Expansion chamber dent removal

[tri boy]

Has any body used any tried n true methods for removing dents? (about 1/2" deep).
I have heard of both the low compressed air and gentlely heating the dent method.
The "freeze the dent out" method.
And finally "tack a bit of welding rod on the dent, heat n pull" method.
I would like to hear from those that have actually had good success at any of these methods, or any others.
Cheers.
There are two dents. One slightly creased, and the other a smooth dent.

[ozrobo]

ive seen the last done it works well its all good if you dont arc out

[tri boy]

Ya lost me on the "arc out" bit mate.
Could you please elaborate.
(I was under the impression that it would work by fusion/gas welding say a 2.25 gp arc welding rod (minus the flux), to the approx centre of the dent, and then heat the dented area up, while trying to pull the dented area up.
The finish mightn't be as good as some of the pressured systems, but less likely to rupture the pipe, or turn it into a overpressurised bomb.

[MXNUT]

Has any body used any tried n true methods for removing dents? (about 1/2" deep).
I have heard of both the low compressed air and gentlely heating the dent method.
The "freeze the dent out" method.
And finally "tack a bit of welding rod on the dent, heat n pull" method.
I would like to hear from those that have actually had good success at any of these methods, or any others.
Cheers.
There are two dents. One slightly creased, and the other a smooth dent.

I use the compressed air method with a gas torch with excellent results.The trick is to not use too much heat ( very dull orange ) or too much air pressure.The smooth dent will come out a lot easier the the creased dent.
Advantage of this method is it leaves no tell tale marks on pipe.

[Motu]

The old school panelbeating method was to braze a rod on for pulling,then it could be removed easily with out damage.These days they use a stud gun which spot welds a stud for slide hammer use...a twist and they come off with hardly a mark.Pressure and heat with one of those would be the go.Ginger uses his water blaster at home to blow up two dimensional expansion chambers.

[tri boy]

Cool. That was the method I was leaning towards. I have a regulator for the air, so would 10-15psi sound about right?
Also, what is your preferred end capping system?
I was thinking of modifying some engine block "frost plugs" to suit, and fit a tyre valve to one of them to facilitate air control. (it would also be cool to monitor pressure rise via an air gauge pushed onto the valve ocassionaly).
Do you braze the end caps on for safety, or just clamp?
Sorry bout all the questions, but this is one type of repair I have never done, and doing a good job is rewarding.
Cheers.
Thanks also Motu, I was typing as you replied.

[MXNUT]

I have never got that technical to use a regulator so dont know about exact pressures.As for blocking the ends i use rubber bungs and just get a helper to hold 1 of them in place.Larger end bung i got from place that sells parts for milking machines. Smaller end rubber bung (think i got from para rubber ) i drilled hole through centre and just use an air duster gun in short blasts.

[tri boy]

Cheers for that.

[zxcvbnm]

Car shock/suspension bushes are good and I use a mag wheel valve stem on the small end. I think I get to around 60psi depending on the dent sometimes, just make sure the ends of the pipe are pointing at something solid.

[gazza2008au]

u can drill a small hole in the dint use a slide hammer used for pulling dints in car pannels than tack weld the hole grind it off done deal

[KDXKID]

just fixed a massive dent in ktm200 exhaust.
welded lug to centre of dent and the heated outside of dent line, pull lug with slide hamer and bingo ,fixed.

[RMS eng]

i have fixed a lot of dents in pipes for customers of mine,useing gas torch and compressed air,but you need to have the inside of the pipe cleaned well.as old oil,gas or carbon could make your pipe in to a bomb.and the end caps need to be wired on or they could kill some one.check out my web site,it is alittle old but has a photo of a pipe that i repaired
www.rms-engnz.netfirms.com