I was just wondering if anyone already have a formed opinion about this new product
I don't think the Rohloff is stepless like the Nupace claims to be. In any case, why do you think the Rohloff is better?Originally Posted by Raiyn
The Rohloff 14-gear version has 13.6% steps, AFAIK.Originally Posted by halfspeed
What a deal, only $995. Something about that website just says scam to me though.
It is a 14 speed, planetary geared hub instead of a mere 7. It's gearing range is the same as that of a 27-speed mountain bike drivetrain, and has a 526% increase in gear ratio between the lowest and highest gear. Couple this up with a larger ring up front and you could more than duplicate a typical road bike range.Originally Posted by halfspeed
The quality of the unit is basically unmatched. I'd equate it to a Chris King product in terms of the precision involved.
To be more accurate it's between 13 and 14% depending on the specific gearsOriginally Posted by CdCf
It looks like the real deal to me. I've been anticipating a CVT for bicycles for several years.
I think that it'll be awhile before it makes it's way into the mainstream. At around $1,000, it isn't cheap and it isn't going to be as efficient as a derailleur drive train. That's two fairly significant strikes against it.
what is cvt and how does it work?Originally Posted by Retro Grouch
I believe it means continuously variable transmission, this thing looks pretty cool but too damn expensive. The 2120 gram weight of the system sounds huge, until you think about being able to lose the weight of your entire rear cluster and one or two front chainrings....Originally Posted by genericbikedude
2006 Gary Fisher Marlin MTB
2004 Salsa LaRaza aka "Mmmm, Blue Salsa" (853 steel is real, baby!)
2003 Kona Humu Humu Nuka Nuka Apua'A Singlespeed - Gone, but not forgotten
1998 Diamondback Outlook MTB
1990 Centurion Cavaletto 'Gaspipe Beater' Roadie
1978 Volkscycle 'Frankenbike' CroMo Tourer
And FD and RD. Still, seems a bit heavy. I hope it's not a scam or vaporware, as it sounds like a really nifty piece of hardware.Originally Posted by BubbaDog
I wonder how it works.
Looks cool enough. I'd expect poor efficiency and weight scaring off performance-oriented riders.
What if you controlled the gearing ratio electronically? You could have a auto transmission that maintained your favorite cadence!
Me too. I can't make out the shifting mechanism from the cut-away.Originally Posted by Phantoj
After staring at their CAD rendering and also a couple of the pictures from their patent for a few minutes, I understand how their mechanism works. I will try to describe it to you.
The relevent US patent is 05971877.
Explaining the mechanism from the axle outwards, and neglecting literaly hundreds of bearings, we have:
1. A fixed axle and associated torque arm. They don't clearly show the torque arm in their diagram, but it must be there and it wouldn't be very interesting if it was. The axle is eccentric in the middle section, standard in the portion that joins with the frame. The axle only moves when your torque arm rattles loose and beats the hell out of your rear triangle.
2. One Eccentric sleeve with engages the axle in the portion where it is itself eccentric. This is reminiscent of an eccentric bottom bracket. By turing this sleve relative to the axle (By having the stop for a boden cable on the torque arm and the cable clamp on the sleeve), the amount of eccentricity of the outer diameter of the sleeve can be changed relative to the axis of the axle. The sleeve only moves when you shift "gears", and it does so continuously rather than being indexed.
3. Four pawl holders, which are concentric about the outer diameter of the larger eccentric sleeves from (2). They do not engage with anything except the pawls they are holding. Each pawl hoder has two sets of pawls oriented in opposite directions.
4. Pawls. Each pawl is held in by a spring mechanism, rotates about the end in the pawl holder, and has teeth on the outside, which engage with (from chain side to drive side):
5. An outer toothed ring that is fixed to the rear cog.
6. Three more toothed rings. Each toothed ring engages with two sets of pawls, one from each pawl holder. The two sets of pawls associated with each toothed ring are oriented in opposite directions.
(Parts 3 - 6 are all moving whenever you are pedaling.)
