2nd broken frame

Discussion in 'Motorized Cruiser Bicycles' started by captainrichhill, Aug 6, 2010.

  1. captainrichhill

    captainrichhill New Member

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    I found two cracks in my Wal-Mart Point Beach which I really love. Anyone else have broken frames from the vibrations I guess? I don't know if I should be looking for a NEW frame/bike of try to get this one welded up. The other crack is a the weld where the seatpost passes the backbone.
     

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  2. GearNut

    GearNut Active Member

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    Aluminum frames are more prone to cracking from engine vibration than mild steel or chromoly frames. If you get your frame welded, there is no guarantee that it will not crack again. I am sorry to say that your safest bet is to get another bike that does not have an aluminum frame.
     
  3. Kevlarr

    Kevlarr New Member

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    Cracked frame you ask?
     

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  4. captainrichhill

    captainrichhill New Member

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    Kevlarr
    I have a hairline crack in those same spots. I guess we know where the weak spots are.

    I guess I'll start looking for a new frame.
     
  5. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    I had the small welds where the seat post goes through the cantilever bars crack on and older (60's) steel frame.
     
  6. midnight_rider

    midnight_rider New Member

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    That sucks, especially on a bike you really like, luckily mine hasnt done anything yet and I chack it over all the time whien I'm cleaning it
     
  7. azbill

    azbill Active Member

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    I cracked the seat tube (over and under the top bar) on my Deviate chopper (RIP)
    I only weigh 145lbs, so I attributed it to vibrations as well as the severe angle of the seat post

    gallery384
     

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    #7 azbill, Aug 7, 2010
    Last edited: Aug 7, 2010
  8. captainrichhill

    captainrichhill New Member

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    Just bought a new bike from Walmart. It's the same bike but in a steel frame. Best of all, it was marked down from $139 to $105. I went to just look but I couldn't pass this one up.
     
  9. wheelbender6

    wheelbender6 Active Member

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    Well done. Steel just handles the engine vibration better.
     
  10. Allen_Wrench

    Allen_Wrench Resident Mad Scientist

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    As a preemptive measure, after I restore my old Higgins frame, I'll be moving the motor and stuff into it. That's a solid old frame there, the Higgins. If you can get a good steel frame for a steal, do it.
     
  11. BarelyAWake

    BarelyAWake New Member

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    I could be wrong and in the end it doesn't matter anyway = broken is broken...

    But I'm thinking it's not engine vibration that's contributing to frame failure so much as sustained "high speed" (comparative term ofc lol) impacts from uneven road surfaces on the unsuspended rear portion of the frame. These reported failures are all in high load areas, exactly where the most shock would be as it travels up from the wheel to the dropouts, rear stays to seat post - localized where the most weight is, the rider.

    I would think if the engine vibration was at fault - you'd see signs of fatigue closer to it - near the motor mounts and/or where the Dtube connects to the crank/head...
     
  12. captainrichhill

    captainrichhill New Member

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    Barelyawake,
    That's a good point. I didn't think of the shock loads from the bumps in the road. I will keep a closer look at the frame periodically. At least I can weld up any cracks I find in a steel frame.
     
  13. Kevlarr

    Kevlarr New Member

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    I have to agree. Also think about it, my frame cracked at around 1000 miles, how many Huffy cruisers get 1000 miles of regular riding put on them? A lot of us are riding our bikes well beyond their usable service life in just one year.
     
  14. BADBOOH

    BADBOOH New Member

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    I agree, with the last post, however, I believe that you get what you pay for. I ride a Alpha Aluminum Trek Cruiser Classic. I have well over 1000 miles on her, and (not by choice) happen to ride over crappy roads, most of the time. The only cracks or breaks that have come so far (knock on wood) was the cheap studs used to hold the motor to the frame. Chinesse cheap steel. Replaced these with the best studs I could find. So far so good. I know other guys around me who have steel frames, from huffy and micargi, who have had similar cracking issues. Like I said earlier, I paid $319. For my Trek. Even though shes aluminum, shes a tank.
     

