LEGO CVT (Continuously Variable Transmission)

Greetings with my next post: a very special transmission. This is a CVT (continuously variable transmission), and it can switch smoothly to any gear ratio possible. So essentially, it has infinite gear ratios. This particular transmission is actually an IVT (infinitely variable transmission), which means that the gear ratio range is from 1:- infinity to 1: infinity. I know that many builders have made CVTs with two cones and a rubber band, but they are no good because they easily slip. Other CVTs and IVTs use ridiculous numbers of moving parts, resulting in a huge, impractical design with tons of friction. But mine only has 15 gears and 2 differentials, and that includes the control mechanism and everything from the motor to the wheels.

This transmission splits the motor speed into two parts with a differential. One part is geared up and the other is geared down before a second differential combines them again. The final gear ratio depends on the split in the first differential. The control motor sets the split and therefore the gear ratio. However, it is possible for the split to be beyond the normal, for example -50% on one side and 150% on the other. This is why this CVT can use any possible gear ratio – not just any ratio within a certain range. The control motor can be used to set either the lower or higher ratio split, but since the motor will add a little extra power, I chose the higher split to give the transmission a boost in high gears.

Feel free to use it (giving credit) in a vehicle or other application. For a better explanation, see my Youtube video.


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