Big Ben Fact File
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The following is a summary of the main facts about the clock, tower and bells.

The Clocktower

  • The total height of the tower is 316 feet
  • The height of the belfry is about 200 feet
  • There are 290 steps to the clockroom and 340 to the belfry

The Bells

  • The quarter chiming bells are in the key of F
  • The hour bell (Big Ben) is note E and weighs 13.5 tons and has a maximum diameter of 9 feet
  • The hammer of the hour bell weighs 4 cwt.
  • The four quarter bells weigh (in order of size) 1 ton, 1.25 tons, 1.6 tons and 3.5 tons

The Dials and Hands

  • The diameter of each of the four dials is 23 feet
  • Each dial contains 312 panes of glass (and we are happy to dispel the myth that there are 365, one for each day of the year, yes, we've counted them!)
  • 28 bulbs are used to light each dial from behind
  • The hour hands are 9 feet long and weigh 0.8 cwt.
  • The minute hands are 14 feet long and weigh 2.5 cwt.
  • The Roman numerals are 2 feet high

The Clock Movement

  • Three train flatbed movement with Grimthorpe's double three-legged gravity escapement and two-second pendulum
  • The frame of the movement is about 16 feet long and the entire machine weighs 5 tons
  • The driving weights weigh 2 cwt. (going), 1 ton (striking) and 1.25 tons (chiming)
  • The chiming and striking trains have been wound by motor since 1912 but the previous hand winding took two men 5 hours per train
  • The going train is still wound by hand which takes less than 30 minutes
  • The overall length of the pendulum is about 14 feet and it weighs 2.5 cwt.

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