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Biggles567
@M_V
How much heat does it take to distort a tube?
Less than I thought it seems.
I’m doing a top tube replacement on an S&S couplered Thorn Nomad. Im only replacing from the coupler forward.
Did the fillet brazed joint between the top tube and headtube the other day and with the coupler half just slid (but really snuggly) onto the other end of the toptube the frame fit together super nice.
Silver brazed the coupler half and the cable guides along the bottom of the toptube today and when I undid the couplers to pull it apart to soak the flux off, it pinged.
The ends of the tubes had moved closer together. Still horizontally aligned but vertically out by around 3-4mm.
I can’t see that brazing the coupler half onto the end of the tube could have caused this so it must have been putting the cable braze-ons along the under side of the tube that did it.
Holding a 6” steel rule along the top of the tube does maybe show a slight convex distortion at the point of one of the braze-ons. I might just be looking at it too hard though!
Its not a problem, I’m certain I can cold set it out but it was just really interesting that the heat from attaching braze-ons could do this. I suppose this will be happening in normal frames too it’s just that the couplers make it much more noticeable.
Explains why every single frame I’ve ever cut up (and I’ve cut up quite a few) has done that ping.
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