Shiftable Gears

Discussion in 'Performance Mods' started by SlicerDicer, May 5, 2007.

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  1. SlicerDicer

    SlicerDicer Guest

    Ok I had a thought. Rear derailer? out of the question. Front! might just work? Crude image below and I will explain.



    Fixed the image as noted in post below.

    Ok there is multiple rear sprockets I can get in size. I am thinking if I stack 3 of them. 48, 44, 36. Once stacked I can run a stainless steel pipe so that I can mount a crankset front derailer on it. That would allow the chain to pass through and kick from one cog to another on the rear allowing for use of all 3 cogs? More or less giving the capability to have somewhat shiftable gears?

    What do you think? By the way I am horrible at explaining myself but I hope that this works. I am not a mechanic I am a computer nerd :lol:

  2. gone_fishin

    gone_fishin Guest

    using the front-derailer is a new concept here i think, i can see how it might be worth a shot, tho...
  3. SlicerDicer

    SlicerDicer Guest

    I searched around looking for information on it but I figure a front derailer can be used as its wider and able to handle the chain and really no "force" is pushed on it to a degree. So you would turn the wheel cogset almost to a crankset cogset so to speak. That was my thought

    oops I just noticed I connected the chain to the crank... Yeah its horrible drawing... I was meaning to connect that chain that is on the crank to the engine :razz:

    Would anybody be able to get me the width of the chain used on a 80cc?

    Image Credit to

    As seen in this image if needed I should be able to expand the size of the cage with the cage screw? As well I might be able to just bend the cage itself and make the chain fit.

    if my brain is working right a derailer like this should fit just fine ontop of those cogs and allow for changing? As most front derailers move up/down as well as in/out.
  4. Guest

    Guest Guest

    415 or .081 is the size I believe you are looking for.

    BTW- "empirical testing" is always the best!
  5. joeranton

    joeranton Guest

    By using front deraileurs, how would you go about keeping the chain tensioned? I am a visual learner, so I would appreciate some pics or somethin that I can put in my mind.
  6. Bikes with front derailleurs still require a rear derailleur or spring-loaded tensioner in order to work, otherwise you wouldn't be able to change the gears.
  7. SlicerDicer

    SlicerDicer Guest


    Ok another terrible crude image.

    The way it will work on this "does not include stack/derailer".

    The roller will be one of the rollers I can get for the chain but instead of it being just fixed. I will attach it to a simple hinge and then attach that to the bike frame so it can move up/down. Once that is done I will take a spring attach it to the hinge/roller and then attach that to the bike frame. Once done the spring will be under tension as soon as the roller is lifted. This will allow for a bit of tension to be adjusted as the chain moves up/down and should not need that much more play.. if it does I supose I could come up with something a bit more complex but this is a starter idea.

    I may need to make a roller fold in on itself similar to a rear derailer but that should not be too difficult to do. In all honesty I have no idea how I would do it till I have it in my hand. But I am sure there is a way to do it and this is just a start idea... Not to mention these are extremely hard for me to draw :) I need a dang tablet.. maybe I will just render it in Povray and be done with it.
  8. gone_fishin

    gone_fishin Guest

    i don't have much input about the gear-topic, but the simple spring-tensioner you'll be needing will be an easy "afterthought"...i'd love to see this work 8)

    edit: you were a step ahead of me :lol:
  9. SlicerDicer

    SlicerDicer Guest

    I wont embed it as it will be huge. I am rendering the bicycle here if you wish to see the start of it. I will be updating it as i get more and more completed. This is just the bike frame and tire so far.

    EDIT: This is a mtn bike frame as it is easier to render.

    I just completely changed the lighting of it to be able to see it easier. All that is lacking in the rendering above is the labels as well as the front derailer to make a better drawing of it :)
  10. SlicerDicer

    SlicerDicer Guest

    Alrighty! I got the image done.
    MBc EDIT: i removed the image tags, click the link for the pic. ".png" files are much too
    large for dial-up members to wait for.

