Launched in the spring of 2007 the 300 piece limited edition Seiko Spring Drive Chronograph SPS001 is manufactured in a special alloy titanium case that is highly resistant to scratches and is GMT equipped.

 

 

 

 

 

Dial side all functions are easy to read and properly positioned. From the center are the hour, minute, chronograph seconds hand, and GMT hand in red. It is the chronograph seconds hand that is most intriguing and special about this watch. Unlike all other chronograph watches that start and stop from 5 to 10+ times per second depending on the frequency of their mechanical lever escapement. The Spring Drive chronograph seconds hand is totally fluid due to the Spring Drive movement that is in constant motion avoiding the jerky motion of typical chronographs. You might not believe me when I say you cannot appreciate the graceful fluid motion of this chronograph until you hold it in your hands and experience it yourself.

 

 

 

OK, lets get back to the dial and its other features. Applied hour markers are polished and beveled with GMT hour indications between and a simple date window at 3:00 o'clock. At the 9:00 o'clock position is the continuous seconds' chapter ring and at 7:00 o'clock the power reserve indication of 72 hours. The two remaining chronograph indications are the 30 minute chronograph register at the 1:30 position and the hour register at the 4:30 position. I should also note that all of the Spring Drive Chronograph hands are in continuous fluid motion when in-function except the minute register hand that is semi instantaneous (jumping once per minute). Why is it that the minute register hand is not continuous? After using the chronograph I understood that it could be possible to misread the minute indication if it was not changing precisely at each minute interval, good thinking!

 

 

 

The crown at 3:00 o'clock is responsible for setting the hour/minute, adjusting the GMT hand, adjusting the date, and of course winding the movement in case you let it sit idle for more than 72 hours. Located at 2:00 is the chronograph start/stop button and at 4:00 the chronograph reset button as is typical. But, "typical" ends when you actually use the chronograph buttons. Seiko developed a push button system in the 1960's called "ready-set-go". Unlike many other chronographs that have a slow reaction time for the starting and stopping of the chronograph Seiko developed a very rapid mechanical release and stop mechanism for their stop watches used to time international sporting events. So what does "ready-set-go" mean? Well at first you set your finger on the start/stop button (ready), next you depress about half way until slight pressure is felt and the start function is cocked and ready (set), and finally at the moment of truth the button is pressed gently further and instantly the chronograph is in operation. Super smooth and fast is the only way I can describe it.

 

 

 

Looking from the back a sapphire exposition crystal gives a clear view of the movement including the winding rotor (did I mention this is an auto-winding watch with 72 hours power reserve?).

 

 

 

At the heart of the chronograph functions is the column wheel (center picture with V-shaped steps), considered by most to be the "classic" way of functioning a chronograph. To bring things into perspective I would like to mention the Seiko calibre 6139. Introduced in 1969 it was one of the first auto-winding chronograph watches that also incorporated a vertical clutch system and was controlled via a column wheel. To my knowledge this was the first chronograph to incorporate automatic-winding, column wheel functionality, and a vertical clutch system.

 

Given that, lets have a closer look at how the Seiko Spring Drive chronograph operates.

 

Above are most of the chronograph components. We will not concentrate on all of them but rather on those of importance to the basic understanding of functionality. As a brief overview I'll point out some of the more important components.

 

• 01 is the start/stop push button
• 010 is the return-to-zero (reset button).
• 05 is the column wheel.
• 019 and 08 comprise the center chronograph wheel assembly. This wheel assembly has a long thin shaft that passes entirely through the watch movement and carries the chronograph seconds hand on the dial side. Also incorporated in this assembly is a vertical clutch system that engages and disengages the chronographic seconds and minute recording. We'll explore the vertical clutch in more detail later in the article.
• 020 and 024 comprise the minute recording wheel assembly, including its heart cam and counter weight. As with the center chronograph wheel this wheel assembly has a long shaft that passes through the entire movement, as does the hour recording wheel, and carries the minute recording hand.
• 021 and 029 comprise the hour recording wheel.
• 06 and 07 are pivoted levers that open and close (disengage/engage) the vertical chronograph clutch.
• 017 and 018 are the "hammers" that when set against the heart cams of the hour, minute, and seconds wheels resets them to zero.
• 029 and 021 comprise the hour recording wheel assembly. As mentioned above this wheel assembly passes through the entire movement via a long thin shaft and carries the hour recording hand.

 

 

 

 

 

 

 

As mentioned earlier at the heart of the chronograph function is the column wheel 05. The column wheel is responsible for engagement and disengagement of all chronograph functions. It is the V shaped columns and the spaces between that control the actions of the levers and arms. In other words all chronograph functions begin here, either directly or indirectly.

 

 

 

At the center of the Spring Drive chronograph is the center chronograph wheel assembly that incorporates the vertical clutch mechanism. As compared to some chronographs that use horizontal coupling to engage and disengage the chronograph, the vertical clutch has some distinct advantages. First it is almost virtually instant in terms of engagement/disengagement, there is no lag time. Second there is no possibility of the seconds hand jumping either forward or backward when the chrono is started, something horizontal engagement can suffer when two gears are suddenly meshed together. And third it is very compact in terms of size.

 

So how does it work? Well let's say it has a lot in common with the clutch in a manual transmission automobile. Wheel "A" is driven via power from the barrel and is in constant rotation. "B" is the clutch plate that is attached to wheel "A", and "C" is the clutch that is rigidly connected to the long shaft that carries the chronograph seconds hand. When the clutch is closed (engaged) power from the barrel is transmitted to the chronograph seconds hand, and when the clutch is open the clutch is disengaged and the seconds hand is stopped.

 

 

 

Drawing #1

 

 

Drawing #2

 

 

In drawing #1 levers 6 and 7 are not engaged with the vertical clutch mechanism allowing the clutch to engage and the center chronometer seconds hand to rotate and mark the elapsed seconds.

 

In drawing #2 levers 6 and 7 are engaged with the vertical clutch which in turn disengages the clutch stopping the chronograph seconds hand from receiving power. The action of the column wheel on the beak of lever 6 at point "A" is responsible for either engaging or disengaging both levers 6 and 7 simultaneously since they share a common point of contact with each other at point "B" while the curved tail "C" of spring 7 acts as a spring to keep both levers united in their actions.

 

 

Drawing #3

 

Drawing #3 illustrates the return to zero (reset) function of the Spring Drive chronograph. I should note that this function is blocked while the chronograph is in operation and can only take place when the chronograph has been stopped. When the reset button is pushed the two hammers 17 and 18, which are connected together in a semi-rigid manner, are released in the direction of the solid green arrow contacting the hour wheel heart cam "A", the minute wheel heart cam "B", and the seconds' wheel heart cam "C". Since the heart cams are eccentric to the central axis of each wheel the cams are forced by the flat hammer faces to assume a static or "zero" position.

 

 

There is a very nice video of the Seiko Spring Drive Chronograph located on the Seiko Spring Drive web site. Click here to discover more.

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