NOTES FROM THE BENCH
Clock Repair Archive - - Definitions:
These are the definitions we use here in this journal. Many of them are standard. Some of them are not.
Some of these are called different names in different parts of the world.
Verge: also called anchor, pallet, or escapement
Chime: also called chimes, gong, melody
Gong Rod: also called chimes, gong, strike
Main wheel also called great wheel, spring barrell
Second wheel this means the wheel next to the Main wheel. We generally assign numbers to each
wheel, up from the bottom of the gear train, to refer to that wheel.
Centerpost this means the post the minute hand fits on
Centerpost gear this means the gear on the centerpost ( sometimes called the 3rd wheel )
Hour tube the sleeve that the hour hand fits on
Pendulum also called pendulum ball, pendulum bob
Suspension also called the suspension arm. The pendulum is attached to this part. When a user
"puts the pendulum on the clock," this is what it is usually attached to.
Suspension spring this means the spring that the suspension hooks to that provides recoil for the
swing of the pendulum
Suspension post this means the post that the suspension is hooked to
Adjusting nut this means the nut at the bottom of the pendulum bob that allows for timekeeping
adjustments. (The adjusting nut is not always at the bottom of the pendulum.)
Strike The sound the clock makes when it counts the hour. Do not confuse this with the
Ratchet wheel Part of the mainspring ratchet assembly. The ratchet wheel is a gear, with a square
opening in the center that fits the mainspring arbor precisely. This gear usually
has slanted teeth with valleys that fit the end of the click (ratchet dog)
precisely, thus keeping the mainspring from releasing and destroying, gears,
person's fingers, and other clock parts. This is the device that holds the
mainspring tight after each turn of the key. When fully wound, this device has the
full power of the mainspring on it. The stored energy ( potential energy ) of the
mainspring is held by the one single active tooth on this wheel in conjunction with
the ratchet dog. Failure at this point causes massive damage.
Click Part of the mainspring ratchet assembly. The click is often called the ratchet dog.
Click spring Part of the mainspring ratchet assembly. The click spring causes the click (ratchet
dog) to snap into the valleys of the ratchet wheel.
Maintaining hook A hook that holds a spring tight inside the main wheel of many weight drive clocks.
This spring applies pressure in a reverse direction to the pull applied by winding.
The reason for this is that when the clock is wound while it is running the power
to the gear train is briefly interrupted which makes the escape wheel stop.
Occasionally the verge will then come down right on top of one of the teeth of the
escape wheel, causing it to be bent. With the spring and maintaing hook in place
and functioning correctly, enough pressure is maintained on the escape wheel while
winding the clock to prevent damage by keeping just enough power to the escape wheel
to keep it from stopping.
Isochronal error A fancy way of saying a mainspring has more power when it is fully wound, than when
it is run down. The power curve of a mainspring is non-linear, thus resulting in
timekeeping errors. ( see the section in trouble shooting more info ).
Fusee ( Fuzee ) A design by which the power from the mainspring of a clock is delivered to the rest
of the system through a spiral cone shaped spool with grooves for the cable. The
top end of the mainspring power is delivered to the smallest diameter of the fusee.
This reduces the ampount of power delivered because of the difference in diamters.
The bottom end of the mainspring power is delivered to the largest diameter of the
fusee. This increases the amount of power available with respect to the top end,
thus effectively eliminating the effect of isochronal error by mechanically
equalizing the power delivered by the mainspring.
Platform escapement Usually found in ships bell clocks, and expensive french carriage clocks. This
usually consists of a balance wheel and associated parts, a verge which is often
jeweled, and an escape wheel. The design of these balance wheels is very similar
to what is found in large pocket watches. Some of the higher quality balance
wheels have timekeeping adjustment screws in the wheel itself.
Sequence The sequence of the operation of the gears and / or hammers and / or shutoff and
/or trip levers of a particular section of a mechanism to produce the correct
result of sound or mechanical operation.
Top end power Fully wound mainspring.
Bottom end power Mimimum mainspring power. Power delivered at the "almost totally unwound state"
of a mainsping's power curve.
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Copyright (c) 2002 David Tarsi.
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