Smoothing welds

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  • Been building a few Felt road bikes at work and they have these slightly smoothed out welds. Not a real smooth transition like you get on a Cannondale but just like they've taken the ripples out of a standard weld. Bottom bracket welds are of the regular chewing gum variety so I'm thinking the rest of the welds probably started as something similar.

    Just wondered if anyone knows anything more about the process and if anyone's had a go?

    Thinkin it might be nice just to tone down the welds on my Pre Cursa if nothing else.

  • Under the paint I'm guessing you'll find a skim of putty to smooth the basic weld .. thats common practice on painted aluminium frames. Cannondale’s uses a double-pass weld .. a crude description of the process is a 1st "chewing gum" weld for structural strength with a 2nd aesthetic weld to fill the "chewing gum" and smooth the finish.

    A good aluminium weld is a thing of beauty .. Frank the welders work

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  • I was under the impression that Cannondale smoothed the welds purely by removing material, hence their reputation as 'Crack'n'fail'.

    I'd be exceedingly surprised if the Felts were filler, far too time and labour intensive.

  • That's a beautiful piece of welding and If the welds on my frame looked anything like that, I'd be all for keeping them. Suppose Felt might use filler. As far as I can tell, Boardman frames are half made of bodge so I don't think there can be any kind of cost issue associated with it.

    Unfortunately my frame's lookin like it's going to end up bare metal so I might just have to give em a bit of a sand and leave it at that.

  • I was under the impression that Cannondale smoothed the welds purely by removing material, hence their reputation as 'Crack'n'fail'.

    A smooth weld should actually be stronger - obviously there is some balance between 'physically larger but unsmooth weld' and 'physically smaller but smooth weld', if you see what I mean. The pits and valleys in a 'chewing gum' weld are all stress raisers - cracks are more likely to start/propagate in valleys and less likely to start/propagate over smooth areas. Cannondale's reputation (if true) is presumably more to do with the design rather than the manufacturing.

  • Yeah, I don't think I've ever seen a Cannondale fail because of the smooth welds. They tend to crack where the tube meets the weld but that's very common in frame failures from any brand.

  • Sorry for old bump but I'm contemplating using Sugru or something similar to smooth out the welds on my stripped Pre Cursa frame. Is this a terrible idea or is there an alternative I should consider?

  • Automotive body filler would probably be easiest

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Smoothing welds

Posted by Avatar for Chris_Borneo @Chris_Borneo