Today I made the pendulum and its hanger assembly. The hanger is modeled after that found on cheap Korean-made movements -- even bad movements can have good points. It is basically a suspension spring with the top held in an arbor with pivots. The arbor is spring-loaded, which promotes lateral stability, but at the same time allows the pendulum to hang free. The pendulum can be removed from the hanger just by pushing the pivot assembly to one side, compressing the spring.

The pivot assembly is made on the lathe from 3/16" brass. Half of it is cut down to 1/16". The suspension spring has a hole in it, which permits the spring to be slipped onto the 1/16" side of the pivot assembly, to be held in place by a washer. The washer is made to an interference fit on the 1/16" of the pivot assembly.

The pivot swings between a pair of arms made from 3/16" brass. The arms are sawn in a single piece using a Deltacad template. The arms are then soft-soldered onto a piece of round 1/2" brass, only 1/16" thick. This piece acts as reinforcement, since there must be a hole through it big enough to pass a 6-32 screw. This screw is actually one of the four post screws -- one screw does a double duty here. (Incidentally, all visible screws will later be replaced by homemade blue screws -- much more handsome!)

The top of the pendulum (which holds the bottom of the suspension spring) is made of 3/16" brass. There is a 3/32" hole drilled in one end for insertion of the pendulum rod. This piece has a slit in for the suspension spring. The slit is made by clamping the 3/16" material in the tool-holder on the Unimat, then sawing it with a 0.010" wide slitting saw by advancing the lathe crossfeed -- a quick way to do a milling job.

A hole must be drilled through this piece which will hold a pin which will secure the suspension spring in the slit. The piece is center-punched and drilled with a small drill. The piece is held straight for drilling by inserting a razor blade into the slit. When the drill is about to reach the hard blade, it is removed and the hole finished.

The suspension spring is too hard to drill, so holes must be punched through it. Holes are punched in the top of suspension spring by a punch made of 1/16" music wire -- the spring being laid on a small block of lead, which acts as a "die". The lower hole is punched through the existing holes in the piece at the top of the pendulum, also using a bit of music wire -- the "die" being the holes in the part itself -- this assures a fine fit.

The pendulum rod is made of 3/32" drill rod. The bob is made from 3/4" brass rod, with decorative tapers made with the compound on the Unimat. The compound is set at 5 degrees.

This pendulum, according to the clock design, will beat with 2.25 beats per second -- slightly less than a 1/2 second pendulum. As shown in the photo, it's set to about the right length, as timed with a stopwatch.

The only piece left to make before the clock can run is the pendulum driving crutch -- usually an easy job.

Todays links:

Pendulum cock.
Hanger pivot assembly.
Pendulum top.
Sawing slit in pendulum top.
Drilling pendulum top.
Music wire punching hole in spring.
Top of pendulum.
Pendulum complete.
Top of clock.
Current state.