Dorrin K Mace, Horologost

Dorrin K Mace, Horologost
The Clock Man in a pensive moment

Friday, May 31, 2013

How Did the Mechanical Timer Come About and How Does it Work

With the fairly consistent and measurable burning of a candle, a common use was to tell the time. The candle designed for this purpose might have time measurements, usually in hours, marked along the wax. The Song dynasty in China (960–1279) used candle-clocks.  By the 18th century, candle-clocks were being made with weights set into the sides of the candle. As the candle melted, the weights fell off and made a noise as they fell into a bowl. A form of candle-clock was used in coal-mining until the 20th century.
In the days leading to Christmas some people burn a candle a set amount to represent each day, as marked on the candle. The type of candle used in this way is called the Advent candle, although this term is also used to refer to a candle that decorates an Advent wreath.

Mechanical timers use mechanical clockwork to measure time. Manual timers are typically set by turning a dial to the time interval desired; turning the dial stores energy in a mainspring to run the mechanism. They function similarly to a mechanical alarm clock; the energy in the mainspring causes a balance wheel to rotate back and forth. Each swing of the wheel releases the gear train to move forward by a small fixed amount, causing the dial to move steadily backward until it reaches zero, when a lever arm strikes a bell. The mechanical kitchen timer was invented in 1926 by Thomas Norman Hicks. More inaccurate, cheap mechanisms use a flat paddle called a fan fly that spins against air resistance; mechanical egg-timers are sometimes of this type.
The simplest and oldest type of mechanical timer is the hourglass, in which a fixed amount of sand drains through a narrow opening from one chamber to another to measure a time interval.
Mechanical timers depend upon force provided by the user. When you turn the dial to set a mechanical timer, you also provide the power needed by the timer to complete its cycle. Turning the timer compresses a spring. As this spring unwinds, it turns gears, which in turn causes the dial on the timer to move. When the spring unwinds completely, the timer finishes it cycles. This triggers the sounding of the bell that occurs at the end of mechanical timer cycles.
The escapement controls the speed at which the spring within a mechanical timer unwinds. In doing so, the escapement ensures that a unit stays in sync with time. Basically, an escapement constitutes a type of catch. This catch catches, or stops, the teeth of the gears of a mechanical timer, then releases them. This catch-and-release cycle creates a rhythm that keeps a mechanical timer in sync with the passing of time, allowing a unit to accurately keep track of time.
One of two devices controls the rhythm of the catch-and-release cycle of an escapement in a mechanical timer, a pendulum or a balance wheel. A pendulum swings back and forth at a rate determined by its length and the weight at its bottom. A balance wheel turns one direction then the other, back and forth, in a continuous cycle, with force provided by a tiny spring. The timing of the pendulum or balance wheel controls the length of time an escapement catches the teeth of a timer gears, determining a timer’s ability to accurately keep time.
Well-built mechanical timers with good mechanical parts should keep accurate time and last. However, mechanical parts suffer physical wear and tear that may cause problems with a timer and affects its ability to keep accurate time. You can take a mechanical timer to any shop that repairs watches or clocks for refurbishment rather than purchase a new one. Mechanical timers appear in numerous devices in addition to standard kitchen timers.

No comments:

Post a Comment

Note: Only a member of this blog may post a comment.