Knex Clock
https://www.youtube.com/watch?v=zvmOLhV_NYE
Brilliant design for the hand. Over comes the lack of correct gearing.
Differential: https://www.youtube.com/watch?v=rBfQeRWtpxQ
Sizing
The whole thing will be 7' tall.
I'm not sure I want to use corner connectors - I don't think I have enough. Instead, alternate yellows with corner bracing to hold the shape.
Hands
Rather than gears, we'll use rods for transmission. The minute hand will have essentially 2 teeth (two rods at 180°). That goes to a 3:1 reduction, which goes to an 8:1 reduction; for a total of 24. The 3:1 will be a little janky, but feasible.
Winding and Weights
I'd like to do all this with Knex chains rather than string - more authentic; but I'm afraid of how much friction that incurs.
For string, I think I'll use the mason line I have. Fishing line would hold it's shape, causing weird fluctuations in power.
The weights will drop down the center, I need to add a guide track.
The winding mechanism will of course go through a differential gear. Also need a ratchet for that to work.
Pendulum
As tall as the clock. The pendulum will actually rock in a cradle rather than spinning on a rod - lower friction.
A 6' swinging pendulum has a period of about 2.7s.
Torsion Tests
| Arm Length | String length | String Type | String Spacing | Weights | period |
|---|---|---|---|---|---|
| 1 red | 18" | mason | 1 connector | 1 wheel each | 16s |
| 1 red | 18" | mason | 2 connectors | 1 wheel each | 16s |
I had to do a little testing and adjustment to get this to work. I didn't even try single stranded, double through one connector was to finnicky to be practical. Double spaced with one connector seemed pretty solid.
Escapement
I've seen some good Arnfield escapements.
I'd really like to do an Anniversary (Torsion pendulum) escapement. It's Lego, but this is a good demo.
I may be able to combine an Arnfield with a torsion pendulum.