Ellsworth/NuVinci's CVT concept bike

So the biggest promise of the whole show may come from the Ellsworth/NuVinci concept bike.

Its NuVinci drive system is the latest shot at what many engineers have called “the Holy Grail” for inventors, a continuously variable transmission. The idea of a CVT is that instead of having distinct gears, a mechanism somehow provides a way for an input and output to change their relationship smoothly to “gear up” and “gear down” smoothly, without jumping from gear to gear.

Here's the page on CVTs from Howstuffworks: It notes that the first CVT patent was granted in 1886, and that US carbuyers have been able to buy CVT autos since 1989, but that most automotive systems use a pulley system, where a belt moves higher or lower in a gap between two cones, changing the effective size of the pully.

The NuVinci system, on the other hand, borrows from planetary drives, enough that its manufacturers call the NuVinci a “CVP” system, or Continuously Variable Planetary. In this design, a series of 3-12 drives function as the “planet” gears in a planetary system with a movable cage altering their relationship to the “sun” gear. The whole thing is bathed in a new fluid from Valvoline called Inveritorc.

Cars generally control their CVTs through onboard control computers, figuring what ratio is best for given engine horsepower and torque. The NuVinci leaves that to the rider, so you will have an adjustable input, probably like a motorcycle throttle, that lets you choose “harder” or “easier” in any interval at any time. Suddenly hit the bottom of a big hill? Twist that grip all the way down. Want to pedal 3 more rpm on the flats? Twist it a little.

Of course, only time will tell whether this mechanism's going to stand up to everday (ab)use.

The Ellsworth is deserving of mention even if it were sporting a Sturmey-Archer 3 speed hub: It's a gorgeous combination of cruiser-bike and motorcycle styling cues, slathered in immaculate Ferrari red, and even includes partial fenders.

Technorati Tags: Interbike, Ellsworth, NuVinci

Comments

[DL Byron]

Excellent post Frank. Thanks. I tried repeatedly to ride the Ellsworth but was denied (WSJ did get to ride it and I've been checking for an article). I did ride the NuVinci test bike on a trainer and it works just like described. A road test is a real test, but I can say it feels like nothing you're ridden before and it'll frustrated traditional roadies who try to describe it with rations, cadence, and efficiency. As I understand it, NuVinci is 10 yrs in the making, 18 months testing and it works because of the valvoline fluid, which is technological breakthrough in it's own right.

[tcs]

American companies Salsbury and Cushman began to offer CVTs to the public in the 1930. Most motor scooters sold worldwide in the last 25 years have used CVTs. They are entirely mechanical, robust, compact, lightweight, easy to use, inexpensive to manufacture, and relatively inefficent.

tcs

[DL Byron]

A similar point was made by a press conference attendee. I didn't get his name, but he'd been around since penny farthings, wrote reviews for bicycle magazine, and had a new book. He asked for efficiency numbers, which NuVinci offered to provide later. We'll ask that in our interview. He also noted how poorly Nexus did in the midrange. I talked to him later and he was genuinely enthused by NuVinci. His main point was if the price is right it'll sell, but the market for "transportation solution" bikes is at $500.00 - $800.00, which is a problem if you want that hub and a decent frame and group to go with it.

[Frank]

@TCS:

I've actually crashed a scooter with a CVT, so I knew that, but it also used a belt-driven system that's not well suited to the bicycle.

Skeptics say the bicycle is a bad environment for a CVT of any sort because of the relatively high torque and low RPM riders generate.

The NuVinci is trying to modify the planetary gear system that's widely used in bicycles with spheres in cages that can vary their position serving as the planetary gears. Its efficiency is therefore unlikely to be the same as the pulley-based systems. It could be better, could be worse. We're working on some more indepth stories on the NuVinci system, and that's definitely one of the areas we'll try to get into.

[Andrew King]

HI,

NuVinci Hubs are great but until now they were not affordable to most.
We (King's Sales & Service) will change that by offering factory new 2008 model NuVinci Hubs and Controllers for only $275 Delivered to the lower 48 States. In time, we hope to lower our prices. We are a Manufacturer and Dealer. You can find us on Motorbicycling.com
Thanks
Andrew