To jackshaft or not to jackshaft..

Discussion in 'Motorized Bicycle General Discussion' started by breno, Jan 24, 2011.

  1. breno

    breno New Member

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    I'm wondering about ppls true opinions on the jackshaft kit.
    Do the fellas that race these things use them?
    I have j/s kit and I'm torn between the the 2..
    J/s kit or 36 tooth on a hd rim.
    I know it might seem it would be best to try 1 way or the other but I don't wanna have to muck around with my exhaust header with the 2 dif. Arrangements.
    Thanx for your input
     
    #1 breno, Jan 24, 2011
    Last edited: Jan 24, 2011
  2. Goat Herder

    Goat Herder Gutter Rider

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    I enjoyed the J shaft personally best for these reasons. The engine Idles and coast like a dream. Gas on then a perfect quiet normal bicycle again to where I could hear tires scrubbing the pavement etc no obnoxious rattling chain. I found personally that without the gears I would tend to go too fast everywhere in light of not bogging down the motor. So it calmed me down considerably going through neighbor hoods where speed would be obnoxious to others, and made me a much more safer driver. Then of course gears. Last the gas mileage for me was about 20 more miles to the gallon in light of the superb coasting ability, I think really contributed to that.

    You have to consider keeping good chains with it tho. If that part troubles you just keep it to a single speed. The derailleur gear chain for me was good to about 3000 miles stretching it. A fair second sometimes sooner with the rest of the chains. If you set it up right it can be rewarding.

    With the chains out of the equation I think one direct chain to the rear wheel can pull more raw torque to the pavement . Depending on what your really wanting from it? Gears can prolly easily make up for that tho.

    Setting up the chains perfect is key to this set up in my H.O. slack etc. I have not tried the newest kit looks like this is accomplished very nicely now.
     
    #2 Goat Herder, Jan 24, 2011
    Last edited: Jan 24, 2011
  3. breno

    breno New Member

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    Cheers for the reply GH.
    Im also intersted in what ppl are using in these death races J/s kit or the "standard setup"?
    I was watching some clips on youtube but its too hard to see what the leaders are running.
     
  4. Goat Herder

    Goat Herder Gutter Rider

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    Can't really answer that. I know the folks that have won the last three races did it with out one.
     
  5. breno

    breno New Member

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    U d'man thanks mate.. That's all I wanted to know
    Cheers Breno
     
  6. heyscuba

    heyscuba New Member

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    so, a Jack Shaft I'm guessing would not work on a 1 speed old coaster brake bike right?
    and how many gears is workable with this set up,..?
     
  7. killercanuck

    killercanuck New Member

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    I think Death Racers are running 26's(or smaller) and pedaling like crazy to get back up to speed.

    heyscuba, running a J-shaft on a single speed would be a waste of money, you'd want to have at least a 3-speed hub(low-med-high/hill-cruise-flat), but alot of those can't handle the torque. You can get 6-8 speed hubs to make you more efficient, or even use a NuVinci infinitely variable hub if you have the $.

    But there is a whole section here just on hubs, the frequenters there will be able to give you more solid answers than us General guys :p

    Motorized Bicycle: Engine Kit Forum
     
    #7 killercanuck, Jan 26, 2011
    Last edited: Jan 26, 2011
  8. buzbikebklyn1

    buzbikebklyn1 New Member

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    Its long been my stance that a properly set up jack shaft system and secondary dive (the bikes derailleur system) will always be superior to a left side sprocket set up for anything BUT all out racing.
    I just got my hands on a S6-T Morini engine and I'm building a jack shaft based set up using 415 type primary drive cogs and chain-
    Engine out put, left side jack shaft, right side jack shaft and driven chain ring will all be 415 pitch.
    Then reaching back into the past for the inner derailleur drive chain ring, an old style(new old stock) 5 speed chain with a 5 speed rear cassette stacked up on a 9 speed shimano XT type disc hub using spacers.
    I've tested this chain with a hydraulic ram and it took twice the amount of force to stretch and then break it than modern 7, 8 or 9 speed chain.
    Remember, this is old coaster brake chain that was designed to take the forces of a coaster brakes.
    The next weak link was the derailleur its self, I'm using an old XTR derailleur that I installed super heavy springs in, and I spaced out the pulley cage with slightly longer bolts with washers to take the thicker chain and used aluminum pulleys with roller bearings, I'm using a 10 speed quick click shifter pod that ill have to double click to shift.
    The last potential weak spot would be the dreaded chain slap, which can happen in non motored bikes...
    I've designed a lower chain tensioner with a sliding roller skate wheel on a longer shoulder bolt as an idler that will follow the chain as it moves up and down the cassette.
    CHAIN LINE CHAIN LINE CHAIN LINE!
    I cant over state the importance of proper chain line!
    YES... the chain will stretch, but in a controlled manner.
    Lastly, THROTTLE CONTROL! no power up shifts please!
    even Shimano suggests that you back off (not stop!) on the peddles before up shifting. Use the peddles to shift, then eeeease into the throttle, just whacking it open will snap a chain.

