11. Each beat gives the balance wheel an impulse, so there are two impulses per cycle. 12. Many clocks keep time by mechanical resonance in a balance wheel , pendulum, or quartz crystal. 13. Out-of-balance wheels and poor alignment could eat up much more than 10 percent of your fuel. 14. The clock movement had a balance wheel regulated to beat at the rate of 2 seconds. 15. The balancing wheel of PSMT ran on the roads and did not interfere with normal traffic. 16. The first clocks in northern Europe used foliots, while those in southern Europe used balance wheels . 17. Synchronous motor clocks are rugged because they do not have a delicate pendulum or balance wheel . 18. The bimetallic compensated balance wheel was made obsolete in the early 20th century by advances in metallurgy. 19. Such schemes consisted for example of small bimetallic arms attached to the inside of the balance wheel . 20. The bimetallic temperature-compensated balance wheel was made obsolete by the discovery of low-thermal-coefficient alloys invar and elinvar.
