Not only the visual image of Big Ben is significant, but the sound of its chimes are perhaps equally recognizable the world over – even if not everyone will necessarily associate the two. One such penny added will increase the rate by two fifths of a second per 24 hours. Adding the penny moves its center of mass up and effectively “shortens” it by a tiny amount. It is not the weight of the penny that affects the interval of the pendulum’s swing but rather that the pendulum’s center of mass is changed. That is by adding pennies in a stack to a small shelf near the top of the pendulum as it swings – and not just any pennies, but specifically old pre-decimal English pennies, like the one shown above. If it is found to be running at all fast or slow, they must essentially “regulate” it to correct the deviation.Īmong the more marvelously quaint and charming parts of the whole thing is how the regulating is done. They record the results along with the barometric pressure and temperature in the clock room in a log that has over 100 years of records – the actual recording today is on A4 paper on a clipboard and computer software is also used, of course, rather than some giant gilded book one might imagine. They do this by taking a reference time by telephone, noted on a hand-held stopwatch, and then checked against the bell. The clockmakers also do a time check three times per week and oil the gears to keep Big Ben constantly accurate to within +/-2 seconds. The weights for the bells are wound with the help of an electric motor, but – and I’m not sure why this is necessary – the weight for the going train is cranked back up by hand three times a week by the three resident Westminster clockmakers or “clock managers.” There is the strike train of gears which controls the Big Ben bell that sounds the hours, the chime train for the four bells that mark the quarter hours, and the going train for displaying the time on the clock faces. Big Ben is a “three-train flatbed clock,” and its mechanism can be divided into three parts each requiring its own power source. Big Ben and clocks like it are powered by weights on steel cables with pulleys that drop slowly and must, of course, be wound back up regularly around a large drum.
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