    Be not afraid of the jack shaft... its a good thing... really!
    BBB
     
    #8 buzbikebklyn1, Jan 26, 2011
    Last edited: Jan 26, 2011
  9. heyscuba

    heyscuba New Member

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    I really feel the need to get one of these "Jack Shafts" because my Dad's name was Jack,.. (R.I.P.) we called a lot of things Jack-this or Jack-that around his house, the most common use of the term was the "jack-pack" which was a 12 pack of beer in a box that he would cut in half with a razor knife and turn them up and you'd have 2 six packs of beer with easy access, when the beer was done the boxes would hang around and many times you would leave his house with a jack-pack full of tomato's of vegetables or tools or wires and batteries what ever it was that you needed,...
    with my great Dad in mind I had a storage problem and I had to channel my Dad's great mind and come up with a solution and I ended up inventing the Jack Stack a few years ago,...
    see it here,...



    YouTube - Lawn mower storage problem and solution

    (also, I have many fun and easy bar/dinner party tricks on there,...)

    so, you can see why I have to get a Jack Shaft
    thanks for letting me rant on my Dad,....

    heyscuba

    dance1
     
  10. Goat Herder

    Goat Herder Gutter Rider

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    buzbikebklyn1 been my experience that the Morini will be less powerful after you get the clutch to behave in this ordeal. Top speed will be less. My next is Morini will be all out for the power single speed. It worked for me ! Tho to me with all that power was just to many moving parts more especially for all the power. A china motor to me being less powerful is very doable in the type set up and perhaps more appropriate. I made it to about 3000 miles. I want a simple one now.

    I ran a Nuvinci Wheel with a simple single speed chain. At the time I cobbled up my sprockets I was going to use gears and a derailleur. Sadly in my for sight I could not fit in a 410 chain which would have been way better. My run of the mill single speed chain was only good for about 500 miles until snapping it. At 10 dollars a pop I trudged on it was simple enough for me. This was occurring after I had a proper right off Idle engaging clutch for this criteria. http://motorbicycling.com/attachments/f47/24399d1273697332-morini-time-full-sus-project-p1010008.jpg http://motorbicycling.com/attachments/f47/14908d1256281481-morini-time-full-sus-project-p1010008.jpg http://motorbicycling.com/f47/tame-morini-clutch-20970.html

    To me the derailleur chains don't stand a chance. I tried them with a bone stock 5.8 motor. The china don't put out near this power and with a maintained J shaft is fine.. After taming my clutch for this I always wanted more power too. But that's just me. Especially after tasting what it could do on a stock engagement of 5500 to 6000 rpm too. The stock red springs on a two shoe are for this said engagement.
     
    #10 Goat Herder, Jan 26, 2011
    Last edited: Jan 26, 2011
  11. Goat Herder

    Goat Herder Gutter Rider

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    On a three shoe clutch you will find that after making it engage early that under the right load around 4000 to 5000 rpm at a very slight incline making a casual speedy run the clutch will grab and break traction again. The weight of the shoes them selves are meant to grab perfectly at around 6000 rpms. Simply put the shoes them selves are not heavy enough IMO. What I did was set my three shoe clutch up for immediate engagement so to speak to sanely compliment the first foremost easiest gears. It never slipped in these gears. It would occur at speed.

    You may have better luck with the two shoe? As it is designed for a less powerful motor and earlier engagement. I did most of my own study with the three shoe as it had infinitely more adjustment to it at the time.

    I did however slightly stretch the springs on the two shoe at one time as well to get my early engagement. At the time there was no replacement springs for the two shoe anywhere. Everyone was out of stock and I could not make up my mind.. I was impressed enough with the Morini to get a three shoe and try it. The three shoe proved to have a awesome finesse done directly off Idle [for gears] for me a more precise slip at immediate engagement.. I did finally get some lighter springs but never tried them as with the N.V. duty cycle and all I had seen enough. On really long rides 15 miles [ think hills] it would get very hot to the touch at the hub. Camlifter never had any luck with the N.V. Mine never broke.

    The sweet spot for the 5.8 Morini and the 9.4 hp is 5500 to 6000 rpm where their power band shows up. The 9.4 Morini will seam ridiculous new when you get it? As the factory ships the three shoe 9.4 hp Morini to engage at about 10,000 rpms. Hope that helps.

    Edit I re read I see you are getting the S6.T. one
     
    #11 Goat Herder, Jan 26, 2011
    Last edited: Jan 26, 2011

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