220 Wall Clock
Introduction: 220 Wall Clock
1 Overview
I modeled this design after a Urwerk UR220-SL watch. It has been scaled up to be a wall clock sized version.
This model is LARGE, at about 236x232mm. My printer has a 210x210 print bed, so any parts that are too large for it are also available in right and left half STL files. Also many parts are available as sets of files that can printed on printers with a multi-color capability.
And it's powered by an 110V AC Synchronous motor.
The STL files to print this clock are available at: https://cults3d.com/en/3d-model/gadget/220-clock-model
Supplies
2 Parts list
Here are the parts that I used. You can use hex socket or Philips head screws, your choice. I paid about $1 a piece for all the ball bearings on eBay or Amazon.
Some of the “2mm” steel shafts that I’ve picked up on eBay or Amazon have been slightly oversized, just enough so the bearings won’t fit on to them. Look for a slip fit of the shaft in the bearing. DON’T force the bearings on the shaft. Excess force can jam the bearings, making them useless. My solution was to order shafts from another vendor. Maybe you will get lucky the first time.
Refer to section 6 for a list of the STL files.
2.1 Summary of non-printed parts
(6) 2x5x2.5mm MR52-ZZ ball bearings
(14) 3x6x2.5mm MR63-ZZ ball bearings
(1) 6x10x3mm MR106-ZZ ball bearings
(6) 8x14x4mm MR148-ZZ ball bearings
(2) 20x27x4mm 6704-2RS ball bearing
(1) 3x22.5mm shaft, one end rounded (Geneva Pin)
(5) 3x23mm shaft
(3) M2x35mm threaded rod
(1) AC Plug for lamp cord.
(21) Screw M2x6mm Flat Head Hex
(32) Screw M2x8mm Flat Head Hex
(22) Screw M2x10mm Flat Head Hex
(2) Screw M3x8mm Cap Head Hex
(36") Music Wire, 0.025" OD (For Hour Arm spring)
(1) Acroprint Time Clock Motor for 125 and 150 Models
(~8ft) Lamp cord.
Refer to section 5 for sources of selected parts.
Step 1: Spring Assembly
3 Assembly
The STL files for this project require a printer with a minimum of a 210x210mm print bed.
3.1 Sub Assemblies
3.1.1 Spring Assembly
Included in the files is an Hour Arm Spring.STL file. This file allows you to print a plastic spring (using supports). 807
It is painful to clean out the support material, but it does result in a working spring. However the problem I had after printing it in PLA was that under tension it would ‘take a set’, losing tension over time and the Hour Arm would not snap all the way back. I rotated the Base Spindle several times to add more tension, but after a while this stopped solving the problem.
PLA works for springs only if the normal state of the spring is zero tension, e.g. for a balance wheel in an escapement. If you clamp a piece of PLA and hold it bent for a day or so, when you take the clamps off, it bends back to its original shape a little. But the longer it is bent, the less it recovers its original shape. Someone who knows more about plastics can explain this phenomena better, but I call ‘taking a set’. The Hour Arm Spring is under constant tension, so PLA at least does not work well for long term use.
I would highly recommend making the Metal Spring Assembly. The plastic spring will allow you to debug it, but it will only work for a couple of weeks. Or you can try printing it in some material other than PLA, which might work better.
Metal Spring Assembly
To assemble the Metal Spring assembly you will need the following parts:
· Metal Spring
· Hour Arm Spring Metal Top
· Hour Arm Spring Metal Bottom
· Spring Mandrel
· .025in (0.64mm) Piano Wire (~30 inches long.
The first step is to make the metal spring itself. There are several ways of doing this. I used my lathe, however you could also use a drill, a drill press, or a real spring winder if you own one. Figure 1 shows the steps that I went through.
Print the Spring Mandrel. 646