From Fusee to modern barrel

[FredWJensen]

The fusee used a tapered chain winder to equalize spring strength differences as the spring unwound so that the movement was always subjected to the same force to insure steady motion. How is this accomplished on the typical barrels used after the end of the fusee?

[Tom McIntyre]

The improvement in mainspring quality led to a longer and longer segment of the spring that provided an essentially constant force. In early high quality going barrels, stop works were used to restrict the spring to the linear portion. As springs continued to improve, stop works were discarded and only a recoiling click was needed to avoid the very short non-linear section. The extra bit of reserve takes care of the other end of the spring if the watch is wound daily.

At the same time improvements in the adjustment to isochronism allowed the watch to perform well with significant variation in power during the run of the watch. A properly set up balance is inherently isochronous, but the speed of the escapement changes with changing power and the escapement error will affect the time keeping. The overcoil is adjusted to compensate for the escapement error in very high quality work.

[FredWJensen]

That is great to know.
I am trying to build a crude verge watch, and the fusee is practicaly impossible to make without a fusee engine. I will substitue a standard barrel.
Thanks

[Tom McIntyre]

Fred,

The verge is not a detached escapement, so it is much more important that the mainspring force be constant. If you can use a long spring with stop works you may be able to get it to keep some sort of time. It won't be any problem getting it to run, of course, only a problem to keep time.

You might want to compromise and use an existing fusee. The verge escapement is actually a recoil type escapement that is more dependent on the power than deadbeat escapements like the cylinder or duplex. It might be easier for you to start with a duplex than a verge.

[FredWJensen]

I guess I have to do my homework before I begin.
I really wanted to attempt to build a representation of the world's first pocket watch.

[FredWJensen]

The Nuremburg Egg question turned up a great response from a German Gentleman. The German site actually had great photos and even a movie of the first pocket watch. It used a fusee. The fusee was amazing. Crude but amazing. It looked like it was filed by hand. And cat gut was used instead of a chain which was not invented yet. I may either try to file my own, or search for a large enough screw to modify for use as a fusee.