Chain Tensioner Chain Tensioner? Pffff. The Half Link

Discussion in 'Transmission / Drivetrain' started by KCvale, Apr 29, 2010.

  1. KCvale

    KCvale Motorized Bicycle Vendor

    I built my first MB with a Grubee kit in April 2010 and thought putting a big honking ugly tensioner pulley on the drive chain just to make the kit easier to install was a really lame solution to a mechanical problem.

    So on my next one I sized the drive chain to be tight with the wheel about 1/4 to a 1/3rd of the way back in the rear mount grove, and then worried about the pedal chain.

    The drive chain is in motion when the bike is, the pedal chain is hardly ever in motion so right off the bat you eliminate the need for some big industrial grade pulley.

    The first thing you will find when you do it this way is your original coaster bike chain will be about 1 link too short.
    No problem, I just pulled a link out the excess chain the Grubee kit came with, and used their spare master link to add it to the bike chain.

    The tensioner works dandy on the pedal side, but it is still a big, ugly square plate of steel on an otherwise pretty and rounded bike, even if you paint it.


    I tried one of these $20 bike chain tensioners...


    But then the pedal chain was too long for the reach of the small but far better looking bike pulley!

    By using the big pedal sprocket to line up the chain it turns out the chain is a 1/2 link too long with the extra link in, and 1/2 a link too short without it.

    The Half Link

    What a wonderfully simple $1.99 fix.


    No tenioner needed at all.



    The drive chain is tight with about 20 miles on it, the pedal chain has about 1/2" of play and stays on fine for the little use it gets.

    Now as the drive chain stretches I can just pull the wheel back to tighten it back up ;-}

  2. KCvale

    KCvale Motorized Bicycle Vendor

    I would have figured someone would have a comment, or was my innovation just old hat here?
  3. Gh0stRider

    Gh0stRider Banned

    I like it!
  4. motorpsycho

    motorpsycho Active Member

    That's exactly what i did last year to my chains.
    no tensioner at all on either side, and it works just fine.
    i had to add the 1/2 link to my pedal chain just like yours.
    and what you say is very true, especially with my bike & the way i pedal chain is hardly every used except for when i apply the brakes or, I run out of gas.
  5. azbill

    azbill Active Member

    I like the idea of not using the cotter pin :),,,
    that was always the weak spot in using a half-link ;)
  6. KCvale

    KCvale Motorized Bicycle Vendor

    Yep. And you shouldn't even need the extra master I show.
    I broke a link on my pedal chain and had to put a new one in, hence the extra master.

    They make 1.5 links too.
    Then you don't have to mess with pushing the pin on the big side in to attach it, you can just use a second master and be done in no time.

    It REALLY helps to break the pedal chain, get the drive chain where you want it, and then put the pedal chain on so the ends are at about 4 O'clock on the pedal gear (like my picture) to see what you need.
    Trying to get legnth by eye between sprockets just don't work.

    One other newbie reminder note about chains...
    You can't remove just 1 link.
    The 2 remaining ends need to be the same, both thin links so you can drop a master on*.

    * There are of course special links, the half link is one, but when you size the chain pay attention to how it will hook back together too ;-}
  7. jroyse

    jroyse Member

    I like it!! Thats kinda what I'm doing on my 1999 Whizzer. I'm gonna re-name it 1999 Hopeless, cuz it is. Soon as I get my half link I'll be able to put the chain back on it AND SELL IT!! Back to your chain set up, I like the idea of no tensioner. Seems like I'm always adjusting the thing on my China bike. I'll try your way and skip the tensioner.
    Nice pix. Thanks