7. The hub shell, which engages a single set pawls, i.e. the leftmost set. This set of pawls freewheels when you are coasting. The hub shell rotates axially about the center of the axle.
To understand how the pawls work, imagine a very flexible person standing on skis that are parallel, one slightly forward. Now assume said person passes out. Gravity pushes said flexible person down and he/she does the splits, pushing one ski forward and one back.
Gravity <--> Eccentric sleeves acting as a cam relative to the hub shell / toothed rings.
Skier <--> Pawl Holder
Pawls <--> Legs
Skis <--> Two adjacent toothed rings
So on one side, say the front, of the hub you have pawls engaged with teeth and expanding, and on the other side, say the back, you have pawls contracting and engagine with new teeth. The more eccentric the outer diameter of the outer sleeve, the farther down the pawls "squish" during each cycle.
The design does have some elegant properties:
- You don't have to change the dimensions of any of the parts relative to each other to change the gearing range of the hub. This is in contrast to the much seemingly difficult to design and dimension gears in a traditional gear hub.
- While there is a rediculous number of parts, there are not really very many types of parts.
- It may not be as difficult to service as it seems; It seems like each pawl holder and associated two sets of pawls stays together when you pull the mechanism apart.
- I could imagine it being very smooth when in good working order and at lower speeds. I imagine the pawls whining a bit at higher speed, i.e. not when they are engaging, but when they are slipping to new teeth.
- It is, IMHO, easier to understand than a rohlhoff.
- Does not rely on friction like many other continuous gearboxes.
So no, they don't seem to be a hoax, yes, it seems that have a workable mechanism, and no, I wouldn't recommend buying one until they bring the price down by a factor of ten or so and hire a competent marketing department.
Originally Posted by awagner
Almost sounds like that one from Honda I saw in DirtRag last year, only their's, I believe, didn't "step" at all.
What are ya gonna do? Bleed on me?
[QUOTE=awagnerSo no, they don't seem to be a hoax, yes, it seems that have a workable mechanism, and no, I wouldn't recommend buying one until they bring the price down by a factor of ten or so and hire a competent marketing department.[/QUOTE]
Actually, with no gear-to-gear drive, that sounds to me like a pretty efficient power transmission. It's a little pricy, but it's still in the early stages of it's development. They'll get cheaper. Actually it's not that far off of the price of a Rohloff hub. Keep in mind that it replaces the rear hub, cassette and both derailleurs so it's cost, while still high, isn't too far out of line. I think that it'd be fun to build up a bike with one to see how it rides. I wonder what the OLD is.
Oh my gosh, there goes my screen name again!
After looking at the cutaway drawing and reading the above description of operation, I find it amusing that the company refers to the conventional derailleur as a "contraption".
It's funny that the company failed to mention the efficiency of their transmission and how it compares to the derailleur and chain contraption.
For those who think they got the thing figured out: If it's a true CVT, then it has to have a friction-based transmission somewhere. Period. If not, it's a pseudo-CVT with many gears and microscopic gearing steps, which means something somewhere has a very large number of very small teeth, which isn't exactly the most mechanically reliable thing.
In short: either the hub is real and it's no wonder they don't publish any efficiency figures, or it's a scam. Given how childish and unconvincing some of the mechanical explanations are on the webpage, I vote for the latter.
By the way, I keep wondering why cyclists are so obsessed with CVTs: CVTs are desirable to compensate for engines that have a narrow range of working rpms, typically internal combustion engines that have a very narrow band in which they can output power efficiently. Human legs however, work efficiently from 0 to 120 rpm with standard cranks, and can even spin much higher if needed. A cyclist may want some gears to protect his knees in the long term, and for comfort, but really he can ride on a single gear bike without any problem, so what's the big deal with wanting CVTs on bicycles so bad? Heck, even car engines make do with only 5 speeds.
Yeah, a real CVT would use opposing cones with a belt that slid up and down the cones as their spacing changes. Effectively you're changing the diameter of the gears in smooth, continuous steps. None of this 13-14% steps, you can vary gearing by 1% at a time or 0.5% or 0.01% if you wanted.
