The Ball for BMW TMT is one of the most recent — and most distinctive — additions to the series of watches that the Swiss brand with railroad-timing roots launched in a partnership with the German sports car marque in 2012. The watch, which we had a chance to get our hands on this week, is equipped with a complication one doesn’t see very often: a mechanical thermometer.
The Ball for BMW collection, whose development was headed up by noted BMW designer Magali Metrailler, is heavily influenced by the aerodynamic lines and ergonomic details of BMW cars and their engines. The watches feature alternating polished and satin-finished surfaces and screw-down crowns that evoke the detailing on BMW dashboard knobs. The grille-motif dial designs are influenced by the cars’ dashboards and the shape of their disk brakes, and each features a BMW logo. The dials’ hands and diamond-cut metal indices contain micro-tubes of luminous H3 gas (14 of them on this watch), a Ball Watch hallmark. BMW’s signature color, Inka orange, is used on details such as seconds hands and subdials. The watches feature a patented, micro-mechanical anti-shock technology called Amortiser, which absorbs lateral impacts to protect the movement when the watch is on the wrist.
The TMT model, which comes in a black DLC-coated stainless steel case, is powered by the automatic caliber BALL RR1601-C, a COSC-certified chronometer, which has been enhanced with Ball’s patented mechanical thermometer module (“TMT”). The thermometer function is used to measure outside temperatures between -31 and +113 degrees Fahrenheit (-40 to +50 degrees Celsius) to an accuracy of 97 percent. Creating the module was a challenge for Ball’s technicians, because it required fitting the bi-metallic spring at the heart of the thermometer mechanism within the height of the milling of the mainplate and bridge; the entire movement is just 5.1 mm thick. Ball has patented the screw regulation system that stabilizes the position of the bi-metallic coil but allows it to adjust with changes in temperature; this is the crucial part of the mechanical thermometer achieving high accuracy in its temperature measurement.
The watch’s case is 44 mm in diameter and 13.25 mm thick; it is water-resistant to 100 meters, with a nonreflective sapphire crystal and a screw-down crown, and comes on a rubberized leather strap. The thermometer indicator is in a semicircular scale at 6 o’clock, and the date is displayed in a round window at 1 o’clock. Two dials are available, one with the temperature readings in Fahrenheit and the other in Celsius; seconds hand and thermometer hand are available in a BMW blue (pictured) or in Inka orange. The Ball for BMW TMT is a limited edition of 1,000 pieces; normally priced at $5,299, it is being offered by the company at a special pre-order price of $1,999 until October 16.