This is a nice example of
Elgin's grade 582, 16 size, 15 jewels, a military timer, often called a "jitterbug" (stopwatch) made about 1942.
This one was jammed up somehow so I needed to figure that out before disassembling so that no blocked up tension would send anything flying across the room. Careful inspection step by step through the mechanism reveals that nothing is broken or bent, so I figured the problem had to be the… I’m not sure what it’s called, but there’s a complicated gear-like part at the left that controls the functions start, stop and fly-back. A little gentle coaxing of the lever that is supposed to push that piece around from mode to mode got it all working normally. I guess it’s just in need of a tiny about of strategic grease. It actually doesn’t even look like this piece has seen much use.
Many parts in this piece are off-the-shelf Elgin 16 size pocketwatch parts, but a little different…
This part drives an extra wheel on the dial side that carries the sweep hand. It’s off the 4th wheel, so it’s getting what would be a seconds reading, except on this movement it’s much faster. This is something like watches that have a sweep-second hand except that the extra wheel is under the dial instead of at the back.
Here the movement’s tiny little balance wheel with a normal 16 size double roller assembly and hairspring. Elgin’s design for the timer cleverly used a more or less normal, but much heavier duty, version of their 16 size movement with a balance from, I think, a zero size product? Anyway, the balance is so light it doesn’t even “dangle” from the cock by the hairspring. And it just flies when it runs, at a brisk 144,000 BPH (beats per hour).
A great way to tell that a watch has been treated well by watchmakers is the lack of tool marks on the pallet bridge left by pushing it into place with steel tweezers rather than a stick of pegwood.
At first glance it looks a lot like Elgin’s no-frills automotive and aircraft movements, also based on 16 size designs.
The movement is really, really thick on these timers. The stop works are all under the dial, and very heavy duty - large thick parts. The dial stands high on pillars to make space.
One challenge with these is that in normal operation they ought to be “self-starting”, meaning the escapement starts it’s cycling on its own just through winding. This is not typical of vintage watches, which generally need at least a tiny amount of motion to bump the balance wheel slightly to one side of the other, though getting it all going. Often the movement the watch gets just via the act of winding is enough.
The problem here is that the balance wheel is so light relative to the hairspring that the hairspring can actually keep the balance still. To even approach self-starting therefore the beat has to be dead center, which is hard to do since a timing machine will not read one of these, or at least mine won’t. It’s much too fast.
The hairspring will actually pull the tiny balance wheel to dead center when there's no power. Slight wind will then move the pallet and start the cycle.
It also helps to have pallet locking on the “light” side. This watch looks factory as far as that goes.
1 comment:
Can you confirm which mainspring I need for one of these stop watches. I purchased one used that was not running and figured I would put a new mainspring in it.
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