How To Put Your Anniversary Clock In Beat
Anniversary clocks operate with very little energy. Power is transmitted from the mainspring, through the gears to the anchor pin, to the fork, and down the suspension spring to the bottom block, to act on the pendulum with just enough force to keep it moving once set in motion. In order to keep the clock running for more than 20 minutes or so, the force exerted on the pendulum in one direction must be the same as the force exerted in the other. Adjusting the orientation of the suspension unit so this happens is known as putting the clock in beat.
Begin by ensuring that the clock is perfectly level. The clock should be level when the bottom of the pendulum is resting directly over the center of the pendulum guide cup (if your clock is equipped with one), but some guide cups can be moved around by loosening the screw under the base. To check for level, place a small level on top of the base, and measure in two directions. If your clock is equipped with leveling screws, adjust them as necessary. If not, insert shims (small coins work well) under the clock to level it. Mark one pendulum ball with a small piece of tape.
Start the pendulum in motion by giving it ½ turn in either direction. Listen and observe while the pendulum rotates back and forth to determine what if any adjustment will need to be made. Notice that as the anchor pin and fork move to the left, the pendulum also rotates to the left. As the anchor pin and fork move to the right, the pendulum also rotates to the right. Now listen to the faint tic-toc sound as the anchor pin moves back and forth. The sound is caused by the escape wheel teeth as they strike the pallets on the anchor as the escape wheel advances. You can see this happening either by looking from directly behind the clock through any observation holes cut into the back plate, or by looking from slightly in front of and off to one side of the clock to the front of the back plate. (The minute hand will also slightly advance.) Focus your attention on the sound and movement for a while. Now use your peripheral vision to also observe the rotation of the pendulum. What is important is noticing how much further the pendulum continues to swing after the escape wheel tooth hits the pallet while rotating in one direction, compared to how much further it continues to swing while rotating in the other. (It is possible that, before making any adjustment, or after adjusting in the wrong direction, the escape wheel only advances when the pendulum rotates in one direction, but not the other.) In order for the clock to continue running, this over swing must be the same in both directions, which indicates the clock is in beat, and the distance of the over swing should be 1/2" or more, which indicates that sufficient mainspring power is reaching the pendulum.
If the pendulum travels further while moving toward the right, the suspension unit must be rotated toward the left. Conversely, if the pendulum travels further while moving toward the left, the unit must be rotated toward the right. This is accomplished by rotating the saddle in the direction the suspension unit needs to go. Depending on your clock, you may need to slightly loosen the screw that holds the saddle tight first. On other clocks, the saddle is held friction tight without a screw. If you have a Horolovar beat setting tool, attach it to the saddle. If not, grasp the saddle on one side and the suspension unit holding screw on the other with your long handled pliers. Turn the saddle very slightly in the proper direction, then observe what effect you have made. Expect that it will take several tries to get it just right. As the over swing gets more even, you can use markers to measure it. Cut two toothpicks in half. Place a toothpick piece on the base where the ball that you've marked passes when the escape wheel is released. Do it in both directions. Next, place another toothpick piece at the point where the marked ball stops, again in both directions. Once the clock is in beat, the pendulum will settle into it's natural rhythm. Again, you want at least 1/2" over swing. Anything more is great, but anything less, and the clock will likely stop on it's own at some point before the mainspring unwinds fully. If you are sure the clock is in beat, but the clock still won't keep running, then it's time to have the movement serviced. The most likely cause is excess friction due to dirt and/or dried, sticky lubricant.