To learn more about metal working I bought couple of books from 50's from a shop that sells old/used books. Old books are good since they describe everything from the basic without any automatic options/shortcuts. Books are translations from original Swedish books called "Handbok i verkstadteknik" written by Ragnar Woxén at al. In materials part there was couple of interesting information about brass qualities that were used for kerosene stoves & blow torches. Brass that has 63% Cu and 37% Zn is mentioned to be used for tanks/founts of kerosene stoves and blow torches. It had(old) Swedish standard number 5151. Brass that has 62% Cu, 1,5% Pb and 36,5% Zn is mentioned to be used kerosene stove parts. It had(old) Swedish standard number 5152.
*Very* cool info. Lead (Pb) is often used to improve the machinabilty of brass --it's still used today in cheap brass plumbing fixtures, which can be problematic if they're channelling drinking water. Anyway, lead wouldn't be necessary in the formed sheet metal founts, but would be very useful for the machined parts. Alex
The amount of lead leaching from brass plumbing fittings is unlikely to be a health problem unless you have corrosive water. In the days before premade fittings all pipework was soldered with lead plumbers solder. Its not like the days of Juleus Ceaser when the complete plumbing network was all lead. In his case they should of realised something was amiss when he invented that salad
I wonder if the forming of brass fuel tanks without adequate annealing before deep-drawing/pressing was the primary cause of stress cracks rather than the constituents of the brass alloy.
I would guess yes. I know that in metal spinning of cupric alloys annealing --sometimes repeatedly-- is everything. I have both a brass lamp fount and a brass clock housing that have fatal stress cracks; I always figured it was because of poor annealing. There's only so much movement cupric alloys can take before the work-hardening catches up and the internal stresses find their own way out. Is there any difference in the incidence if stress fractures in founts with hard corners (Pr210) vs. those with softer corners (Op00)? Alex
Wiki has interesting info on brasses, too. This link is to the specific section on "season cracking", but the section directly below it lists various alloys, including Swedish standard 5151, listed there as "common brass" or "rivet brass", and called out for its suitabilty for working cold: https://en.wikipedia.org/wiki/Brass#Season_cracking Swedish standard 5152 isn't mentioned specifically --which I find interesting in itself. I would like to know what considerations went into developing that alloy, and whether it was a pre-standardization version of "free-machining brass" or a deliberate alloy in its own right. Sorry if that's too much, but as a patternmaker at a bronze foundry I can geek out on alloys. Alex
Lead (pb) is often put with alloys and steel's to improve its machinability, and thus labelled 'free machining' . Interesting post
A long time ago (when i had an impressive head of hair !!), I was asked to test a small brass pressure vessel that held light lubrication oil as a font for a very old machine auto lube system. I had just learnt how to correctly use a dial guage so I set up this brass barrel font in a jig and then carefully set up the dial guage. Every test I did by cycling through pressurising and then release caused the guage to pick up the movement of the brass tank sidewall. I cant recall the figures but it did surprise me as proof that the tank was under regular stress cycles during pressurisation and release. I guess paraffin stove fonts do exactly the same over their working lives and the life expectancy of said stove fonts are probably directly related to the accurate tempering and working of the brass whilst being formed as well as the alloying recipe the factory specified from their original sheet supplier. Mike
That brass that contains 63% Cu and 37% Zn seems to be 'a common brass' and good for cold forming: https://en.wikipedia.org/wiki/Brass I have a catalog from a local 'special metals' supplier and their round and hex bar have 58% Cu, 39% Zn and 3% Pb so it should be good for machining or as @Longilily mentions free (for) machining.
Unless the finished component was stress-relieved after the final shaping process, I think that would be very likely. Sharp corners in components (metal, wood or plastic) are notorious stress concentrators; this is a term used to describe a shape which concentrates a high percentage of the total applied load onto a particular spot in a component. A classic example which most of us have seen is when you want to shorten a stick or pole that is too strong to be broken over your knee; apply a fair amount of force to it, and it bends evenly throughout its length. But, if you cut a notch in it with a knife or hatchet, and then bend it over your knee, most of the length bends very little, whereas the notched section bends a lot until it breaks - and it breaks under a much smaller load than it would have done if the notch wasn't there. The other consideration is the ambient temperature in which the material is to be used. Even ductile metals have a critical temperature at which point they rapidly become very brittle, and far more likely to crack. This was one of the prime causes of the serious metal fatigue failures in the early Liberty Ships, of WWII, when they were exposed to very cold water temperatures in the North Atlantic. Though most of the results were limited to cracks in the hulls, and cracks radiating outwards from the corners of cargo hatches, three Liberty Ships broke in half without warning. (It is suspected by many who have studied the available evidence that cold-temperature brittleness was a key factor in the way that the iceberg ripped along the hull of the 'Titanic', and the gash opening up to the extent it did. The grade of steel used was later found to suffer quite badly from low-temperature brittleness, which had not been a problem with ships built of wrought iron, which is considerably more ductile than steel, even at sub-zero temperatures) The problem with the Liberty Ship was solved by Constance Tipper, a metallurgist at Cambridge University. Her research proved that the cracks did not originate in the welding, as originally suspected, but in the brittle metal outside the welds. Once the cracks started to form, however, Tipper showed that there was nothing to stop the cracks spreading throughout the fully-welded hull of the Liberty Ships - whereas in a ship built of separate plates riveted together, once a crack reached the edge of the plate where it started, it could not spread further. (In 1949 Tipper was appointed as a Reader at Cambridge University - the only full-time woman member of the Faculty of Engineering - and was later the first person to use a scanning electron microscope to study fracture faces in metal components) The fact that camp stoves may be used in sub-zero temperatures makes not only the shape of the individual components, but also the choice of metal alloys critical from the point of view of preventing leaks or even total failure under pressure.
@Gunner, yes, exactly! As a patternmaker for a local bronze foundry, I am aware how the junction of planes is of considerable importance. The foundry owner is a stickler for good fillets, to turn corners into fair curves --and with good reason. They are, indeed, stress-risers. Which is why I wondered whether anyone had noticed any difference between the curvier stoves and the more angular stoves re: incidence of stress cracks. The next question, brought up by your post, is whether anyone has observed a higher incidence of stress fractures in stoves used predominantly in cold climates --but that would be a tough one to chronical. (I had heard the theory that Titanic's holing was exacerbated by brittle steel and cold water, but I had not heard the story of the Liberty Ships, their failures, and the subsequent identification/recognition of the problem. *Very* interesting. Thank you.) Alex
@Pitsligo That point about the vital importance of fillets was made by Phil Irving, in his book 'Motorcycle Engineering'. In the section on making a crank-pin for a heavily stressed engine, he stated that a fillet with a radius as small as 1/32" could mean the difference between success and failure, and that room had to be found for it, even if it meant cutting into the shoulder of the crank-pin where it butted up against the flywheels. You're welcome, Alex! Constance Tippett was just one of many women who rendered service of incalculable value to the war effort between 1939 and 1945 - and most of them gained little public recognition for their work.
