Test Jig #3 - Hours & Minutes Clock
by syvwlch, published
This is the current release candidate for the Printable Clock Project. Many thanks to the many Thingiversians who have contributed over the last few weeks!
It is a work in progress and probably will need tweaking to even tick, let alone keep time. It currently has breakage issues in PLA, ABS is recommended.
Test Jig #2 was a major milestone, passing all four tests, featuring in the first video of a ticking printed escapement for this project ( http://www.prototribe.net/vidplay/testjig2.html )and serving as a development base for improvements from multiple Makers. If you want to print something that ticks, print Test Jig #2 with all the latest parts.
Test Jig #3 is intended to regroup all that progress into a new base camp for what we hope is the final push: an actual printed clock that keeps time. If you want to spend plastic and time in support of that goal, print Test Jig #3 and share with us what went right and what went wrong.
This current design is based on feedback from early adopters ssd, rustedrobot and TheRuttMeister, and in particular a very clever rustedrobot design for a ratcheting drum that rewinds the clock: http://www.thingiverse.com/thing:8555 Special thanks to Renosis for rendering gears 02 thru 07 on his machine last night when mine was not up to the challenge!
I've uploaded a snapshot of the code which generated these parts to this page, but the best place to find the latest and greatest is on github:
Major improvements include: the ratcheting drum, countersunk holes for the frame, a snap-fit extendable pendulum, and an escapement design which should tick as printed (little or no hand-finishing required).
I tried to go for a four gear clock, but getting a 60:1 ratio in two gears is just not practical... the pinions get too small. I also went ahead and added hour and minute hands. I can make alternate parts for a hand-less version if the concentric shafts are too much of a problem.
Print one of each STL, keeping track of which gear is which. Since this is a six gear clock, it does not have parts 08 and parts 09. Use four M3 bolts, two to hold the frame, and two to serve as shafts.
The gears are numbered from front to back, starting with the drum (01A and 01B) and finishing with the escapement wheel (07). Gears alternate on either shaft, and the pinions (the smaller gear attached to the center of the larger one) face forward.
The pendulum and the escapement are combined in a single print and snap-fit together (a design idea from Aubenc).
Attach a string by the middle to one of the side holes on the drum, with both lengths wrapped around the drum in the same direction. That way, when one length unwinds as the clock runs, the other gets wound up. Attach a weight (100g, perhaps?) to the length which locks the ratchet against the stops (clockwise from front), and a smaller weight (20g?) to the length which unlocks the ratchet in the opposite direction.