This is a simple CVT (Continuously Variable Transmission) model that demonstrates the concept behind a CVT. It represents a less common and simplified version of those found in many automatic transmission vehicles.

It uses no gears and is 99% 3D printable. All you need is a small rubber band to connect the cones, as shown in the pictures.

Assembly is straightforward: insert the shorter end of each cone into the designated hole, and pop the other end through the top. Be sure to attach the rubber band before securing either of the cones.

The ends of the cones can fit into a drill chuck for better visualization.

During testing, one of the shafts of the cones broke along the layer lines after some time. To address this, I modified the 3MF file to give that part 4-layer-thick walls to help prevent the issue.

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To use the transmission, either spin one of the cones by hand or use a drill. As you move the rubber band up or down the cones, you will see the output shaft speed change (it’s easier to observe the speed variation by attaching a piece of paper to the end).