Making The Mainspring And Escapement Pallets, by Clickspring.
In this video I reach a significant milestone for the clock, the very first tick of the escapement.
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Abbreviated Transcript:
00:36 The purpose of the escapement is twofold: Firstly, it releases small amounts of energy to the pendulum to replace what it loses to friction, and so keep it oscillating. And secondly, it effectively counts those oscillations, and through the attached gear train keeps a running total, that we see displayed as the time.
01:45 Old fashioned trial and fit on a depthing tool is still the accepted method to inspect the escapement action, and decide on the required adjustments to the pallet profile. The process of roughing out the pallets is much like you've seen in previous videos for parts like the click and clickspring. A paper template marks out the perimeter, as well as the hole location on some O1 tool steel.
04:29 And at this point the recognisable shape of a set of recoil pallets is starting to emerge, although there's still quite a lot of fine adjustment required to get them to perform correctly.
06:00 But the general idea appears to be gradual removal of excess metal, whilst incrementally pushing the pallets into closer engagement with the escape wheel teeth. The ultimate goal is to have a minimum drop onto both the entry and exit faces, and an easy clearance at each of the discharge corners. While at the same time ensuring that the pallets at the correct theoretical depth.
07:52 Like most of the other steel parts in the mechanism, its important that the pallets be hardened to ensure they have a long service life. And you might recall that when I made the hands, I used a custom tray to contain the boric acid glaze during the heating.
09:22 All pallet surfaces now have the required finish, and I used a fine oilstone to break the sharp corners, and leave a presentable edge. So with the pallets complete, along with a small fastener that I turned up off camera, I can fit them to the mechanism and see how they perform.
10:55 But with a slight turn of the bushing, the drop can easily be minimised to what it should be for maximum energy efficiency. The escapement feels nice and slick. In fact a light touch on the center wheel is enough to set the pallets off and running, and the bushing can be further adjusted so that the teeth just pass the pallets.
14:20 The spring is then wound up just enough to allow the barrel to be slipped over, and then the barrel hook is engaged with the outer hole in the mainspring. The tension can then be slowly released by reversing the winder, and once all of the force has been removed, the spring can be unpinned.
14:58 A few drops of oil are enough to lubricate the coils, and will be enough to eventually cover the entire length of the spring as it's continually discharged and rewound.
17:42 Its not a long enough test period, and its unlikely that the clock could maintain this performance long term, particularly without temperature compensation or a fusee. But its an encouraging start, and certainly a much better result than I expected. I'll leave it running on test over the next few weeks, while I work on the last remaining components of the build: The stop work mechanism, a winding key, and of course the final polish and assembly.
References:
John Wilding "Large Wheel Skeleton Clock" construction book can be purchased online from Ian T Cobb:
www.clockmaking-brass.co.uk/cl...
Making The Mainspring And Escapement Pallets, by Clickspring.