Additional Math Pages & Resources

Wednesday, August 18, 2010

Ping Pong, Hong Kong, Ding Dong

The blog today is NOT about table tennis, a large city in Asia, or door bells. It's about time and math. However, the title was chosen because I was trying to find words to rhyme with the blog titles from the last few days - How Strong, How Long and How Wrong.

In my search I found Ping Pong, Hong Kong, Viet Cong, Mahjong, Sing Song, Ding Dong, and so on. Ding Dong caught my eye because I was adjusting some clocks yesterday. Take a look:


These two 7" brass Seth Thomas clocks are more than 50 years old. The left clock has an internal bell and the right clock an external bell. The movements inside are otherwise the same.
  • Each clock requires 12 twists clockwise of the key on the left-hand shaft (near the 8) to wind the strike spring.
  • Each requires 15 counterclockwise twists of the key on the right-hand shaft (near the 4) to wind the main spring.
These marine clocks strike ship's bells. That's a shipboard tradition dating back at least 500 years. Visit the US Navy's Historical Site to read about how bells play an important role on ships even today.

Ship's bells communicate to a group of people standing watch on a ship; people whose eyes should be on the horizon and not on the clock!

A watch is a 4-hour shift doing a specific job. A bell is rung every 30 minutes to indicate the passing of time. Let's say you and your pals start on watch at 12 noon.

12:30   1 bell    ding
13:00   2 bells  ding, dong
13:30   3 bells  ding, dong, ding
14:00   4 bells  etc.
14:30   5 bells
15:00   6 bells
15:30   7 bells
16:00   8 bells! Your shift is over and a new one begins

16:30   1 bell
17:00   2 bells, etc.

At some point the term 8 Bells became slang or shorthand for dead (your life's shift is over).

The good things about this system are:
  • Everyone stays on the same time
  • You can tell the time in the dark
  • You don't need a clock for every person
  • You don't have to count too high
  • You get a reminder every 30 minutes
  • You can't easily fall asleep with the loud bell ringing
The bad thing about these clocks? You can't easily fall asleep with the loud bell ringing. You have to throw a couple thick towels over it because the strike spring doesn't run down for about 3 days!

Here's one clock striking 6:30 - it's the clock with the external bell. Be sure to turn on your sound first.



The two clocks striking 7 over each other. The later one has the internal bell; its ring lasts much longer.