[ Dylan Anderson wrote in 091021 MMDigest:

> The mainspring has broken and I would like to just buy and screw in
> the replacement.

Hi Dylan,  In response to your MMD posting seeking a main spring and
bell housing for a Reuge musical box --

I'm sure I can supply you with the part(s) you need, but I'll need
a bit more specific information about the size of your particular
Reuge mechanism.  I act as the North American parts and after-market
service provider for Reuge SA and Reuge USA and I stock many different
current and vintage Reuge main springs and their associated bell
housings, et al.

It sounds like you are looking for the complete mainspring assembly
in the housing already attached to the winding arbor.  In that case,
you are correct that it doesn't look too difficult to simply change
out a mainspring housing assembly with the spring already installed.
However, there are other considerations and complications to be wary
of!  What looks so simple may be far more complicated than it looks.

The admonition about leaving main springs repair and replacement to
the professionals still has validity here, too, although generally
directed toward those working on and with larger antique and clock
mainsprings, where the torque on a coiled spring can be well over
400 pounds and an accidentally released spring can certainly do a lot
of physical damage to surrounding equipment and personnel.

The other unseen nuances and inter-related involvement of associated
and connecting parts can make what looks like a "simple" spring
replacement a real migraine headache!

Reuge musical mechanism main springs, and their associated bell
housings, are very much like Rolls Royce engines -- they are made
in different sizes with different configurations, for different
applications, have different specifications and even the "same engine"
size will have had parts changed as the composite engine evolved over
time.

Reuge made, and still makes, many different size mechanisms (e.g.,
18-, 22-, 28-, 36-, 50-, 72- and 144-note) and the specifications
for each are different as to the length, thickness and width of their
mainsprings, the size of the bell housing, with or without a Geneva
Stop & Maltese Cross, the thickness and threading of the central
winding arbor, the gear ratio and # of teeth on the winding gear that
connects with the drive gear on the cylinder, not to mention the size
and positioning of the hole in the side of the bell housing into which
the central arbor or shaft of the cylinder fits and rides as the
mechanism plays.

Additionally, technical changes in construction and design have
occurred over the past 100 years.  Therefore, contemporary parts,
though they are from the same size and configuration mechanism, and may
look the same, won't work if installed into a vintage mechanism without
modification because some other related component has changed.  That
is why music box repair people generally only replace the physical main
spring avoiding the other unrelated/unknown/unforeseen factors that
could complicate the repair process.

Please call me to discuss your specific mechanism and needs.  If this
is a small 18-note mechanism it may be more efficient, and more
economical, to simply replace the entire mechanism, if that tune is
still available, than to repair the existing unit...

Diagnostic questions I'd need to have answered, are

1. How many teeth on the musical comb?

2. How many tunes is it designed to play?

3. Does the cylinder shift side to side?

4. Does the mainspring wind from above the bell housing or from below
the base plate, or perhaps from the side or back?

5. Is the winding stem square cut/slotted using a watch/clock key?
If so,  What is the thickness of that square stem?

6. Is the winding stem round & threaded, and if so what is the diameter
of the stem 3 mm or 4 mm?

7. Are you sure that the spring is broken?  (Did you remove it from its
housing and have two or more sections?)  Could it be detached from the
arbor, could the winding ratchet be broken, or the drive gear chewed?

Most sincerely,
Don Caine, Proprietor
The Music Box Repair Shop Unlimited
Lomita, Calif.
tel.: 1-310-534-1557