A Schatz standard 400 day clock didn’t run well after repair. I had cleaned the movement and adjusted the fork on the suspension spring, yet the pendulum rotation was only about 3/4 of a turn with the mainspring fully wound. I installed a new mainspring, and the motion was slightly less. I polished the pivots, with very little improvement.
Finally, I replaced the suspension spring with a new Horolovar 0.004 inch spring (I hadn’t done so previously, because the old spring was flat with no kinks. It did have a slightly matte surface). The pendulum rotation increased to 4 1/4 turns when fully wound! (And almost as much with the mainspring wound only 2 turns.)
Here’s a list of the various things I did. Pendulum rotation is expressed in “balls”, where 4 balls is one turn.
Didn’t run well
Smooth and clean suspension fork
Escape arc: 1.8 balls; running arc 2.7 balls when wound 1.5 turns.
Fork was too low, raised it: rotation = 3 balls
Disassemble, clean, smooth broach pivot holes, polish anchor pin, oil T1 only. Escape arc: 2.1 balls; wound 1.5 turns: 2.8 balls rotation; wound fully: 3.2 balls; wound 2 turns: 3 balls.
Raise fork slightly (was mislocking a little). Escape arc: 2.3 balls; fully wound: 3.2 balls.
New mainspring installed. Lube T1 only(Castrol 5W30 synthetic motor oil). Wound 1.5 turns: now stops, new mainspring slightly less powerful than old one. Wound 2 turns: rotation 3.2 balls.
Polished the pivots. Wound 2 turns: 3.3 balls; fully wound: 3.5 balls. (very slight improvement)
Added Butterworth Nano-10 oil to T2 pivots: 2 turns: 3.3 balls; fully wound: 3.4 balls. (no improvement)
Tried moving anchor closer to escape wheel: made it worse, put it back to where it was.
Unwound 1 turn (from fully wound): there is slight mislocking. Unwound 1 more turn: still mislocks. Lowered the anchor slightly.
Replaced suspension spring (Horolovar 0.004 inch): Wound 2 turns: 4.8 balls rotation! Fully wound: 5.1 balls! Escape arc: 2.5 balls.
The old suspension spring appeared to be perfect. It had a matte finish (not shiny like the Horolovar springs). Replacing it with a Horolovar spring made the clock work properly.
Repair job 5341. The movement has no date. It was made around 1950 – 1952. Says Schatz on the dial. Earlier examples have no name on the dial. Horolovar plate no. 1278.
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