchant for paying close attention to minute details, and as such, it’s not uncommon to see a discussion...

nthwatches.com

It states the 9015 is ...

" ...tested between 10 minutes and 60 minutes of being fully wound (at full power), to avoid the effects of isochronism (a metric for which, Miyota does not provide in their technical documentation)."

 

[retroorange]

I have to say my recent experiences of Miyota movements 9039 & 90s5 have not been good. Both are in quiet expensive micro brands too.
The 9039 is + 20 sec per day and as for the 90s5 the watch is on its 3rd new movement within 7 months of ownership. Original movement and replacement both started running slow and then just stopped. All sorted under warranty thankfully and the replacement was fitted in a different country to where the watches are assembled! I was informed it was a QC issue on a certain batch of movements.
I hope yours sorts but I am going to stick now to Swiss movements only unless it’s a Seiko.

 

[julesd68]

It is frustrating as I'm not expecting COSC accuracy - just some consistency within the stated specs!

Plenty of other 9015 owners seem to be quite happy with their performance.

I will email the watch manufacturer for their thoughts.

 

[MX793]

I think it is most likely the effects of isochronism at play here. I found this article interesting -

Watch-geeks and the Zen of Accuracy

On accuracy Despite the fact that most watch collectors understand a mechanical watch is inherently less accurate than a quartz watch, the hobby tends to attract people with a certain penchant for paying close attention to minute details, and as such, it’s not uncommon to see a discussion...

nthwatches.com

It states the 9015 is ...

" ...tested between 10 minutes and 60 minutes of being fully wound (at full power), to avoid the effects of isochronism (a metric for which, Miyota does not provide in their technical documentation)."

I would recommend manually topping off with the crown for a few days to verify it's isochronism and not something else.

 

[julesd68]

Thank you - after I give it another full wind I will do as you suggest and see how it goes.

 

[blackcutlass]

I currently own two Miyota 90s5 powered watches, and had a previous 9 series I no longer own. All of them have performed admirably (ranging from +3 to +6 seconds a day). I store them dial up (no winder) and wear about 13-14 hours a day. Stuck at home but I still try to get movement in. When I feel particularly sedentary, I find myself fidgeting with my wrist to ensure some semblance of movement. From dead, I wind them 40 full turns to ensure I’m starting from 100% reserve.

 

[julesd68]

Thanks for the feedback, that is most helpful.

Since we are treating our watches pretty much the same, I wonder if there is an issue with a recent batch of 9015 movements. I actually had to return the first watch I received as it only lasted 3 days on a full wind! This replacement has been running 7 days now but the accuracy is horrible.

 

[Nokie]

Most of my Miyota movements are good, but I do have a couple that are all over the place, so I know where you are coming from.......

Good luck.

 

[ffritz]

I work an office job and if I take my watch off at the end of the day and let it run to a stop, I never get the full PR from the time I take it off on any watch I've owned. I get somewhere between 20 and 25 hours from my ETA/Sellita movements after a work day (wearing the watch 14 hours or more).

That's interesting. I've had two Miyota 9100 powered watches, so basically a 9015 with PR indicator. After giving them some few rotations with the crown to get them started, it took about 6-8h to reach a full day of power reserve, and after 10-14h they would always be at 100%. Maybe I just shake my wrist more, I don't know. Never had any issues with automatics not keeping powered personally.

 

[MX793]

That's interesting. I've had two Miyota 9100 powered watches, so basically a 9015 with PR indicator. After giving them some few rotations with the crown to get them started, it took about 6-8h to reach a full day of power reserve, and after 10-14h they would always be at 100%. Maybe I just shake my wrist more, I don't know. Never had any issues with automatics not keeping powered personally.

I have no trouble keeping them running as long as I wear them every day. But if/when I switch up to another watch for a day or two, I've noted that the watch I'd been wearing generally stops well short of it's PR, meaning it wasn't fully wound when I took it off in the evening. My Seiko seems to be a little better in this regard. Those wind more efficiently than 2824s/SW200s.

 

[mleok]

Usually, in a cheap mechanical movement, the high average daily accuracy arises because of anisochronism (rate depends on power reserve), and positional variance (rate depends on the direction of gravity with respect to the movement). Often, a watch might gain time when worn and lose time when at rest, and these errors cancel each other out, and this cancellation effect may be enhanced by appropriately choosing the resting position (by exploiting positional variance). Some people go further, and change the resting position depending on whether the watch is fast or slow, which works best when the watch gains time in a particular resting position and loses time in another resting position.