Dual Drive Sprockets

Discussion in 'Performance Mods' started by etheric, Jan 29, 2007.

  1. etheric

    etheric Guest

    There has been a bit of brainstorming over here and I know this idea is still coming along, so lets get the juicy bits into the tech forum.

    The idea is to mount two different drive gears on the rear, basically a pulling gear and a speed gear. But clearly we want it to switch with as little work as possible.

    This guy did it by adding/removing a length of chain everytime, which seems like way too much effort to me.

    I wonder if a giant (chainring) ghostring could work for the speed gear, then just switch to a cassette sprocket ghostring for the climbing gear?
    I am having trouble imagining how much slack would be present and if that could be eaten up by the the ghostring.

    They mentioned in the Motokruisers thread that the guy had to use single speed/BMX chain so that alignment wasn't as big of a pain as it would be with the fatty chain that is provided.

    Also, I think this may be relatively easy on some bikes, clearance wise, but I could see some bike frames not being accomidating at all for the multiple chain lines.
     

  2. pianoman8t8

    pianoman8t8 Guest

    yeah, i figured that if i had a 44 tooth chain sprocket compared to a 30 tooth sprocket, there would be just under 7.5" of slack added on to whatever slack there already is on the stationary chain tensioner... i have a couple ideas, but i'm gonna wait until i get my license back from the state (dang speeding tickets) and then i'll bring my bike here to college with me, where i can work on it in the machine shop, where i have the materials to work with on hand, and where i have more tools and time rather than just on the weekend. The use of the regular bicycle chain sounds good, thought, seeing as it is much thinner/narrower, (if that's word), and it would take less room to "shift" over to the other sprocket. Also, with the bicycle chain you could have more "freedom" of alignment depending on the thickness of the gears, but i'll have to wait and see again when i get the bike down here, because we have some plate steel that is around 90 or 100 thousanths thick (.09"-.1") which would be ideal for making a little thinner for the bicycle chain. There again, I would have to purchase dax's 10 tooth bycycle chain sprocket for the engine side of the drive because the 9 tooth that is currently installed is too thick for the bicycle chain, as it's made for the thicker #415 chain. But there again, if you used regular sprockets like the 44 tooth and such, I've noticed that there is quite a bit difference between what the inside of the chain can take and the thickness of the sprocket. All rambling aside, I think I'll stay with the #415 chain because first, i have plenty of room to work with between the frame and the tire, and the chain is wide enough to have some side/angle play/clearance if it were to shift over 1 or 2 or 3 degrees from where it currently is.......wow....lot of thought....When I get more into actually making this contraption, I'll have more info or something...But it won't be too hard to make the sprocket. Could you tell me what a ghostring is? I have no idea what that is. My idea for a tensioner is the take the one that's on there, and instead of having the chain go "over" the top of it, take the tensioner and move it "down" the frame tube towards the front of the bike and run the chain "under" the idler wheel, so that the chain is pulling up on the wheel, and not forcing it down when starting the engine. Then the rest idea is to have a somewhat stiff srping to pull down on the top part of the drive chain. I wish i could draw a picture of what my idea is...maybe i will, then scan it, then post it...but beware my drawing skills are at best minimal....
     
  3. pianoman8t8

    pianoman8t8 Guest

    so, this is a ROUGH IDEA of what I might try to do...obviously this sketch is basic, just enough to get an idea of what i might try to do...I figures out how much slack there would be, and drew accordingly. The one with all the idlers is how much slack there would actually be if i went from 44 to 30 teeth. I'm gonna try to come up with somethingthat looks better and requires less work to make if i were to make it. and less hardware. ei: springs, idler wheels, etc...

    289_img001_2.jpg

    289_img002_1.jpg

    keep in mind that this is a rough idea, not exactly what i'm gonna try and do.

    -Ryan a.k.a. pianoman
     
    Last edited by a moderator: Apr 3, 2008
  4. Blaze

    Blaze Guest

  5. nogoodnic42

    nogoodnic42 Guest

    Hi guys, when talking about taking up six or more teeth of slack (three + inches of chain) I don't think the ghost ring will work. I'm afraid that in order to get a large enough GR in place you will have frame clearance issues...Kelly
     
  6. apratt

    apratt Guest

    Instead of a dual rear sprodket, because you end up with so much chain slack. Would it be posible to have a dual front sprocket (the motor drive sprocket), just may have to deal with the cover. Just a thought.
     
  7. pianoman8t8

    pianoman8t8 Guest

    I was thinking about that a little while back, but then you'd have to make a new cover thing, and then extend the clutch mechanism thingy... I don't know, i'll have to look into it some more, because I can also make little sprockets like that, too.
     
  8. pianoman8t8

    pianoman8t8 Guest

    if you can go 38 MPH with the 9 tooth sprocket along with the 44 tooth chain sprocket, then the engine will revving 9,000 RPM. Using that number, putting on a 12 tooth sprocket, well, wait a minute..... there wouldn't be any room for a larger diameter sprocket...crap...because of the other cover next to the cover that covers the 9 tooth sprocket....hmmmm but anyway, if you put on a 12 tooth sprocket, you can max at 45.7 MPH, and using a 15 tooth, max at 57 MPH...I'm not sure if i'd want to go THAT fast, but I would sure like to try it! There's a long story with me and a bike accident when i was kid, ended up losing a kidney, but I haven't learned one bit. In the past 3 years, I've gone through 4 mountain bikes, 2 BMX bikes, and a road bike (27" tires)..but anyway, I'll have to look closer at the idea of adding sprockets at the engine end of the chain.....
     
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