Kenny--Trials Posted June 5, 2015 Author Report Share Posted June 5, 2015 It was bearing precession I was thinking of... I don't know what stage you're at, but you could maybe just try buying some pre-built BB shells? Companies do sell ready-made parts like that which might help you out if you're struggling. I cannot find anywhere which sells pre tapped aluminium shells in the grade that i want is the issue Would be pretty difficult to tap a thread that large nice and square , as above get hold of a bb she'll or ask a machinist to screw cut one for you tapping it square isnt the issue because of the way the tools are designed. the machinist idea is pretty good though but i feel like it would be quite easy for them to get it wrong Quote Link to comment Share on other sites More sharing options...
Mark W Posted June 5, 2015 Report Share Posted June 5, 2015 I cannot find anywhere which sells pre tapped aluminium shells in the grade that i want is the issue Which grade is that? Quote Link to comment Share on other sites More sharing options...
Alex Dark Posted June 5, 2015 Report Share Posted June 5, 2015 Wouldn't be too hard to machine a 1.37" x 24tpi thread. Pm me Quote Link to comment Share on other sites More sharing options...
Kenny--Trials Posted June 6, 2015 Author Report Share Posted June 6, 2015 (edited) Which grade is that? i think its 6082 ive found some press fit ones but ive been advised not to use them by co-workers because as i weld it up it will just distort like hell and then the bearings wont fit in Edited June 6, 2015 by Kenny--Trials Quote Link to comment Share on other sites More sharing options...
Mark W Posted June 6, 2015 Report Share Posted June 6, 2015 Well, they'll possibly still fit but they won't run particularly smoothly. That's why BMX frames almost all have post-weld machined BBs and head tubes. I've used a press-fit frame in the past that didn't have that, and the bearings would feel silky smooth just in your hand, but as soon as they were pressed into the frame they felt poop. I managed to sand the shell so it wasn't quite as ovalised and that made things better, but it still wasn't ideal. Quote Link to comment Share on other sites More sharing options...
aener Posted June 6, 2015 Report Share Posted June 6, 2015 Just to throw a spanner in the works, the frames I made didn't have post-weld machining done for the press-fit BB's and they were absolutely fine Quote Link to comment Share on other sites More sharing options...
Mark W Posted June 6, 2015 Report Share Posted June 6, 2015 Were they the ones with the Solid (?) made BB shells? Were they pretty thick walled? Quote Link to comment Share on other sites More sharing options...
Alex Dark Posted June 7, 2015 Report Share Posted June 7, 2015 6082 is the uk equivalent of 6061, far lower strength than 7075 that most trials frames are made from. you'll buy at t6 temper presumably but after welding will be at t0 at the haz ( heat affected zone ). Without heat treating the area around the welds will be significantly weaker due to the rapid cooling of the metal resulting in the crystalline bonds in the metal not aligning correctly. Pretty sure I'm right in saying that. 1 Quote Link to comment Share on other sites More sharing options...
Kenny--Trials Posted June 7, 2015 Author Report Share Posted June 7, 2015 (edited) 6082 is the uk equivalent of 6061, far lower strength than 7075 that most trials frames are made from. you'll buy at t6 temper presumably but after welding will be at t0 at the haz ( heat affected zone ). Without heat treating the area around the welds will be significantly weaker due to the rapid cooling of the metal resulting in the crystalline bonds in the metal not aligning correctly. Pretty sure I'm right in saying that. im almost certain that frames arent made of 7075 because 7075 is virtually impossible to weld without it cracking due to it cooling so quickly in relation to the rest of the material. i did look into making it from this but it just wouldnt work. it wouldnt be that hard to heat treat the welds would it? Well, they'll possibly still fit but they won't run particularly smoothly. That's why BMX frames almost all have post-weld machined BBs and head tubes. I've used a press-fit frame in the past that didn't have that, and the bearings would feel silky smooth just in your hand, but as soon as they were pressed into the frame they felt poop. I managed to sand the shell so it wasn't quite as ovalised and that made things better, but it still wasn't ideal. the proiblem is that i dont have access to a lathe big enough or a cnc machine to do that haha Edited June 7, 2015 by Kenny--Trials Quote Link to comment Share on other sites More sharing options...
aener Posted June 7, 2015 Report Share Posted June 7, 2015 Were they the ones with the Solid (?) made BB shells? Were they pretty thick walled? Yes and yes Don't know exactly how thick but I'd wager 1.5-2mm. Quote Link to comment Share on other sites More sharing options...
