When I was 18, I envisioned an automobile transmission that used some sort of cone-shaped gear that would allow the engine to turn at the exactly correct speed for maximum efficiency. Instead of spooling up, shifting, spooling up, shifting, etc., it would simply hold the rpm at the perfect torque, and the driver wouldn’t feel a shift at all. My “friends” at the time, two rich douchebags who thought they knew everything, laughed at me. (One of them was heavy into a conspiracy theory about the oil companies suppressing a carburetor design that allowed cars to get hundreds of miles to the gallon just be heating the fuel-air mixture to a very high temp before induction). In fact, these guys laughed at a lot of my ideas.
On Friday, I bought a new Nissan Rogue that has just such a transmission, which they call a “Xtronic CVT® (Continuously Variable Transmission).” It probably uses a system of belts to get past the shifting, but it is essentially the device I envisioned 28 years ago.
So my next invention will be a time machine, so I can go back to 1982 and tell those guys to shut the f*ck up.