Installing NuVinci hub,things to watch out for

Discussion in 'Rack Mounted Engines' started by duivendyk, Mar 17, 2008.

  1. duivendyk

    duivendyk Guest

    In my Staton/NuVinci installation I have encountered a few problems which I think are worth communicating to members who might have similar objectives&interests.
    The NuVinci hub was designed for European style bicycles with steel frames and with longish horizontal dropouts,not for aluminum framed mountain bikes,or tamer versions of these for street use,such as are common in the US.It can be adapted for installation on these bikes but this may have side effects which need to be dealt with for a successful application.
    An inherent feature of the NV hub, and for that matter, all internally geared hubs,is that they will transmit a significant torque reaction via the hub axle to the frame of the bike,the flats on the axle serve to transmit this torque by way of serrated steel washers,which are clamped to the dropouts by the axle nuts.For the NV, with its wide range, the torque reaction can be as large as 100% of the hub input torque ! (in the lowest speed setting).Most bikes used in this country have derailleurs and don't have to cope with any torque reaction, they also have rear wheel dropouts pointing downward,instead of parallel to the ground, which makes sense since chain adjustment is not required.
    All this creates problems,to begin with, the serrated steel washers are not compatible with the soft aluminum of the dropouts,which get chewed up and causes them to fail,also the rear deraileur hanger is usually an integral part of the right dropout and needs to be kept there,this can add to the width of the dropout which can lead to another problem (about this later).
    Staton Inc found out about all of this and supplies torque bars with their NV kit,they fit quite accurately on the axle flats,but need to be rigidly connected to the bike frame somehow,they provide you with a 1/8 " steel connection bar to accomplish this (No specific instructions are provided for NV installation,except for the Company info which is pertinent only to Euro type bikes ).
    The straightforward way would be to bolt this bar to the end of the torque bar and make a vertical connection to the rear fork by bending it in a U shape & bolting it to the fork,however, with the torque bar pointing downwards at about a 50 degree angle this would put a lot of force sideways on the rear fork,moreover bending the bar end into the required U shape was beyond my capability anyway, so I angled it sideways and fashioned a bracket to clamp it solidly to the rear fork. This easily doubles the leverage and reduces the lateral force on the fork.I also used two bolts to make a rigid connection between it and the torque bar,turning the combination into a rigid unit.
    Compared with my problems with the torque bars,mounting the Staton gearbox on the bike was fairly straightforward,I did have to cut off part of the forward bottom mounting brackets to clear the rear frame stays, I used only two 1/4 " bolts to mount the whole shebang on the dropout (lack of space,maybe locate high strength bolts ?).
    So far so good,however there is a potential problem lurking within the NV hub itself.To explain what this is about, it's useful to review how the hub is controlled,The transmission ratio is controlled by rotating the "Cruise Control" located on the handle bar,this causes the shift control rod in the hub to rotate,this rod has a helical drive on it which screws the shift actuator in&out in order to change "gears".For this to work properly the rod must be kept in the same position axially instead of being permitted to screw itself in or out,when it is being turned (with the actator staying put).
    The shift contol rod is installed by screwing it into the hollow hub axle from the right until it bottoms,it has a collar on it, which then will be flush with the edge of the right side axle end of the hub,then the shift rod retaining nut is screwed on,the inside of which seats on the axle end and the shift rod collar too.This locks the shiftrod into position so that it has no axial play.If the retaining nut is not screwed in all the way in the result will be that you will have a "dead zone" in the shift control (sort of like having a lot of steering play in an old car), you will also lose some control range
    The question arises how it is possible for the retaining nut to be kept from seating properly on the axle end,the fact is that it is not the only actor on the scene,the retainer nut serves as a carrier for the axle nut (which secures the hub to the bicycle frame),the axle nut is first screwed onto the retainer nut as far as it will go,then the retainer nut/axle nut combo is screwed on tight on the axle,but then the axle nut should STILL be free to turn CW some more until it contacts the side of the dropout.If it already tight against the dropout when the combination is screwed on all the way onto the hub, then the shift rod retainer nut cannot yet have made contact with the axle end !!, and consequently the shift rod will have axial play,which will have to be gotten rid of.
    This can come about because the combined thicknes of the dropout width +the torque bar thickness + the inside measurement of the axle nut edge to the inner flange of the retainer nut (with the axle nut all the way screwed on the retainer) exceeds the axle lenght from the right side hub mounting flange to the axle end.(21.8 mm.)
    On my Raleigh bike I was short about 3 mm., this was due to the thickness of the dropout+extra thickness of the derailleur hanger (7mm. total), and the exta axial space taken up by the torque bar (5mm.),that left 9.8 mm. for the axle nut/retainer combo inside space,which measures close to 13 mm.Therefore the retainer nut was close to 3 mm away from seating (about 1/3 turn of the shift control rod),max. range is 2 1/2 turns.Of course this situation cannot possibly occur in more "normal" applications (without the torque bars)
    I solved this by filing down the derailleur hanger some to reduce the dropout width,I also ground down the axle nut until it was flush with the end of the retainer nut.That did it.About the shift rod retainer nut,take care not to cross-thread the thing, due to the flats on the axle about 60 % of the thread on it is missing and it is not all that hard to mess up when putting it on.
    I realize that some of this stuff may be hard going,it's not easy to be clear without drawings about mechanical intricacies,but I hope that for interested readers it has provided useful info.The hub is an expensive piece of machinery and should consequently be treated with TLC
    I will now proceed to check out the bike in a non- motorized form before installing the engine.
    From the clash of opinions,the truth may emerge,JJ
     

