Mechanical Clock
Sept 2024
GOAL: Make a mechanical clock
SKILLS: Gears, Fabrication, Mechanical Design, C programming
This is an analog clock with a digital style display. I wanted to create a mechanism that only requires one motor with consistent actuation, and uses mechanical means to affect the other number places.
These mechanical means are inspired by mechanical counters and rely on modified compound gears to accomplish movement that displays time accurately and discretely.
Video
VIDEO
CAD
Design Features
Due to gravity, smaller back gears fall and do not mesh exactly. To fix this, a ramp was added to the large 2 notched gear and part of the smaller 2 tooth gear was shaved down. This guides the 4 tooth gear into place and allows it to mesh.
In order to reduce the friction between the wheels/gears and the shaft, I added bearings to the shaft. To minimize the 3D printing needed and create an interface between the wheels and the bearing, I CADed this bearing hubs that can be screwed into holes in the laser cut pieces.
Gear Math
The first wheel is turned by the stepper 1/10th of a rotation every minute. On the other side, there is a special gear with 6mm of its thickness being a part with two teeth, and the other 6mm of thickness being a part with just a notch between those teeth. This way, the next wheel only turns when the notch goes by, which is associated with a certain number on the first wheel. At all other times, the outer rim of the notched part keeps the smaller gear from spinning. The gear ratios make the timing accurate according to this math:
The wheel for the 10s place of the minutes has 12 sides, but only 6 different numbers because there is 2 of each number : 0 0 1 1 2 2 3 3 4 4 5 5. This is done to streamline the gear design, since you would need, for example 16 teeth instead of 8 to achieve a 1/6th turn of the 10s place for every full rotation of the 1s place. By having two notches in the gears colored neon green above, the 10s place rotates when the 1s place goes from 9 to 0, AND 4 to 5, which is why the numbers are doubled.
Code
Clock Code - Google Docs.pdfCode Summary
Wiring
IMAGE
Things to adjust in the future:
periodic friction from warped wood --> use acrylic instead...
decrease size & weight
make less loud with less torque on stepper
make stepper hub easier to access and tighen
make safer to use as a tactile, accessible clock