A Clock or Watch Escapement: Captain Hook’s Greatest Fear?

January 6th, 2010 | 3 Comments



Besides Peter Pan, Captain Hook’s greatest fear was the ticking crocodile, a metaphorical reminder of time’s passing (and a literal reminder of his hand being bitten off).

crocodile

Ever wonder why a clock or watch ticks in the first place? In the case of clocks and mechanical watches, the part responsible for the ticking sound you hear is the watch escapement.

What is an escapement, what is it comprised of and how does it operate? Find out here.



What is a clock or watch escapement?

An escapement is a device in both mechanical watches and clocks that drives the timekeeping element, typically a pendulum (in clocks) or balance wheel (in watches). It converts continuous rotational motion from a weight or spring into a harmonic oscillating (back and forth) motion.


pendulum


It gets its name “escapement” from its function: it allows the gears to “escape” in fixed increments of time with each swing and to then move the timepiece’s hands steadily forward. In other words, the escapement divides the time into equal segments. It also keeps the timekeeping element moving by giving it a small push with each swing.



What is a watch escapement comprised of?

The main parts of a watch escapement include the balance wheel, the balance wheel staff, the pallet lever and the escape pinion and wheel.

The balance wheel is comprised of the impulse jewel or pin, impulse roller, safety roller and balance pivot.

The balance wheel staff has two cap jewels to limit the end shake of the balance wheel and to allow the balance staff to have a conical pivot. A conical pivot minimizes friction and maximizes the strength of the staff.


pallet-fork-escape-wheel


The function of the pallet lever is to alternately stop and release the escape wheel, which means it carries out the timing function of the balance. It includes the lever, the pallet fork, the entry pallet, the exit pallet, the safety pin, the pallet lever bridge, the banking pins, the upper pallet staff jewel and the lower balance wheel.

The safety pin allows the escape wheel to unlock only when the balance wheel is centered and the impulse jewel is inside the pallet fork.

The escape wheel has at its center the pinion gear which has “leaves,” while the escape wheel itself has “teeth.”



How does the watch escapement operate?

An escapement is “an impulse-driven lightly damped second order oscillatory system.” In layman’s terms, this means there is a vibrating element, the balance wheel/hairspring combination, that oscillates at its natural frequency and loses a small amount of energy with each swing. This energy is restored by an impulse from a tooth of the escape wheel, striking the impulse jewel on the pallet fork that gives a measured increment of angular moment to the balance wheel.


watch-escapement


Each time the escape wheel and pallet jewel collide, a mechanical watch makes the ticking sound that sent Captain Hook running.

Basically, the escapement operates as follows:

  1. Impulse jewel makes contact with the pallet fork.
  2. Upon contact of pallet fork, impulse jewel starts to move the pallet lever off of its banking pin.
  3. Entry pallet releases the escape wheel tooth.
  4. Escape wheel tooth slides up the face of the pallet giving the balance wheel an impulse.
  5. The pallet lever rocks to the opposite banking pin.
  6. Exit pallet locks the next tooth on the escape wheel.

As long as the balance wheel settles into a stable back and forth mode attributed to the proper design of the escapement, a mechanical watch will stay pretty accurate. Small timing errors occur due to momentary external disturbances, and eventually, these timing errors can result in accuracy degradation. So proper care and maintenance of a mechanical watch is essential.


kara-a-orient-photo

  1. 3 Comments | Tell us what you think!

  2. By Peter Gardner on Jan 6, 2010

    The ticking of a watch is one of the most soothing noises I know. My first automatic mechanical was a true no name beater, but had a very calming click that made taking it off my wrist very difficult. In my mind, the awe of the tiny mechanical efficiency of a wristwatch is a chief reason to wear a watch rather than rely on the many banal time sources in life (cell phones, computers, etc…) Interesting to read the how and why-

  3. By Tsiulin Alexander Victorovich on Jan 7, 2010

    Ae.

  4. By levani on Apr 28, 2010

    ai vish orient

3 comments | Tell us what you think!