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  1. #1
    You know you want to. Eatadonut's Avatar
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    fixie chain tensioner

    Someone call me stupid. What would be the problem with a screw-adjusted chainstay-mounted tensioner? It seems to me like that would allow you to quickly and easily turn any junker into a fixie (provided you have a wheel) for less than $10 in parts without worrying about chain tension/length or finding a magic ratio. Plus when the rusty chain gets longer, you just tighten it up.

    Obviously this is a solution looking for a problem on pricier bikes, but for the dumpster bikes you take barhopping, it seems like a good idea.
    Weather today: Hot. Humid. Potholes.

  2. #2
    70mm4$!n! freeskihp's Avatar
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    those types of chain tensioners can't take the stress of backpedaling and so they are fine for SS but not fixed
    "The only reasons anyone should ever ride in the rain is because a) youíve had your license to operate a motor vehicle suspended by the state. b) youíre in a bike race in which case youíre not allowed to use fenders anyway. c) youíre from Portland- in which case my main problem is with your neck beard- not your bicycle...If you need to train when itís pissing rain- buy a trainer or one of those cheap charter flights to Mallorca."

  3. #3
    You know you want to. Eatadonut's Avatar
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    Quote Originally Posted by freeskihp
    those types of chain tensioners can't take the stress of backpedaling and so they are fine for SS but not fixed
    Where's the weak point? I can't believe the chain pushes that hard. I could do the math if someone could provide me a ballpark of the coef. of friction between a 23mm rubber tire and smooth concrete.
    Weather today: Hot. Humid. Potholes.

  4. #4
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    Quote Originally Posted by Eatadonut
    Where's the weak point? I can't believe the chain pushes that hard. I could do the math if someone could provide me a ballpark of the coef. of friction between a 23mm rubber tire and smooth concrete.
    1.00 - 4.00 Static (your call)
    0.80 Kinetic

  5. #5
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    nevermind what these bikenerds say i say do it, with platform peddals.
    wrangeling dudes

  6. #6
    You know you want to. Eatadonut's Avatar
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    Why did I suggest I could do this? It's been 3 years since I did a single math problem more complicated than figuring the tip. It's coming back, but slowly.
    Weather today: Hot. Humid. Potholes.

  7. #7
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    go ahead, but when your chain derails and locks your wheel, don't come running to us complaining how much it hurt when your face skidded down the street. which I really really hope never happens to you or anyone else.
    Quote Originally Posted by erikinop
    i used to wear a faceless, CCM hockey helmet that i spray painted chrome. some thought it was cool. others thought it was entirely ghetto and stupid. regardless, it was all i had after getting two concussions in a week. the second one knocked me out cold on the side of the road. straight up **** victim style, in a ditch, body all mangled. fortunately i came two after a car honked a horn and a friend took me to the e.r.

  8. #8
    You know you want to. Eatadonut's Avatar
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    From some math, I've figured the most a 200 lb rider like myself could push downward at the tensioner, assuming my bicycle geometry (1984 trek 540), with all my weight on the back wheel, before skidding, is 84 pounds.

    can anyone tell me the crumple load of a standard road chainstay (EDIT: reynolds 531)? I suspect it's more than that, since I've stood on my chainstays before and had no problems. So I believe the frame, at least, is not the weak point. Then the tensioner can be the only other question - and I don't see how that could be the weak point. Making a steel tensioner that can handle even 100# of vertical force should be pretty simple. A coke can will handle that.
    Weather today: Hot. Humid. Potholes.

  9. #9
    You know you want to. Eatadonut's Avatar
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    Quote Originally Posted by heebro
    go ahead, but when your chain derails and locks your wheel, don't come running to us complaining how much it hurt when your face skidded down the street. which I really really hope never happens to you or anyone else.
    Why do people make posts like this? Do you think it helps?

    And for the record, if I did this and it failed in a spectacular fashion, you can bet your sweet heiny I'll be back on here with pics. I might even mention how much it hurt.
    Weather today: Hot. Humid. Potholes.

  10. #10
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    Quote Originally Posted by Eatadonut
    Why do people make posts like this? Do you think it helps?

    And for the record, if I did this and it failed in a spectacular fashion, you can bet your sweet heiny I'll be back on here with pics. I might even mention how much it hurt.
    ok, you are right. go for it!

    I did think it was helpful actually.

    seriously, if you are going to make the thing urself then it might work. I actually thought you were referring to a surly type tensioner. now realize I wasn't paying attention.

    that said, IMNSHO your efforts would be better spent learning to build wheels and making yourself a nice inexpensive rear wheel that you can swap from one beater to another as you grow tired of them/break them etc. A sun cr18 rim, formula hub, and DT spokes won't hurt your pockets too much.

    and FYI I don't think reynolds ever made 531 stays. and you did ask for someone to call you stupid. also let us know where this dumpster full of reynolds 531 frames is...

