How do I change one piece crank to 3 piece crank?

Discussion in 'Motorized Bicycle General Discussion' started by toker_ace, Sep 12, 2009.

  1. toker_ace

    toker_ace Member

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    Here is a scrap part bike I'm building and I have a 3 pice crank I want to put on this bike.How do I do this? Its amazing what a set of $7.00 Cannondale Stickers from Ebay does to a Roadmaster frame. He HE! laff
     

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  2. silverbear

    silverbear The Boy Who Never Grew Up

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    This past spring I picked up an extra wide three piece crank to replace a one piece on an old Huffy frame in an attempt to make room for a pull start engine. I discovered that the diameter of the frame opening where the bearings fit and the crank goes through was different. As I recall the one piece was a good deal bigger. I gave up on that approach and installed a one piece short armed crank from a 20" bike. I still have that three piece wide one, but haven't found a use for it yet since I pretty much work with old cruisers. I don't know if there is some kind of reducer so that a three piece would fit or if there are different sized three piece cranks, but would like to know.
    Silverbear
     
  3. Retmachinist

    Retmachinist New Member

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    Jeff, You will have to buy a bottom bracket adaptor. It's something you will probably have to order, unless you know a good machinist that would make you one. It might get a little time consuming though.

    John
     
  4. Kevlarr

    Kevlarr New Member

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    Slick Bike Parts sells a 3 piece crank adapter kit as well as a some online bike parts vendors.
     
  5. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

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    The 3-piece crank bearing adapter is a very common item. any bike shop can get it.
     
  6. NEAT TIMES

    NEAT TIMES New Member

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    The Lowest Price I Have Seen For The Adapter Kit Was About $18. Plus S/h Ron
     
  7. silverbear

    silverbear The Boy Who Never Grew Up

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    I'm glad to learn about the adapter. Thanks.
    You know, being on this forum is like going to school. I've learned so much here in the past month from you good people and have enjoyed the camaraderie of others who also love fixing up and riding their motorbicycles.
    Kind of off topic in a way, but thanks to whoever it is who created and maintains this site. It is superlative! You guys are the best. I wish you'd come out from behind the curtain sometime and take a bow center stage.
    Silverbear
     
  8. bairdco

    bairdco a guy who makes cool bikes

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  9. Retmachinist

    Retmachinist New Member

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    Just today I had the same problem, needed to change an old one piece crank to a wider 3 piece crank that will clear the motor on a West Coast Chopper Bike.
    I took a long bottom bracket shaft from the loose ball set up and machined it for 5/8" I.D. sealed bearings. They are pretty tough so I had to use Ceramic tooling.
    Then I removed the bearing cups for the original bearings and machined bearing caps from 6061 aluminum to support the sealed bearings. Worked out pretty slick.

    John
     

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  10. silverbear

    silverbear The Boy Who Never Grew Up

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    Is the three piece crank "better" than the one piece in some way, other than having to do with clearance issues?
    Silverbear
     
  11. Gr4yb3ard

    Gr4yb3ard New Member

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    No real mechanical difference, but you can install better bearings and sprockets up to the max.

    I'm sorta considering one of the aluminum tank frames, rockshocks on the forks, and a high-end crank/derailer groupo.

    I'd have a buddy of mine (think West Coast Choppers on TV) do a real slick mounting job with milled parts, install a stage 3 engine, and send it to a custom paint shop

    Maybe fire engine red paint and find a Ferrari decal for the tank, that will turn some heads I'll bet, He-he-he
     
  12. TakeiT

    TakeiT New Member

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    Undo the nuts on the side of the 1 piece crank, and take off the pedals. You should be able to snake the cranks out one end. Remove all pieces and clean up the grease. The new crank will slide in, and bolt on the same way. Make sure to put lithium grease on it. The new crank arms will simply bolt up.
     
  13. Nashville Kat

    Nashville Kat Active Member

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    The three piece crank gives you more option of spindle length- sick bikes has extra wide spindles, but usually a fairly normal length will clear a china girl with no pull start-

    You can use a lighter crankset then too, and maybe even some titanium spindle bolts- it all saves weight, if you want to keep the bike lightweight.

    There are actually about three designs- a couple of which use the smaller 3 piece bottom bracket cups and bearings, and one that uses the larger single speed bearings and locking cups- the latter doesn't give you an option for choosing the spindle length though.

    If you are wanting to keep the bikes weight down, and get a really easy pedal- but don't want to change the one piece crank, you can also get a really small sprocket- like 25 or 28 teeth, and that not only saves a lot of sprocket weight, but you then also cut the chain length way down as well- like 10 or 12 links- a substantial weight savings.
     

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