CVT Nuvinci/ worthless for hill climbing

jawnn

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The Nuvinci gear-hubs for bicycles are worse than useless, they can't handle more than 26 gear-inches of torque with human legs meaning that any motor will make them slip. :eek:

The maximum torque before it starts slipping is 130Nm or 96 LbFT . One wheel revolution to one crank revolution is the lowest gear possible.


Some one told me they saw a video of some guy jumping on the pedals, and thought that it showed how strong the thing is. All it really shows is that it takes much more leverage to move in higher gear. And it shows how strong the chain is; I have torn chain links just climbing hills in low gear.

However there is an application that my be useful; let the motor do the job of bringing the bike up to a speed that you can pedal in high gear. the motor will have to be connected to the other side of the wheel.


Has any one experienced this device differently?
 
Am I wrong?

gosh I was hoping that some one would prove me wrong by now.

I realy like the idea of this device...:giggle:

If any one can climb a steep hill with one fo these please tell the estimated total weight and the grade of the hill and the speed.
 
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gosh I was hoping that some one would prove me wrong by now.

I realy like the idea of this device...:giggle:

If any one can climb a steep hill with one fo these please tell the estimated total weight and the grade of the hill and the speed.

I have ridden my red barron in shell beach.... it almost idled up a hill I could not have pedaled up on a regular bike with a fixed gear to save my life. I would have definitely had to walk the bike up the hill. TOM knows what I am talking about... I am sure he has ridden his bike there.

I have to respectfully disagree... maybe it was your clutch???? The way the nuvincci hub is designed... there is no metal to metal contact, nothing to slip... the torque transfers through a fluid. There is NO WAY for the nuvinci hub to slip.... NO WAY, NOT POSSIBLE
 
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I've climbed long steep dirt roads and trails with mine that are literally a workout just to walk up hauling a pedal bike, which I've done several times. Just enough throttle to engage the clutch is all it took to haul my 200lb arse, the bike and the NuVinci kit. I don't know where you got your information from but I think these hubs would explode before they slipped. Theres absolutely no give in them. As far as them being impossible to pedal, it all depends on the sprockets you're using to drive the hub. Generally mine feels like it gears down to the pedal cadence of first gear on a 21 speed. A virtual crawl when pedaling.
 
.......any motor will make them slip...


Has any one experienced this device differently?

While I have NEVER rode a Shifter Kit bike with a NuVinci - YET - we have sold quite a few Shifter Kits to people with NuVinci's. In fact the some of the first kits two years ago were sold to a fellow with NuVinci's. Not one person has ever reported slipping.
 
is this hub usable on steep hills?

I have been trying to understand how to use a Nuvinci hub to climb steep hills. But I just can’t get past the idea that I may neede too much torque for the hub. And what if anything will happen to the hub if over torqued.

The Nuvinci forum is usless for information.

5mph with 400 to 500 lbs on an 18% grade powerede by a reasonable size motor,up to 750 watts, 36 to 48 volts.

We use 20” drive wheels and don’t care to go faster than 20mph. we can not use V belts because of the extreme humidity here. Timeing belts work but not on an expanding pully.

Is it possible to reduce the torque for the hub simply by reducing the seed before the hub?

What is the maximum grade we can expect to climb with the hub?

We need photos of a bike or trike set up correctly.


It seems very difficult to get info about these things......what WOULD happen if over torqued?
 
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I don't have one either, but it would slip given sufficient tq. How could it not?
They give you a torque rating, meaning- go over that and it slips. The reason it doesn't slip even for a big rider is the reverse gear ratio going from the crank back to the hub - your foot lbs. of twist gets cut down by the final drive ratio.
I would also be surprised if anyone- even strong guys can put down,say 200 lbs/ft. of tq, since the pedal crank is a lot shorter than a foot and some body wt. is not being used.

In the case of the off road use, you still stay under the rating because the miniscule torque generated by the engine(even multiplied by a gear ratio) is again, under the tq. rating.
As was mentioned the principle is very similar to the old Paxton blowers only, there is a very different viscous fluid internally. Cleaver engineering.
 
professor: Per their site, it "uses rolling traction to transfer torque." Ref the drawing from fallbrook's site, below. Depending upon the unit, three to twelve metal balls, mounted on an axis which can shift angles, placed between a pair of discs. There IS a lightweight oil inside, but, it's not used to transfer the torque.
edit by loquin: My bad. The special oil is used in a thin-film state, and under pressure it does act to increase the transfer torque from rolling ball to disc surface. Apparently, a thin film, under pressure, requires a high shear force before it breaks down. In the words of the manufacturer, it acts like 'liquid gears.'

jawnn: Suppose you weigh 200 pounds, you're on a standard bike, with a 38 tooth chainring and an 18 tooth freewheel. And you stand up on the front pedal. Your weight of 200 pounds is supported on first one pedal, the the other. Since the length of the crank is about 6 inches, the torque at the crank is therefore 200 * 6 inches / 12 inches per foot, or 100 foot-pounds.

Now, the chainring is 38 teeth, and the rear sprocket is 18 teeth. So, the torque at the input of the Nuvinci becomes 100 * 18/38, or 47 foot-pounds.

Since the hub is rated for 96 Ft-Lbs, you're good. On the above bike, the rider's weight would have to be more than 408 pounds before he would see any slippage when standing on a pedal...
 

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I do recall something (might have been in the Nuvinci video) about a special fluid they use that is key to it working - I just went to the Utube vid (can't figure out how to link) named" NuVinvi bicycle CV "and they explain about the fluid in the model demo.
I suppose whatever drag is in the system is caused by the fluid.
 
O.K., It's obvious somebody here had to use one of these things!

How are they mating the engine drive sprocket to the hub? Is it for use w/shift kit (right side drive) only?
 
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