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  1. #1
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    Dual drive system

    Hey fellas,

    I've been searching the web for a system like this. Basically, I am looking to complete a bike with two chain rings at the crank and having dual freewheels on the back hub. Is this even possible? Please give any input you want, stupid idea, good idea, etc. Any info will help. I will post a drawing of what I am thinking of for all of you visual learners.

    Thanks

  2. #2
    Senior Member seau grateau's Avatar
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    Don't.
    Quote Originally Posted by adriano View Post
    thanckx.
    Quote Originally Posted by Nagrom_ View Post
    "I made love to your mother dozens of times last week, and she doesnt know what a worn chain ring looks like"

  3. #3
    Morton Nagrom_'s Avatar
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    Theoretically I assume it would be possible if you used two of the same drive crank arms, and a symmetrical BB, and the same gearing on each side.

    Sounds kinda neat actually. Serves no purpose, but eh.
    Quote Originally Posted by seau grateau View Post
    No offense but you're an idiot.
    PedalRoom

  4. #4
    Senior Member Bat56's Avatar
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    It's possible. It's been done. It's pure novelty, no practical use; just extra weight.

  5. #5
    Veteran Bastard Scrodzilla's Avatar
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    SSFG engineering at its finest. You should have put the word "thread" in the title so Carleton could **** his pants.

  6. #6
    THE STUFFED Leukybear's Avatar
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  7. #7
    Senior Member Adrian_'s Avatar
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    I understand how it could work fixed but with freewheels wouldn't the freewheel on the left side just spin not doing anything?
    Who needs a sig....oh wait.

  8. #8
    Senior Member seau grateau's Avatar
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    I'm pretty sure it would prevent you from coasting.
    Quote Originally Posted by adriano View Post
    thanckx.
    Quote Originally Posted by Nagrom_ View Post
    "I made love to your mother dozens of times last week, and she doesnt know what a worn chain ring looks like"

  9. #9
    Veteran Bastard Scrodzilla's Avatar
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    Quote Originally Posted by seau grateau View Post
    I'm pretty sure it would prevent you from coasting.
    You know...just like a fixed cog but more stupid.

  10. #10
    Veteran Bastard Scrodzilla's Avatar
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    Quote Originally Posted by Leukybear View Post
    Both chains upside down FTW.

  11. #11
    ÖöÖöÖöÖöÖö Dannihilator's Avatar
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    Quote Originally Posted by Adrian_ View Post
    I understand how it could work fixed but with freewheels wouldn't the freewheel on the left side just spin not doing anything?
    ACS makes a left side drive freewheel, called the south paw.
    Strike like an eagle and sacrifice the dove.
    Words and Stuff.

  12. #12
    THE STUFFED Leukybear's Avatar
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    Quote Originally Posted by Scrodzilla View Post
    Both chains upside down FTW.
    What kills me is a well respected shop built this monstrocity.... the same guys that make the broakland bikes...

  13. #13
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    They do make left side drive freewheels: http://www.amazon.com/ACS-SouthPaw-L...uckduckgo-d-20

    It's been done, in practice they would never both be engaged at the same time.

    Examples: http://www.ridemonkey.com/forums/f85...a-unit-130683/
    Last edited by wesmamyke; 09-07-12 at 09:10 PM.

  14. #14
    ÖöÖöÖöÖöÖö Dannihilator's Avatar
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    I think it's the dumbest thing since the slapchop.
    Strike like an eagle and sacrifice the dove.
    Words and Stuff.

  15. #15
    7-speed doomsday prepper ThermionicScott's Avatar
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    If you looped one of the chains into a figure-eight, you could have a retro-direct. But that would disqualify you from the Single-speed forum...
    Quote Originally Posted by chandltp View Post
    There's no such thing as too far.. just lack of time
    RUSA #7498

  16. #16
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    Haha wow I did not expect to have this many replies. Thanks for all the heads up, I was just looking at doing something different and a new project to play around with. I appreciate it fellas and I look to be talking with you guys more on here. Take it easy.

  17. #17
    Sir Fallalot wroomwroomoops's Avatar
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    Quote Originally Posted by Leukybear View Post
    What I see here are two track cogs on the rear wheel. If that's the case, then this setup can't possibly work well, because either one of the track cogs will be stripped, or at the very least be loosened from the hub, immediately. IOW, one of the drivetrains is just tagging along while the other one does all the.... driving.

    A stupid way to add 1 Kg of unnecessary components to your bike, plus it will actually make the power transmission less efficient. And it becomes horribly inefficient if you don't maintain (clean, lube) the "inactive" chain.

    EDIT: not sure what would happen if one used two freewheels, though. Maybe then it could work? Didn't think through that scenario.

    EDIT2: I came to the conclusion, after some thinking, that this setup could work (correctly, i. e. with drive on both drivetrains) if one had cogs that aren't threaded onto the hub, but bolted or splined - and provided that the two cogs are exactly identical. And that the chainrings are symmetrical.
    Last edited by wroomwroomoops; 09-09-12 at 07:12 AM.

  18. #18
    Elitist carleton's Avatar
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    Quote Originally Posted by Scrodzilla View Post
    SSFG engineering at its finest. You should have put the word "thread" in the title so Carleton could **** his pants.

  19. #19
    Kitten Legion Master
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    Quote Originally Posted by carleton View Post
    Did you just say Kilo TT?!

  20. #20
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    Quote Originally Posted by wroomwroomoops View Post
    What I see here are two track cogs on the rear wheel. If that's the case, then this setup can't possibly work well, because either one of the track cogs will be stripped, or at the very least be loosened from the hub, immediately.
    If properly installed, it will work just fine. You shouldn't strip or loosen a cog. My thought is that since the cogs are threaded on, the will most likely be within a couple degrees of each other, so unless they and the hub are machined perfectly, one cog will be doing more propelling and one will be doing more braking.
    Quote Originally Posted by Santaria View Post
    because physics has more street cred than tarckstars.

  21. #21
    Sir Fallalot wroomwroomoops's Avatar
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    Quote Originally Posted by ianjk View Post
    so unless they and the hub are machined perfectly, one cog will be doing more propelling and one will be doing more braking.
    IOW, the setup will never work well: you have to spin both chainrings and pull both chains all the time, so the efficiency is reduced while only one drivetrain is actually doing the driving.

    I'm glad we agree on the main points.

  22. #22
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    Wouldn't your left pedal keep coming unscrewed? Or is there some kind of tandem crankarm you'd have to use on the left side?

  23. #23
    Senior Member Spoonrobot's Avatar
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    You can prevent precession by using a conical washer.

  24. #24
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    Quote Originally Posted by Mr Yum Yums View Post
    Hey fellas,

    I've been searching the web for a system like this. Basically, I am looking to complete a bike with two chain rings at the crank and having dual freewheels on the back hub. Is this even possible? Please give any input you want, stupid idea, good idea, etc. Any info will help. I will post a drawing of what I am thinking of for all of you visual learners.

    Thanks
    op specified freewheels & did not say anything about requiring the rings & fws to be on opposite sides of the bike...


  25. #25
    Sir Fallalot wroomwroomoops's Avatar
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    ^^Good point!

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