Bi directional is more efficient in my experience.

 

If all else is equal, bi-directional winding automatic movements will obviously be more efficient in winding a mainspring to a full power reserve and more efficiently keeping it wound than uni-directional winding automatic movements. However, if the wearer's activity level is high enough, it becomes inconsequential. For my relatively low activity level and wear pattern, both types of automatic winding movements stay running throughout the day, but both also do not reach a fully wound power reserve very often unless I hand-wind them to full before putting them on.

 

With the natural swing of one’s arm one of the downswing or upswing I’d imagine would charge even a uni directional just fine for most every day scenarios.

 

So if a watch checked all the other boxes, yet had a uni-directional rotor, sounds like that shouldn’t be a deal breaker 👍🏻

 

Correct, if your activity level and wear pattern has the watch moving around enough. And if you are like me (and do not wish that upon anyone), it is still not a deal breaker because even a bi-directional winding movement is generally not efficient enough to keep the mainspring fully wound anyway.

 

It would not stop me from buying a watch I liked regardless if it was bi-directional or uni.

Both methods wind the watch properly, which is all that matters.

 

It would not stop me from buying a watch I liked regardless if it was bi-directional or uni.

Both methods wind the watch properly, which is all that matters.

^^^This. Plus with the unidirectional movement, it is always nice to feel and hear the movement's rotor spin at times.

 

I wear my watches on my right wrist so bi-direction winding or manual winding is a must.

 

So do I, and so far it was never an issue. However, on a rare occasions when unidirectional watch is on my left wrist, it definitely is wound better. Funny, I never thought of this before.

 

I wear my Miyota 9015 on my right wrist and haven't had any winding issues.

I wonder if a unidirectional self-winding complication can potentially be more robust than a bidirectional complications due to fewer components? May be too close of a race to matter.

 

Yes,my thinking too. Unidirectional is a lot simpler,so maybe it is easier to turn, as I never had any problems with the winding of an ancient uni auto I had in the past

 

There’s been countless discussions on the merits of one vs the other in terms of efficiency. The bi has the advantage of winding with more diverse arm movements, but loses efficiency when the rotor changes direction. The uni naturally only winds in one direction, but no efficiency is lost to changing direction and can keep going longer in the same direction as anyone who has owned one can attest.

Personally I don’t think it matters much. If one does have an advantage over the other, it’s probably not that great.

 

I have not noticed a difference in winding efficiency. Both methods work equally well in normal everyda life for me.

 

Efficiency depends on several things. But don't overlook minimum winding angle.
Probably more important than anything.

 

No idea what this means, will research.

 

Only difference I've noted is the 9015 Miyota is a bit noisier than the Seiko 7S26 and considerably noisier than the ETA 2892.

I only notice this is in dead quiet environments with the tinnitus less noticeable and the watch relatively near near the ear.

As far as staying wound goes...they all seem adequate as long as you're wearing them and doing something. Extended time sitting about usually means the ones with more complications run out first (the ETA can't make it through a full weekend of hardcore power lounging). The others can usually make it through Monday morning and the 9015s can even do three day weekends without much trouble.

 

I think the Miyota movement noise has always been over exaggerated. I have owned Miyota 90** movements and always found their noise to be slightly more than other movement, but not to the point that I need to be reading about it every week. I have owned 2824, 3135, sw200, 7750 based, and 2892 based movements and never found the Miyotas to be a “deal” breaker in comparison due to their noise. Unidirectional and bidirectional winding have all worked fine for me.

 

I've seen 8 series Miyotas that had noisy movements, but never noticed it being unpleasant with the 9 series. It may well be the more modern 8 series are better as the movement has been modified a time or two. Some Swiss movements like JLCs have used unidirectional rotors which some consider to be quite nice because of the noise.

 

I believe bi-directional is definitely better, here is my logic;

Some companies make the claim that uni-directional winding is more efficient (I think JLC does this), some companies make the claim that bi-directional winding is better- in both cases there are massive financial ulterior motives for making either claim, true or not.

We know anecdotally, on a massive scale, that neither form of winding makes a significant difference to the overall population that wear the same watch most days of the week, even for half a day regularly. Things such as power reserve would be a bigger factor here. Therefore I believe that whether bi-directional winding or uni-directional winding is more efficient, is virtually a moot point, as the difference to the every-man is of such little significance. Further to that, the cost for servicing and service intervals don't appear to be significantly related to the type of auto-winding being uni-directional or bi-directional.

However, one point which is relatively objective, is that uni-directional winding is nearly always noisier, has rotor 'wobble' and spins freely in one direction that has a velocity somewhat felt on the wrist. Most people, but not all, don't like this sensation. It is more pleasant to have the least amount of noise, and rotor wobble on the wrist. In this regard, bi-directional winding is certainly better.

