What's the real reason for Chain Tensioners

Discussion in 'Motorized Bicycle General Discussion' started by Cheech, Mar 16, 2010.

  1. Cheech

    Cheech New Member

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    Could someone pleeeze tell me the real reason why we use chain tensioners at all? I've had over 20 motorcycles,motorbikes,mini bikes in my life and never needed a chain tensioner.Is it because it's in your kits? Throw them in the corner and learn to mount the chain correctly the first time. Is it because of chain stretch...get a quality 415 chain from a local motorcycle dealer.Really the only time I really see a purpose is as an idler for stretch bikes chain support.The truth is they are sooo much fun to work with and they look sooo damn cool up against that brand new paint job you just finished.Of course I know that no one here has eeevver pulled one into their spokes,spent the day picking their teeth out of the handle bars and unwinding that brand new useless rear wheel.Just as you got it perfectly aligned(...and wrecked your frame drilling a bolt hole to lock that bastard down)that big smile on you face turns a cursing fit because the idle wheel loosens up and you just wrapped your chain around the hub,knocked that sprocket that you worked so hard on,out of alignment,bent or broke your chain and again knocked your other tooth out.Just then(bleeding profusely)you search through that 40lbs. of tools you need to carry in your backpack just for these emergencies,you realize 12Km from home you forgot your chain-breaker or spare master link.Well as you limp home in the dark cursing at the moon and thanking the gods for peddles,you swear on your handy 10mm wrench that you will invent the next the greatest thing since sliced bread...TADA! the new and improved no-fault,never-fail Chain Tensioner!!!!!
    The next day when you get back from the Dentist you set forth to create this savior of men on two wheels you realize that other guy sitting next to you at the Dentist had already tested your patented technology with typical results.And so it goes..."Resistance Is Futile"!
    Wanna discuss my crash theories?or maybe talk about your adventures? please can we see the pictures of your wrecked bikes and dental X-rays ....by the way I to still use some sort of tensioner on most of my bikes...Damn...Cheech :-|| P.S. I've burned most of my crash pictures...
    Hey,guys before everyone gets real serious it's just a "been there,done that" post .Just thought I'd get some funny or even tragic stories about chain tensioners.So keep it light. We all know the real reason....to sell more chains and rims...hehehe..Peace ...Cheech
     
    #1 Cheech, Mar 16, 2010
    Last edited: Mar 17, 2010
  2. BarelyAWake

    BarelyAWake New Member

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    o_O

    Could someone pleeeze tell me the real reason why we don't research a problem at all?

    Ofc it's just I love the chain tensioner - I install them on non-motorized bikes alla time just for kicks [​IMG]

    The sad fact is many bikes need them for a few reasons, not least of which is chainstay clearance. Were I do as you suggest - the chain would saw through my Schwinn's chainstay in about twenty feet of use, my Rollfast - the same problem, but it'd last a quarter mile or so 'cause it's at least steel. As for a "quality 415 chain" - good luck with that, it's far easier to get a quality 410, but unless you change those sprockets too you'll be amazed how much that chain will still "stretch".

    Hey - if ya can get away w/o a tensioner - awesome! Do remember that motorcycles, motorbikes & mini bikes were designed with an engine in mind, complete with horizontal drop outs - another thing many bicycles no longer have.
     
  3. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

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    The chain tensioner makes installation of the engine kit much easier & quicker.
    Some bikes don't have adjustable rear dropouts to adjust the chain at all, & on coaster brake bikes it's very difficult for newbees to get both chains adjusted... & then there are all the reasons that Barley mentioned above. ;)
     
    #3 Venice Motor Bikes, Mar 16, 2010
    Last edited: Mar 16, 2010
  4. Cheech

    Cheech New Member

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    Hey,guys before everyone gets real serious it's just a "been there,done that" post .Just thought I'd get some funny or even tragic stories about chains and tensioners.So keep it light. Somehow I knew I would get all the Pro answers.Please finish reading my post before giving all the wrong answers.We all know the real reason....to sell more chains and rims...hehehe..Peace ...Cheech laff
     
  5. bairdco

    bairdco a guy who makes cool bikes

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    i think the real reason is to make the kits more adaptable to all the different models of bikes, and the skill level of the builder.

    i totally agree that the best way is to do without it, learn the tricks to adjusting both chains, but when it comes to certain bikes, it's necessary.

    the copper bike i built has a chainstay rubbing problem, so i need to figure...actually, i figured it out, i just need to build it.

    i don't have any humorous stories, because i never run them. except i do like using the clamps for all kinds of other things, like mounting speedometers, cameras, antenna balls...
     
  6. civlized

    civlized New Member

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    Great stories, Cheech. I agree that the purpose could be to keep selling wheels and chain. Did you know that cooking oil and deep frying was invented by a doctor?(not really, but the logic is there) In Alabama, meteorologists have stock in bread and milk companies. Everytime they say it's going to snow or be bad weather, everyone makes a mad dash for the store for milk sandwich supplies!

    I haven't had any bad experiences with the tensioner, so far. I can see the potential if it isn't installed correctly.
     
  7. Tad Bit Tipsy

    Tad Bit Tipsy New Member

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    Two words "Rubber Bands" not the small ones, but the big white thick ones, like those that come with punching balloons. Cut one and wrap it around where your going to put the tensioner clamp. Then tighten that puppy down good. It almost seals the thing in position. When I try to adjust(laterally) my tensioners now, they just spring back into the place, a miracle... or just good whitey wiring, redneck engineering, etc.

