What was the reason behind the bumper automatic instead of

hejsam · Nov 15, 2022

It might not be a technical point and might just be the successive improvement of the water resistance of the cases but I always find the bumper movement watches thinner (with the exception of the micro-rotor movements), and therefore sits nicer on the wrist.

Archer · Nov 15, 2022

Dan S
Full-rotor movements with uni-directional winding are still widely used, e.g Valjoux 7750. I doubt that it they are more efficient, but it seems they are efficient enough on the wrist. However, bidirectional watch winders don't always keep them well-wound in my experience.

It's an interesting discussion. Therre are pros and cons to each design. I've written about this before, but in a bi-directional system, there is a bit of the rotor movement that is taken up by the system changing direction. This is called the dead angle - the arc where no winding occurs because the mechanism is making the change from winding in one direction to the other.

If you are an active person, and the rotor is moving through large arcs because of that, the dead angle won't have any real effect, because it will be swamped out by the winding that happens with the larger sings of the rotor.

If you are a relatively inactive person, with smaller wings of the rotor, a greater percentage of the rotor's movement is taken up with the dead angle. This can drastically reduce the winding efficiency over time.

For this second group of people, who are more sedentary, the rotor that winds in only one direction can give more winding at the end of the day than a rotor that winds in both directions, all else being equal.

Cheers, Al

Archer · Nov 15, 2022

JimInOz
Rolex was also guilty (in my eyes) of perpetuating the fact that Abram-Louis Perrelet invented the first automatic watch, and not Hubert Sarton.

Indeed, as we have discussed previously, the full rotation bi-directional winding system was invented in 1777...by Sarton...

dsio · Nov 15, 2022

tamura
For me, the nicest omega case designs have bumber movements.😀

I have a lot of love for my bumper automatics too, for a design that outdated it’s actually rather surprising how well they work and that they stay wound quite well on modern winders that aren’t designed for them

sheepdoll · Nov 15, 2022

I went through a phase where I was intrigued by automatics. Even to the point of getting a large coffee table book on them. Of course I wanted a Bidynator. One of the Mart dealers used to package movements in coin sleeves. Which I though a clever way to display movements. This is the only one I have like that though.

My favorite Swatch is an automatic with an ETA 2842. Showing it's age a bit now.

johnireland · Nov 16, 2022

JLC owners must be the more sedentary types because JLC uses the Unidirectional system for their current watches. In their research, they assumed the bidirectional would be more efficient, but the Unidirectional won the day and that is what they use. I've had Rolexes for about 25 years and never had one quit on me while wearing it. I still find the three I have kept to be outstanding in design and engineering. I just don't care for the new larger versions. Yes I'm very comfortable with my 39mm and 40mm JLCs. Just very different styles of watchmaking.