SBP jacksaft length, do I need extra?

Discussion in 'Transmission / Drivetrain' started by FurryOnTheInside, Apr 29, 2016.

  1. FurryOnTheInside

    FurryOnTheInside Active Member

    I would like to use the left hand side chain tensioner and also run my right hand side chain 5mm further out from centre than normal (on a standard 148mm x 68mm ISIS bottom bracket). Do I need to get a longer than standard jackshaft?
    Thanks :)

    (Oh, and it's for a 66cc HT if that changes anything)
     
    Last edited: Apr 29, 2016

  2. KCvale

    KCvale Motorized Bicycle Vendor

    You shouldn't need a longer shaft, even if it's just a little short of where you want the sprockets it OK for the shaft to be inside a bit, the set screws still reach shaft.
     
    FurryOnTheInside likes this.
  3. FurryOnTheInside

    FurryOnTheInside Active Member

    Thanks, I will try to not worry about it. I am just having nightmarish visions of sprockets and bearings teetering halfway off the tips of the jackshaft, twisting out of alignment during acceleration and wrecking the js, chain, sprocket teeth, my leg... :( I think I may have to just buy the 10" to be certain! I have about two weeks to decide anyway as I haven't actually saved enough for the (transatlantic) shipping yet.. Don't even know how much that will be but I definitely don't want to pay it twice. :eek: I will go and measure the bike and chainring again, and um and arr about it.... :rolleyes:
    Thanks :cool:
     
  4. KCvale

    KCvale Motorized Bicycle Vendor

    If you need a longer shaft it will fit in a mailing envelope and ship for like $1.
     
  5. FurryOnTheInside

    FurryOnTheInside Active Member

    Transatlantic? I haven't actually emailed the guys at SBP and asked for a shipping estimate yet as I have _only_ just saved up enough for the SBP parts I need (it adds up so fast) so I don't actually know what I'll have to pay, no point in asking until I get paid again.. I do know to expect it will take ages to arrive while I pull my hair out (I have no patience!). I have been trying to not get any more than the essentials but I have eighteen items already on my list, just from SBP, counting the shift kit as one item LOL.
    And I laughed my head off when I got my happy time engine last week because it really is as ropey as everyone says they are. I must be :confused::confused::confused::confused::confused: to spend more than ten times more on parts for it!
    "But it will be unique!"
    Im my own worst enemy, best ignore me haha. ;)
     
  6. KCvale

    KCvale Motorized Bicycle Vendor

    That's a lot of parts if the whole shift kit is only one item.
    Guess it's best to stock up if you have to ship a long way.
     
  7. KCvale

    KCvale Motorized Bicycle Vendor

    Going longer has no ill effects.
     
  8. FurryOnTheInside

    FurryOnTheInside Active Member

    Thanks for your responses KC. :)
    I will have to talk with the guys at SBP about this when I get around to ordering (hopefully end of next week).
    I'm sure I will be back with more questions in a new thread soon.
     
  9. KCvale

    KCvale Motorized Bicycle Vendor

    FurryOnTheInside likes this.
  10. Rob H

    Rob H Member

     
  11. Rob H

    Rob H Member

    U should use the 10inch shaft then cut it down after u get the right length the standard 5 inch shaft will be too short to run in the left side bearing
     
  12. FurryOnTheInside

    FurryOnTheInside Active Member

    Thanks for confirming what I suspected. :)
     
  13. Rob H

    Rob H Member

    Anytime I wish I would have been more tech savvy when I started my builds I'm not really into smart phones and computers
     
  14. KCvale

    KCvale Motorized Bicycle Vendor

    I advise not cutting the shaft, if it's too long it don't matter unless it's soo long you get past the keyway, cut it however and getting the sprocket and washers on will just add to the frustration.
     
  15. FurryOnTheInside

    FurryOnTheInside Active Member

    Oh, so the keyway doesn't run the full length of the shaft? I have looked at the product picture on the SBP website and it shows a jackshaft with a keyway running the full length.
    I don't mind cutting and rounding the end. Although it will be tricky to get the cut straight with a hacksaw.

    Is there _any_ of the standard kit jackshaft still protruding from the ends of the sprocket (or LHS bearing) when the LHS tensioner is fitted?

    Also, related question: is the chainguard (small sprocket cover thingy on RHS) made of a flexible or hard material?
    I need to be able to remove the RHS chain without tools, by just pulling it off the RHS tensioner and peeling it away from the chainring then lifting it off. If the chainguard is flexible enough to fanangle the chain out then I can use it, and having the small sprocket 5mm overhanging (as long as it still definitelyyy works) would be okay -ish.
    If I can't get the chain out that way then I will have to drill, tap and make a disc a-la-fabien to give some protection. I suppose it won't matter if I have a stack of washers in there but I was hoping it could be a bit tidier..

    Long distance theoretical engineering o_O:rolleyes::rolleyes::confused::D hahaha
     
  16. KCvale

    KCvale Motorized Bicycle Vendor

    Actually yes, the SBP keyway goes the whole length, I was thinking about my 10G shafts.

    The SBP chainguard is ridged plastic in 2 parts.
    You glue one part to the cover, and other piece with the guard screws onto that.

    [​IMG]

    I don't use them much, either a disc wider that the sprocket on the end or a custom cover.

    [​IMG]

    [​IMG]

    The only time you really need to worry about that chain guard is if you wreck and get trapped under the bike with long pants that get caught in it.

    [​IMG]

    It's not the least bit friendly.

    [​IMG]

    Not not friendly at all.

    The full topic about that is here.
    It's gruesome.
    http://kcsbikes.com/topic.asp?TOPIC_ID=163
     
  17. FurryOnTheInside

    FurryOnTheInside Active Member

    I've read it, it's quite eye wateringly gruesome. :(
    Thanks for the info re the type of plastic. I'll hopefully be able to get a disc, then. I thought I would have to. Wish the shafts came drilled right through and tapped at one end..
    I finally found exactly where it was I got the idea about the sprockets hanging off the shaft.. It's the yellow and black GT LTS (3?) 21 speed built by gasbikesproject some years ago. My LTS 5 should be here within the week, hopefully I can make it better having seen a lot of examples of what can be done. :)
     
    Last edited: May 10, 2016
  18. KCvale

    KCvale Motorized Bicycle Vendor

    My 10G 4-stroke long shaft transfer cases shaft comes drilled and tapped.
    Heck, even the stock 4G's come that way for the left side drive.

    [​IMG]

    I just cut a disc out of the flat plastic plate the shift kit uses bigger than the sprocket and screw it to end to keep long pant legs for getting caught in it the same way the chain guard does on the lower sprockets.

    Heck, I seldom wear long pants at all (hitting 100F already here) but safety first, especially considering what CAN happen in a fluke wreck.
     
  19. FurryOnTheInside

    FurryOnTheInside Active Member

    Yes indeed, safety first!
    I won't be able to use a chainguard on the outer chainring because of the planned method to make it pedal powered/ legal on public roads. But
    I will make sure to wear goggles to drill the hole for the guard disc. :cool:
     
  20. KCvale

    KCvale Motorized Bicycle Vendor

    Hehehe, I must have 1/2 a dozen pairs of safety glasses all around my shop, everywhere there is equipment, even hand tools.