I bought this Petromax back to Germany from Italy.It was apparently used little. However,it had two built-in defects,which certainly explains why it was used so little.It had a crack in the riser pipe from top to bottom.Luckily I had such a vaporizer in my spare parts inventory. But there was something else. The preston loop was thicker than on Petromax lanterns usual.I've only found these thick tube on Petromaxlanterns made in the early 1940s. Well ,it doesent work properly.Then I installed a pre-war vaporizer for 500 HK lanterns from my inventory and from then on the Petromax 826 lit up perfectly.
Congratulations on the restoration. I think a lantern is only truly valuable when it's lit. Even so, it looks quite beautiful for a pre-war lantern.
Very nice. The two screws on cap design was no longer used in this 1941 Px826. I can see it still retained most of the pre-war design features. Except, I think, both the outer and inner hoods had changed more towards the post-War designs common for units made in Altena. The hoods are not yet completely like later Altena models though. The two flat-nuts for J-tube still present. I personally still prefer this look over the later models.
Regarding thick tubes I have one vaporizer with particulary thick tube - it is approx. 9,5 - 10mm diameter. It comes from green 1941 821 lamp. Pictures attached with several other thick and one "normal" vaporizer. There were planty of different variations of Px lamps manufactured during the war so everything is possible. From the other hand, that tube was repaired (soldered) in the past, so maybe that affected tube thickness somehow... Anyway, this is a really good looking 826 lamp that you have @Reinhard all the best, Piotrek
What is the normal outer diametre of the tube that forms the loop on Petromax vaporizers? I have measured them before but couldn't quite remember the exact dimension. I could only recall those that I measured were less than 3/8"(9.525mm). Maybe something closer to between 5/16"(~7.94mm) to 11/32"(~8.73mm)? I even bought a few brass tubes of various diametres some years ago, anticipating that I might make some of the Preston loops myself someday .
Tube diameter in my most "normal" Px lamps (two prewar 827 and one prewar 826) is approx. 7-8mm depending where I meausre it. My war time lamps have approx. 1mm thicker tubes (just like the subject 826 example) and the one I mentioned above with exceptionally thick tube has approx. 9,5-10mm. As I mentioned I have very limited number of "regular" lamps so others may know better. Bend tubes have no circular cross-sections so it hard to determine orginal pipe diameter.
It isn't so easy to accurately measure the diametre of a tube that has already been bent into a loop. Normally, I would close in the calipers from this direction:- Jaws of the caliper lined-up so that it forms a straight line intersecting the approx. centre point of the loop. (Roughly so). A clamping point which I think the bending radius of the loop wouldn't affect or distort the tube's "cross-sectional" diametre so much.
Hi @MYN So when measuring as above I get higher results approx. 8mm for my prewar lamps and approx. 9mm for wartime lamps. When you measure like Reinhard did you get approx. 0,5mm less. I wonder how tube diameter impacts lamp performance. I personally would prefer these thicker tubes, because they are less prone to be clogged and easier to clean inside. Thicker tubes most likely have higher heat retention, but I am not sure if that really matters. I never do any micro adjustments to get highest possible light output. It seems that the tube diameter is just some more or less interesting fact for and apparently for not-German as well
I can't say for all situations. In my opinion and from my experience, it depends on the tube wall thickness too. Tube outer diametres might affect vaporization up to some extents. The optimum loop temperature should be not too high. Just enough to fully vaporize kerosene but not so high that it would cause rapid and severe fuel carbonization. I do have at least two Petromax where their looped section would become glowing red-hot during operation.(in my opinion, it isn't ideal in the long term). If the loop contains more brass material, (i.e., thicker, heavier), it would have a higher heat capacity and be less likely to glow red from locallized heating from the mantle's emanation.
