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Different
Types of 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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