Are there technical advantages to small second dials?

watchos · Sep 5, 2017

Apart from the athletics and design choices, are there any technical benefits to having a small seconds dial as opposed to a traditional seconds hand in a chronometer? I understand rhat a chronograph might use it since the large seconds are a key part of the chronograph. I particularly find it interesting that the “dirty dozen” watches were requested by the British military with the small seconds dial when they could have had a normal seconds hand. Are they more resistant? Require less amount of mechanical energy?

Thanks in advance for your replies.

jguitron · Sep 5, 2017

Good Question. In fact, the center seconds hand is considered a complication. The original, standard movement/dial had the small seconds hand... later on it was moved to the center and considered as one of the first complications.

Our generation (don't mean to date anyone) grew up with the center seconds as the norm and instead, the small seconds hand seems the unusual kind.

No more or less energy needed either way.

Cheers.

watchos · Sep 5, 2017

jguitron
Good Question. In fact, the center seconds hand is considered a complication. The original, standard movement/dial had the small seconds hand... later on it was moved to the center and considered as one of the first complications.

Our generation (don't mean to date anyone) grew up with the center seconds as the norm and instead, the small seconds hand seems the unusual kind.

No more or less energy needed either way.

Cheers.

Thanks for that. Didn’t know the small seconds was the norm before. Great insight.

Foo2rama · Sep 5, 2017

jguitron
Good Question. In fact, the center seconds hand is considered a complication. The original, standard movement/dial had the small seconds hand... later on it was moved to the center and considered as one of the first complications.

Our generation (don't mean to date anyone) grew up with the center seconds as the norm and instead, the small seconds hand seems the unusual kind.

No more or less energy needed either way.

Cheers.

Thanks! I was going to nerd rage about that after @Archer corrected me about that 6 months ago.

Deafboy · Sep 6, 2017

jguitron
In fact, the center seconds hand is considered a complication.

Indeed, It needs an extra wheel (i.e. gear) and the hand arbors are bit more involved (because all the hands are co-axial).

Koen · Sep 6, 2017

Always thought it had to do with the sweeping, the shorter the hand the smaller the steps..

Archer · Sep 6, 2017

The answer is, as usual, "it depends"...

The first sweep hands were driven indirectly, by a wheel that was pressed onto an extended post on one of the train wheels. To prevent the stuttering that is associated with that design, they typically had friction springs added. As the name implies, they added friction, and therefore load to the train that would reduce amplitude. This would be taken into account when designing the movement so one could assume that more power was needed for this design than the equivalent movement with a sub-seconds hand.

Since most modern movement incorporate the seconds hand directly into the wheel train, there is no need for a friction spring, so only the friction of the wheels in their respective jewels would be added to the train.

So here is a movement that uses a sub-seconds:

Here is a movement that uses a sweep seconds (from the same "family" of movements), so you can see that there is a large wheel pressed onto an extended post of the third wheel at the red arrow, and another small bridge added:

And under that small bridge is the extra pinion that goes through the center wheel and that the seconds hand is pressed onto. The arrow on the left is pointing to the friction spring that lifts that pinion up into the jewel on that bridge to put some friction on it:

Cheers, Al

Canuck · Sep 6, 2017

Early watches with centre sweep seconds hands usually did require an extra wheel, extra pinion, extra bridge (some used a cock over the sweep pinion), and tension spring for the centre sweep pinion. But later ones do not require these two extra parts. Specifically, no extra train wheel. The earlier indirectly driven sweep seconds arrangement doesn't constitute a disadvantage over the subsidiary seconds hand arrangement. But these earlier ones with their extra wheels, pinions, and extended pivots can be a challenge to service if a person isn't equipped with the necessary tools.

Rather than to hijack this thread, I have started a new thread on an unusual Tavannes (Cyma) movement from a watch in my collection.

Archer · Sep 6, 2017

Canuck
But later ones do not require these two extra parts. Specifically, no extra train wheel.

It depends on the specific way the sweep seconds is incorporated. For example modern ETA movements like the 2824-2 or even the Omega 1120 don't have an extra train wheel, but a Rolex 3135 does (the minute pinion) so it varies based on how the specific manufacturer approaches the overall design.

TropicConnie · Oct 19, 2017

All bases look to be covered on the topic but these are worthwhile reading.

The Pursuit of Center Seconds - Part 1

The Pursuit of Center Seconds - Part 2

Professor · Mar 25, 2018

This answers something I've wondered about. My wind up ZIM has an unusually deep case back that looks more suited to a self winding automatic.

I haven't opened it but the seller's images showed the movement and there's a high bridge across the center that must be part of the second hand drive train.
I suspect the ZIM movement was originally an older sub second type later redesigned and adapted to center second. IIRC The Russian Moscow Watch factories had bought the design for their movements from the French.

Foo2rama · Mar 25, 2018

Professor

This answers something I've wondered about. My wind up ZIM has an unusually deep case back that looks more suited to a self winding automatic.

I haven't opened it but the seller's images showed the movement and there's a high bridge across the center that must be part of the second hand drive train.
I suspect the ZIM movement was originally an older sub second type later redesigned and adapted to center second. IIRC The Russian Moscow Watch factories had bought the design for their movements from the French.

Small second is actually easier to do on a watch, center seconds is actually the complication. as I was politely informed by @Archer when I thought I knew something.

Are there technical advantages to small second dials?

watchos

jguitron

watchos

Foo2rama

Deafboy

Koen

Archer

Canuck

Archer

TropicConnie

Professor

Foo2rama

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