Riefler escapement electric motor every 30 seconds, to eliminate the effect of changes in drive force on the mechanism. Working Riefler precision pendulum clocks on display to the public are located in the lobby of Olin Hall at Carleton College in Northfield, MN, the Deutsches Museum in Munich, the National Watch and Clock Museum in Columbia PA, the Musée international d'horlogerie in La Chaux-de-Fonds and the Musée d'horlogerie in Le Locle (both in Switzerland), the Deutsches Uhrenmuseum in Furtwangen, and at the US Naval Observatory (by appointment only) in Washington DC. Riefler escapement The Riefler escapement is a mechanical escapement for precision
Lever escapement the escape wheel must recoil a small amount during the unlocking. The draw holds the lever against the banking pins during the detached portion of the operating cycle. Draw angle is typically about 11-15 degrees to the radial. Early lever escapements lacked draw (indeed some makers considered it injurious as a cause of extra friction in unlocking); as a result a jolt could result in the escapement unlocking. Most modern mechanical watches are jeweled lever watches, using manmade ruby or sapphire jewels for the high-wear areas of the watch. A cheaper, less accurate version of the lever escapement is used