Ash-Kennard Posted June 8, 2015 Report Share Posted June 8, 2015 im almost certain that frames arent made of 7075 because 7075 is virtually impossible to weld without it cracking due to it cooling so quickly in relation to the rest of the material. i did look into making it from this but it just wouldnt work. it wouldnt be that hard to heat treat the welds would it? I seem to remember that 7075 is great for machined parts, 7005 and 6061 are often used for frame tubing. I was under the impression that the whole frame is usually heat treated? 1 Quote Link to comment Share on other sites More sharing options...
Kenny--Trials Posted June 8, 2015 Author Report Share Posted June 8, 2015 when we order in tubing at work we order it in pre heat treated and when you weld it up it looses that treatment. That's why I just assumed it was just the welds that need treating but I may be wrong Quote Link to comment Share on other sites More sharing options...
*gentlydoesit Posted June 10, 2015 Report Share Posted June 10, 2015 Nah, the whole structure would need annealing then re ageing to get consistent temper. If you bake t6 it gets to t9 (or something like that from memory ) and becomes brittle. It's almost impossible to isolate only the welds for treatment. Quote Link to comment Share on other sites More sharing options...
Kenny--Trials Posted June 12, 2015 Author Report Share Posted June 12, 2015 Got the bottom chainstays and most of the jig done today 1 Quote Link to comment Share on other sites More sharing options...
Kenny--Trials Posted July 17, 2015 Author Report Share Posted July 17, 2015 The frame is almost done, just have to cut the top chainstays in and sort out the dropouts but I'm now thinking about strengthening plates. So where is the most common places for frames to crack so I can make sure I make those areas as strong as possible Quote Link to comment Share on other sites More sharing options...
Herbertlemon102 Posted July 17, 2015 Report Share Posted July 17, 2015 Bb shell, head tube. Also, the opposing side to your front foot chainstay from failed sidehops, or would be good to see some extra strength there Quote Link to comment Share on other sites More sharing options...
Kenny--Trials Posted July 17, 2015 Author Report Share Posted July 17, 2015 i had those places in mind but i was just wondering where exactly, like is it the welds that crack or is it just next to them? Quote Link to comment Share on other sites More sharing options...
Herbertlemon102 Posted July 19, 2015 Report Share Posted July 19, 2015 It depends really but mostly they crack at the weld or very close to it. Not much help I know but Quote Link to comment Share on other sites More sharing options...
waybe2014 Posted July 19, 2015 Report Share Posted July 19, 2015 Also depends if it's disc brakes or rim brakes or both. Could always try carrying the welds on past where they would normally end. Quote Link to comment Share on other sites More sharing options...
Kenny--Trials Posted July 28, 2015 Author Report Share Posted July 28, 2015 i plan on running duel maggies, what do you mean carrying the welds on past where they normally end? Quote Link to comment Share on other sites More sharing options...
Mark W Posted July 29, 2015 Report Share Posted July 29, 2015 Like this: Quote Link to comment Share on other sites More sharing options...
waybe2014 Posted July 29, 2015 Report Share Posted July 29, 2015 That is what I meant but it only applies for disc mounts Quote Link to comment Share on other sites More sharing options...
Mark W Posted July 29, 2015 Report Share Posted July 29, 2015 You can do it with 4-bolt mounts too, theoretically. I think Try-All (or someone like that) did it at one point. Quote Link to comment Share on other sites More sharing options...
forteh Posted July 29, 2015 Report Share Posted July 29, 2015 Rockman spade and some tryall forks used the bead of weld to help transfer stresses away from the hs33 brake mounts. Quote Link to comment Share on other sites More sharing options...
Kenny--Trials Posted October 14, 2015 Author Report Share Posted October 14, 2015 Update: I'm so close to finishing now! It's all welded up, just got to put a few gussets on and make the brake mounts and it's done! 6 Quote Link to comment Share on other sites More sharing options...
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