My first petromax, little problem with flames in the mixing pipe

  • Hi all,

    After long consideration bought my first 500CP.
    Also bought the heater and the cooking attachement, as well as a couple of reflectors.
    At the local dump I bought an old German army metal transport case, for just 25 euro's, including some tools and old mantels from various brands.

    After unpacking I checked all the screws. Some needed tightening. I felt the nozzle with the regulator wheel on 12 o'clock, I didn't feel the needle. With the wheel at six o'clock, I removed the nozzle and there it was, a bend needle. I replaced it with the spare one that came with it.

    Because of testing and tinkering with the heater element I used a couple of the old mantels that came along with the transport case, and I have to say, there's a lot of difference inbetween them. Some burned really bright, others not so.

    At the moment I got a little problem, I'm using a Petromax Helox mantle now, burns perfect, nice shape, but after a while the lamps makes a sudden loud PUFF, the light goes down, big time halo, and then the flame goes into the pretty red hot mixing pipe. Sometimes rotating the regulator wheel helps, but most of the time I have to bleed the air and let the lamp cool down. Any thoughts on this problem?

    Many thanks in advance.
    Kind regards

  • Hi all,

    After reading this forum for a couple of hours (tons and tons of info) I think I found the problem. :rofl:

    The reason for the mixing pipe to become this hot is that there was too much air in the mixture. I was a bike mechanic for a couple of years, and when a mixture is too lean, it gets too hot. :explode:

    I checked the height of the mixing pipe (original manual sucks big time in this area, nothing mentioned about adjusting the mixing pipe with the Petromax multitool), and it was 16 mm. It's supposed to be 14 mm. :wallbash:
    With the bend needle in the back of my head, and some other things, I'm under the impression that my lamp must be assambled on a monday morning by a crackpipe hitting guy/doll who just came rolling out of a bar after a serious drinking competition or sumthing like that... :frau:

    I tested the lamp with the mixing pipe 14 mm from the nozzle, and after a while, a big PUFF, and the same problem.
    Then I lowered it to 12 mm, and TADAAA: the problem was gone. One happy Dutchman :) :bounce:

    One must keep in mind that this lamp is ancient technology, and no lamp is the same. Every lamp is unique, and one must tinker with it a bit to get it adjusted perfectly. Also, the fuel we use nowadays is quality wise science fiction with the fuel they had 100 years ago when the lamp was designed, the fuel from today burns waaaay hotter then yesteryears fuel, keep that in mind.

    For fuel I use the normal lampoil they sell in the supermarket over here, Farmlight. Simple clear lampoil with an evaporation point of 61 degrees C. Pretty cheap too, about €1.75 per liter, better then the so called special fuel they sell here for €5 or more a liter, after all, I'm Dutch, and together with the Scott's we got a name to keep high, haha.

    Kind regards,

  • Hey Dutch,

    good you fixed the problem.
    But be aware: glowing mixing tube can also occure with a too fat mixture (flaming aura around the mantle will heat up the tube)!
    Normally, a well adjusted lamp (if you don't have a Petromax.tool, you can use a AA-Battery - diametre is the same!!) should not fire back into the tube at appropriate pressure! If pressure is too low, that can happen and you hear that strange noise!
    Please also check that ceramic-burner, mixing chamber and nozzle are well screwed in place!
    Farm-Oil is just perfect! I am using it as well (about 30l left!). And then for preheating the ethanol from C1000 at 1€something!
    Nothing compared to german prices!



  • Good morning Arminth,

    I got 2 petromax wrenches, one came with a metal German army transport box I bought at the local dump.
    When on the appropriate height (14 mil) it still 'backfired'.
    Got it on 12 now, and it runs perfectly.

    Also, I've been using these lamps for a long time in the past (in Africa, various brands). An old bloke showed me all the little tricks then, some I had forgotten, but a lot, I stil knew, and was resurected by this great forum.

    I always tighten the mixing chamber and burner, check the regulator wheel etc. before lighting it. It's amazing how loose they are sometimes. And, after all, you're working with an easy to burn/explosive fluid, so better be safe then sorry. I don't use the stainless steel burner, and after reading the comments about that one on this forum, I'll never touch it.

    Regarding German prices: a lot of things are cheaper in Germany, hence to our hidious taxes over here. VAT is 21% at the moment, crazy. Taxes on fuel are insane, €1.82 for a liter of 98 petrol at this moment.... C1000 is taken over by JUMBO over here, but they stil sell the lampoil, and also the cheap 'brandspiritus', ethanol, 84%.

    I have been thinking about the spiritus/alcohol modification, but since the alcohol percentage is 84%, and it's already leaving some residu in the spirit heating cup, I'm not sure that's going to be good fuel for the lamp. Second, the lamp isn't designed for alcohol, alcohol is way more volitile then lampoil and I don't want a ticking bomb in my hands if you know what I mean.

    Kind regards,