John B Shadle, CMC
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John B Shadle, CMC
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Here's a preliminary drawing for a new clock, begun in August, 2007. This one has an innovative remontoire: Clock springs provide more torque when newly wound, and even weight-driven clocks provide variable power because of gear train friction, so it's advantageous to have a power source close to the escape wheel.
In this case, power is provided by a long torsion spring, which dircectly drives the escape wheel. The torsion spring is 18" long, and contained in a vertical tube (shown on the right) which keeps it from distorting. The torsion spring is attached to the tube only at the very bottom of the tube, where there is a little tension adjuster. The tube turns to twist the torsion spring which drives the escape wheel.
Once per minute, the torsion spring is re-wound, and when this happens the hands are also advanced one minute.
It has a large, three-inch, 90-tooth crown escape wheel, since the crown wheel's vertical arbor will fit well with the torsion remontoire, whose gear train is also vertical. The remontoire design also lends itself to the use of miniature ball-bearings.
It will have a large 6-inch main wheel, for looks, and it will be powered with a reverse fusee which I've described elsewhere on this web site.
It stands 24" tall, and should be an impressive clock.
On the left shows the escape wheel for this clock. It has 90 teeth. The back slope on a tooth is 20 degrees, with a slope of 2 degrees on the front of the tooth. It is 3" in diameter.
On the right is the remointoire mechanism, now mostly finished.
A contrate center wheel (not shown) turns the pinion at the bottom of the mechanism. The vertical escape wheel shaft and the vertical remontoire shaft are aligned, but not connected -- exept through the torsion spring, a small amount of which shows on the right.
The escape wheel takes two minutes to revolve, so there are two pins on the trigger cam, shown on the left. As the escape wheel runs, it triggers the remontoire through the trigger cam, which unlocks detents on the locking plate which then turns to twist the torsion spring one-half turn. Unlocking is a two-step process which functions in exactly the same way as in the strike train of a striking clock.
Next, I'll build the pallets and some plates, and perhaps we'll see the clock run, in preliminary fashion.