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  15. BADBOOH

    BADBOOH New Member

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    OK, one thing that did break on the bike, due to vibrations was the rear fender stay, replaced and the same thing. Then I welded the two stays together, and so far so good. I hate riding without the rear fender.
     
  16. happyvalley

    happyvalley New Member

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    Some of each probably but I've seen an uncanny number of frames cracked directly right at the mounts....almost like a sawzall was attached there rather than a motor. Noted, these were all using china girl engines with stock kit mounts.
     
  17. The 26incher

    The 26incher New Member

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    I've broken a Murry frame and a set of knock off BMX forks...
     
  18. scotto-

    scotto- Custom 4-Stroke Bike Builder

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    Broken frames? Gee...really? With a motor or without....steel, aluminum, titanium, M2, carbon fiber.....they ALL break and for various reasons.....what's the big stink? I would say the most common place for frame failure is on the downtube, just past the head tube and the reason?....stress!

    When I was a kid my 20" Stingray was not a lead sled Schwinn....it was a cheap a$$ monarch (made in Japan). It had no motor but I used to jump that thing to the high heavens and where do you think that frame broke every couple years? You might have guessed, it's that place right behind the headtube where the forks are attached.....the downtube. That frame had more weight in welds in that spot than the frame itself! And that is why you see on many, many frames.....especially ALUMINUM....a gusset welded between the underside of the downtube connecting to the headtube in that spot.

    Have you ever seen a bottombracket spindle break? How about a handlebar snap? A wheel axle perhaps? I've seen them all and the reason is just plain and simply stress......nothing more! BarelyAWake basically nailed it!
     
    #18 scotto-, Aug 10, 2010
    Last edited: Aug 10, 2010
  19. BarelyAWake

    BarelyAWake New Member

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    scotto-...right, it's true stuff breaks - but I think this may be about whether or not the engine itself is primarily responsible, if the lower end bikes are truly suitable, and if there's any frames in particular that should be avoided because of that.

    lol - ya go jumpin' everything in sight and ofc yer gonna break stuff engine or not, I too "fondly" remember breaking the Dtube/head weld on various bikes jumping stuff, mostly unsuspended bikes not made for that sorta shenanigans - and not motorized.

    If you track down the source of that "stress", practice a lil postmortem forensics - there's much to be learned. For instance - cracked/broken welds on the Dtube (unmotorized) are usually a sign of landing front wheel first, but may be just poor welding skills, undercut in particular. A jumping bike should have additional gussets in that location, as you've noticed. Bottom bracket breakage is primarily the fault of insufficient quality components - it is after all where ALL your weight is when you land... if yer still on the bike heh, handle bar breakage is usually a sign of bars that are too long (excessive leverage) and/or don't have the crossbrace - all of this is obvious after the fact, but would still be a problem if people didn't think about the cause and take steps to prevent it.

    Ignoring and dismissing the causality of component failure only dooms ya to making the same mistakes again ;)





    Really? I've not seen or heard of this... My first thought was the U bolt style oversized tubing mount or the drilled Dtube method... but you say stock mounts? Do you have any pictures?
     
    #19 BarelyAWake, Aug 10, 2010
    Last edited: Aug 10, 2010
  20. scotto-

    scotto- Custom 4-Stroke Bike Builder

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    Just want too say that the same spot I was referring too isn't prone to breaking just because of jumping.......I've also snapped an aluminum frame on a $2000 Mtn. bike in 1990 by stuffing my front wheel in a rut of the same size at the bottom of a gulley on a downhill decent. This is opposite force that resulted in a fractured frame in the same sweet spot. No motor involved, same result shall I say......over-stressed. As in stress and fatigue....and I'm not neccesarily talking about weld failure, but the double-butted tubing itself. Thank you for fixing the quote and we all know suspension rules and hard tails drool.....don't we?
     
    #20 scotto-, Aug 10, 2010
    Last edited: Aug 10, 2010

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