Any tricks to pushing dent out of head tube?
08-24-18, 05:38 PM
#1
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Any tricks to pushing dent out of head tube?
I jumped at a bargain, and when I got it home and started the cleaup I found a nice dent on the headtube on the inside of the frame triangle. t The steate tube seems unaffected and the damage seems to be cosmetic. The bike has no intrinsic value beyond being another project so I'm looking to fix this my self with out any significant investments. That said my plan so far is to find a piece of PVC pipe that will fit in the head tube past the dent with a slit cut in it with a 1" ID. I figure if I set the slit 90 degree to the dent and then insert a quill stem with the wedge behind the dent I should be able to push the dent in a controlled manner.
Any other Ideas? Thanks, Woody
Any other Ideas? Thanks, Woody
Last edited by bark_eater; 08-24-18 at 06:01 PM.
08-24-18, 05:50 PM
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Lookin at it a little closer and it looks like ti was caused by being overstressed. The rest of the tubes look ok and the fork looks reasonable. the wheels look undamaged. I guess it could have been a crash with this being the only damage.
Last edited by bark_eater; 08-24-18 at 06:11 PM.
08-24-18, 10:25 PM
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Yes it has been over stressed but not likely by any crash. Since there's no outward deformation, only inwards to my eyes, The most common reason is a force from the outside pressing inward. Like when placing the bike on a car rack arm and the bike gets hit from the front end or some other object with a soft surface presses against the backside of the head tube. The lack of paint marring suggests a possible factory boo boo before the paint was applied. As long as the bike tracks well I would leave it as is. But an instrument repair person might have the right sized mandrel to force the dent out. I suspect this has been there for many miles. The beauty of mid grade steel is it's robustness in this kind of thing. Just think about all the chain stays with dents... I mean clearance crimps. Andy
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AndrewRStewart
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08-25-18, 12:20 AM
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One thing to keep in mind is that when you get a dent, the metal stretches.. it's not going to shrink back up. So, don't convince yourself that it's possible to just "pop it" back into place. You may be able to minimize the deformation, and I doubt you'd make it any worse with your quill idea... so by all means, try it. Before you do that, you may have more luck heating it with a hot air gun first and/or spraying it with cold air (transitioning between the two sometimes has an effect (although, probably unlikely in this case). Just make sure that you keep the pressure over as much surface area as possible... if you start sticking metal bars into the tube, there's a good chance you'll end up cracking it at the dent. If it doesn't affect steering, I'd just use some JB Weld to fill in the gap and paint over it. If you want to fix it right, talk to a frame builder.. (maybe one will chime in).
08-26-18, 04:44 AM
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Well it worked. The dents swaged right out. The original deformation looked a little like a pinch in clay, with a ridge in between so there were some paint cracks. The paint is a little worse but I think some clear nail pollish will hold the edges together. This bike is a Motobecane, and a search for for simular damage came up with a couple more Motobecanes with deformed head tubes.
