Printing and Remixing the A26 Clock

Several years ago, thingiverse user A26 published a model for a simple clock. I made one version of this in 2019, and was never very satisfied with it. Following from making Steve Peterson's clock recently, I decided to have another go at it, and to make some design changes to improve it. The first change I made was to adjust the tolerances on some of the parts. Several of them fitted together very loosely so that, for example, gears would slip on their shafts, and bearings come loose. I think this is likely due to variation between prints and slicers.

The most serious problem was in the design of the anchor. It uses a knife edge: basically a V-shaped pivot which rests in a groove. A gust of wind can make the pendulum swing about the vertical axis (if you see what I mean), and as I found with my original build, if you are clumsy as I am, you can easily knock it out of place entirely. I therefore redesigned the anchor somewhat along the lines of the Peterson clock, so that it is mounted on a 3mm shaft. This entailed extending the frame of the clock to allow extra room. The result is much more stable. I haven't yet tuned the timing of the clock or allowed it to run for a long time, but so far it seems to be working well.

Here's some pictures and video:

The filament is PLA throughout. Most of the parts are directly from the original design or my modifications of them (thingiverse remix), with the drum and ratchet from the self-winding version. (I started on adding the self winding mechanism, but got frustrated with it and gave up). The face also comes from this design, held on with some clips that I knocked together. I added a couple of small clips that slide tightly onto the pendulum shaft and help stop it from slipping. The main shaft and pendulum shaft are stainless steel, as I had pieces about the right length. All the other shafts are brass. I much prefer brass as I can cut it without power tools. I've been using this saw, which allows very clean and precise cuts with minimal effort.

To set the hour, the best approach is to hold the part called Wheel 4A stationary (see the original design for which this is), and turn Wheel 5. The shaft that connects Wheel 4A and 4B is snug but not so tight it can't turn. I glued the 4B end of the shaft in place. For the minutes hand, I hold Wheel 3 stationary and rotate the minutes hand on the shaft. The first time I did this, the hand broke, so I made a new version which is stronger. I am using about 200g weight.

Adjusting the beat (that is making the ticks and tocks of equal duration) and the timing (beats per hour) is difficult. For the beat you have to have the pendulum shaft exactly centered and the weights at exactly the same distance from each end. For the timing, you have to move the weights in or out on the shaft. Fine adjustment is tricky; the designer of the self winding version addressed this by threading the pendulum shaft and weights, but I am not able to do this.

Note that my change to the anchor means that you can't get the timing right. The clock needs to tick at 3600bph, and the slowest I could get was around 4400bph. This can be fixed by either using a longer pendulum shaft or modifying the pen weights so that they have a longer stem. I used both: the shaft is 250mm, and the longer stem pen weights allow for a bit more range of adjustment (not shown in the pictures above). The fine adjustment is tricky. What worked for me was to measure the beat rate with the Cuckoo Clock Calibration app, move the weight on one side to make the clock faster or slower, then move the weight on the other size until the pendulum shaft was horizontal. Towards the end of the adjustment, you may need to move the pen weights as little as 0.5 or 1mm, which can be hard to do precisely.

Another nice design - many thanks to A26.