NuVinci CVT Developers Kit

[Andrew Schreiber]

Originally Posted by IKE

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 can vouch for that book, very informative, I was curious how they worked and the book did a wonderful job explaining the concepts to me, a very non technical person.