Expert: Martin Meyer - 7/7/2009

Question
Hello, I am in possession of a Regulator Clock that I believe is from the 1800's.  I cannot see the paper too clearly, but I do know it is a Regulator.  It is an 8-Day wind, unfortunately I am unsure of what Regulator it is, but when I was winding the clock today the main spring broke.  I was wondering if you would be able to point me in the right direction to locate the full details on the clock, and then hopefully by doing that being able to figure out what spring is needed.  Thank you very much in advance.

Answer
Hi Sue,

There is no source for detailed specifications on antique clocks. To replace the mainspring, the entire movement must be disassembled and cleaned. When clockmakers do this, they also replace all worn bearings with bushings and reface and polish all the pivots (ends of gearshafts that turn in the bearing holes). Antique clocks usually have a large amount of wear in their bearings, so having the movement overhauled and the mainspring replaced by a professional clock repairer may be a good choice.

The size of the new mainspring is determined by measuring the old mainspring. Mainsprings have three dimensions, plus the end type. Your clock will have a "loop end" mainspring. The dimensions are width, length and strength (thickness). These dimensions should be measured accurately with a machinist rule and a micrometer. Many clocks like yours have a 3/4" x 96" x .018" mainspring. Yours may have this size, but you should measure first to be sure. If your clock does have this size, it is recommended that you replace it with a 3/4" x 96" x .0165" mainspring, because the original mainsprings were overpowered, and the slightly thinner spring will keep more consistent time. If your mainspring is another size, replace it with the same size as the original. The selection of mainsprings available does not include all possible sizes, so you may have to find the closest match that you can, if you have an unusual size mainspring. Mainsprings are available from any good clock supply house, such as  Timesavers (www.timesavers.com) or Merritts Antiques (www.merritts.com).  http://www.clockmasteronline.com