I just picked up two svea 157 stoves that the seller said were in good condition with no dents or damage. The stoves looked very dirty and they were sold as one double burner stove with the connector for the two. The pictures showed both stoves connected , but one of the pumps was pointed to the rear, so I knew that they were the same model and were not supposed to be joined together to make a double burner as the 156 model should have been the stove with a right side tank. I did not notice any major damage in the pictures, but I was wrong. The stoves arrived and they both have badly dented endcaps, directly below the pump assemblies. The package was very well packed and the damage appears to have been there for some time. The seller made it right with me and issued a partial refund, but I would like to find a way to repair the dents if there is a way available without cutting the tank in half. I was thinking about pressurizing one of the tanks with a shrader valve and an air compressor, but am a little hesitant about the safety factor. Anyone have any other ideas that might work? I have been working on the worst one for the last day or so and have it cleaned up a bit and working very well on kerosene thanks to a Sefa pump leather, nitrile rubber, an acetylene torch and Kerophiles burner washers. I thought it would be setup for alcohol, but someone installed the same size jet and needle that my 111T's have . I am now a huge fan of the 1915 burner!!! I'll post some pics later. Thanks in advance for any help. Dan
Hi Dave, 1. It is very dangerous to pressurise vessels with a compresssible fluid like air or other gas. The amount of "stored" energy in the system means that if the vessel ruptures you are likely to have flying debris....Don't do it! 2. When professionals pressure-test vessels, they ensure that most of the internal space is taken up with an incompressible inert fluid, like water. Only a small amount of gas pressure is then needed to pressurise the vessel to the desired level. If the tank fails you get a "BANG" and a spray of water but usually no flying metal! 3. However you are also up against the laws of Physics, If you have a cylindrical vessel of thin,uniform, wall thickness, and you pressurise it, it is possible to calculate the stress (load per unit area) in each part. What you find is that the hoop stress is twice the longitudinal stress. This means that if you test to destruction the vessel will probably fail with an axial slit, rather than a radial split or blowing an end out. The geometry of stove tanks is complicated by domed ends, rolled/soldered seams, leg or bracket attachment points etc. but by applying pressure you will likely bulge and damage the main body of the tank before you push out dents in the ends of the cylinders. http://www.efunda.com/formulae/solid_mechanics/mat_mechanics/pressure_vessel.cfm 4. A general difficulty with any dent is that the material is "work-hardened" by the local distortion at the dent. It is therefore stronger and less ductile than the surrounding material! Best Regards, Kerophile.
Hello Dan, Kerophile has the authoritive answer, and I agree. The pressure trick only can work with slight dimples and such, where, importantly, the metal is not creased. Body shops use the method of weld-tacking a bolt, or eyelet to the metal to provide purchase. Then, with a sliding hammer or similar, you could "hammer out" most of the dents. With bare brass, you realy should consider whether the manufactured result would be an improvement over an honest dent. Show us some pics and you might have a worldwide vote on the matter! Regards, Mike
Thanks George and Mike. I would like to remove the dents, but would be worried that I would ruin the tank for future use, or even possibly have it blow up on me and send pieces flying. I will probably just leave the tanks the way they are. Here is a few pics for your review. The stove on the left that is burning was the worst of the two as it is heavily dented just below the pump tube. The stove on the right has a dimple that is pretty visible, but the rest of the stove is in better shape than the one on the left. Hopefully, this weekend, I'll have the second one up and running. Take care and thanks again. Dan
Hi Dan, great photos of two smart stoves. The "dents" are hardly noticeable and not worth removing IMO. Best Regards, Kerophile.
Just what I was about to write until George beat me to it! Great info George - nice to have some science & explanation behind why such attempts can fail. I agree - nothing too serious IMHO, although annoying if that's contrary to the description on ebay.
Hi, Just as an intellectual exercise; I was thinking how one might get these dents out if one really had to.....without dismanting the tank completely. If you were to "pull" the pump tube after un-soldering it, it would be possible to get a strong hook-shaped tool with a rounded end into the tank, and bearing on the dent area. It would then be possible to apply pressure selectively from the back wall of the tank-end. I am told by the experts in auto-body repair shops that dents which have developed "eye-brows" are the most difficult to deal with and you have to start by working inwards from the edges of the dent making small incremental "pushes" from the back wall, working towards the centre of the dent. I guess if you were concerned about the dent being harder and stronger than the surrounding material you could anneal it with a gas torch first. Once the dent is satisfactorily removed you can re-solder the pump-tube into the tank...... I certainly wouldn't advise such extreme actions, I like the character that the stoves have developed during their life-time. Just Thinking, Best Regards, Kerophile.