    Quote Originally Posted by erikinop
    i used to wear a faceless, CCM hockey helmet that i spray painted chrome. some thought it was cool. others thought it was entirely ghetto and stupid. regardless, it was all i had after getting two concussions in a week. the second one knocked me out cold on the side of the road. straight up **** victim style, in a ditch, body all mangled. fortunately i came two after a car honked a horn and a friend took me to the e.r.

  11. #11
    You know you want to. Eatadonut's Avatar
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    Quote Originally Posted by heebro
    ok, you are right. go for it!

    I did think it was helpful actually.

    seriously, if you are going to make the thing urself then it might work. I actually thought you were referring to a surly type tensioner. now realize I wasn't paying attention.

    that said, IMNSHO your efforts would be better spent learning to build wheels and making yourself a nice inexpensive rear wheel that you can swap from one beater to another as you grow tired of them/break them etc. A sun cr18 rim, formula hub, and DT spokes won't hurt your pockets too much.

    and FYI I don't think reynolds ever made 531 stays. and you did ask for someone to call you stupid. also let us know where this dumpster full of reynolds 531 frames is...

    Well, the frame I based the geometry on is supposedly 531, according to the year and model number I found on a website that may or may not be reputable, and the half-destroyed serial number on my bottom bracket. Maybe the stays aren't 531 *shrug* I don't know.

    I actually build most of my own wheelsets these days. This thought arose this morning when I stared dolefully at the fixed (used to be a coaster brake, but it rusted into a fixie) cruiser that is sitting on my lawn. The nuts are so rusted you can't wrench them off, they'll dissolve first, so there's no adjusting the chain tension that way.

    And the dumpster full of 531 frames is at any college apartment complex in any college town, I would bet. That's where I've found a decent complete bike, a decent frame with rusted parts (the one I'm using now), and numerous craptastical bikes that I mangle in various ways. Just a quick glance in any time I took out the trash is all it takes.
    Weather today: Hot. Humid. Potholes.

  12. #12
    70mm4$!n! freeskihp's Avatar
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    straight from sheldon

    You cannot use a derailer on a fixed gear bike, even as a chain tensioner, because when you resist the rotation of the pedals, you would bend the derailer. This presents a problem if you want to use a frame with vertical dropouts as a fixed gear, because there's no easy way to adjust the chain tension. This is also true of chain tensioners sold for singlespeed coasting bikes, such as the Surly Singleator.

    Even the chain tensioners used for downhill mountain bike racing are not strong enough to withstand the stress of resisting the pedals. These tensioners have to clamp on to the chain stay, which is more or less round. There is no way to make one that would be secure, short of installing some sort of brazed-on fitting.
    "The only reasons anyone should ever ride in the rain is because a) youíve had your license to operate a motor vehicle suspended by the state. b) youíre in a bike race in which case youíre not allowed to use fenders anyway. c) youíre from Portland- in which case my main problem is with your neck beard- not your bicycle...If you need to train when itís pissing rain- buy a trainer or one of those cheap charter flights to Mallorca."

  13. #13
    we are 138 Philatio's Avatar
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    I remember seeing a fixed bike from fgg here a while ago (maybe a month or so?) that used a chain tensioner with a piece of rubber + ? added so that when you backpedaled the tensioner would stop at the chain stay and not break off or whatever. I am not really sure that's exactly how it worked, and I looked around the site but I wasn't able to find it again. Just thought I'd throw it out there, so I assume it is possible.

  14. #14
    Dog is my co-pilot 2manybikes's Avatar
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    You can make a bike with vert dropouts work without one anyway.
    Sheldon Brown has the insrtuctions, it worked great for my friends bike.

    Find my post Sheldon Brown.
    [SIGPIC][/SIGPIC]

  15. #15
    :jarckass: deathhare's Avatar
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    Quote Originally Posted by heebro
    go ahead, but when your chain derails and locks your wheel, don't come running to us complaining how much it hurt when your face skidded down the street. which I really really hope never happens to you or anyone else.
    Dude.... decent tensioners cost 5 bucks...which is WAY! too much to spend toward something as trivial as your safety and well being

  16. #16
    mousse de chocolat Moose's Avatar
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    Quote Originally Posted by deathhare
    Dude.... decent tensioners cost 5 bucks...which is WAY! too much to spend toward something as trivial as your safety and well being
    Dude...read the thread, he ain't talking about chain-tug type chain tensioners. What he's referring to does not exist, at least not for $5 anyway.

  17. #17
    Gone, but not forgotten Sheldon Brown's Avatar
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    Quote Originally Posted by 2manybikes
    You can make a bike with vert dropouts work without one anyway.
    Sheldon Brown has the insrtuctions, it worked great for my friends bike.

