derailer,as chain tensioneer?

Discussion in 'General Questions' started by jeffrey kleinknecht, Nov 9, 2011.

  1. jeffrey kleinknecht

    jeffrey kleinknecht New Member

    I had quite a bit of trouble getting my stock chain tesioner to work properly,so,I ended up finishing the build without one. Aside from the problems getting both chains to the same tightness (ended up removing a link from the pedal side) it has been trouble-free since.
    I heard someone mention a spring loaded tensioner,and was intrigued by that idea.
    As I was looking around my garage,I began to wonder if there might be some way to fashion a spring loaded tensioner,using parts from a derailer,after all,one of it's functions is to maintain chain tension.
    Have any of you tried this? If so what were your results,and can you offer me any advice to avoid some of the problems you may have had?

  2. motorpsycho

    motorpsycho Active Member

    yep, it can be done with the right amount of engineering.
    here's one that i made from downhill bicycle tensioner.
    this tensioner takes the place of the derailer, when you make a multi speed bike one speed.
  3. cloud_2901

    cloud_2901 Member

    I managed to score an old derailleur from a mate's bike whos rear wheel was stolen (honestly who just takes a rear wheel), been trying to work out a way to mount it, i was looking at where the standard tensioner is though, thats a much better idea motorpsycho.. off to fiddle
  4. retromike3

    retromike3 Member

    chain tensioner top mount

    the main problem I see with the top mount chain tensioner is when the motor engages the "slack" is taken out of the top leaving the loose part of the chain at the bottom. I see this as a potential problem.

    Is this right? or am I seeing things?

  5. motorpsycho

    motorpsycho Active Member

    nope not at all.
    mine has been this way for 3, almost 4 years now with no problems.
    In my opinion, it doesn't really matter which side of the chain gets the tension. (top or bottom).
    if you think about it, when the engine pulls the chain to turn the sprocket, the pull is on the top of the chain, not the bottom.
    the tensioner i made moves up & down with the chain as it tightens up and loosens (on the throttle / off the throttle).
    I have never had a chain come off, and both of my bikes have the chain tensioners on the top of the chains.
    the chain is never loose really because the tensioner keeps constant tesnion on the chain.
    there is no "slack" in the chain, top or bottom because of the tensioner. this tensioner keeps the chain in adjustment all the time.
    Last edited: Nov 10, 2011
  6. Cavi Mike

    Cavi Mike Member

    The tensioner should always be on the slack side, especially if it's spring loaded. You will never find a tensioner on that side in any application.

    *edit* And using a derailleur as a tensioner isn't a good idea anyways because when you bump-start the engine it causes the slack side to become tensioned and will yank the derailleur and damage it.
    Last edited: Nov 12, 2011
  7. motorpsycho

    motorpsycho Active Member

    well,'s a tensioner made from a derailer on THAT side of the chain that i made almost 4 years ago and it's still going strong. (see pic in other post)

    #2, bump startring will not damage the derailer if it's set up and installed right. the derailer will go with the chain, not against it.
    a chain yanking on a derailler is normal in EVERY derailer application so how could it get damaged? every time you shift gears on a 10 speed the chain is yanking on the derailer. (and you can generate more horsepower and torque by peddling than one of these engines can generate)
    the only weak point to most derailers is the plastic gears, but you can find them with steel gears (like mine)
  8. Cavi Mike

    Cavi Mike Member

    When you pedal, the tension is at the top. When you bump-start, the tension is at the bottom, where the derailleur-tensioner would be. This is not really a difficult concept to understand. Plus, I don't really care that you put a tensioner on the wrong side of the chain, that doesn't mean you'll find one anywhere else from timing-chains to lawnmower belts. The tensioner is always on the slack side. Period.
  9. motorpsycho

    motorpsycho Active Member

    so what you're saying is that when you bump start the chain is pushing the rear sprocket from the bottom? i don't think that's possible.
    If you think about it, the chain is ALWAYS pulling at the top no matter what because the engine sprocket turns counter-clockwise so it's pulling the chain not pushing the chain.
  10. Barnfresh

    Barnfresh Member

    You can't push a chain any more than you can push a rope. While bump starting you're rolling along (dead engine) while both front & rear sprockets are in motion. You slowly let out out the clutch (or just dump it) resulting in some serious drag on the front sprocket while it engages the rest of the engine to turn over. At this point the rear sprocket continues "pulling" on the bottom of the chain making it the "tight side" until the engine fires. Now MP's chain tensioner is mounted on the slack side taking up the chain "slack" which is now on the top. So see you are both right! :grin:
  11. I used an old Schwinn derailleur and mounted it with a muffler clamp. It worked very well. I also used a skateboard wheel that I made a groove in with a drill and file...chucked the wheel into a drill press and used a file to "route" the a chain guide and mounted this with a muffler clamp also. The muffler clamp "legs are long enough to extend into the chain path there by making them very useful for improvised guides, tensioners etc. This was on a homebuilt recumbent a few years ago.
  12. jeffrey kleinknecht

    jeffrey kleinknecht New Member

    That is very useful information. Thank you!