Hi Steve... I'm a bit confused with the total length of the SP7 pendulum. In the manual it states the pendulum is 10" or 250mm. When I put the upper and lower pieces together in my slicer and measure tip to tip, it's almost 11.9" or 303.564mm. Since I have the regulated pendulum driver board now set to keep perfect time on the SP7 clock, I was using that length for some other clocks but the board would not maintain time. So I measured the pendulum and saw it was almost 12" So I printed that size and the board seems to maintain correct time with it auto correcting here and there (like it's supposed to do) . So is it 250mm or 303mm.... I also redesigned the bottom portion of the pendulum arm to attach the magnet(s) without glue or tape. I'm using 2 rare earth magnets since the coil and regulated board really need much stronger magnets. You might be able to get away with one magnet, but it seemed the clock would stop more often and using another magnet ... the clock never stopped. See attached pics....
The effective length of the pendulum is what determines how fast it will swing. The bob is the heaviest component, but all parts of the pendulum help determine the center of mass used to set the effective length. The long lightweight tip determines the overall length but barely changes the effective length.
It's great to see the stronger magnets making the clock run better. It must be with the newer electronics. The old electronics uses two side by side magnets. I never measured them to see if they are the same polarity or opposite on each end.