    Find my post Sheldon Brown.
    http://sheldonbrown.com/vertical

    Sheldon "Shazam!" Brown
    [COLOR=blue][CENTER][b]Harris Cyclery, West Newton, Massachusetts[/b]
    Phone 617-244-9772, FAX 617-244-1041
    [URL= http://harriscyclery.com] http://harriscyclery.com[/URL]
    Hard-to-find parts shipped Worldwide
    [URL=http://captainbike.com]http://captainbike.com[/URL]
    Useful articles about bicycles and cycling
    [URL=http://sheldonbrown.com]http://sheldonbrown.com[/URL] [/CENTER] [/COLOR]

  18. #18
    Taking "s" outta "Fast" AfterThisNap's Avatar
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    Newsflash:

    The physics are totally different if you use the springy type chain tensioner (surly), but put the pulley on the underside of the chain of a fixie. I'll let you guys battle it out.

    Carries suspicious allegiance to Brooklyn Machine Works.

  19. #19
    mousse de chocolat Moose's Avatar
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    Quote Originally Posted by AfterThisNap
    Newsflash:

    The physics are totally different if you use the springy type chain tensioner (surly), but put the pulley on the underside of the chain of a fixie. I'll let you guys battle it out.

    You can't use a spring loaded tensioner because when you apply backward force to the pedals, an inevitability on a fixed, the tensioner will give way and the chain will go slack above the chainring and cog. This can end up bad in many ways. The simple answer is you cannot use a spring loaded tensioner reliably on a fixed gear bike regardless of the direction it pushes the chain.

    Now if someone wants to try and figure out a way to make a rigid adjustable roller to take up slack in the chain, there's more room for debate.

  20. #20
    jack of one or two trades Aeroplane's Avatar
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    Quote Originally Posted by Moose
    The simple answer is you cannot use a spring loaded tensioner reliably on a fixed gear bike regardless of the direction it pushes the chain.

    Now if someone wants to try and figure out a way to make a rigid adjustable roller to take up slack in the chain, there's more room for debate.
    Some folks use a spring loaded tensioner in push-up mode with a cable-tie holding the tensioner to the stay. This would work pretty well in theory, at least as well as a rigid adjustable roller (rollenlager type).

    Using any sort of a tensioner is pretty half-assed though. Might as well do it one of the hack ways like Sheldon or LF used.
    Quote Originally Posted by Dr Irwin Goldstein
    Men should never ride bicycles. Riding should be banned and outlawed. It is
    the most irrational form of exercise I could ever bring to discussion.

  21. #21
    mousse de chocolat Moose's Avatar
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    Quote Originally Posted by Aeroplane
    Some folks use a spring loaded tensioner in push-up mode with a cable-tie holding the tensioner to the stay...
    These folks are puttin' the "OH!!" back in ghetto.

  22. #22
    Bike fiend. Analog's Avatar
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    Quote Originally Posted by Moose
    Now if someone wants to try and figure out a way to make a rigid adjustable roller to take up slack in the chain, there's more room for debate.


    I have one of these, and they include a rigid (and beefy) chain tensioner. I would think it could withstand a whole lot of force.

  23. #23
    Strange As Angels Fixxxie's Avatar
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    Quote Originally Posted by Analog


    I have one of these, and they include a rigid (and beefy) chain tensioner. I would think it could withstand a whole lot of force.
    Correct me if Im wrong but that isn't a fixed gear
    Quote Originally Posted by sefb222 View Post
    a good reason to form a demolition derby, for fixed gear bikes and the fools who love them.

  24. #24
    Strange As Angels Fixxxie's Avatar
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    I had an idea for building a tensioner that has two pulleys one above the top of the chain above the chainstay and one below the bottom of the chain under the chainstay that kind of floats there and maybe connect to the chainstay somehow
    BUT then I figured might as well just use a frame with the proper dropouts
    Quote Originally Posted by sefb222 View Post
    a good reason to form a demolition derby, for fixed gear bikes and the fools who love them.

  25. #25
    mousse de chocolat Moose's Avatar
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    Quote Originally Posted by Analog
    I have one of these, and they include a rigid (and beefy) chain tensioner. I would think it could withstand a whole lot of force.
    No way, I have already had to tweak one of these that had been bent to the point that it would no longer take up tension even at it's furthest adjustment. It is not nearly as strong as it looks, trust me. In fact I was quite disappointed with the rigidity of this thing.

    No offense to anyone using this setup, it's fine for SS, the owner of the bike probably bent it while grinding a rail or something. But it was so easy to bend back that I doubt it would hold up on a fixed gear.
    Last edited by Moose; 02-02-07 at 08:55 AM.

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