Hello, if your clocks a 40 minutes slow in, lets say, 12 hours, you have an immense error of arount 5%. It is (40 minutes / 720 minutes) * 100%, am I right?. That is so much, that you should be able to verify that with a stopwatch. Take the time for 100 pendulum swings of the correct watch and compare it to the others. However, it don't think, the pendulum is the cause, the swingtime is just physics. Maybe, there is some slipping internally? I'd check the friction clutch. Good luck, Frank

Hi Steve, thanks for your fast reply. I already printed most of my clocks with PETG gears and for me it works just fine. To me the gears appear to be a bit more flexible but it they seem to work with little friction. However PETG prints less cleanly and a little bit slower, so for memore time and effort is required.

Hallo, you can‘t. Steve has modified it, for example adiitional bearings, hooks and the connection to the side parts.