Mechanical advantage is the single most important principle in mechanical engineering. Archimedes is quoted as saying “Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.” We could say the same of gear reductions, but they have the added advantage of fitting into a very compact space. To prove that point, Sunday Robotics’ INFINITY GEARS has a final gear that will only make a single revolution once every 346 quintillion years.
To put that time frame into perspective, consider that our universe is roughly 13.8 billion years old. You would have to exceed 25 billion similar spans of time before the final gear in this device made a full revolution. Thanks to the power of gear ratios, this device achieves that using only 41 individual spur gears (plus the motor’s input gear). The input motor spins at 250RPM and each stage has a gear ratio of 1:5. The final gear ratio, from input to output, is 1:5^41. Not only does that mean the output is spinning extremely slow, it also means that it has an incredible amount of torque — though friction losses keep it from reaching insane levels.
You can build an INFINITY GEARS machine yourself using a handful of common parts and components, including an Arduino Uno board, a 250RPM geared DC motor, and 3D-printed gears. That final gear is hard-mounted and cannot rotate. But, because the gear before it is rotating so slowly, the heat death of our universe will occur long before the gear’s teeth ever begin to grind. For fun, each of the five black gears has a magnet that the Arduino uses to count revolutions. Those revolution counts display on an LCD. The first will tick up quickly. The second will only tick up once every 135 days. The third won’t tick for 3.6 million years.
INFINITY GEARS does a fantastic job of illustrating both the passage of time on a cosmic scale and the vast power of gear reductions.