  2. VTBikeman

    VTBikeman Member

    All that being said, how did it work out on your bike?
    G
     
  3. duivendyk

    duivendyk Guest

    It worked out OK,as far as the functioning of the drive train itself was concerned,but the bike's handling is rather different with the weight concentration towards the rear.Ordinarily you would adapt to this,however I also ride a normal comfort bike around town,so I keep being reminded of this change.It's not exactly unsafe I'm not one of these speed demons,20 mph is plenty fast for me,but I would feel uncomfortable going much faster.I just need to get up steep hills.What did not work out all that well was keeping the front deraileur.When pedalling hard the chain would skip teeth on the rear sprocket.It turned out that the teeth profile was not helping matters,the flank was at a shallower angle than normal rear cassette teeth.so the rollers tended to ride up on the sprocket causing the chain to start skippimg.I cured the problem after a fashion by increasing the chain tension with springs I installed on the rear deraileur (which functions as chain tensioner).The front deraileur still works but is harder to operate,it's more like if you're speeding on the flats, then get into high gear,so you're not using it all that much.I like to pedal along,feel kind of stupid just sitting there.The Mitsu TLE 43 was noisier than I expected for what was heralded as a "quiet" engine,I don't care for noise at all, so I crafted a muffler for it which does an adequate job.There is a post by me "easy to build muffler" Summing up it's a nice package if you live in really hilly terrain.The downside is, the bike feels more cumbersome and there is a lot of added weight.The drive train works quite well,the NV has tobe looked upon as a gearshift i.e. throttle back when shifting,doing it under load takes effort.
     
  4. SirJakesus

    SirJakesus Guest

    This I can agree with completely. Statons setup would be made better by using a smaller lightweight gearbox connected to the engine and enlarging the nuvinci engine drive sprocket to compensate for the lack of reduction on a smaller gearbox. The weight is noticable back there. I wouldn't say it makes the bike any less safe or anything but it's definitely not as nimble as a regular bike. It's very much worth it if you need lots of low end power but don't want to be stuck in first gear when conditions allow for a higher cruising speed.
     
  5. 4950cycle

    4950cycle Member

    Well ?

    How did that NV hub work out long term ? Now that you had plenty of time to evaluate it. I would appreciate an in depth review. :confused:
     
Loading...