Tandem w/ shift kit?

Discussion in 'Motorized Bicycle General Discussion' started by smittyman, Feb 18, 2009.

  1. smittyman

    smittyman New Member

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    Hey all you master fabricaters...I have been dreaming of a tandem with a shift kit from SBP. I am thinking that if you had both chainring sprockets freewheeling that it would work perfectly and there would be no need for the long drive-chain setup. Has anyone done this yet? I have been shopping for used tandems that I can try this on. Any thoughts, problems or ideas? Thanks, Smitty.
     
  2. Ghost0

    Ghost0 New Member

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    I would love to assist you with this project but until I can see the bike, its mounting options and drive train there is not much I can do at this point. Start posting photos of possible donor bikes and I will make some recommendations.
     
  3. mwarning

    mwarning New Member

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    May I submit a donor bike?! I've got experience building two motorbikes in the past year and am ready for my next challenge. The biggest drawback to these things is riding side by side while trying to talk to someone....down right dangerous! So why not a tandem? I started poking around on the Forum for info while at the same time looking for a bike to be my next victim. Just picked up this 5-speed tandem on Saturday.

    This post led me to your site, and I think a shift kit would be the right way to go on a tandem. I really don't need 2 big long chains slapping around. After looking over your kit, here's my thoughts

    Mount the motor up front in the "normal" spot. Jack shaft across, and then chain back to the free wheel sprocket in the second rider's(2) position. Somehow we'd have to add a sprocket to the "hard" side of the (2) freewheel sprocket, and chain that up to the first rider's(1) crank...that way no mods would have to be done to the (1) assembly. From the pictures you can see the (2) sprockets are bolted together, so it would nice to take the sprocket we need and add it to your freewheel assembly.

    What do you think? Any info you can provide would be helpful---looking forward to getting started!
     

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  4. Ghost0

    Ghost0 New Member

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    I think your idea should work. My only concern would be the chain from the jackshaft to the stoker crank will be a bit long but it shouldn't be a problem. Now that we have a good selection of chainrings you should be able to get the gearing you like. Oh but you would need a freewheel on the front crank as well or your pedals would be spinning. So you would need freewheels on both cranks.
     
  5. mwarning

    mwarning New Member

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    Hi Ghost0, thanks for the quick response! I've never been able to see the shift kit in 3-D, so I'm guessing how this thing is built. I would like to connect the captain's crank sprocket to the freewheel portion of the stoker's crank (I googled "stoker crank" so now I know the correct lingo). I envision a sprocket attached to the stoker freewheel assembly that I can connect to the captain sprocket....both will freewheel together...I think.

    Are there better pictures of the assembly somewhere out there in case I am totally missing the boat on this thing?
     
  6. Ghost0

    Ghost0 New Member

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    Download the installation instructions and it gives you a pretty good idea of how it all works.
     
  7. ...ladies

    ...ladies New Member

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    I'v got a tandem but it wouldn't work with a happy time.. Might try a rear rack engine sometime tho.. :)
     
  8. mwarning

    mwarning New Member

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    OK, Ghost0, I looked over the manual and have a good idea how it works. Can you tell me the difference between the Standard front freewheel and the Heavy Duty version? How does one determine if the Heavy Duty version should be used over the Standard version? Hard to tell from the pictures, but I'm pretty sure each has the internal threads on one end and the 4 lobe crown on the other, right?

    Sorry for all the questions but I would like to make somewhat sure the unit can be modified to do what I need.
     
  9. Ghost0

    Ghost0 New Member

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    Functionally they are the same as one is just a direct replacement for the other. One is made in Taiwan and one is made in the USA. I think that pretty much sums it up.
     
  10. mwarning

    mwarning New Member

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    10-4, I can do that math. Just a little more cipherin' to do and I can get this project underway----
     
  11. mwarning

    mwarning New Member

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    Couple more questions for Ghost0----my seat tube diameter is 1.010". Do you need this info just to size the pipe clamp for the jack shaft? If I pick the 1.125" from the order form, will that work OK?

    Also I will be needing the 3 piece conversion for the crank. The bike has a total width of just under 3" (about 2" from bearing race to bearing race) and an inside through clearance of 1-5/8"...see any problems with the conversion kit fitting in there?

    Thanks again for the answers!
     
  12. Ghost0

    Ghost0 New Member

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    The 1.125 should be fine but if it were me I would go get some 1" clamps to replace the 1.125 that come with the kit. The size is also critical for the jump stop that comes with the kit. They don't make smaller than the 1.125 but should be easy enough to shim it. The bottom bracket conversion should fit fine.
     
  13. mwarning

    mwarning New Member

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    Got 'er done! This was done using just one free wheel. The engine on this bike is pretty lame, so it doesn't push our 400 pounds very well, but having the gears sure helps! Has anyone out there come across any other tandems with a shift kit on the forum? I'd like to swap stories....
     

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  14. Pablo

    Pablo Master Bike Builder & Forum Sponsor

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    One word: Whoa. Ok two words. Wow.

    Nice work.
     
  15. BarelyAWake

    BarelyAWake New Member

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    Sweet ride mwarning! Those chainguards are awesome - you musta fabbed them yourself? Very, very nice (^)

    "The engine on this bike is pretty lame" :(

    Ya know, peerin' at yer pics it looks as if ya might have one of the dreaded catalytic converter mufflers on there, I've two different friends that have had that pipe on their ride and it alone seems to sap a lot of power - you may wish to replace it with a tuned pipe...

    You're prolly not interested in speed - but it does help with low end power as well as waking up the powerband a bit. I dunno if you altered the intake and exhaust gaskets any, but they too can act like a "governor" and limit the power output - particularly at higher RPMs (like when yer about to shift). It's a "quick and easy", as is modding the manifolds themselves, here's a link if yer curious: http://motorbicycling.com/f13/basic-porting-16646.html

    No any one thing really gives you gobs more power, but all together it can really help for a stronger, smoother runnin' engine.

    Ya defo outa hand yer cam to yer passenger to make a lil vid if ya can ;)
     
  16. pj-pirate

    pj-pirate New Member

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    When you get a shift kit---GET the HD freewheel! My standard one lasted just short of 5 miles before the Asian parts turned loose--the HD American made one I replaced it with has over 300 miles of many shifts in mountain trails.
     
  17. toker_ace

    toker_ace Member

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    Put you a SCRAM I-Motion 3 speed hub on the rear and you'll be set-up! I've had my hub on my shift kit for about a year now.I highly recommend these hubs over all others!
     

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