Using the Nu Vinci hub?

[duivendyk]

Not any hub as far as I know,there have been busted dropouts,esp aluminum frames (which means most bikes these days).The hub axle may transmit considerable reaction torque to the bike frame,in the lowest gear,i.e. 50% speed reduction mode,corresponding with 2/1 torque multiplication,the reaction torque from the axle equals the input torque to the hub !.This is why Staton-Inc supplies torque bars mounted on the hub axle to transfer this directly to the frame instead of via the dropouts,
From the clash of opinions the truth will emerge,JJ

 

[grndslm]

the good news is that SO FAR we have NOT heard of ANY busted NuVinci hubs ...
Am I right?

I sure hope so...

Once I hit the jackpot, I plan to put one of these on the front wheel of a trike, with a rack-mounted mitsubishi tle43 or robin-subaru... Brilliant!

 

[fastboy9]

If anybody is unsure on how this NuVinci thing works, there is a fantastic video that explains it very well on youtube. http://www.youtube.com/watch?v=kVPjhmTThPo

This really has a lot of potential, going to try this i think.

 

[SirJakesus]

Great link fastboy, thanks!

 

[Zomby Builder]

NuVinci ROCKS

With a set up like this one it works GREAT! I have torsion bars to stablize the dropouts....

Check this....

http://www.youtube.com/watch?v=p7PE3sz83A8

 

[vyzhion]

Ok so this was mentioned earlier in this thread but not really explored all so much... Could the nuvinci be used for a right-hand drive version of Dax's Titan? It has the pto on the right side and uses a jackshaft to transfer back to the left. Could we just omit the use of the jackshaft and connect it directly to the nuvinci? It would be much more centered over the wheel than the Staton rack-mount setup and the Titan seems to be a really good engine. Any of you nuvinci users have any thoughts on this? Is there anything preventing one from doing this?

 

[SirJakesus]

As long as you could align the engine and NuVinci sprocket correctly I don't see why it couldn't be fairly easily done. The only problem I could imagine is that the staton gear box is 18:1 reduction while I think the PTO on the titan is much less reduction so you would have to get an engine drive sprocket for the NuVinci that had many more teeth than what staton uses, otherwise you would be overgeared in the high gear setting on the hub, and you wouldn't get as low a low gear as the staton either.
The real question should be why go with a titan when the staton gearbox gives you much more flexibility of engine choice and replacement AND it freewheels which the titan does not. If you're worried about balance issues just use the left side of the staton rack for cargo or fuel storage. My bike is VERY balanced from left to right and I'd be willing to bet the staton rack will handle more cargo to be stowed and last much longer due to the fact that it's incredibly heavy duty. Don't shortchange yourself by running a precision NV hub with a chinese honda clone engine. The titan is great as a low-cost rackmount option, but if you're going to spend big bucks on the NV hub you might as well go all the way and buy the most versatile system available.

 

[duivendyk]

I basically agree,it will be difficult but not impossible to gear down low enough.In a previous post I gave a formula for relating engine rpm, road speed and the overall reduction required, which gives some insight (26" wheel).The formula is:
S = 0.075*rpm /R ,lets say you would like to run 20 mph at 5000 rpm,plug in the numbers, 20 = .075 * 5000/R
(* means multiplication, / means division) or R = 375/20 ,
R= 18.6.I believe the internal Dax reduction is 5:1,so the required addition reduction in the chaindrive to the NV hub becomes 18.6/ 5 or 3.72 .The NV hub as a ratio of 0.54 to 1.87 so lets say you have a 10T to 36T sprocket ratio ,than at 5000 rpm your min/max speeds become:
375/18 *( 0.54 resp. 1.87) Smin = 11.2 mph, S max= 39 mph.You will have a fair amount of hill climbing ability.
That overall reduction is still on the low side,it would probably be better to use a larger rear sprocket if that's possible,mine had 27T,earlier units had 36T I believe ,and I used a 16T sprocket on the gear box.(I need to climb steep hills)
As SirJakesus has pointed out it's desirable (but not essential) to have a freewheel sprocket on the engine output in order to avoid having to drive the internal 5 to 1 engine step up to the centrifugal clutch in the emergency mode.I don't know the output capability of the Dax's engine, prob. about 2,5 hp, with max torque in the 5000/5500 rpm range,nor it's durability.As far as I am concerned it's a dark horse and I would be reluctant to bet on it,but I'm a cautious sort.

 

[kevbo]

You could still use the jack shaft to get a first stage of gear reduction. Just put the two sprockets on the same end of the jackshaft, far enough apart to keep the chains from rubbing. This puts a little less strain on the jackshaft bearings, as the tension in the two chains partially cancles the force on the bearings.

 

[duivendyk]

Great idea,it gives you more reduction capabilty and flexibility It would be really nice if you could turn one of these into a freewheel sprocket, I don't like these tiny 10T sprockets much,then you would also be able to use somewhat larger ones and still get the overall reduction needed. There is prob. a minimum size for freewheel type sprockets (16T?)