Work has let off a bit and over the weekend I managed to get the pendulum electric clock dialled in. I actually used all of the techniques for minimising friction that you mention for the pendulum wall clocks and hence my amplitude is rather large and I had to have a few goes at tweaking the length and position of the static and active paws.
I am now pretty sure that I do not get any "2 second" pushes which would make the clock run fast. I will be checking this over the next few days.
It actually looks really great.
However, with the pendulum bob all the way at the bottom I am seeing the clock running about 1 to 2 minutes fast for every hour.
Assuming that I do not get any 2 second pushes I'm really not sure how to slow it down because the period of the pendulum is governed by the length of the pendulum and I cannot take the bob any further down.
That's good to hear. The accuracy seems similar to my clock. The pendulum length will change with temperature. PLA or any other plastic has a fairly high coefficient of expansion with temperature, but I find that most of my clocks are still reasonably accurate.
I don't think the carbon fiber shafts used in some of my earlier clocks are worth the extra effort. It might have been different 200 years ago when houses had large temperature swings every day. Modern heated and air-conditioned houses reduce most of the need for temperature compensation.
A final report.
The clock is going really well. Has been going for over a week now.
Have got it accurate to about 15-20 seconds a day. This seems to be temperature dependant to some extent.
Thanks for a great design once again.
I am actually getting a double tick very occasionally which I did not register at first.
Sorry for the false alarm.
The clock is actually going really really well.
My clock runs with an accuracy of about a minute every 2-3 days and there is about 1cm of range left to lower the bob if needed.
My guesses are either some occasional double ticks or the bob is not heavy enough.
1) Try raising the pawls 1 or 2 notches to see if it helps. I have been running with the ratcheting static pawl. The clock was very stable for a week using a fixed length static pawl, but then started missing ticks overnight when the temperature drops a few degrees. It seems to be more reliable with the ratcheting static pawl.
2) The pendulum arm is fairly heavy which raises the effective center of mass. My bob weighs around 95g consisting of 29g PLA, 60g US pennies, and 6g screws. I use 24 copper coated zinc pennies. The older pure copper pennies would weigh 74g. Running the clock without the bob makes the clock 5 minutes fast per hour. If you are certain that the clock is not double ticking, then see if you can add some additional weight to the bob.