Aluminum questions

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Cracked factory welds on a Kick scooterFrom the Factory:Aluminum 6061 T5 CertifiedTig WeldedT4 and T6 Heat treatedWhat causes such a failure?The Scooter decks have come a long way since the little Razor Foldy so these "Stunt" scooters see a wee bit of abuse.Ed Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:I think it's a no brainer, LOL, stress and abuse.
Reply:Originally Posted by DanthemanI think it's a no brainer, LOL, stress and abuse.
Reply:That whole design is all wrong..It's one big stress point without a gusset that can't be installed in the first place......zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Originally Posted by zapsterThat whole design is all wrong..It's one big stress point without a gusset that can't be installed in the first place......zap!
Reply:the weld looks like crap.  corners don't even look like they were wrapped.  just clean and try laying in a couple of passes.if you're worried about someone coming back in a cast you could weld a piece of plate inside the top part and through bolt.  doesn't look like it would interfere with anything.  then weld it up.seriously, that weld was not done well.Last edited by fdcmiami; 06-01-2012 at 09:49 PM.
Reply:Unlike carbon steels it's typical for aluminum welds to crack right down the center. This indicates a sound weld in a lot of cases. That means it's helpful to pay attention to the places where the weld didn't crack in a predictable way.I agree with Zapster.  Due to a faulty design leading to a stress concentration at the start/stop of the weld. The second factor was probably existing defects at the start/stop.The crack initiation point is fairly clear. You can see a bit of tearout of the base metal in picture #1.  To me, that kind of indicates fatigue, or in other words the material is too thin to support the shock loads in that area. there also a fair amount of lack-of-fusion. Existing weld defects caused a further stress concentration which led to fatigue failure, at which point the entire weld failed..I don't see any weld at the front side of the bottom plate at all. Last edited by Joshfromsaltlake; 06-02-2012 at 02:35 AM.
Reply:Agree with Zap, regarding bad design in the first place.A better solution would have been to notch the base and allow the vertical member to protrude thru to the bottom of the standing plate.  That way it could have been welded both top and bottom.Repair is not going to be easy since the part appears to have been heat treated and anodized post welding.  If it was mine, I would seek remedy/replacement from the manufacturer.  There's got to be a liability associated with this type failure.  My guess is that they'd replace it rather than take a chance on being sued.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:although the design does look bad, it appears there are lots of these things rolling around out there.they are made of 6061 T5 and if you are really interested... or bored.  you can go to:http://www.districtscoot.com/go to the drop down menu, choose decks;  you can then view a 360 degree rotation of the unit, in an enlarged format.   click the arrows to move the picture in increments.  the front view, the one not seen in the photos provided, was a surprise.  to me it seemed the weld profile should have been more convex.Last edited by fdcmiami; 06-02-2012 at 05:58 AM.
Reply:Fatigue never sleeps.
Reply:fdc,Interesting.Surprisingly, to be considered a "state of the art" piece, the tig welding left A LOT to be desired.  Actually, that sample shows welds even worse than those on the one that failed.Must have some strong "warranty disclaimers" in their literature.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Just go to 3:37 and it really isn't a surprise that these things "fail"Ed Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge