This is a small stepper driven clock mechanism, there is no clock face. The files include some very basic hands, but better to add your own.
I originally tried this clock, but wanted to see if I could make something much smaller. This design is 7cm X 6.5cm X 5cm (including the stepper motor.
It uses brass tubing for bearings - sizes from 2mm to 5mm.
In the end I wrote some python code that uses solidpython and scad gears 5.1 to do the heavy work. The base plate is setup for a 28BYJ-48 stepper motor which I converted to bipolar and drive from a Raspberry Pi using a smart drive chip (TMC5130). The stepper drives an intermediate stage bewteen the second hand and the minute hand, so flat out the clock can almost go at 4 hours per minute. At normal speed the stepper gives a slight tick to the movement of the second hand.
python gearbox code
I generate the gcode using Prusa's version of slic3r, and use the default 0.1mm detail setting.
I've printed using Prusa PLA and PLA from 3dprintz with no problems.
The base plate is designed to take a 28BYJ_48 stepper motor.
You will also need various lengths of brass tubing in various sizes. This is brass tubing in 1mm increasing sizes and each size is an easy fit in the next size up - it makes really nice bearings for small projects. Get it from a model shop.
2mm brass tube
35mm - second hand shaft - adjust length for required height of second hand
3mm brass tube
2.5mm - inserted into lower plate as bearing for the base of the various hand shafts
20mm - 2 off - auxiliary shafts between base and top plates
22mm - minute hand shaft - leave the second hand protruding about 3mm - adjust to suit
4mm brass tube
14mm - hour hand shaft - leaves the minite hand protrding about 3mm - adjust to suit
These are all short lengths inserted into the various gears to provide a smooth, free running, bearing. Make sure they do not show proud of the gear - slightly to short is fine.
9.4mm - 2 off
5mm brass tube
3mm - this is the bearing in the top plate that the concentric hand shaft emerge through.
Start by inserting all the short stub tubes into the relevant gears, and the longer shafts into the gears that drive the hands. The shaft for the second hand protrudes slightly below the gear to fir into the bearing tube in the base plate.
The photo below shows (from left to right) the second, minute and hour gears with their shafts.
Use a drop of glue to fix any shaft that is not a tight fit.
Then assemble the base plate...
the shafts and gears that drive the hands
base plate with motor, bearing for hand shafts, and the 2 additional axis shafts
After placing the two shafts and the short bearing for the hand shafts into the base plate, add the intermediate gear for the second hand (1 hole), and push the driver gear onto the motor shaft (2 holes). The driver gear should be a snug fit on the motor shaft. Then the long 3mm shaft can be inserted into the smallest gear, with a short length protruding out of the base. Drop this into the short bearing.
now with the motor shaft gear, and the gears used to drive the second hand
Now add the remaining gears. Note the number of holes relates to the gear order (apart from the final hour hand gear which only has 4 holes, but only 1 set of teeth)
all gears in place - ready for the top plate and hands to be added
Finally push the short bearing tube into the top plate then add the top plate to the assembly and then push the hands (hour, minute, second) onto the shafts. The hour hand has the largest hole, followed by the minute and second hand.
The complete assembly.