    This is my idea. I however flipped the chain tensioner around and did a bit of playing with it. The reason for this is due to the way the chain goes around. I assume from just thinking about it that the bottom chain will be the driving and top will be return. However this leaves me with a bit of a pickle as I need to switch it around to where the derailer is on the bottom at the drive chain. I will update the image to reflect this when I have a bit more time. This is why I did not label the derailer or cogset. I will also render the cogset/derailer itself and make it understandable a bit easier.

    This is my plans for now of course that does not mean they will not change. I took the design for the tensioner from a normal rear bicycle derailer as it seems that would allow for more slack chain being usable. Right now the pipe that runs from the seat is the rear carrier :)

    Ok question.

    44, 42, 36, 30? doable? will that sprocket work? or one like it?
  11. azbill

    azbill Active Member

    I believe that you will want the tensioner on the bottom of chain, the engine will pull from top, and shred tensioner quickly, at least, thats what I was told about the tensioner in the bike kit
  12. SlicerDicer

    SlicerDicer Guest

    It really makes no matter on top/bottom to me. I am just guessing here as I do not have my engine yet.

    I do know that the tensioner needs to be on the return leg as there is really no tension on the chain on that side. Not like the driving side of the chain anyway.
  13. Lukass

    Lukass Guest

    The bottom of the chain is the return.

    As much as I would love to see this work (48 and a 36 would be sweet you wouldn't need the one in between) I'm pretty convinced it just isn't going to happen.

    Have you ever looked at a bike cassette or the ring gears? You will notice they have cut down teeth in some spots and teeth machined on an angle to allow the chain to run off the gear it is currently on. When you actually get a sprocket and chain in your hands you will appreciate how hard it is going to be to get the chain to run off this gear.

    Based on the thickness of the chain and the sprockets you will have roughly 15mm between the centreline of the two rear sprockets. I don't know your exact length but I work that out to be roughly 3 degrees deflection from the front sprocket centreline. This is an awful lot for a chain, you can get away with it but it will be noisy as hell and create extra drag.

    Have you got enough chain clearance from the frame to fit another sprocket?

    You can't run a spring loaded tensioner because the slack side of the chain becomes the loaded side when you pop the clutch to start it.

    There is nothing insurmountable there but I think you have your work cut out for you.
  14. This is how I am planning on shifting gears on my mountain bike.


    I'm probably going to have to remove my pedals becuase i fear i may injure myself if my feet were to come in contact with the crank.

    I have sheetmetal to make a guard for

    Comments are welcome, yays and nays.
  15. SlicerDicer

    SlicerDicer Guest

    lol I thought you were going to rip your legs off till I read about the crank. Why not just drive the rear sprocket and use that if your going to remove the pedals?
  16. Because then I would be limited to only one gear while riding....

    doing it this way would enable me to run through my 6 rear gears while already in high gear up front, the 3rd gear.

    The centrifugal clutch on my engine should allow me to pedal when the engine is idling...

    Atleast thats the plan, lol.

    I gotta get a picture of this thing soon...
    I'll probably get laughed right out of here, lol.
  17. gone_fishin

    gone_fishin Guest

  18. I have a 1 piece crank.

    So by buying the...

    -Freewheel crank adapter
    -Cyclone crankset

    I'd be well on my way, but...

    Aren't these a direct replacement for 3 piece cranks only?
  19. JosephGarcia

    JosephGarcia Guest

    How about using a Jackshaft to transfer engine power to the bicycle drive chain, using the bicycle gears. It would require a chain that not only fits the bicycle pedal drive, but also handle engine torque. It would also require abandoning the pedals as an alternate power source. Maybe keeping them on (but not actually connected to the rear sprockets) to be "legal" They will not notice a small chain missing from that sprocket to the rear.

    If this has been mentioned already, it's becuase I'm tired and will read all of your guys posts later, :grin: in which case this post will be edited.
  20. azbill

    azbill Active Member

    if you make it and show pics
    (even if it doesn't work)
    aint nobody here gonna laugh (at least, not too hard) 8)
    too many tinkerers and mad scientists :lol: :lol: :lol: