Can anyone explain to me what "stop works" is and what it does?
Thanks
Ed

function was to prevent overwinding of a watch. Try doing a search on this forum for "stop works" and you'll get to see several.

I am compelled by my own work with Geneva Mechanisms to add that the "stop works" that is designed to limit the isochronism effects of the mainspring at BOTH ENDS of the winding cycle is actually an abberration of the Geneva drives (That I have designed into things many many times) that were meant to "cycle" a mechanism VERY accurately and especially to CONTROL THE ACCELLERATION/DECELLERATION of the motions involved. The range of uses goes from watch and clockworks to 20 MM gatling Guns and every possible thing in between. I employed them in machinery to manufacture things very fast and accurately such as 5.56 MM Cartridges @ 18/second (E.W.Bliss Co., Gulf & Western), Tape Cassette Record/Erase Heads @ 10,000/day (Nortronics Co.), etc., etc.

You can see a good action flick of this type mechanism at;

http://en.wikipedia.org/wiki/Maltese_Cross_mechanism

Thanks you all for the lesson.

Can you tell if a pw has a stop works by looking at the movement or does the barrel have to be disassembled?

Ed, I have only seen external stopworks on the Howards. The Elgins and Hampdens have it buried under the barrel cover, and (sadly ) the "watchmakers" of the period threw out the works parts rather than re-assemble them correctly to the watches, so they are very rarely found "complete" in those watches where they are "hidden". You can only see the machining details of where they should have been.

Edward, generally if a watch has 'Stop work' fitted, the winder will 'stop' solid when fully wound as the 'pip' locks into the maltese cross, instead of the usual 'springy' feel - that is, unless the 'pip' has broken off at the barrel arbor, when it will have the same feel as a standard winder.

This was a very common device fitted to higher end Swiss movements, both Cylinder and Lever types.
Usually the device isn't visble on these though unless the dial is removed.

John

John,
Thank you for the tip.

David,
I read something to the effect the watchmakers did not reassemble the stop works when working on a watch. This goes against what I have learned about what type of person it takes to be a watchmaker. Do you know what their reasons were?

I think these were of the same "ilk" that tossed out the dust rings and replaced broken jewels with brass friction bushings. Basically sloppy, lazy, and careless people who could usually clean a watch and maybe get it back to running again.

The extremely competitive market for watches was (unfortunately) a little "lax" on the quality of service supplied by the seller-watchmaker's. That helps explain the necessity of "certifying" the RR watch inspector/repair people.