Using the Nu Vinci hub?

[Zomby Builder]

Thanks

Yeah I need all the help I can get with providing the manufacturer with more reason / evidence to void my warranty.

 

[kevbo]

Torque from the engine is increased by the gearing in the same proportion that speed is reduced.

130 N*m of torque is 95 lb*ft. A 250 pound clydsdale like me standing on a 170mm (6.69 inches, or .558ft) crank, with a 2:1 chainring:sprocket ratio (52 gear inches on a 26" bike) would apply 69 lb ft of torque to the hub.

When the hub is operating at less than 1 gearing (a reduction) all the output torque that is not supplied by the sprocket has to come from the axle, and that axle must have something to push against, hence keying it to the dropout.

Note that this same applies to coaster brakes, which depend on reaction arms to handle the torque, not axles keying into the dropouts.

So is there any good way to add a reaction arm to the hub? Possibly you could cold set the stays a little wider, and add a steel arm that picks up the keyed axle?

 

[Zomby Builder]

got it covered

Yes the dropouts are taking a lot. I thought with both engaging though they would be strong enough. Wrong. They fit this frame perfectly. Staton is sending me just what you have described. They look like dual coaster brake arms. Should take care of it.

 

[Alaskavan]

That's cool. Sounds like it all may get back on track here. I've been busy lately, so I haven't had time to really let the data sift around in the brain. After looking at the posts here, and reading the Staton and Nu Vinci info, I doubt that you exceeded the the power that the hub is supposed to be able to handle. Adding the torsion bar set (I presume that's what Staton is sending you) should remedy the problem. I think you could probably design something that looks a little nicer than the Staton bars. I hope the damage incurred when she let loose isn't too bad. Anything further on the fluid leak?

 

[Zomby Builder]

fluid

Hey V. The fluid is supposed to be there. Staton told me that if I turned it on it's side it would leak out. I'm getting over it. I can repair the damage. It's only to my dropouts. He's got the t-bars installed on his test bike for the same reason & he has way less HP than me. and yeah they are freakin UGLY huh... This hub Really needs a MC strength frame. So I may just take it off this bike. Put it on Zena??? She has a Robin 35, & a stronger set of dropouts. Shame on somebody for the no warning.

 

[Alaskavan]

So how about using the Nu Vinci in the Mid Drive configuration? That might be a way to use it and still maintain the bike's aesthetics.

 

[OldPete]

I just got off the phone with NuVinci.
Output torque is limited to 130NM or 95'lbs. Do the math.
They feel max hp to be about 2.5, maybe a tad more.
They stated that the hubs do run fairly cool considering what is expected of them.

I still want one for the next project.

 

[MtnGoat]

New estimated max torque rating

Torque from the engine is increased by the gearing in the same proportion that speed is reduced.

Ahha! So the engine rated torque can differ dramatically from the torque applied to the hub. Thanks for that insight, kevbo. Well if the torque is increased in the same proportion as speed is reduced, then follow my logic for roughly calculating the input torque applied to the NuVinci hub.

The R/S 33.5cc with a maximum torque rating of 1.76 Nm @5000 rpm without gear reduction yields appx 387 mph @5000 rpm using 26 inch wheels. Pairing this with the Staton 18.75 to 1 gearbox, then 18 tooth from the gearbox to 36 tooth at the NuVinci hub, 5000 rpms now yields a speed of 10.3. The speed reduction attained is 387/10.3 = 37.6 times. So if the torque is increased by the same proportion that the speed is reduced, then the original torque of 1.76 has been increased by a factor of 37.6 at the hub, or from 1.76 to 66 Nm. This is less than 1/2 the 130 Nm limit. So one could more than double the torque provided by the R/S 33.5cc and still be within the allowed range.

Please correct me wherever I've gone wrong in this exercise.

So if my logic and calculations are correct, Zombie Builder has not come anywhere close to exceeding the input torque of the NuVinci, and his warranty should be GOLDEN.

 

[beast775]

wow

im thinkin i better say sumthin.my buds got a torqued out 49cc honda 4 stroke mated to a nuvinci hub,we terrorize that thing.no problems i can see. ill do video of the torque we have put these hubs through.ok pics and vid tommorrow

 

[hotsauce492003]

Ok 775, I am waiting to see ur pics and video on the Nuvici been used the way it should be...to da max!!