- Plain Barrel
-
Elgin Database Mainspring Barrel Code: None, Elgin didn't use this.
The easiest solution is to take a post, fasten one end of the spring
to the post, and fasten the other end of the spring to a barrel with a
gear attached to it. To wind up the spring, you turn the barrel/gear
one way, and the spring tightens up around the center post. When the
clock or watch runs, the gear slowly turns the other way.
One problem with this solution is that while the clock or watch is
being wound, there is no maintaining power to keep the gears turning.
Thus, you lose time every time you wind the timepiece.
Another problem is that when the spring is fully wound, it pushes the
gears much harder than when it is wound down.
A third problem is that when the spring breaks, and any watch made
before around 1960 you can count on breaking, the spring will whip
around and slam against the outside of the barrel, turning the barrel
in the opposite direction that would normally go. This is exactly
like what happens when you pull a rubber rubber band apart and let go
of one end. The other end receives a nasty snap. This snap can
damage gear teeth, break jewels and cause a great deal of other
damage.
While there were probably watches made using this kind of plain
barrel, they were probably all made before 1850 when the Americans
started making watches.
- Barrel and Fusee
-
Elgin Database Mainspring Barrel Code: None, Elgin didn't use this.
To solve some of the problems of the plain barrel, watchmakers
invented a somewhat conical shaped device called a "fusee".
The spring barrel was attached to the fusee via a tiny chain, or in
earlier times, cat gut. When the spring was fully wound, most of the
chain was wound around the fusee all the way up to the narrow end of
the cone. As the watch runs, the chain unwinds down the fusee to the
wide end of the cone and wraps around the spring barrel. This means
that the lever arm of chain pulling the fusee is weakest (shortest)
when the watch is fully wound and strongest (longest) when the watch
is unwound.
By carefully crafting the shape of this cone like device, the spring
can be made to deliver almost a constant force to the gear train.
Another advantage of the fusee is that when the spring breaks, the
barrel may whip around, but since you can't push a chain, this watch
is much less likely to be hurt.
The Barrel and Fusee system still has the problem of not having any
maintaining power while the watch was being wound. Some watches that
used a fusee solved this problem with some extra springs and ratchets
and gears.
While the fusee solved some problems, it created others. First the
fusee took up a great deal of space in the watch, and required the
watch to be quite thick. Secondly, the fusee and the fusee chain are
very hard to make and greatly increase the cost of the watch. This is
especially true if you add in all the extra springs and stuff needed
for the maintaining power.
The Barrel and Fusee system was heavily used by the English in their
watches up until the 1890's, and were used in marine chronometers
through WWII.
- Going Barrel
-
Elgin Database Mainspring Barrel Code: gb
Another technique to solve some of the problems with the plain barrel
is to turn the center post into an axle, or in watch terms, an arbor.
You can then turn the axle (arbor) to wind the watch, and as the watch
unwinds, the outside barrel will turn. This means that there is
always tension on the spring so the "gears keep going".
There are a couple of techniques can be used to solve the problem with
unequal power. These are discussed in the
isochronic adjustments
section of the
adjustments
web page.
The problem with the damage caused by a broken mainspring can be
solved by using a "safety pinion". The gear that is driven by the
spring barrel is screwed onto the axle (arbor). When the spring is wound up
and trying to turn the gear in the right direction, it just screws the
gear on tighter. If the mainspring breaks and the gear gets turned
the other way, it unscrews and disconnects that rest of the gear train
from the spring. The barrel just twirls for a while and stops.
The going barrel was used in most American and Swiss watches since the
1850's.
- Motor Barrel
-
Elgin Database Mainspring Barrel Code: mb
Another technique is to reverse the connections that the going barrel
uses. Instead of winding with the axle (arbor) and driving the train with the
barrel, you can wind the barrel and drive the train with arbor. Then,
when the spring breaks, all the damage is done to the winding gears,
which can easily be made strong enough to handle the force. The
result is called a motor barrel or a safety barrel.
You still have the problems with unequal forces, but you solve them
the same way as with the going barrel.
The motor barrel required significantly more parts, mostly plates and
screws, than a going barrel. It has the advantage that since the
power comes off the center arbor, the barrel only has to slide on its
bushings when it is being wound. This means that a weaker, less
breakable mainspring can be used to transmit the same amount of power
to the gear train.
Elgin started using the motor barrel on some watches, mostly the
higher grade ones, starting in the late 1890's. I believe several
other companies had been using the motor barrel for years by that
time.
You can tell if an Elgin watch has a motor barrel by the three small
screws on the mainspring wheel.
- Jeweled Motor Barrel
-
Elgin Database Mainspring Barrel Code: jb
Since the mainspring arbor of a motor barrel is just like all the other
arbors in the watch, it too can be jeweled in order to reduce
friction. While these jewels doesn't provide that much of a
real benefit, they are "functional jewels" and they can be used to
increase the jewel count of a watch. As explained in the
Watch Jewel
web page, many people will think a watch is better just because it has
more jewels.
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