Calibre 174 was an important development for Jaeger-LeCoultre and the watch industry. In addition to a 2-axis tourbillon, it was the first wristwatch to feature a cylindrical balance spring. Patented in 1782 by Englishman John Arnold, the cylindrical balance spring makes a watch more isochronous thanks to two Phillips terminal curves. But the technology had never before been miniaturized and used in a wristwatch before the 2008 introduction of Calibre 174 in the Reverso Gyrotourbillon 2. And in this case, it was even smaller than normal, having to fit inside a miniature tourbillon in a Reverso case.
Introduced in 2004 in their Calibre 177, Jaeger-LeCoultre's spherical tourbillon is technically very impressive. It features two tourbillon carriages: The outer carriage rotates every sixty seconds and carries an inner carriage with the balance wheel, balance spring, and escapement. This inner carriage rotates 3.2 times per minute, exposing the 14 karat gold balance wheel once per minute. The entire tourbillon mechanism consists of 90 parts yet weighs just 1/3 gram thanks to aluminum and titanium construction.
Unlike JLC 177, calibre 174 operates at 4 Hz (28,800 A/h) and pairs the mainspring with a torque restricting device on the barrel. This allows Jaeger-LeCoultre to guarantee a full 50 hour power reserve, with the watch stopping at 50 hours when the torque is too low. It also prevents over-winding the manual mechanism. Overall, the 174 is made up of 373 pieces. It has 58 jewels.