Rich Posted January 9, 2012 Report Share Posted January 9, 2012 As per pics, I'm replacing the front frame tube on my early 350LC for a later one with the built in stabiliser mounts (sourced from a scrap frame). I have cut out the old tube and positioned the replacement using a set of scrap crankcases as a jig. However, there are some gaps in the joins as it's quite difficult to shape the ends to fit perfectly round the curved surface of the downtubes and get it back in! The biggest gap is about 4-5mm. Will this matter or could a good welder fill those gaps ok? Plan is to get a mate to tack it in place with a mig then will get the whole lot welded up by a pro. Cheers Link to comment Share on other sites More sharing options...
speedy sie Posted January 9, 2012 Report Share Posted January 9, 2012 yep good welder can fill any gap...even the old camel toe gap!! and looking at the gaps yes they can be filled,but best to be closser. Link to comment Share on other sites More sharing options...
RonniB Posted January 9, 2012 Report Share Posted January 9, 2012 It can be done, but if you should do it is another matter. Problem being that metal will tend to pull toward each other, meaning in this case that your frame rails will distort inwards. But it's definatly doable, just do it slowly, you (your mate) basicly tackweld all the way round, giving it plenty time to cool off. Then when all the gaps are filled, you grind the weld down and redo it. This advice is not based on being a welder of any special sort, had some formal training long time ago, and have knocked out the odd subframe, bracket and paddock stand from time to time. But nothing broke yet.. Link to comment Share on other sites More sharing options...
Rich Posted January 9, 2012 Author Report Share Posted January 9, 2012 Cheers guys. Link to comment Share on other sites More sharing options...
kja.busa Posted January 9, 2012 Report Share Posted January 9, 2012 Have it tig welded and done in stages spreading the heat, this will lessen the distortion. Its an easy job to do too for someone in the know. Link to comment Share on other sites More sharing options...
Gregorious77 Posted January 9, 2012 Report Share Posted January 9, 2012 That would take literally mins to MIG up, it will pull in and close the gap up though unless clamped so it cant move. IMO TIG will put a lot more heat and therefore distortion into the metal. (slower) Link to comment Share on other sites More sharing options...
porter_jamie Posted January 9, 2012 Report Share Posted January 9, 2012 see, what i would do is: cut out that portion of the donor frame, and cut it in half lengthways. use this to take up the extra width you need, (obviously you will need to dress it out a bit so the radius fits. and as a bonus you get some extra strength in that area. dress it up so i looks like it's supposed to be there, weld it to the frame (carefully), even drill a hole in it, and weld that too, so it is fixed on properly where the cross piece fits. Weld the cross piece to the new slightly narrower frame. not sure i have been very clear, sorry. Link to comment Share on other sites More sharing options...
2T Institue Posted January 9, 2012 Report Share Posted January 9, 2012 Gaps are bad news for frames as are MIG welders. A "good" welder would tell you to make the tube fit better. Filling gaps with MIG is a bodge of the highest order. There is the big possiblity that you will over heat the tube which will lead to cracks. Build the ends of the tube up with the MIG and shape with a die grinder until the gaps are around 1mm. Then braze (manganese bronze) or TIG in. Before you do that, you need to gradualy heat the tube, cheap flood lights get the tube up to 80 or 90 deg C and make it much easier to weld.Leave the flood lights on after welding and wrap in old fire blanket. Worst thing ever for a frame joint is to be brittle, fast heating and cooling leads to embrittlement. HTH Link to comment Share on other sites More sharing options...
speedy sie Posted January 9, 2012 Report Share Posted January 9, 2012 lets get with the program chaps...it a tube with some engine brackets on...throw this is the bin,and make up a new part...its not that bloody hard,and looking at the gaps in the tube now!!!...well look at the bloody slugs holding the mount on now...scrap this and make a new. Link to comment Share on other sites More sharing options...
vfiend Posted January 9, 2012 Report Share Posted January 9, 2012 That would take literally mins to MIG up, it will pull in and close the gap up though unless clamped so it cant move. IMO TIG will put a lot more heat and therefore distortion into the metal. (slower) TIG will take longer and put lots of heat in the frame, I've twisted a subframe out of line taking too long to tig up some bracing, learning by mistakes, woop. Mild steel tube is dirt cheap, so is plate. You could spend only a little bit of time making something really nice, Grinding off little by little and gently tapping in can get a really nice fit too. Link to comment Share on other sites More sharing options...
porter_jamie Posted January 9, 2012 Report Share Posted January 9, 2012 lets get with the program chaps...it a tube with some engine brackets on...throw this is the bin,and make up a new part...its not that bloody hard,and looking gaps in the tube now!!!...well look at the bloody slugs holding the mount on now...scrap this and make a new. or, do this. the new bracket does look like a bit of a dogs dinner. a nice made to measure one would be a lot better tbh Link to comment Share on other sites More sharing options...
speedy sie Posted January 9, 2012 Report Share Posted January 9, 2012 Link to comment Share on other sites More sharing options...
kaighn80 Posted January 9, 2012 Report Share Posted January 9, 2012 i'm of the same opinion as some of these guys, throw that piece away and start fresh, where are you rich? i have some cds tube you could have but i'm in essex, then you'll need some plate, make the tube fit properly then make brackets from steel plate and roberts your cross dressing monkeys uncle fucker. get your mate to tack it in place with a couple of tacks here and there, don't go overboard, than have it tigged up. leave the case in as a frame jig. Link to comment Share on other sites More sharing options...