    I guess what I'm pointing out is more ingenuity has come from these bad mechanically designed little problems that we all share. I for one have redesigned the tensioner hundreds of times in my head, but my rubber band has still been the quickest fix ever.
     
    #7 Tad Bit Tipsy, Mar 16, 2010
    Last edited: Mar 16, 2010
  8. civlized

    civlized New Member

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    I completely agree with the rubber band idea. I didn't mention that I use a rubber tape on all of mine. It looks kind of like electrical tape, black and a little thicker, with no adhesive on it. That really does help with potential hazards. You know what is crazy, the accelerator assembly has a stud in it so you can drill a hole in your handlebar TO KEEP IT FROM TWISTING!!!! Novel idea. And the tensioners don't, go figure.
     
  9. Tad Bit Tipsy

    Tad Bit Tipsy New Member

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    I know why... your handlebars only take the weight of your arms, not the entire bike and you like the chain stay does. I wouldn't drill my chain stay for any reason, ever.
     
  10. civlized

    civlized New Member

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    Yeah, I never have either, but I know many people here have and had great results from it. Doesn't matter to me either way. The rubber has done the trick, so far, for me.

    And you are absolutely correct, the handlebars don't have much weight or torque to support. Even the accelerator handle doesn't have much on it, why does it need a stub in it? I have always broken or grinded them off anyway. I don't want to drill on my bars either.
     
    #10 civlized, Mar 16, 2010
    Last edited: Mar 16, 2010
  11. AussieSteve

    AussieSteve New Member

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    The real reason for the tensioners is a massive surplus in the nylon roller industry.

    ... Steve
     
  12. exavid

    exavid New Member

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    I'm running an old Schwinn Mesa Runner mountain bike without an idler. To do so I had to modify the chainstay a bit. I cold formed a piece of 3/32" x 1" x 6" to fit the outside of the chainstay and welded it in place. With the torch I heated the inside of the chainstay tube in the area where the chain crosses and dented it in so the chainstay is about half its normal diameter in that area. A little bondo to fair edges in and some primer ande it looks pretty good. I haven't painted the bike yet but so far there's no marks in the paint on the chainstay from the chain. It sure runs more quietly than it did with the idler. Luckily the bike has nearly horizontal drop outs and a seven speed freewheel so there's only one chain to tension. I've ridden the bike about 120 miles so far with no problems. The only thing I would do different now would be to find a bike with V brakes, the old side pulls take a lot of pull with a double cable lever. I ended up extending the lever a couple inches for more advantage. It's working okay, but would be better with anything other than the side pulls it has.
    I'm working on installing a four stroke on a cheapo mountain bike. I welded a 1"X1" square tube to the frame above the bottom bracket to attach the engine to. It looks like I might be able to eliminate the idler on this one too. If not I'll weld a strap to mount the idler so there's no chance it can move. I already experienced the 'fun' of having an idler drop the chain and lock up the rear wheel. Dirt bike experience helps with that but I still got dumped.
     
  13. Cheech

    Cheech New Member

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    Nice one Steve...Cheech
     
  14. AussieSteve

    AussieSteve New Member

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    Things were getting serious - can't have that.
    (I read your posts.)
     
  15. Cheech

    Cheech New Member

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    "I already experienced the 'fun' of having an idler drop the chain and lock up the rear wheel. Dirt bike experience helps with that but I still got dumped."
    exavid,
    all the rest of your post is very informative and thanks for that but,the above statement is exactly what I was looking for.I mean adventures in smash,crash,black and blue,wound up spokes,destroyed paint jobs,"I wish the f*ck I'd never wasted good money on this stupid piece of junk","Thank god I've still got peddles","I need a hug a band-aid and a 15mm so I can get back on the road stories...get a kiss for that knee booboo ....have at it boys....Cheech.duh.
     
  16. exavid

    exavid New Member

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    I stopped by a local bike shop a couple days ago and noticed that they had a coupe electric bikes for sale. The interesting thing about them was that they have shaft drive from the pedals to the rear wheel. Too bad those bikes are so pricey it would fun to try rigging up a shaft drive MB.
     
  17. AussieSteve

    AussieSteve New Member

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    A friend of mine has a motor on a chainless bike. He loves it.
    Both the engine kit and bike came from Rock Solid Engines in Oz.
    Here's one of the bikes, without an engine:-
    [​IMG]
     

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    #17 AussieSteve, Mar 17, 2010
    Last edited: Mar 17, 2010
  18. chrisme

    chrisme New Member

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    I use a tensioner because otherwise my chain won't clear the fork going to the back wheel. I'd love not to have to use one though! I've had so many tensioner related issues. For a tensioner I'm not using the stock crappy thing though, I'm using a skateboard wheel that I've lathed out the middle of for the chain to sit in.

    For chain I have a nice KMC 420 chain, a tad wider than 415, but it doesn't harm anything.
     
  19. exavid

    exavid New Member

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    I like the skate wheel tensioner, if I need to use one on the 4 stroke bike I think that's the way I'll go too.
     
  20. chrisme

    chrisme New Member

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    The skateboard wheel tensioner works awesome.
     

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