How a Tachymeter Works
How a classic racing tool became one of the most iconic features in watchmaking.
Picture this: you’re strapped into a white Porsche Speedster, its optional four-cam enginepositively humming behind you, anxious to get off the line. (Please feel free to exchange this forthe ride of your choosing.) Glancing down at your wrist, you activate the pusher of your trustychronograph as you drop the clutch and accelerate off the line, the seconds hand beating outthe acceleration as you deftly move through the gears in pursuit of pure, straight-out speed. Intoday’s chronicle, we’re talking tachymeters - the what and the why behind that feature on yourfavorite chronograph. So buckle up, it’s lights out, and away we go.
Wrist watches are indelibly linked to racing. From modern brand partnerships ranging fromraces like the 24 Hours of Daytona to entire series like Formula 1, motorsports and wristwatchesmaintain a close bond beyond their historic purposes. After all, timing is everything whenfractions of seconds determine who wins and who loses.Enter the tachymeter. Not to be confused with the tachometer in one’s car, a tachymeter usestime and known distance to calculate speed. Both come from the same Greek roots — tachreferring to speed and meter referring to measurement — but their usage over time has resultedin a subtle yet meaningful difference. Thus, while a tachometer, speedometer, and Tachymetermight all mean measuring speed, in practice, they are used to refer to measuring revolutions perminute, measuring speed, and measuring speed based on time and distance.
How it works is simple. The scale is based on mathematics (stick with us). The equation is aseasy as T=3600/t — Tachymeter value (often miles or kilometers per hour) = 3600 (the numberof seconds per hour) divided by elapsed time. Let’s step back to our intro. Say that our intrepiddriver in the Speedster is trying to establish a top speed over a mile-long stretch of track. Uponleaving the start, the chronograph would be activated — as soon as the driver reached the endpoint, the chronograph would be stopped. The seconds hand will then indicate the speedreached during this exercise. Easy! (At least, easier than the slide rule on a Breitling Navitimer.)
The most famous examples of Tachymeter-equipped watches emerged following the Second World War, corresponding with the rising popularity of motorsports and general aviation.Omega’s Speedmaster — released in 1957 — is stated to feature the first Tachymeter scalefixed on a watch’s bezel. The Rolex Daytona, synonymous with racing for many, included thetachymeter bezel beginning with the reference 6239 in 1963, back when it was still called theCosmograph. (A little trivia for you — Daytona was added in 1965.) Other popularchronographs, like the Aquastar Deepstar of the early 60s, began to feature the useful scale.Heuer — today known as TAG Heuer — incorporated a rotating tachymeter bezel into theirAutavia chronograph to measure speed over sequential miles beginning in the late 1960s, afurther evolution of the chronograph as a tool for automotive enthusiasts.
While their functionality, though very real, may not be essential for most users, chronographswith tachymeter scales remain popular due to images they conjure of daredevil mid-centuryracing drivers plummeting down course straights at breakneck speeds, little more than lap belts to restrain them from being tossed clear of their vehicles. As with many watches, it’s theconnection to the past and the romance that drives their popularity. With their history andcopious amounts of style, it’s easy to see why they’ve remained so popular.
We hope this brief guide sheds light on the scale gracing your favorite chronograph. Want tocheck out some of our favorite watches with tachymeters? Head over to the Chronograph pageon the Windup Watch Shop. As always, the Windup Watch Team is available via consultation toanswer any questions you have. In addition, all of these products are eligible for free domesticshipping across the US.
