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  1. #1
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    Home-brewed Belt-drive system [research stages]

    I've recently been looking into the Gates belt-drive system. (Mostly out of intellectual curiosity since i probably won't be able to afford it.) The first thing I noticed is that it looks strikingly similar to a to a timing belt system on a car, or any number of industrial applications.


    After finding the specs (tooth count/pitch for belts and pulleys) on the Gates/carbondrivesystems website,
    http://carbondrivesystems.com/cd_specs.php?lang=us, I decided to check my favorite online "hardware" store http://mcmaster.com. It turns out they have belts and pulley in similar sizes (tooth counts and dimensions) to many of the ones produced by Gates. They even have carbon reinforced belts of the same tooth count and pitch (8mm) which is used widely in the automotive world. This got me thinking... how hard would it be to adapt a 50tooth cam gear onto a crank. I would wager that the two below could be adapted to a crank rather easily with minor machine work (milling, drillling/tapping), by the looks of the you could even choose your own offset for correct chain-line (belt-line?)





    The rear gear/pulley may not be as easy to source, ( at least one that will fit with minimal modifications) However, it shouldn't be hard to find one with the correct tooth count and pitch since 8mm pitch is pretty standard. I'm thinking a water pump pulley may be the ideal candidate. Here is a Honda timing belt picture, notice 4 different potential rear pulleys, and this is just one car.



    Anyways, just wanted to share my recent brainstorming. I intend to go to the junkyard pretty soon and do some poking around and teeth counting. If i can do this for cheap enough I may just try it.

  2. #2
    Senior Member Steev's Avatar
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    My only suggestion is to start from a disc hub and use the 6 bolt pattern to connect the rear pulley to the hub rather than going for the thread-on system, assuming you're talking fixed rather than freewheel.

  3. #3
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    Seems to me that the car parts would be way overbuilt for a bike, and a car belt possibly too stiff since it's designed to deal with the stress and heat of much higher RPM and tension and runtime

    also you have to cut your seatstay.

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    Senior Member rustybrown's Avatar
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    As for the crank, it might be easier to run a keyed pulley with a one piece crank.

  5. #5
    * adriano's Avatar
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    how are you getting the bent on?

  6. #6
    Hiphopopotamus coma061's Avatar
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    I have had passing thoughts of a belt driven bike, too. What are the advantages? Is it just quieter? I will definitely keep tabs on this thread, especially if you figure it out with a "minimal" cost!
    Also, I think automotive belts would be ok as they are not hard to bend even when cold. However, the pulleys themselves may be overbuilt as far as weight is concerned. Please keep us posted!
    [SIGPIC][/SIGPIC]

  7. #7
    Fresh Garbage hairnet's Avatar
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    seems pretty cool. it would be nice if you knew someone with access to a mill.
    Quote Originally Posted by Scrodzilla View Post
    I'd rather ride a greasy bowling ball than one of those things.
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    Thanks for the input guys, I don't believe that the gear being over-engineered would be a problem. So long as the gears are fitted to the bike properly the only drawback would be they are slightly heavier than the Al ones that carbondrivesystems offers. The carbon reinforced belts at mcmaster.com are not automotive belts. If it is a problem, the gates belt could be used with the modified automotive pulleys with no problems since the tooth pitch and shape is the same.

    The necessity of frame modification is a huge drawback for me, which may derail (no pun intended) the whole idea. I have been talking about making a bamboo bike with a friend of mine. Maybe it will be our test mule.


    For $32 + the cost of welding this could be an option worth looking into (as far as cutting the seat stay)

    Last edited by Rapport; 05-26-10 at 09:02 PM.

  9. #9
    K2ProFlex baby! ilikebikes's Avatar
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    it will be cheaper to buy one, you'll see.
    You see, their morals, their code...it's a bad joke, dropped at the first sign of trouble. They're only as good as the world allows them to be. I'll show you. When the chips are down, these...These "civilized" people...they'll eat each other. See, I'm not a monster. I'm just ahead of the curve

  10. #10
    .;/., cleanupinaisle3's Avatar
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    Cool project. Good luck with it!

    Now, for my real question,

    can someone explain to me how a belt drive is different from a regular drivetrain besides the cog, belt or chain and chainring? Or is that it? Is the eccentric hub on that bike just for... belt tension? Or is there something I'm missing?

    i'm also very confused why that bike has a cha... i mean, belt guard. aren't they squeaky clean?
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    Fresh Garbage hairnet's Avatar
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    Quote Originally Posted by cleanupinaisle3 View Post
    i'm also very confused why that bike has a cha... i mean, belt guard. aren't they squeaky clean?
    well, still dont want pants to get caught and im sure road grim still works its way around the drive train
    Quote Originally Posted by Scrodzilla View Post
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  12. #12
    Goon
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    So, what's the downside to th belt drive? is it heavier? less efficient energy transfer?

    What about those shaft driven bikes?

