1 pc vs 3 pc crankset?

Discussion in 'General Questions' started by atombikes, Aug 6, 2008.

  1. atombikes

    atombikes Member

    Hi all,
    I'm still very new to this motered bike scene, but I'm pretty deep into the recumbent bike building scene. I notice almost all of the 2 stroke bikes seem to use a one piece "Ashtabula" crankset instead of the more modern 3 piece crank/bottom bracket. Is there a reason beyond "that is what the bike was before I added the HT engine"?
    Thanks
     

  2. jimraysr

    jimraysr Member

    I suspect that one piece are common in China. Many of the kits I have seen pictures of include a one piece wide crank. The 2 cycle I don't think require changing the cranks.

    My Grubee 4 cycle kit that I got for a Honda GXH50 came with a wide one piece for a 2" bottom bracket. My Schwinn has a 1 1/2" BB bolt retained cranks and I found a dealer that has some China 3 piece cranks that I needed.

    Most if not all frame mounts and 2 cycle direct mount are made for 1" tube frames which muxt be the standard in China for domestic use. Of course most frames made for the American market have larger bottom tubes and larger top tubes as well. The seat post doesn't seem to be a problem.

    I had to grind out a lot of the front aluminum block for my adjustable steel mount to get it to fit the bottom tube and then use a 2" exhaust pipe clamp part ( not the U bolt part) to bolt the mount in place

    That is my observation so far.

    Jim
     
  3. atombikes

    atombikes Member

    So is the width of the HT (or other) engine a factor for the wide cranksets? On a 3 piece crank, the distance between the pedals is based on the bottom bracket width (called the Q factor). Usually the width is determined by personal preference.

    I'm just wondering why I see so many of these bikes in the pics that have the one piece cranks?
     
  4. Irish John

    Irish John Guest

    You don't need a wide crank for the HTs but you do need one for the 4 stroke frame mounts. The wider the crank the easier it is to hit the road with the pedal when banking around bends so why anyone would choose a wide crank on a narrow 2 stroke stumps me.
     
  5. srdavo

    srdavo Active Member

    that's the only reason.

    a lot of these bikes are older... only available with one piece cranks.
     
  6. bluegoatwoods

    bluegoatwoods Well-Known Member

    I don't know if this fits in the discussion, but I actually prefer one piece cranks because you never have to buy a new one. There's always bicycles around in the trash and they all seem to be completely interchangeable.
     
  7. atombikes

    atombikes Member

    I DO link dumpster diving, and you're right, alot of those bikes do have the ashtabula crankset. I suppose as long as the crank lengths and width are what you want/need, there's no compelling reason to not go with what you have?