Adapting 8mm Chain To Internal Hubs

Discussion in 'General Questions' started by 5-7HEAVEN, Oct 17, 2010.

  1. 5-7HEAVEN

    5-7HEAVEN Guest

    As I'm working on my bike chain on the roadside for the umpteenth time, I'm thinking to myself...Self, multi-speed cassettes aren't working for you. If the skinny chain's not breaking, the derailleur's getting out of adjustment.:sweatdrop:

    Remember that crash at 25mph, when the chain jammed at the cassette and tossed you off the bike? There HAS to be a better, more dependable way WITH stronger components.:ack2:

    Since I'm cheap, it has to be with readily-available parts and a minimum of custom work. Pocketbike parts come into mind for me, especially their strong(made for engine power) 8mm(T8F) chain and sprockets. Since 8mm chain teeth are closer together, that makes for smaller-diameter sprockets and less clearance issues at the chain ring. I'm running an 11-tooth/63-tooth 8mm sprocket for my drive system. The 63t cog measures 6" in diameter, 72t sprocket measures 7.25" as compared to a 44-tooth bike sprocket, which measures 7" across. My bike chainring is 22-tooth; it will need to be changed to larger sprockets, maybe 36t at the rear hub and 72t at the chainring. That'd be .5:1, which is recommended by NuVinci specs.

    The beauty of it is that these sprockets are drilled for 4-bolt freewheel mechanisms, which is what I use on my driverings' shift kit. The only welding/machine work is to adapt the 8mm pocketbike sprocket onto the rear internal hub's/NuVinci's sprocket. Since the hub's only spinning at maybe 100 rpm instead of 10,000rpm, specs, trueness, balance, welds aren't as critical.:detective:

    Thinking about using Shimano 8-speed internal hub or a NuVinci hub. I bought a NV hub recently for my 29er MB project. Maybe I'll use that. Sure, the NV hub will add weight to my 60# bike, but I'm VERY strong for a 64yo retiree. I can easily roll my 60# bike UP two flights of stairs.:jester:

    So my big question is.....has anyone adapted a different driven sprocket onto their internal hub or their NuVinci hub?:detective:

    As I mentioned elsewhere, the "Achilles' heel" on my motorized bike is its chain. Not surprising, since I'm running 4.2hp(plus expansion pipe) thru an 8-speed chain.

    Thanks for any help or feedback.
    Last edited by a moderator: Oct 17, 2010

  2. 5-7HEAVEN

    5-7HEAVEN Guest

    Woo Hooo! No Machine Work Necessary!!!

    I am so stoked!

    I unscrewed the NuVinci hub's bike sprocket/freewheel mechanism. Then my pocketbike's freewheel mechanism threaded onto the NuVinci hub!!!

    No welding/adapting necessary!!! Now ANY pocketbike sprocket will bolt directly onto the NuVinci hub!!

    The pocketbike 36t sprocket and freewheel will bolt directly onto my NV hub. Hopefully, my 72t chainring sprocket is small enough to clear the frame's bottom bracket. If not, then 63t or smaller.

    I'll ask my friend Rick to help me install the NV. He has one on his 460-powered Specialized bike.

    The 36t and 8mm chain is reasonably priced on ebay, my favorite store.:jester:

    This opens up great opportunities for others who need lower gear ratios without a jackshaft or the 5:1 pocketbike transmission. My spare Polini uses a larger-diameter clutch than the standard 76mm clutch setup, so the 5:1 transmission won't fit. Now all I have to do is find an 8mm sprocket with 6 to 10-tooth bellhousing sprocket for a good gear ratio with an NV hub. Final gear ratio with 6t/72t sprockets WITHOUT a jackshaft can be as high as 42:1 with the NuVinci hub!

    Oops, jackshaft is needed to reverse engine rotation, if not using 5:1 gearbox.:detective:

    Last edited by a moderator: Oct 17, 2010
  3. 5-7HEAVEN

    5-7HEAVEN Guest

    Well, I bought the 36t sprocket, 78" of 8mm chain and a master link, all on ebay. I have everything else.

    Now the engine drive chain and the bicycle chain will be the same kind. Less parts to have on hand:idea:

    Rick, my friend, I'll be needing your help soon to install the NV hub!:jester:
    Last edited by a moderator: Oct 17, 2010