    Chain is better than shaft driven bikes, but is belt driven superior in all ways? Are you, like shaft driven, unable to have anything but SS or internal shifting?
    No matter how bad things get, they can't get any better, and they can't get any worse, things are what they are, so you better get used to it Nancy, quit your B*tchin'

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  13. #13
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    Quote Originally Posted by ilikebikes View Post
    it will be cheaper to buy one, you'll see.
    Well i am confident I can adapt a 50t cam gear into a front "chainring" for cheaper than ~$150 As long as I can find a rear gear to make work with minimal machining then I will be in business, and much cheaper than the ~$400 it will cost to buy the parts (not counting frame modification). Point is, if I can't do it for cheap i'm not going to do it, but you may be right.

    Quote Originally Posted by cg1985 View Post
    So, what's the downside to th belt drive? is it heavier? less efficient energy transfer?

    What about those shaft driven bikes?

    Chain is better than shaft driven bikes, but is belt driven superior in all ways? Are you, like shaft driven, unable to have anything but SS or internal shifting?
    A chain is really hard to beat, and the advantages of belt drive are few. It's slightly lighter, more durable, cleaner, quieter, and of comparable efficiency if it's a SS. BUT it can only be a SS or internally geared.

  14. #14
    Goon
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    Quote Originally Posted by Rapport View Post
    Well i am confident I can adapt a 50t cam gear into a front "chainring" for cheaper than ~$150 As long as I can find a rear gear to make work with minimal machining then I will be in business, and much cheaper than the ~$400 it will cost to buy the parts (not counting frame modification). Point is, if I can't do it for cheap i'm not going to do it, but you may be right.



    A chain is really hard to beat, and the advantages of belt drive are few. It's slightly lighter, more durable, cleaner, quieter, and of comparable efficiency if it's a SS. BUT it can only be a SS or internally geared.
    How would it be lighter? I mean, Sure the belt itself is lighter, but the larger cog/chainring would balance that out at least somewhat, so for an SS it might be ok, but if you add an Internal Shifting system, those tend to be much heavier than traditional derailleurs.
    Last edited by cg1985; 05-26-10 at 10:18 PM. Reason: sleepy.
    No matter how bad things get, they can't get any better, and they can't get any worse, things are what they are, so you better get used to it Nancy, quit your B*tchin'

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  15. #15
    coasterbrakelockup lz4005's Avatar
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    Quote Originally Posted by coma061 View Post
    I have had passing thoughts of a belt driven bike, too. What are the advantages? Is it just quieter?
    I think the biggest advantage is that you never have to lubricate them. Having a clean, maintenance free transmission would be an advantage for people who do multimodal commutes on folding bikes* in fancy office clothes. Same for rental fleets near salt water.

    For most bike applications, though, they aren't better than a chain. Or at least the disadvantages (SS or IGH only, proprietary parts, etc) probably outweigh the benefits.


    *some folding bike designs also wouldn't require a gap in the frame, if the rear isn't triangulated.
    Ride lots, have fun, skid often!

  16. #16
    K2ProFlex baby! ilikebikes's Avatar
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    Quote Originally Posted by Rapport View Post
    Well i am confident I can adapt a 50t cam gear into a front "chainring" for cheaper than ~$150 As long as I can find a rear gear to make work with minimal machining then I will be in business, and much cheaper than the ~$400 it will cost to buy the parts (not counting frame modification). Point is, if I can't do it for cheap i'm not going to do it, but you may be right.



    A chain is really hard to beat, and the advantages of belt drive are few. It's slightly lighter, more durable, cleaner, quieter, and of comparable efficiency if it's a SS. BUT it can only be a SS or internally geared.

    Please do count the frame and the modification. ;0)
    You see, their morals, their code...it's a bad joke, dropped at the first sign of trouble. They're only as good as the world allows them to be. I'll show you. When the chips are down, these...These "civilized" people...they'll eat each other. See, I'm not a monster. I'm just ahead of the curve

  17. #17
    AEO
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    find a frame with elevated chainstays
    weld or braze one some horizontal dropouts to it.
    Food for thought: if you aren't dead by 2050, you and your entire family will be within a few years from starvation. Now that is a cruel gift to leave for your offspring. ;)
    http://sanfrancisco.ibtimes.com/arti...ger-photos.htm

  18. #18
    Senior Member FlatSix911's Avatar
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    Interesting idea ... more project photos please ...
    You cannot help the poor by destroying the rich.
    You cannot strengthen the weak by weakening the strong.
    You cannot bring about prosperity by discouraging thrift.
    You cannot lift the wage earner up by pulling the wage payer down.
    You cannot further the brotherhood of man by inciting class hatred.

  19. #19
    THE STUFFED Leukybear's Avatar
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    Quote Originally Posted by AEO View Post
    find a frame with elevated chainstays
    weld or braze one some horizontal dropouts to it.
    Cool it'll be a starfµckers xenon then!

  20. #20
    AEO
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    I think most manufacturers have that silly cutout because they're just retrofitting their existing frames with inferior cutouts for belts, instead of a proper frame that avoids the cutout all together.
    Food for thought: if you aren't dead by 2050, you and your entire family will be within a few years from starvation. Now that is a cruel gift to leave for your offspring. ;)
    http://sanfrancisco.ibtimes.com/arti...ger-photos.htm

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