A recent Tilley pork pie i purchased must have been used by the previous owner to support something heavy. As a result the brass hood has squashed downwards by a cm or two, closing the vents. (I can post a photo tomorrow if that would help to describe the situation.) The brass sections between the open vent sections have folded over under the weight. I’m wondering how to approach straightening them without cracking the brass. Is this likely to work and would doing this at high temp be best? Any advice welcome.
With these old pork pies, and their thin brass hoods, I usually just dismantle the components and reshape the hood by hand, then use a small peening hammer and a parallel-sided adjustable spanner to get the last kinks and dents out. Tony
As Fireexit1 said, anneal first, let it cool then straighten the hood. After getting the worst of the damage fixed, it might be worth annealing again before finishing the repair.
After annealing the brass will be nice and soft, as you bend it it will work harden and you will feel it getting less bendy. You will need to anneal it again and bend it some more. If it is really bent you may have to anneal several times, if in doubt remember you can't anneal to many times but you can crack it if you don't. Hope this helps James
To anneal properly you need to heat and quench.. not sure if that would make it too soft but as said the re-bending will start to stiffen/work harden Has someone already covered repairing these in a tutorial?? It’s a common fault with the early caps ?
I need to do more research to make sure I have my facts correct, but when I was a lad we were taught how to anneal brass and steel. I was told that the two metals are exactly opposite in terms of how you either soften them (anneal) or harden them. Brass is hardened when it is heated to 370C and allowed to cool slowly. It is softened when it is heated to the same point and cooled rapidly - quenched in water usually. Steel on the other hand is hardened when it is heated to cherry and quenched. It is annealed by heating it and allowing it to cool slowly... very slowly which will affect the metals crystaline structure. As I say, I need to check this thouroughly but I believe this is the case.
As I understand it, brass is annealed as a result of heating process. Quenching stops you burning your fingers but doesn't affect the brass.
If there are any metalurgists out there who could clarify the correct processes involved that would be great.
In practice, I have greatly soften a bunch of springy-stiff brass wires by heating it to red-hot, hold the temperature at a specific temperature range and then quenching it in water. To harden them again, you need to work-harden it.
I seem to recall from metalurgy classes at college (a long time ago) when studying mechanical engineering it is about relieving internal stresses (or dislocations of molecules) caused by stretching the crystalline nature of the alloy. These metals also harden with age certain aluminium alloys especially prone to it). Heating allows the molecules in the crystalline structure to move about to a more regular arrangement (de-stressing them). Brass alloys can be quenched but it is not neccesary. Steel must not be quenched for annealing but cooled slowly - otherwise you are tempering it.
Thanks again for the advice. As it turned out the hardest part was getting the old burner out of a squashed hood - tubes jammed on tight angles and no room for tools or fingers. In the end I took a destructive approach to removing the insect screen and things got easier from there. Here are some photos, in the first one it’s just been degreased. I was keen to try the annealling because fixing it if it cracked is beyond my tool/skill level. Its closer to straight than it looks in the photo. The burner dome is dented too, so that’s the next task.
Glad to see you managed to straightened it out without breaking the three small tags, that's an achievement in itself, replacement enamelled caps are available from julian shaw at tilleylampsandstoves. Regards Ian.
Straitening out the legs that support the top hood is always a challenge. If someone has a good way of how to do this i would be happy to hear it. Especially with many legs or holes like a petromax and a overhanging top you can't get a pair of pliers or clamping thingy on it.
@Tony Press the strips of metal between the top side openings. Or the legs that make these holes. The parts that kep the top disc up. its not a simple flat piece but curves with the diameter of the hoods outside. Depending the model you have four or more. In this case you have easy acces but if you have a petromax style or the older models with round(ed) holes, rebending isn't that straight forward.
I had good success several times using a glass bottle that either fits snugly in the remaining round or is only slightly smaller than the remaining opening between the bent legs. Then I carefully roll the hood with the bottle in it back and forth on a flat, hard surface, slowly straightening out the bent legs. It may be necessary to use several bottles of different diameters in succession so that the pressure on the bent legs is distributed over as large an area as possible. Obviously, this only works when the cap had been taken off.
It’s now had a very thorough clean inside the fount, a light clean on the outside so as not to disturb the patina and a few new seals - I bought some gold paint but i quite like it as it is! Perhaps just a bit more cleaning?
Its great as it is with the patina. Painting it would destroy the time-acquired aged-look. A non-collector would then not be able to distinguish it from a recently-made copy(if there are any) by first impression. The choice is yours, of course.
