Continuously Variable Transmission
 

A co-worker showed me this bike with a sealed hub, continuously-variable transmission based on Leonardo DaVinci's sketches. WOW - is this really new, or have I just never heard of it before? I know Audi's have had variable trannies, and my old lawn tractor has one, but I've never seen one small/light enough for a bike. Now my brain is flashing with images of a fixed version for a unicycle!!

More here: http://www.ellsworthride.com/

That sounds pretty awesome, but sounds like a ***** to maintain/repair.

Popular science had an article on this invention in their last issue. They gave it one of their innovations of the year award. They had it on their beach cruiser "like" bike because it is too heavy for a road bike.

Search the forums for nuvinci and you'll find other discussions about it.

There are cheaper options on the market than the Ellsworth bike. None are currently listed, but there have been bikes on ebay with the hub for around $500.

http://www.fallbrooktech.com/NuVinci.asp

It's huge, weighs a ton, and is a hell of a work horse of a hub. For utility applications it's close to ideal.

that sucker is a work of art. WOW

It shouldn't need much of anything. By all accounts (and from appearances), the hub is wicked robust. Pretty cool system!

Bicycle chains and toothed gears have been around for a long time, for a reason.

I've been looking at this thing for some time and I have heard that it weighs a lot but how much is a lot. I haven't seen any numbers. My idea of heavy is HEAVY and not measured in grams. I leave the yard at about 250 pounds. I am more concerned with the cost. This sucker ain't cheap..:)

I understand it's based on a drawing by da Vinci so it has to be art. When I was much younger and thought that someday I would be a great inventor or at least a useful engineer I thought that the only art was da Vinci.:)

Uh-huh. Verrrry specific.

CE has it right. Mine weighs something like 10 pounds, and my rear wheel built up is over 12 pounds. Costs are around the $300 price point. I'm using it on a XtraCycle and it has preformed very well.

Originally Posted by Fallbrook Technology Website
What is the ratio range and efficiency of the NuVinci CVP hub?
From bench and road testing by potential consumers and industry experts, the NuVinci CVP compares favorably with the internally geared hubs on the market today and has the same or better ratio range.
Uh-huh. Verrrry specific.

Gear range is 250%. Don't know about the efficiency, but by the way it rides it feels no more or less draggy than the SRAM, S-A, Rohloff and other internal hubs I've owned.

Wired had an article on this some months back. It's a gorgeous bike, but I dunno about those handlebars.

Sounds heavy.

What's wrong with cables, cassettes and derailleurs?

They don't provide enough ballast. Thats important in the snow. :o

I keep wondering whether the wider gear range of the Rohloff would provide more of a benefit than the NuVinci CVT. The Speedhub 36 500/14 has a gear range of 526%, so over the entire range, shifts increase or decrease in even increments of 13.6%. That seems almost as good as a CVT, plus the total gear range is 50% larger.

Paul

Wow, unicycle application FTW !!!!!!

What is this snow of which ye speak? :D

SRAM iMotion9: ~40% of the weight, ~2/3 cost, ~x1.4 range.
S-A XRF-8: ~30% of the weight, ~1/3 cost, ~x1.2 range.

TCS

15 years ago: "internet? what's wrong with the telephone? who can type anyways?"

No technology is perfect, especially not a new one. The point is to make progress and constantly evolve, hopefully towards something better. Maybe it'll be race ready in 10 years? Who knows?

That looks really awesome. The only thing I can think of that may be a problem down the road is when the fluid ages, will it start to slip? Is there a way to replace the fluid?

Also, If you leave it in a particular gear range for a long time, I can see ruts developing on the balls. Then it will always want to go to that spot. But that's pretty far down the road.

$4K for a 30 lb bike? Oooooooh, sign me up!

My motorcycle has a CVT, best thing since sliced bread. No clutch to worry with, engine always running at it's most efficient speed, fast, smooth, and has the feel of effortless power. As for fitting one on a bicycle.... can't say it's ready for real world use at this time for that service. As others have commented it's heavy, complicated, and will it slip under high torque conditions when hill climbing under a professional cyclist when it has a few thousand miles of use. It's going to be very hard to show an improvement over current chain drive and dérailleur systems.

Well, it's not as though this is new technology...:rolleyes: And I've driven a few vehicles with CVT tranmissions and a slushier drive you'll never have.

In addition to the weight, I'd bet this thing has quite a bit of friction and parasitic losses. These may be tolerable on a powered vehicle, but when you're dealing with the 1/4 hp or so of a human being, it may be intolerable. And judging by the (excellent) animation, it appears that overall gear range might be fairly narrow, much narrowere than even the current internal gear hub systems.

