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Balance
Wheel
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If you do not know what balance wheel is, you can go
through Lesson 3
and Lesson 4 first
!
The 5 most common types of balance wheels will be introduced:
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There are many different types of design of balance
wheel because there is temperature change.
A rise in temperature will cause an increase in the
thickness, the height and the length of the balance
spring, and a reduction in the "modulus" (elasticity)
of the spring. The total effect of increasing temperature
on the spring decreases the rate of a watch (run slower)
because of the change in modulus (the other three effects
tend to cancel each other).
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| Glucydur Balance |
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Although it has the simplist shape, it can be
found in many C.O.S.C. certified movement.
it is made of beryllium, copper, and iron (berrylium
bronze), this new alloy was trade-named Glucydur.
It is exceptionally hard and stable, very resistant
to deformation, non-magnetic, and non-corrosive.
For other lower grade watches, the similar shape
is used but cheaper material is used instead of
alloy.
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| Bimetallic Compensation
Screwed Balance |
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The screws around the perimeter of the balance
can be moved in and out, moved to different holes,
and small washers can be placed under them to
increase their weight. They are used initially
to poise the balance, in order words, remove heavy
spots and balance the balance.
When the screws near the cut ends of the rim
are moved in or out, they effect the amount of
temperature compensation the balance provides.
This allows matching the compensation effects
of the balance to the temperature error of the
particular balance spring. Adding weight near
the cut end of the rim or moving screws to holes
near the cut ends increases the compensating effect
of the balance for both heat and cold.
Besides the screws, the balance is made of two
different metal in order to compensate the effect
of temperature.
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| Screwed Balance |
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Around 1930, a number of new alloys (cold-worked
and heat treated) became available for balance
springs. The most famous of these new alloys was
a combination of nickel, chromium, berrylium,
titanium, aluminum, and iron and was trade-named
the Nivarox. The best grade of Nivarox springs
(Nivarox I Highest) provides a temperature error
of only about ±0.3 seconds per °C per
day.
The new alloy allowed the use of monometallic
balances because the balance no longer needed
to provide compensation for the temperature errors
of the spring.
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| Adjustable Mass Balance |
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Because the slot in the weight reduces the mass
of the weight at that point, rotation of the weight
adjusts the distribution of mass around the balance
rim. If a pair of opposing weights are adjusted
equally, the daily rate of the watch can be adjusted.
More mass towards the outside of the balance (slot
towards the center of the balance) increases the
effective diameter and slows the daily rate. Weights
may also be rotated individually to adjust the
poise of the balance.
This design can be found in many Patek Philippe.
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| Rolex Balance |
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This can only be found in Rolex and
shoud be adjusted by special Rolex's tools. |
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