Village Idiot Posted January 20, 2005 Report Share Posted January 20, 2005 Just fitted my new cranks, and found a small crack where the right hand side chainstay meets the bb. (will try and upload a pic soon). I'm not too sure what to do about this. I've heard of people drilling a hole to stop the crack from getting any bigger but don't really know how to do this. Also, could overtightening the bb when fitting it have caused this, as I didn't notice it until after fitting the cranks, or it is just likely to have happened due to use - (my frames a t-raptor and I've had it 18 months). Quote Link to comment Share on other sites More sharing options...
tipsy Jock Posted January 20, 2005 Report Share Posted January 20, 2005 (my frames a t-raptor and I've had it 18 months). ← theres your answer :(" drilling a hole will make it last a little longer, but expect to be buying a new frame soonish :( Pete Quote Link to comment Share on other sites More sharing options...
Mark W Posted January 20, 2005 Report Share Posted January 20, 2005 You drill a small hole at each end of the crack, as it stops there being a focussed pressure point for the crack to extend down, just so you know... Quote Link to comment Share on other sites More sharing options...
squince Posted January 20, 2005 Report Share Posted January 20, 2005 Hey, if you now a good welder or any of your friends do then get it welded :(. However, i took my bike with a small crack in to somebody out of the paper :( and the frame gave way within 2 days. I think if you heat the frame up to much whilst your welding the frame it weakens the metal causing it to last no where near as long as it would if you just left the crack (i could be wrong). So try and get some one who has been recomended by some one. cheers andy Quote Link to comment Share on other sites More sharing options...
Tartridge Posted January 20, 2005 Report Share Posted January 20, 2005 Alternatively, you can get a new one for £80, or, have £80 off the price of another Onza frame. Quote Link to comment Share on other sites More sharing options...
Lee_Buchanan Posted January 20, 2005 Report Share Posted January 20, 2005 To be honest you cant really be moaning about a frame beign cracked after riding with it for 18 months,that is a heck off along time for a frame to last.Especially when the t-raptors are prone to snapping there anyway u shud be glad yours has lasted you that long,never heard about the drilling a hole thing in the crack??Does it actually work ? Lee (Y) Quote Link to comment Share on other sites More sharing options...
Tartridge Posted January 20, 2005 Report Share Posted January 20, 2005 never heard about the drilling a hole thing in the crack??Does it actually work ? ← Yup. Cracks form at stress risers. A stress riser is where theres a sharp corner. The end of a crack (theoretically) has a radius of zero, therefore theres an infinite stress at that point. If you drill a small hole at the end of the crack, that 'zero radius' area is then turned into a 1.5mm radius (if you used a 3mm drill bit, say), and the stress is reduced (Y) Its also advisable to do this before welding over a crack too. Quote Link to comment Share on other sites More sharing options...
Mark W Posted January 20, 2005 Report Share Posted January 20, 2005 Theoretically, yes. 'cos cracks are generally formed where pressure's built up on a fault in the frame, and it expands from there to the next fault where pressure builds up, and so on. If you drill it, there's no obvious route for it to choose, so it tends to slow it down. That's a brutally, brutally simplified version of it, but you get the point? Quote Link to comment Share on other sites More sharing options...
Dr. Nick Riviera Posted January 20, 2005 Report Share Posted January 20, 2005 just for the record t-raptors are alu so welding will be difficult Quote Link to comment Share on other sites More sharing options...
Mr Motivator Posted January 20, 2005 Report Share Posted January 20, 2005 just for the record t-raptors are alu so welding will be difficult ← Welding alu isnt 'difficult' but you need to heat treat it to retain any strength what so ever Quote Link to comment Share on other sites More sharing options...
Dr. Nick Riviera Posted January 20, 2005 Report Share Posted January 20, 2005 ahh nnoo if you weld it the area around it becomes brittle Quote Link to comment Share on other sites More sharing options...
tipsy Jock Posted January 20, 2005 Report Share Posted January 20, 2005 My housemate had his raptor rewelded, still in one piece now :( wasn't heat treated either, dunno how much longer that will be thou :( Pete Quote Link to comment Share on other sites More sharing options...
Will Arnold Posted January 20, 2005 Report Share Posted January 20, 2005 My housemate had his raptor rewelded, still in one piece now :( wasn't heat treated either, dunno how much longer that will be thou :( Pete ← he's only ridden it once or twice since then though :P yeah, it was a good weld though. i've heard that aluminium gains strength after time just sitting about because it reacts with the air or something :- Quote Link to comment Share on other sites More sharing options...
Village Idiot Posted January 21, 2005 Author Report Share Posted January 21, 2005 You drill a small hole at each end of the crack, as it stops there being a focussed pressure point for the crack to extend down, just so you know... ← ok, cheers. just a few questions: what size hole is best - its just a hairline crack that goes from the top of the chainstay to the underside? also, is it ok to use just any drill and is there a preferred speed to drill at? Quote Link to comment Share on other sites More sharing options...
Wayne-king Posted January 21, 2005 Report Share Posted January 21, 2005 i've heard that aluminium gains strength after time just sitting about because it reacts with the air or something :blink: ← no, aluminium becomes more brittle during it's life, and once a frame has been sprayed or lacquered the oxidation reaction between the aluminium and the air is stopped. Quote Link to comment Share on other sites More sharing options...
Tartridge Posted January 21, 2005 Report Share Posted January 21, 2005 just a few questions: what size hole is best - its just a hairline crack that goes from the top of the chainstay to the underside? also, is it ok to use just any drill and is there a preferred speed to drill at? ← Use something small - 2-3mm diameter is about right. Any drill will do, drill at approx 30m/minute... so... basically, as fast as you like. Quote Link to comment Share on other sites More sharing options...
andyroo Posted January 21, 2005 Report Share Posted January 21, 2005 Id say £80 of a new T-Rex frame sounds like a good option! Quote Link to comment Share on other sites More sharing options...
colly Posted January 21, 2005 Report Share Posted January 21, 2005 Its also advisable to do this before welding over a crack too. and v the crack out so it cant spread, just get a m-a-d for £100 or get a base ta26. :blink: Quote Link to comment Share on other sites More sharing options...
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