Removing dents from frame tube

johndjmix

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Has anyone found a good method for this? I have one on the lower front tube behind the wheel that i need to get out.

I was thinking of trying the compressed air and torch method. Weld in a fitting, pressurise with 100psi and gently heat the dent and it will come out. This works great on thin tubes, but never tried it on 0.95 or 1.25 tube wall thickness's.

Option 2, heat the dent, drill a few holes and spend hours with a slide hammer. Urgh....dont want to do it this way.

Option 3, replace the tube. Its a long tube with a bunch of bends. Not an option currently.

Any ideas?

--John
 
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cjohnson

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Leave it. If it's so bad it has to be removed then the tube should really be replaced. Another quick and dirty repair is to cut out the bad section and weld in a new piece. Use two pieces of smaller diameter tubing to reinforce the butt welded seams. Use several plug welds to the inner tubes. You have to leave one or both of the inner tubes loose to install this setup in the middle of a tube then slide everything into place using the plug weld holes. Leave enough gap on the other tubes to just fill it in when everything is welded up. Grind it smooth and it will be very strong and nearly undetectable.
 

johndjmix

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Thanks for the suggestions guys. I’ve sleeved tubes before. Just did lower frame tube on my UTV. Just wondering if anyone had a trick.

—john
 

cjohnson

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I see. You could try a stud gun instead of the old style drill and screw slide hammer method. There are clamps that pull on a bunch of studs at the same time. I've had good luck pulling dents out of frames that way. Some people weld washers on edge in the dent, heat, pull, then grind the washer off.

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E.Hagle

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Replace the tube. Not sure how critical or load bearing the section is. You seem to know enough to know that bringing the material back out will only fatigue it further.
 
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Zambo

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Does it need to be pretty or just strong? You can laminate a "patch" over the dent using the next size bigger tubing. I've done this to the tubes behind the front wheels on both sides of my CanAm
 

jon coleman

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Seems to me if you have a tube chassis, every tube is integral to the strength of the chassis. Cut it out and replace it. No tech inspector will pass a bondo'd tube chassis.
oh, i thought it just had to get through the wholesale dealer auction, like when we used to get bikes ready at cycle express in El Cajon back in the day👍😉
 

cjohnson

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Seems to me if you have a tube chassis, every tube is integral to the strength of the chassis. Cut it out and replace it. No tech inspector will pass a bondo'd tube chassis.
I am appalled someone would take bondo seriously for a dented chassis tube when duct tape is a better color match. Silver for raw cages, brown for cages with some patina.🤣🤣🤣
 

johndjmix

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I forgot to post what i did here, but unbelievably, it worked.

Drilled a hole in the tube. Welded on a air fitting about 6" from the dent. Pressurized with about 80 psi of air.

With a welding helmet and full protection on, and from the side i carefully heated the dented area up. I couldn't believe it when i removed the torch, it was poping out. Did it a few more times and the dent was 95% gone. I could have kept going but didnt want to risk blowing it out when i had it so close.

So it works...might not be as strong at it was, but i dont think it weakened it that much. Hit a rock on it at KOH and it didnt dent at all.

Good trick to have in the bag.

--John
 

E.Hagle

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Do a little metallurgy homework and you’ll quickly find out why that worked. There’s plenty of parameters in that arena, but essentially you have weakened that material to about 50% of its original strength at around 1000 degrees. Allowing it to cool slowly is no bueno.

I don’t know much about heat treating but I do know that that you want to cool it quickly and evenly. Something about carbon atoms and such.
 
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JBuggy21

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Oh boy, I feel it… the internet metal experts are amassing…. Can’t wait to be learned…

Side note, I agree with Hagle. After heating atoms align different and it becomes brittle.

But please, let the education begin.
 

jon coleman

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ok;
 

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dirtslinger

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This was actually way more dangerous than you know, 80psi of air in a tube, is a ton of stored energy, if this would have blown out, you'd likely be dead or severely injured. I hope you don't this again.

Look up pneumatic testing, and the danger of stored energy.
 

Sheepdog

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I like the idea of a "patch" over it, diamond-shaped or something, so as not to create any stress points.
 
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johndjmix

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This was actually way more dangerous than you know, 80psi of air in a tube, is a ton of stored energy, if this would have blown out, you'd likely be dead or severely injured. I hope you don't this again.

Look up pneumatic testing, and the danger of stored energy.

Now on this I know all about, stored energy, Espically pressure, is nothing to mess with. This is Exactly why I was no where near the area where I was heating, I was off to the side behind a 5’ piece of 1/8 steel plate with a hole in the center to hold the torch.

You would be surprised how many people repair bike tubes and stand right in front of the spot they are heating with no protection at all! Insane.

—John
 
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