Quote:
Originally Posted by nuclearnerd
They work with friction wheels that turn in a toroidal cylinder (some car CVTs work in a similar method). They're also really wasteful, < 85% efficient. |
I couldn't find a statement in your reference to wikipedia that the efficiency is <85% for the NuVinci transmission, but found 85% used in a hypothetical analysis in a discussion of the tradeoffs between powerplant efficiency and transmission efficiency. There is a comparison in the wikipedia article to the tilting-ball class of transmissions, where the "efficiency of "Tilting-ball drive" type CVTs is typically in the range of 70% to 89%." The article goes on to clarify that the NuVinci geometry "does differ significantly from the Kopp type of tilting ball variator in the reference in that the NuVinci has its torque transfer contacts on the outside diameter rather than the inside diameter," so while this gives a likely comparison, it is hard to say what this means for the NuVinci. Where are you getting your <85% number from?
The best I can find from a quick google search about the NuVinci efficiency is that the company policy is to not publish an efficiency number. That said, there is internet agreement that it is less efficient than the geared hubs. There are some numbers and conjectures in the comments in
this thread, but no clear sources.