A Single-Hand Watch Movement – With Accurate Minute Display

“We need 200 single-hand watch movements with an accurate minute display” These are not words we could use with a movement manufacturer to get what we needed.  Suppose you look at the catalog of some of the largest and best movement manufacturers. In that case, they provide many options, from the very basic automatic movement to a skeleton or a tourbillon. But they did not have what we needed, a movement for a single-hand watch that displayed the time accurately to the minute. 

A single-hand watch is simpler?

It seemed inevitable from the moment Steve and I scribbled our idea on the back of a beer mat that we would have to make our own movement.  This catapulted us into the world of watch movements, ebauches, and modules. 

Our idea was captivating in its simplicity. A single-hand mechanical watch that could tell the time as accurately as a regular analog watch. A single-hand display that makes it possible to intuitively grasp the time at a glance and read the exact time at the same intuitive location. 

We had done all the research for our patent and were confident. If our patent application stood any chance of success, our movement could not exist. If it did exist, then there was no hope for a patent. But if we received the patent, we were creating our own movement.  

It was a catch 22. The idea was valuable because no movement was available in the market where the minutes ran backward and rotated slower. But that meant it would be very expensive. Developing a movement module and producing it in small quantities is time-consuming, which is code for costly. I had experienced this precisely 20 years ago. With this experience under my belt, it was clear that SNGLRTY should be a Swiss watch brand, and the display should be realized with a mechanical movement.

Are Swiss Watches More Valuable?

The turn of the millennium heralded the return of the mechanical movements for the Swiss watch industry. Mechanical movements started to outsell quartz movements, and momentum was on their side. Mechanical movements, manual and automatic, traditionally dominated the upper echelon of watch manufacture. However, from 2000 onward, mechanical movements re-entered and took a significant stake in the mid-range price segment.

The Swiss watch industry almost quadrupled exports of mechanical watches by value between 2000 and 2019, up 388%. During the same period, volume nearly tripled, up 292%.

Everything was leading us to execute our idea as a mechanical Swiss watch. However, to reduce the risk and execute more quickly, we decided to develop a module. A module is an attachment placed on top of a base movement that is purchased in the market. 

In Switzerland, several specialists can develop novel modules for watches. We spoke to a number and decided to work with the young, creative team at Le Cercle des Horlogers (the Watchmakers’ Circle), or CHSA for short.

The Foundations Are important

Choosing the base movement, or tractor movement as they are referred to in the industry, is critical. We wanted the module to be geared to commercially available tractor movements.  The likes of the ETA 2824 and 2892 have become an industry standard. We decided to give preference to Sellita’s movements for two key reasons.

The first was the ease of procurement. Sellita has a good track record of consistently supplying quality watch movements without interruption into the market. The second is that as an independent movement maker, we felt they were more in tune with our business as an independent watchmaker. From there, the selection was reasonably straightforward, and we selected the SW200 and the SW300 to be the tractor movements for SNGLRTY watches.

Is a Date Function a Watch Complication?

As we developed the module briefing, we wanted to ensure the finished product would be flexible to allow many future watch models to be created from our movements. The primary considerations were the size of the module and the minute display. It should be possible to cover large, sporty watches, classic models, and larger ladies’ watches with one module.

One disadvantage of modules is that it sits on top of the tractor. The date, which is part of the base movement, ends up being below the module. This results in the date looking like it is being displayed at the bottom of a well. We did not want this to happen with SNGLRTY.  We tasked the engineers a CHSA to ensure that the date could be displayed on the top of the module and at the largest possible diameter.  This will ensure the most effortless reading.

The Devil Is In The Details

At the time of the initial briefing with CHSA, it was clear that the minute display would run counterclockwise. The hour sweep was fixed and at its regular speed (360 in 12 hours). This ensured that the natural reading of the hour hand is not impacted. For the minutes to be displayed accurately at the hour hand’s position on the watch face, the counter-clockwise rotation speed needed to be slowed. 

The engineers wanted to change as little as possible in the tractor and integrate the module onto the tractor directly. The tractor movements we chose to work with, the SW200, and the SW300, are tried and tested. From our perspective, any change to the tractor increased risk without any reward, so we all agreed.

With these considerations, it became apparent to drive the minute disc directly from the minute wheel located in the center of the tractor.

Watches Have Feet

Another fundamental question was how the module should be attached to the tractor. Dials are usually held by “feet.” These small pins are welded directly to the underside of the dial. The dial is attached by inserting the pins into the movement according to the manufacturer’s specifications and clamped with screws. We wanted to fix our module plate in the same way. However, as the module will be heavier than a dial, the case or the bezel will have to be constructed to prevent the module, with the dial on top, from moving and the feet coming loose. Typically, a small distance is left between the dial and the case or bezel – in this case, that was not going to be possible. 

