Thanks George, I knew there was a ban on importing stoves but assumed they were bashing them out in Birmingham to maintain some form of supply for the domestic market. Makes sense if that were to be two pinters but I stand to be corrected. So it was just the burner design that was developed in war-time? Regards John
Hi @Jeopardy the Burner with top access to the jet was patented in 1943 by Townson and Coxson. It was used on Military contracts, and apppears to have been adopted fairly quickly by other British stove manufacturers, such as Valor for example: https://classiccampstoves.com/threads/valor-no-4601-roarer-burner.17814/ It has been suggested that the military contracts encouraged this adoption of the Townson and Coxson burner and may have specified adoption of this design. Best Regards, Kerophile.
Some additional details. The jet access, the Townson and Coxson patent of 1943 mentioned by Kerophile in his preceding post. In practice. In the Burmos 21 referred to in his post, Kerophile shows the original Burmos tool with a screwdriver at one end for unscrewing the access screw and a socket to fit the jet at the other. Without that tool, a silent burner jet key is an alternative, but only if it can fit through the 9/32 inch (7mm) access hole - not all jet keys are slim enough. A Primus or Optimus one would be but some aftermarket examples may not be. An articulated roarer burner jet key isn’t a possible fall back. It’s too bulky to fit through the space it normally could be accommodated on any other roarer burner, but not the Burmos. Something for @Ed Winskill. Ed, you spoke of the ‘copper’ hue to the spirit cup on your Burmos 21 and indeed that was the colour of mine too. Plenty of use of the stove this week, with much of this ... ... resulted in the spirit cup adopting a distinctly brassy colour. Here, I’ve taken a smidgen of metal polish to remove the brass ‘tarnish’ (for want of a better word). Evidently the brass colour is an oxide/tarnish that is a surface effect only. George (@kerophile), I’d appreciate your thoughts on that phenomenon, given your professional background as a metallurgist and your understanding of the behaviour and characteristics of metals. John
Hi John @presscall it is difficult to answer your question without knowing the precise composition of the brass alloy used to make the spirit-cup. In stove making the ductile 70/30 Copper/zinc alloys were commonly used for the tanks, pump tubes and spirit cups due to their good formability by rolling, pressing and drawing. They can also be soldered and brazed relatively easily. The burners, knobs and riser tubes were likely made from 60/40 Cu/Zn alloys, which offer higher strength and better casting behaviour. Pure Copper forms a copious, black, non-adherent, oxide scale when heated in air. The brass alloys tend to form more brass-coloured, adherent, and protective oxide scales when heated. The scale can be lighter in colour than the parent brass due to its zinc content, or Aluminium oxide content, if Al is a component of the alloy. If the thin protective scale is subsequently removed, the colour of the parent brass can be seen underneath. So, that is some of the theory, but I would need a full chemical composition of your brass spirit cup to be more specific. Many stove manufacturers used brass-plated steel for flame-rings and spirit-cups at times of brass shortages (like War-time production) but I assume that you did test your spirit-cup with a magnet.... Best Regards, Kerophile.
Thank you George (@kerophile) for what I knew would be a comprehensive and knowledgeable reply. Shame on me, no, I didn’t test it with a magnet. I just have and it’s plated steel. Why the plating takes on a copper hue sometimes and brass after a few stove firings is a mystery, but I’d best go easy on the metal polish to bring about a transformation or I’ll be down to the steel. Thanks George. John
Very interesting indeed. The copper-hue is quite distinct and seems clearly deliberate for the aesthetics of the stove. Or so I suppose, anyhow....
@presscall Hi John My two Burmos 21's have now become three! See if you can spot some more bakelite, firstly on my new stove and then on another example from the internet Seems pump rod ends weren't the only items to get made from bakelite! Incidentally, both these caps are from 'engraved' founts as opposed to the 'sticker' variety. Baz
@Go Scout I’ve seen another ‘21’ with an engraved tank (as opposed to logo decal) and a plastic pump knob since posting details of that one of mine, but a keeper cap in plastic/bakelite is a complete surprise. John
@presscall & @Go Scout I have a Burmos with the bakelite/hard plastic keep cap, and what looks like the same material as an (ineffective) pump cup. It’s unfettled, but I’ll get photos later today. Cheers Tony
I have had one of these stoves for more than 10 years never even looked at it before. Fired it up today got a small leak from the centre cap and maybe underneath. Ran ok for no work done. But I have no idea what the metal tube thing is for never seen one before and have a few similar stoves it was just in the tin it came in. I can see from your pics it just sits in a the clip. Thanks.
I do not know the correct name, but its a pilot light tube. It should have a clip to secure it to the burner, the wide end rests in the spirit cup and soaks up some of the preheat liquid, and starts a small flame at the narrow end. When the preheat fluid is spent, this flame burns on for a few seconds. If you close the ventscrew and pump pressure in the tank quickly, the stove will light from this flame. On my Burmos it looks like this: Tron
thank you for such a quick reply i am in australia and thought everyone would be asleep. that is such a good idea I shall give it a go. yours is nice and shiny mine is not, as long as works i am happy. off too make a brew on it now thanks again Tron
we had some restrictions because of virus but pretty much all lifted now. I am in western australia. and can not go to the other states but they are thousands of kilometres away
