Fractured Frame

Discussion in 'General Questions' started by tbeeghly, Oct 3, 2008.

  1. tbeeghly

    tbeeghly New Member

    It's been a while since I've posted, the bike has been running fine for a long time. After about 9 months of riding, and 2 weeks of solid daily riding since school started, the frame finally couldn't take it. It snapped today on my way home from class. Was the frame just too weak? I want to get a cruiser frame for my next build, I think those are much heavier, sturdier. I also want to do a springer fork with much bigger tires, the 1 3/8 provided no support at 35mph. Any ideas?


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  2. s_beaudry

    s_beaudry Member

    Could be a weak frame....

    But seeing that it cracked right where the motor mount is, my guess would be that the motor vibrated or stressed the frame too much where it was mounted.

    Hope you may it home ok when that happened, safety first!
  3. GoblinAero

    GoblinAero Member

    Cracked tube

    Wow, that's amazing.

    'Seems like the frame was made with steel rather than chromoloy. Is that true? I've never seen chromoly do that.

  4. Mountainman

    Mountainman Active Member

    sure is what it looks like

    for these frame mounts -- something should be wrapped around the
    frame so as to protect --
    anything wearing too much will have a cutting effect
    especially with the high vibration

    makes it hard when we wish to --
    Ride That Thing Mountainman
  5. SirJakesus

    SirJakesus Guest

    This has happened to somebody's chromoly down tube as well. It happened to admin tom's seat tube as well as several other bikes having the same failures at the motor mounts. Always with "Happytime" 2 strokes.
    Between this and their tendency to lock up the rear wheel and cause a quarter mile skid, possible wipeout, mangled spokes etc. I really wonder why people trust their lives to these things anymore.
  6. Accender

    Accender Member

    I have never seen steel do that. steel is a mainstay, forgive weight.

    chromoly is to thin (by design) in my book.

  7. Was there any sign of trouble during your normal 'pre-flight' inspections? I fear this happens from the inside out. You'll never see it coming. Failure of the down tube on a cantalever frame, such as on a cruiser, while you're underway, you're probably going 'a$$ over tea-kettle'.:-x Another reason to keep the speed down on these things. Rear wheel lock-up, or frame break at 15mph is bad. At 40mph... R.I.P.
  8. Accender

    Accender Member


    I just looked at that picture.
    Was the section cut out with a saw?

  9. TwoWalks

    TwoWalks Member

    Because they are inexpensive and fun? :grin:
  10. hill climber

    hill climber Member

    i think maybe some folks are not mounting these ht engines properly. they need to be completly seated on both mounts. the mount should set flush on the frame as to not make a chisel edge on the frame. also,with the mounts not setting properly you are trying to bend the frame tube at the mount when tightening the bolts. what do you guys think?
  11. Slay

    Slay Member

    Kind glad I'm using the SBP rear mount with some extra seat shaft down the seat tube. Makes the front mount just extra....but that looks nasty.
  12. Snax

    Snax Member

    Perhaps people should consider doing what I did today, and just look at their frame with the motor running and spinning the rear wheel in the air. The downtube was flexing an alarming amount IMO.

    After reading these posts about tubes breaking, I'm strongly considering adding a supporting member between the down tube and seat tube just under the motor. That should make for a considerable reduction of the flexing and fatigue.
  13. wanger

    wanger Guest

    SPOT ON good observation
    when motor designed there was no suspencion
    frames had spacific angles
    frames have been redesigned last 15 years due 2 front suspencion the angle between seat tube downtube has changed not allways 70 degrees which is the angle between 2 motor mounts so i believe
    Last edited by a moderator: Oct 17, 2008
  14. Mountainman

    Mountainman Active Member

    check it while running

    everyone who has this set up -- should do the same

    ride that thing