The SNGLRTY watch case design has a smaller base diameter than the bezel diameter.  This results in the case sides sloping inwards instead of the more typical vertical sides. For this reason, SNGLRTY is assembled through the crystal side of the case. This is referred to as top-loading construction. The assembled movement with the dial & hands attached is dropped into the case from the top of the case. The watchmaker then presses the bezel into the top of the case and fixes the movement from the back-side.

This increases the number of steps in assembling the watch and requires greater skill from the watchmaker.  SNGLRTY also requires the highest precision in manufacturing the watch case. The bezel is pressed down on a gasket and has to touch the dial softly to brace the module in the watch case. It is only the pressure and tight tolerances of the watch case that then guarantees the 10 bar water resistance.  

Of Unusual Minutes and Ordinary Hours

The design calls for the minute index to be applied to a disc that rotates counterclockwise.  This allows for the minute to be read to synchronize with the location of the hour hand.  We did not want to limit the design options, so we only wanted the area with the minute index on it to be visible. Or, to look at it another way, we did not want the visible center of the watch face to rotate. A cover or small dial in the center would be necessary, but how should this be held above the rotating disc?

The hours are indicated traditionally by the hour hand pointing to the relevant number on the outer edge of the watch face. We desired to keep things familiar where change was not necessary. That would result in the display being unique yet appear very familiar. 

The outer ring with the hour index or numbers on it could be constructed as a “réhaut” and be attached to the watch case. However, this would be too restrictive for future designs, so we gave preference to a classic dial construction. The hour ring should be attached to the outer diameter of the module.  This allows for a more traditional assembly process. The pre-assembled tractor and module with the dial and hand can be placed as a single piece into the case. 

Accuracy With No Compromise

To summarize, we created a dial design with hour indexes on the outside. Inside and concentrically, a rotating minute display is at a lower level. A small, decorative center plate completes the interior of the dial.  The dial could be made from one piece and designed with large openings for the minute indication. However, the opening could not be circular and interrupted with arms to hold the center area.

One crucial argument for SNGLRTY is its accurate minute display. If now we cover the minute display purely for construction considerations, it will no longer be accurate. This is not in the spirit of SNGLRTY: The construction solution must be consistent with the accuracy of SNGLRTY and this required the dial to be of separate parts.

The outer hour ring can be fixed, but the issue was attaching the center dial. How could this be achieved?

There is always an answer!

There were several considerations.  The minute disc should remain as large as possible to allow for different dial designs without adjustments. Second, we were thinking of smaller ladies’ models and other ways of presenting the minutes. Finally, we desired to keep as many options available as possible. 

The minute disc is to be as large as possible and is a ring, like a donut. This center opening would give access to a small, non-rotating platine that can be used to attach dial elements.  Would it be possible to attach the center dial with feet? Unfortunately, that was not possible. There was no access to fix feet in the correct locations. 

Our last option was to screw the center of the dial from above.

The idea to place the second ring in the center arose at this point. So the center disc and the second index disc are screwed onto the small center plate of the module. 

We gave the seconds an additional function. 

The seconds’ display primarily shows the wearer that the watch is running, that the movement has energy. It also allows the time to be set more precisely to the second.

Necessity, The Mother Of Invention

These were the primary considerations for the dial design and the development of the module. The transmission mechanism to reverse the rotation and reduce the minute display’s speed was not the central problem. Instead, the focus was on safety, robustness, simplicity, and design flexibility.

That is why when a fire broke out in my head, I needed to reach Steve urgently. Thus, we made a virtue out of necessity. The problem of assembling the watch face can become a huge advantage and formative for SNGLRTY!

Perhaps I had caught Steve at the wrong moment. We were still suffering from the taxing patent application that had absorbed us for months. “No, the fixing problem is an advantage!” I shouted enthusiastically into the phone, and it was clear to me that I had Steve’s attention.  

“Imagine that our dial has four parts. An hour ring, a minute disc, a center plate, and a seconds ring. All these parts are independent of each other and can be combined in different colors. Just with the colors black and white, 16 possibilities arise. If we combine this with two hands, we are already up to 32 possibilities. We can offer many combinations in the simplest way.” 

This was when the possibility of individual configurations for SNGLRTY was born.

Including the various band options, we now offer over 21,000 combinations. The vast majority are available for delivery within three weeks – provided they are not all ordered simultaneously!  If you are interested you can check out every one of the available combinations HERE.