Cracked Skyhawk GT2 Frame

Discussion in 'Motorized Bicycle General Discussion' started by SuperDave, Jan 21, 2015.

  1. SuperDave

    SuperDave New Member

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    Aw, **** no! My Skyhawk GT2 frame cracked at the pedestal mount. Because its aluminum, finding a decent welder to fix it isn't going to be easy, or cheap. Has anyone else had this problem with this frame? [​IMG]

    [​IMG]
     
  2. SuperDave

    SuperDave New Member

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    For what it's worth, this is after 2 unbalanced SuperRat motors & 3 years.
     
  3. YesImLDS

    YesImLDS Member

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    I would assume it's just from the abuse over time. I was looking into getting that frame quite in depthly and didn't see many problems like that. Aluminum is lightweight, but vibrations are a lot more harsh on it when compared to a steel frame. I'd just look for someone to repair it or I'll take it off your hands!
     
  4. Davezilla

    Davezilla New Member

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    First one I've seen to crack, but looking at how clean it cracked around the weld, it looks like the weld was cold and didn't penetrate into the frame metal, but just the post the bracket is on. If this is the case, that'll cause the crack and for it to spread up the frame tube like that when it's subject to vibration and road bumps etc...
    I'm pretty sure if you can have it re weleded it'll hold better than it held new.
     
  5. YesImLDS

    YesImLDS Member

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    Exactly. I'd just go look for someone who does head reworking because that has to be a good quality weld for it to be machined perfectly. A good weld as well as some good prep and you'll be back on the road in no time. Who knows he might even look over the other welds and strengthen those too!
     
  6. Davezilla

    Davezilla New Member

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    Yup... and most welding shops or even machine shops, especially a performance related machine shop will be able to weld aluminum and if you take it to them clean (paint stripped off the bad welds) and get them interested in what you got, they may give a slight discount.
     
  7. HDCowboy

    HDCowboy Member

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  8. 2door

    2door Moderator
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    Just a suggestion but if you happen to have an old engine case you might want to consider having it bolted on when the welder does his work. Parts tend to wonder around with the heat of welding and if the mount isn't attached the way it's supposed to go it might be way off after the welding process. An engine case mounted will help keep things aligned where they're supposed to be.

    Good luck. Keep us informed.

    Tom
     
  9. Davezilla

    Davezilla New Member

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    Very good idea... Ya never know when something's gonna move or twist when it's heated up like that... and there's no guarantee it'll move and twist back to where it was once it cools back down...
     
  10. maniac57

    maniac57 Old, Fat, and still faster than you

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    Looks to me like the mount was under upward pressure from the rear mount...
    How would it break upwards unless there was a strain on it?
    Just another reason to avoid aluminum frames.
     
  11. Davezilla

    Davezilla New Member

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    It's a cold weld... Whoever welded it originally totally missed the lower frame tube more than half way around that bracket tube, now add 3 years of vibration and hard riding into the mix and things like this happen... That's Chinese quality for ya...
    Here in the states if someone was building frames like these they would all have to be x-rayed to check for voids in the weld, then the rejects marked and re welded to fix teh problem.... Over there it's welded and put in a box... probably while it's still cooling down from being welded, the box is inspected to be sure it's taped down good enough so it won't pop open on it's way over here, and on the ship it goes...

    Sorry, I couldn't pass that up, but I'm still thinking it wa a cold weld from the factory...
     
  12. mapbike

    mapbike Active Member

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    Those aluminum um frames look real good but they do scare me a bit, but on the other hand there are a pile of them out there working g just fine for a very long time.

    Once I had the piece welded back in the correct position I think I would have them weld a small gusset front and back of that raised mount, it would be much stronger there after that and more than likely a permanent fix.
     
  13. Davezilla

    Davezilla New Member

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    Personally I'd have it fixed, then gusseted, then re heat treated... aluminum loses a Lot of it's strength if it loses it's heat treatment. Most heat treated alloys can be every bit as strong as mild steel, and some just a bit stronger (7075 T6 is both stronger and harder than mild steel, 6061 T6 is almost as strong as steel but just a tad softer, and 2024 T3 is about the same as mild steel but maybe a touch harder)
    The problem with these alloys tho is that you can't weld on the 2 series or 7 series aluminum alloys, the 5 and 6 series are very weldable, but not as strong.
    Ya can't tell I used to work aircraft structures for a living for several years can ya? I was also able to take the class for rockwell hardness testing and a few other strength testing methods, it's amazing how strong certain metals are, but they don't look it or feel that way when drilling thru then or working them.
    But for sure, if I got it rewelded, it's into the heat treat oven next.
     
  14. lucajo16

    lucajo16 Member

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    three years of use? Sounds like a good time and distance. I am looking into building off one and want to do my homework. Hope you get it up and running again.
     

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