This DIY Strain Wave Gearbox Is Strong Enough To Pull A Car

The circular spline is the outermost part and has inner gear teeth of conventional geometry. The flexible spline meshes with this circular spline, but only at two opposite points. The wave generator, which is the entrance and the innermost part, has an oblong shape and forces the teeth of the flexible spine into contact with the circular spline. This odd arrangement causes the flex spline to push the circular spline forward about one tooth per full revolution, resulting in a huge reduction. Brocken's design produces a 54:1 reduction, which is incredible for the size. Because there are only two points where the gear teeth mesh, it produces less friction than a typical gearbox and has tighter tolerances thanks to the lack of backlash .

Most of the mechanical parts of this strain wave gearbox are 3D printable, but you will need some way to control the DC motor that drives the gearbox. Brocken used an Arduino Nano board that fits on a custom power distribution PCB. With this, Brocken can use a large power supply and allow the Nano to control an lBT2 H-bridge motor driver that handles up to 43A. By using a conventional brushed DC motor, this gearbox can produce about 3.75N*m. It's similar to a 79cc internal combustion engine and it's enough to pull a Dodge Charger across a flat surface.