Fallbrook Technologies has announced that a NuVinci CVT Developers Kit will be available for $595 starting in December specifically designed to assist hobbiest in development of Light Electric Vehicles (LEVs).
While CVTs are often use in industrial equipment with Fixed speed AC motors, you don’t often see them in EV aplications because an Electric vehicle motor has the properties that a CVT typically has. Usually with a 2-3 speed transmission you can get all the performance and efficiency you want/need. Also, CVTs are are typically a double edged sword on the whole efficiency thing. Almost all use a cone, ball, or belt and sheave system that invariably has a little bit of conflicting friction at the contact patch. This friction tend to make CVTs have a lower prowerr transmission efficiency. Where they do a lot of good though is with motors that have a very narrow band efficiancy range (think A/C motors, or some genertator or governed engines). On these applications the CVT can vary output speed while the motor stays in it most efficient or powerful state.
I am a huge fan of CVTs and even designed a new one while in college. If you want a great CVT design resource check out:
“Traction Drives: Selection and Application [Hardcover]
By Frederick W., III and Shube, Eugene E. Heilich”
This is a great book that devotes 50% to fixed ratio traction drives (think gear systems without teeth), and 50% to all metal CVTs (sorry no rubber belt system).
I got to see this at the makers faire and while it is a cool technology it is very inefficient. They wouldn’t tell me the exact amounts but hinted it was not good. Also the ratio range was 3:1 so it would be just a little more then an andymark from top to bottom. I think it would be cool to play with one of these but putting it on a robot doesn’t make any sense.