On a personal, somewhat subjective note, I also believe bi-directional winding must be better, because the angle in which the gears engage to change direction is so small and virtually negligible, when one considers that a minor flick of the wrist in either direction will likely spin the winding rotor many times. However, if the rotor is spinning in the 'wrong' direction on a uni-directional winding system, then it's not actually winding the mainspring, and further to that, all the kinetic energy of that movement is only distributed over the rotor and main shaft upon which it sits- rather than the entire winding works, mainspring and mainspring barrel.

 

I agree 100% with your above post.
I have had auto-winding issues with my Christopher Ward SH21 Auto, having replaced 4 rotor bearings now.
(3 at CW, under warranty) and the last one myself.
Because i didnt want to wait 12-14 weeks for something i did in 10 minutes.
(Documented on WUS as SH21 rotor bearing replacement)
The Doxa SUB 5000T that i have had longer; no issues at all.
(ETA 2892-A2 Bi-directional auto winding)
You can hear this happening quite clearly.
In some of the literature ref the SH21, it says it is bi-directional auto-winding.
It is not.
Evidenced by the fact that some SH21 have crystal backs, and you can see it not winding in one direction.
Also saw this on the SH21 i repaired myself, when checking rotor movement post-bearing replacement.
The SH21 only auto winds in one direction. It spins freely in the other.
This kinetic energy is unchecked when spinning, but not winding.
So much so, that it feels almost like a gyro on your wrist sometimes.
Your whole arm wobbles.
I think that is exerting a centrifugal force on these bearings, and they give up eventually.
In conclusion. It is my personal belief that the Bi-directional auto-winding is mechanically more sympathetic, and in the end more robust. Offering a longer service interval, and less likely for a blown apart rotor bearing to kamikaze the rest of the movement.
On the basis of this, i would not buy another uni-directional auto-winding watch.

 

I've heard that generally speaking uni directional movements are easier to service as they don't wear down as much as bi-directional rotors.

 

But does it matter if there's fixed price servicing? Which is often the case- I bet the unidirectional JLC movements cost more to service than the bi-directional powermatic 80 movements in Certina?!

 

I have a dive watch with a Citizen 9051 that I think is unidirectional. I don’t hear the rotor spin as much as I did with another diver that had a Miyota 9015. I’m very active, so whatever watch I wear all day is usually at or close to full wind by the end of the day.

 

I personally think bi directional is better as some of the uni directional movements have this rotor buzz.

I have had this 7750 derivative and whenever the rotor is spun anti clockwise (non winding direction), the rotor flies around freely, generating a loud buzz. Some people like it, some people don't.

 

On the cheaper movements, I think the miyota movements are slimmer than most. Should translate to a thinner watch, but I have not seen alot of watches that make them thin.

 

Hmm, what is the conclusion?
Is one better than the other?
Should one avoid one over the other?

BTW: In my MT5612 movement the rotor spin wasn’t noticeable in the beginning, but after two or three months it increased (a little bit).

 

Hmm, what is the conclusion?
Is one better than the other?
Should one avoid one over the other?

Dark beer is definitely better. Cider gives me the wind so I try to stay away.

 

The biggest differences i noticed were that the miyota 9015 i owned was a bit more noisier and felt a little bit wobbly compared to an ETA 2824-2. As far as winding or power reserve i didn’t see a noticeable difference.

 

I have never had any issue with a uni-directional charging system. With the way I move, the watch stays charged the same as with a bi-directional one.

I prefer bi-directional rotors, in the sense that I prefer not feeling the fidget spinner going.

That said, it is not a deal breaker at all.

 

Bi-directional is better but I haven’t found them to be twice as good as a uni-directional one.

 

This is a good way to put it 😂

 

I can see how bi-directional might be more efficient in theory, and even practice, but IRL, I've never had an issue with a uni-directional automatic running out of steam, in use.

Only downside is that some Miyota movements are claimed to be "noisy." Maybe so, but I do stop to check watches with bi-direction winding, coming off continued use of Miyota powered watches, because the bi-directional movements are too quiet.

 

More Importantly: Did you walk to work or bring your lunch?

 

So direction is only important to know how to correctly set the mode on your watch winder. If you have one.

 

Bi-directional (invented by Seiko?) is easily more efficient and more likely to give you the full power reserve advertised by the manufacturer. I wouldn't say it is the most important part of my purchase decision, but it is a factor. Things that bother me more are poor quality control and issues like the jumping/stuck second hand on Miyota 8XXX movements which is really annoying to see as you observe your watch sweeping second hand suddenly stop. It's like a mechanical hiccup.