I ran across this hand-in-hand clock design http://www.instructables.com/id/Hand-In-Hand-Skeleton-Clock/, and I thought it would be more fun as a purely mechanical mechanism. My model uses a 15 tooth, Graham-style escapement and a 480g drive weight. Shafts are 2mm save the two bottom ones which are 3mm. The pendulum is a 6mm aluminum tube that may be adjusted up and down in its mount. It has not stopped on me yet when I've had it running, though accuracy is not the greatest.
Though it works very smoothly at present, the clock is still a work in progress. It requires the following improvements:
- The sprag clutch system that serves as the drum is too stiff. I had to play around with the sprag sizes to find something that marginally works. Re-sizing the wells in the inner drum might allow for 4mm delrin spheres which should improve performance.
- The back frame ought to be augmented. At present it must be mounted to a board or held in place with my hand (as in the pictures) in order to function. Part of the problem is my 6x6x6 print limitation necessitating the jigsaw-style connections.
- I need a more reliable method than shaft friction to lock the main shaft in place. At present, the minute hand tends to wobble.
- Counterweight covers would replace the tacky-looking blue tape holding the coins in place
- I ought to have designed a counterweighted minute hand that is actually longer than the hour hand/gear train.
- I want to add a pulley to the weight to double the clock's run time and also have the weight pull down the center rather than offset.
- Find a way to upload videos of this thing in action.
Most of the gears and the anchor are printed at two perimeters with zero percent infill. All frame pieces and the drum assembly are at 30%.
Update: I uploaded a DXF of the gears that I used. One can offset them to add more or less slop into the gear train based on how your printer performs.