Superdunc Posted January 9, 2012 Report Share Posted January 9, 2012 If you had a bespoke race frame made out of 20g and 18g tube I would say you've fucked up. As it is it'a fairly thick wall tube and would of been mig welded from the factory, probably with similar gaps. A competent mig welder should be able to weld that up for you no problem, it will be a bit of a faf, and will pull a little bit, but you have plenty of safety margin. So while all the advice given is sound, I would be quite happy to mig that on and fill the gaps. should look factory too. Link to comment Share on other sites More sharing options...
kaighn80 Posted January 10, 2012 Report Share Posted January 10, 2012 i had a look at one of them 350z things, it was a convertible one, you could clearly see the welding that reinforced the rear suspension mounts, i'm firmly convinced that if i were to buy one (which cant happen as i have nowt but shirt buttons) i would then spend a few weeks going through it re-welding all the shit joints that had been left by the more accurate robots. Link to comment Share on other sites More sharing options...
Conica Posted January 10, 2012 Report Share Posted January 10, 2012 Just fucking weld it, HTH. Link to comment Share on other sites More sharing options...
kaighn80 Posted January 10, 2012 Report Share Posted January 10, 2012 If you had a bespoke race frame made out of 20g and 18g tube I would say you've fucked up. As it is it'a fairly thick wall tube and would of been mig welded from the factory, probably with similar gaps. A competent mig welder should be able to weld that up for you no problem, it will be a bit of a faf, and will pull a little bit, but you have plenty of safety margin. So while all the advice given is sound, I would be quite happy to mig that on and fill the gaps. should look factory too. ^^This. After all, how do you think the frame was made in the factory? Though it wouldn't look factory, as most factory welding is like bird scutter! manufacturers don't have the time it would take to make sure that every tube fitted spot on, they have to take the close enough approach due to slight differences in the pieces being used and tolerances, I'm not saying your wrong, but the reason the manufacturers do it that way is because its the cheapest and most time efficient after all its easier to weld a gap than to stop a production line because the bit that was just cut to go in the frame at the back end was too long and needs an angle grinder taking to it to make it fit properly. Link to comment Share on other sites More sharing options...
Superdunc Posted January 10, 2012 Report Share Posted January 10, 2012 manufacturers don't have the time it would take to make sure that every tube fitted spot on, they have to take the close enough approach due to slight differences in the pieces being used and tolerances, I'm not saying your wrong, but the reason the manufacturers do it that way is because its the cheapest and most time efficient after all its easier to weld a gap than to stop a production line because the bit that was just cut to go in the frame at the back end was too long and needs an angle grinder taking to it to make it fit properly. Indeed. If it's good enough for Yamaha, it's good enough for the man in th shed. If you have the resources you could build it to motogp standards, but lets not give poor Rich a heart attack, with talk of tig welders, and heat treatmnt. Link to comment Share on other sites More sharing options...
alexp5 Posted January 10, 2012 Report Share Posted January 10, 2012 Indeed. If it's good enough for Yamaha, it's good enough for the man in th shed. If you have the resources you could build it to motogp standards, but lets not give poor Rich a heart attack, with talk of tig welders, and heat treatmnt. ^This. Look at the state of the pigeon shit masquerading as factory welds on that frame. If it was good enough for Yamaha, it'll be good enough for blerk in t'shed. Tig welding and pre/post heat treating = bollocks. That frame would've been built from the cheapest low grade mild steel Yamaha could lay their mitts on. It would've been thrown together in a battered old worn out jig with sloppy tolerances by a bloke who isn't paid enough. The engineering drawings might say tolerances of +/-0.25mm but in reality it'll be more like +/-3 or 4 mm. A gap like that isn't unusal. If you are worried about distortion, an offcut of something like 20x20 box tacked in above or below the piece you want to weld in will stop the frame rails from pulling in. Let it cool down fully before you cut it out. Link to comment Share on other sites More sharing options...
Gregorious77 Posted January 10, 2012 Report Share Posted January 10, 2012 You migged it up yet? Could have done it by now! Link to comment Share on other sites More sharing options...
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