One cool application would be a sprint. You'd start the sprint in a low-gear for maximum acceleration at say... 100rpms. Then as your speed increased, the CVT (computer-controlled of course) would smoothly increase the gearing so that you'd stay at 100rpms the entire time you're accelerating... Then once you've reached the highest gear you're gonna use, the tranny would lock and you'd spin up that final gear to 130rpms for top-speed... Pretty nifty...
The main "problem" with the current chain/cog/derailleur bicycle drivetrain is that it has set the bar so high it's extremely difficult to improve on. It's very efficient, light, reliable, simple in concept and inherently low cost (Campy Record and Dura Ace notwithstanding. Status always costs a lot. ) Therefore, every shade tree inventor just has to try to "improve" it.
So far the only, even slightly, successful competator is the geared multi-speed hub. These are heavier, mechanically complex and less efficient but have a few minor advantages of their own such as shifting while stationary and allowing a perfect chain line and/or an enclosed chain. For certain utility uses these advantages are worth the trade-offs. The ultimate extension of this type so far is the 14-speed Rohloff with it's large gear range and even steps at the cost of some weight and a very high price plus the shifter is not intended for drop bar applications.
ppc is correct that a true CVT has to have friction surfaces to allow continuous, non-stepped ratio changes so the object of this thread doesn't seem to fit this design criterium. If it is a series of very small steps then its strength and durability are suspect. Bicycle riders can genetrate very significant torque values so robust parts are a necessity. That plus a 2000 gm weight disadvantage will be a tough sell even if it's legit.
Well, even if it work flawlessly and does what they claim, a 14-speed Rohloff is probably way better. The greater range is a bigger advantaage then being stepless. The Rohloff is probably more effective as well, although still way worse then my singlespeed (or a derailleur bike, for that matter)
Phantoj: Automatic shifting does exist, but it's useless for anyone but the few people who have more money than riding skill. Shimano Nexus 3-speed.
Nope. That's like saying that an internal combustion engine has to have pistons. Sometimes things that used to be true (as any Mazda owner will tell you) are invalidated by new designs. In this case the continuously changing part is the eccentric pivot for the prawls. It has neither friction driven nor gear-to-gear components so it should be a significantly more mechanically efficient design than conventional internal hubs.Originally Posted by HillRider
This thread is a joke because I'm the one whose supposed to be the retro grouch.
I'll retract my comment that a CVT has to have friction surfaces as your description of the ecentric as the gear ratio control is probably correct.
However, saying this hub isn't an improvement in weight, simplicity, cost or efficiency over the current standard drive train isn't being a Luddite. It's pointing out mechanical facts.
Your comparison to internal combustion engines is similar. No they don't have to have pistons but, so far, that system works best. Wankle engines, as Mazda has returned to in a very limited usage, still fall behind their piston counterparts in several respects including seal problems and fuel efficiency. Note even Mazda only uses it in one specialty car.
Actually, I 100% agree with your earlier comment that modern derailleur drive systems are so efficient, both mechanically and costwise, that it sets a pretty high bar to improve upon. In some previous threads I've even commented that I couldn't understand the attraction of hub gear systems - a comment that drew a LOT of response from the hub gear crowd.Originally Posted by HillRider
I'm attracted to the Nupace because it's a design that I hadn't seen before. I think that it might be interesting to see how it's use might progress in the near future. I suspect that efficiency wise it might already come close to rivaling a derailleur drive system. Weight and especially cost, however, are another matter but they both might well improve with a little bit of development.
I also find the whole thing fascinating and would like to see how well it works in real world use. Indeed, if it proves durable enough and the cost penalty can be reduced it may be a sufficient improvement over hub gears that it replaces them in many bikes. As someone noted, the 14-speed Rohloff isn't exactly given away either.I'm attracted to the Nupace because it's a design that I hadn't seen before. I think that it might be interesting to see how it's use might progress in the near future.
I really hope they succeed and my previous point was only that it isn't magic and isn't going to transform or reduce the effort to ride a bike. We'll see.