Neat idea, more power to them, but better inventions for this particular application have come and gone before.

- Mark

+1
All CVT's use friction. Standard transmissions use gears so the only way they would ever slip is to break off the teeth. That bicycle CVT has balls riding in cones so there is very little friction surface for power transfer. I bet someone with the performance level of Lance could make that thing slip.

Like lots of people on this thread I was interested in this hub, but also a bit suspicious, after all bike CVT systems have a history of vapourware.

So, the only way to find out was to get hold of one.

Luckily due to the weak dollar I managed to get hold of a MK1 (more on that later) hub for a reasonable price. This was laced to a 406 rim to go on my Dahon minibike, rigged up for commuting.

My commute is 8 miles each way over a small hill with a gravel tow path and some heavy city traffic thrown in.

I liked it a lot.

Here's a mini review to give people something to discuss.

Weight: It's heavy, somewhere over 4kg just for the hub. When riding you don't notice the weight, it's low down and behind you. The only time you notice it is when you actually pick the bike up.

Friction and losses: Ok, there are some, this will never be able to be as efficient as a clean, well adjusted single speed or even a derailleur set up, HOWEVER, it's no worse than any hubs I've ridden and perfectly acceptable for non-racing use. It does prefer being spun to mashing but I've never managed to get it to slip (I'm the wrong side of 100kg)

Range: The range is 350%, compared to

Like lots of people on this thread I was interested in this hub, but also a bit suspicious, after all bike CVT systems have a history of vapourware.

So, the only way to find out was to get hold of one.

Luckily due to the weak dollar I managed to get hold of a MK1 (more on that later) hub for a reasonable price. This was laced to a 406 rim to go on my Dahon minibike, rigged up for commuting.

My commute is 8 miles each way over a small hill with a gravel tow path and some heavy city traffic thrown in.

I liked it a lot.

Here's a mini review to give people something to discuss.

Weight: It's heavy, somewhere over 4kg just for the hub. When riding you don't notice the weight, it's low down and behind you. The only time you notice it is when you actually pick the bike up.

Friction and losses: Ok, there are some, this hub will never be able to be as efficient as a clean, well adjusted single speed or even a dérailleur set up, HOWEVER, it's no worse than any hubs I've ridden and perfectly acceptable for non-racing use. It does prefer being spun to mashing but I've never managed to get it to slip (I'm the wrong side of 100kg)

Range: The range is 350%, (SRAM i-Motion 9 = 340%). This gives me 26 to 94 inches per crank revolution. At the very extremes (the last few %) of the range I think I can feel a drop in efficiency, certainly at the top end I go from zipping along with no effort to suddenly having to up my effort for not a huge increase in speed, but there again when i used a 91inch top on my dérailleur set up there was a noticeable increase in the effort too.
cker on their hands.

Customer service: After fitting the hub and riding around for a month a slight fluid leak appeared from the shifter rod. I emailed NuVinci to ask if this was normal. They replied the same day that they had had some leaks and had developed a replacement shift rod with improved sealing and that they would send me new one. Less than 48 hours later a new shift rod with a double O-Ring seal arrived (I live in London). Pretty impressive. A month later I notice a bit of fluid leaking from the main seal (not a rotating seal, the closure cap). Another email to NuVinci and they emailed back saying they would send the replacement unit over. A fortnight later a brand spanking new hub arrived. The first thing I noticed was the hub looked different. It was a Mk2, slightly smaller with some extra holes in the flange. Sure enough the hub is now under 4kg and noticeably lighter than the older hub so they're moving in the right direction. More importantly, I bought this hub knowing it was "cutting edge" technology and there may be a few teething problems, however the customer support from NuVinci has been excellent.

Overall: A good hub, it is too heavy and too expensive at the moment to really hit the big time, BUT i can see both falling as manufacturing and engineering know how ramp up. My ideal would be to drop a few % in the range (say to 300%) if that would allow them to get it down to 2kg or less and the price to the $100 mark. If they could manage that then they really will have a cracker of a hub.

The problem with traditional derailers and cassettes is the inability to shift at a stop. Not a big deal for recreational applications, a very big deal for utility applications, especially in an urban environment. This is the same advantage that any internal hub has (which are older and more traditional than derailer drive trains).

As for slushy, well... I was skeptical too, but the reports are that it is anything but. It operates very differently from traditional CVTs, which use friction belts and such. This looks like it should be a lot more efficient, and that's what people seem to be saying.