geoffbeaumont Posted July 8, 2007 Share Posted July 8, 2007 More for interests sake than anything - this is the chassis from one of a pair of Zip Rover Challenge karts belonging to a charity I work with. The karts are somewhere around 25 years old, and were also stolen a couple of years ago - they were recovered by the police after a few months, but had definitely lead a hard life (the other kart was heavily - and very badly - modified and fitted with bodywork). Shortly after we got them back, cracks started to appear in this kart - it was packed off to a lawn mower repair centre that used to maintain them for us, who decided it was repairable and welded a couple of reinforcing plates on. Plainly it was a bit beyond this because even though it hasn't really been used since a new crack has already appeared just outside the plate. End of the line for this chassis. The original crack: New crack just outside the reinforcing plate: The reinforcing plates - not sure how much I'd trust this welding anyway : Looks like there was another crack welded nearer the front: Just to put it all in context, here's the whole thing (the gaps in the middle were courtesy of an angle grinder not fatique): Quote Link to comment Share on other sites More sharing options...
Les Henson Posted July 8, 2007 Share Posted July 8, 2007 Christ that's awful welding. I would have sleeved over the cracks, I can't see that the plates are doing much good to be honest. Les. Quote Link to comment Share on other sites More sharing options...
Stewart Posted July 8, 2007 Share Posted July 8, 2007 I like repairs like that it makes my welding look good. Stewart Quote Link to comment Share on other sites More sharing options...
disco tony Posted July 8, 2007 Share Posted July 8, 2007 could be a tougher grade of steel tubing for this application, would have a higher carbon content, would be best to weld with oxy/acetylene and post heat treat or at least allow to cool as slowly as possible. Otherwise mig it and heat to red hot after and allow to cool slowly again. Bicycle frames were made from reynolds 501 tubing and were best brazed instead of welded. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted July 8, 2007 Share Posted July 8, 2007 Used to see a lot of cracked kart chassis, since they have no suspension, flex when steering and take a lot of impacts it doesn't take long. Sometimes if they cracked in the right place they handled really well Usual repair was to sleeve it internally. Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted July 9, 2007 Author Share Posted July 9, 2007 Christ that's awful welding. I would have sleeved over the cracks, I can't see that the plates are doing much good to be honest. I don't think they're achieving a great deal either, although they do bridge the original crack - I would have though another pair of plates below would be the absolute minimum though? could be a tougher grade of steel tubing for this application, would have a higher carbon content, would be best to weld with oxy/acetylene and post heat treat or at least allow to cool as slowly as possible.Otherwise mig it and heat to red hot after and allow to cool slowly again. Bicycle frames were made from reynolds 501 tubing and were best brazed instead of welded. Got one of those bikes - my Dad bought it second hand years before I was born. It's about forty years old, weighs next to nothing and is still going strong Given it's cracked in three places already I'm not sure repairing this chassis is at all wise - it'll probably just crack again somewhere else. Used to see a lot of cracked kart chassis, since they have no suspension, flex when steering and take a lot of impacts it doesn't take long. Sometimes if they cracked in the right place they handled really well Usual repair was to sleeve it internally. Could be tricky - the side members are already double walled. Quote Link to comment Share on other sites More sharing options...
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