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Does NASA certification end the debate of Column Wheel Vs. Cam Chronographs?

by Jonathan Ho on April 19, 2017

Debates of technical superiority between Column Wheel and Cam Actuated Chronographs have gone back and forth since the arrival of both innovations in the genre of mechanical chronographs. Horologically speaking, the last two centuries have brought so many innovations to the chronograph, from Louis Moinet’s 1/60th of a second precision measurement to Heuer’s 1/100th measurement; yet, there’s little agreement on which type of mechanism better controls chronograph functions. In terms of mechanical architecture, they’re not dissimilar but there are definite differences which can be discussed quantitatively and thus maybe settle this debate between Column Wheel and Cam Actuated Chronographs once and for all.

 

A Primer: Column Wheel Chronographs

First, let’s acknowledge that general consensus is that a column wheel chronograph is a vaunted symbol of haute horlogerie – it’s harder to produce, more manual labour intensive and arguably, visually dramatic. Miniature triangular pillars of the column wheel mechanism draws in your attention almost as much as the balance wheel and its operation is a feat of animated theatrics. While a column wheel component can be produced via CNC, it needs to be hand-finished to remove the metal burrs on each individual column and base of the raw component.

The Longines Pulsometer Chronograph. It is not just a pretty face; the watch offers a great value proposition as well.

Made (and finished) competently, a column wheel chronograph whether a Longines Monopusher or Grail-level Datograph, actuation of the chronograph by pushing the button is noticeably smoother. Furthermore, the vertical clutch which often accompanies a column wheel offers a smoother start (i.e. sans jerk) when the chronograph seconds starts timing; that’s because the gearing is lifted up and out as the column wheel turns in one swift, direct movement – thus the hand can stop and start with precision. That said, not all column wheel chronographs use a vertical clutch system and higher end models tend to use horizontal clutches for reasons of aesthetics.

Thus, we can conclude that due to the cost of labour and specialised production, pricing for column wheel chronographs tend to be on the higher end of things. This in turn leads specialised high horology brands to focus on this type of chronograph since there’s more value, prestige and challenge in producing one. There’s one caveat, high stresses in chronograph operation means that over time, it’s rare but not uncommon that a column breaks off a wheel – it’s terrible to service when that happens and significantly more time consuming.

Movement is the exceptional Datograph based L952.1, with a perpetual calendar plate.

Famed Column Wheel Chronographs:

Omega Speedmaster Calibre 321

 

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A Primer: Cam-Chronographs

Industrial, robust, enduring – the cam-actuated chronograph is the AK-47 assault rifle of chronographs. It’s tough and it replaces the column wheel with levers and arms manipulated by a cam. By nature of its architecture, the cam’s levers and arms are not as precise as a column wheel which constrains each action within the space of its columns, thus, there’s a lot of free-play when it comes to the cam. That said, levers and arms are simpler to stamp, cut and mill in numbers and these economies of scale tend to reduce costs significantly.

Technically speaking, the “play” of levers and arms in a cam-actuated chronograph does not affect precision of operation or timing but it does affect perception of feel and how it operates. Put a cam-actuated chronograph against a column wheel chronograph and it pretty much runs the same – chronometry and precision is up to the balance assortment rather than the intricacies of how one chooses to activate a chronograph. Its simple construction means that production costs are lower while simultaneously being more robust. Breakage is unheard of with cams but if you manage to wreck one, servicing is easy since the simple geometric lever and parallelogram shapes of the parts makes cleaning and lubrication easier.

The IWC Pilot Chronograph “Top Gun” is running on a movement based on Valjoux 7750.

True, a cam-actuated chronograph feels “rougher” when it comes down to the button push. On a column wheel chronograph, the clutch simply engages and disengages in either an up/down or sideways motion. On a cam, the pusher literally turns the cam and thus needs more pressure in the pusher before it “jumps”.

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Speaking of “jumps”, when a cam-actuated chronograph starts running, it’s a common complaint that the chronograph seconds “jumps” jerkily rather than a buttery run as compared to the column wheel chronograph. Again, like the column wheel chronograph, why this happens (i.e. buttery run or jerky start) has nothing to do with how it is operated – it’s because horizontally coupled gears can start from a variety of positions depending on how they were stopped the previous time – it might look like the seconds hand skipped a little but it hasn’t, the drive gears merely get into position and then start running smoothly.

Famed cam-actuated chronographs:

Anything with an ETA/Valjoux 7750 and obviously, the Omega Speedmaster Calibre 1861

Column Wheel Chronograph vs. Cam Actuated Chronograph: As told by NASA Certification of Omega Speedmaster

The calibre 321 was a column wheel chronograph which was approved by NASA for use in space. Subsequent Omega chronographs cleared for space flight were cam-actuated, is there/what are the technical distinctions that make one “better” than the other? 

The change of the flight-qualified Speedmaster movement had nothing to do with technical changes or details, but with current model availability. Indeed, Speedmaster chronographs reference CK2998 powered with Calibre 321 were privately chosen by NASA Mercury astronauts Wally Schirra and Gordon Cooper for their missions in 1962.

Under the watchful eye of engineer James H. Ragan, towards the end of 1964, NASA embarked on a series of incredibly tough tests in order to select a mission chronograph for the upcoming Gemini and Apollo missions. Of the various chronographs submitted by different brands, only the OMEGA Speedmaster with reference ST105.003 survived the stringent tests and became “flight qualified” for all manned missions by March 1965. This model too was powered by the Calibre 321.

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Later, during the course of the Apollo missions, NASA – based on the original qualification tests – continued to procure Calibre 321 Speedmaster chronographs, this time with references ST105.012 and ST145.012, as these were the most current models available in the market during the respective procurement periods. In fact, during and until the very end of the Apollo program, NASA only had Calibre 321 OMEGA Speedmaster chronographs on their “flight roster”.

It was only during the preparations for the upcoming Space Shuttle missions that, in 1978, NASA had to re-evaluate all flight hardware and the qualification procedure was re-launched. As by that time, the Speedmaster “Moonwatch” chronograph that was current in the markets was reference ST145.022 powered by the Calibre 861, a movement that was a redevelopment of the 27mm Calibre 321 and featured a cam-system to control the chronograph functions as well as a higher frequency of 21.600 A/h.

The change of movement, from Calibre 321 to 861 was in fact based on the fact that NASA always tested and qualified current models (as per market introduction /availability), so until NASA had a requirement for a new set of watches, they kept the ones already qualified (Cal. 321) and when the need for a re-qualification arose, they tested and qualified then-current models. For the OMEGA Speedmaster it simply meant the Calibre 861 powered ST145.022 model.

Is there such a thing as better than? Why is the column wheel considered high horology while something robust like the cam is not?

It’s common refrain in watch speak and marketing collaterals that the column wheel is “high end” when compared to other types of chronographs. By definition of manual labour and greater effort, this is statement is technically true, however this would reduce something like Habring’s 7750-based split seconds chronograph to something of a sideshow rather than a treasured symbol of haute horlogerie.

A column-wheel chronograph is no more reliable than a cam chronograph. But it is true that the column-wheel nowadays has a “higher perception” compared to a cam system. This is due to the fact that the column-wheel is the traditional solution and visually more aesthetic. In the late 1960s, a cam system was more modern and simpler to manufacture compared to a column-wheel.

Deployant would like to thank Omega for technical insight for the article.

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