TubeNet

tuben wrote:Well, without knowing what sort of car this trick was done on..... It is important to remember that steel and brass are very different metals and I'm sure would react differently.

RC

I would tend to agree with this. I will say, however, that it is often heard in avaition circles that the small dents in an aluminum airplane that have been caused by a hailstorm can be removed with dry ice. (I have never seen this done so I have to catagorize this as a rumor.) About removing car dents you can watch this video.

Rubberlips wrote:I've seen a couple of demonstration videos on the net, showing how to remove dents from cars.
You heat up the spot with a hair dryer.
Then you spray liquid CO2 on it out of a can.
When the carbon dioxide ice has melted the dent is gone.
Does this really work?
Would it work on a tuba?
Have you tried it yourself?

This method is used on automobiles to remove small dings caused by hailstones, etc. It probably could work on a tuba, but only for very small dings. I don't think it would be very helpful in removing the bashes from bottom bows and wrinkles in bells.

I'm not recommending that you try this, in fact I'd discourage it. But I'm a life long tinkerer/Do-it-yourselfer so I will try things out for myself where as I wouldn't recommend it to others. But the magnetic dent removal system seems to be a good option for those with out several job specific tools and good soldering skills. But they can be pretty pricey as well. So being the determined sort that I am, I figured that there is a markup of these kits and if I look around on the net I can find the components of these kits and get an idea of the "real cost". I found rare earth magnets of the size in the kits for around $20 delivered and soft polish low carbon mild steel balls in the 1" and 2" variety for less that $10 each. And that is 3 of the 1" balls for less than $10. So as you can see you could get all the components for the magnetic dent removal kit for less that $100 shipped, which is a far cry less expensive than $350 for the kits they sell. I should receive all the components I ordered this week, and then see how it all works. I ordered a smallish magnet first ( $7 with 135lbs of force ). If it isn't strong enough for the job, I will get a bigger/stronger one. You have to be careful with the magnets as the are quite breakable and will fly out of your hand towards anything big and metal and shatter into a million pieces. Ask me how I know.

Next I'm going to try and make my own roller and die to smooth out the bell. Mind you I have allot of metal working tools to help me in my task, so I should be able to build one of these cheaply too.

Back in the seventies I worked at a body shop and we would flash the dent with a torch and then quench the spot with plain old water ice. Quite often the dent would, indeed, pop back up. But if the metal had been stretched too much, or creased, or crinkled... out came the slide hammer, backing shoe, hammer and bondo.

On a side note... I have been toying with the idea of an electromagnet "dent erasing" set up for years. I might dust off those ideas and build something.

The neodymium magnets work in areas where you can get a "big enough" ball into the tube. For 3/4 inch and 1 inch, you can get a neodymium magnet ball to go inside to get extra force with your 1.5 or 2 inch magnet outside. Depending on the thickness of the tubing, you might not get enough force with the 3/4 inch.

If you are doing this for the first time, it is a very good idea to experiment on a junk horn. The first few times, you stand an excellent chance of making things worse until you learn how much force the magnets can apply. A too big magnet with a too big ball inside can pull the metal outward. Get in the habit of looking around before putting the magnet down or moving it, and move slowly, always looking around.

Get a kitchen rolling pin too and a stiff, but not hard, hammer -- something like plastic or rawhide. The last home brew dent removal I did, I ended up using the rolling pin and hammer more than the magnets.

It is unlikely your homebrew dent removal will look "professional" (mine doesn't), but things can look a heck of a lot better than they did.

I'd like to have an variable power electro-magnet, but I haven't found anything. Maybe somebody with decent machining skills could do something with a car starter solenoid.

Do-It-Yourself dent removal? Scares me just to think about it. Somewhat akin to "Remove Your Own Gall Bladder in the Privacy of Your Own Home".

NDSPTuba wrote: You have to be careful with the magnets as the are quite breakable and will fly out of your hand towards anything big and metal and shatter into a million pieces. Ask me how I know.

Ok... How do you know?

MA

MaryAnn wrote:

NDSPTuba wrote: You have to be careful with the magnets as the are quite breakable and will fly out of your hand towards anything big and metal and shatter into a million pieces. Ask me how I know.

Ok... How do you know?

MA

I have more of a problem with steel objects chasing me around the shop! I have one magnet that will suck a pair of pliers off the bench from a foot away! Why do call those tools a PAIR of pliers, anyway?