So being new to pressure kerosene / paraffin lamps with a removable top (I have owned a coleman dual fuel lantern for years), I thought I'd adjust the J tube on my Chinese Petromax 829 to see if the slight pulsing increases or decreases in frequency depending on the gap between the nozzle and tube. I'm an engineer, its hard wired into me to figure everything out. Although after this I have to really reevaluate my job role. So I took the chimney off and put it down, then took the J tube assembly off and put it down Anyone care to fill in the next bit....
We'll, some photos would definitely help. When the j tube is raised it creates a larger gap between it and the jet which allows more air to mix with the vaporised kerosene. This adjustment allows you to alter the fuel/air mix as the jet slowly gets enlarged. A jet's orifice will increase in size simply due the abrasive action of the fuel. This happens very slowly of course but when you fin an old lantern that has been well used, the j tube often needs tweaking. At the end of its life, the jet will need replacing but for Petromax style lanterns you can find these fairly easily and inexpensively. Hope this helps.
So now I had destroyed the mantle - Doh! The replacement burner I had fitted wasn't finished very well, it had bits of ceramic sticking out where the holes were and some holes were blocked, so I used a bit of old sandpaper to clean up the face of the burner and a bit of wire to poke every hole through. Fitted a new Peerless mantle, adjusted the J tube, ever so slightly down and got the lamp burning again. The slight pulsing was still there but a bit slower. Left the lamp burning whilst I sat back outside with a glass of vodka and orange juice.
Dirt or carbon buildup in the vapouriser can cause pulsing. If the vapouriseris clean a piece of brass gauze (75mm x 25mm) wound around the pricker rod inside the vapouriser will usually remove the pulsing. If gauze is not available a piece of brass or copper wire will also help.
It's a brand new Chinese Petromax. It works, just this slight pulsing noticed. Currently trying a few J tube adjustments to see if it has any affect on the pulsing. Best way to learn by doing.
Apparently all lanterns pulse but they do it either so fast or so minimally that you don't notice! I've got afew Chinese Petromax clones and one genuine Chinese Petromax and a good method of lessening the pulsing is to wind brass gauze or copper/brass wire round the pricker rod that goes up inside the vaporising tube. It can be a bit fiddly but it definitely cured any pulsing issues I had. Apparently it increases the surface area which transfers the heat to the kerosene more efficiently.... I think. It's a bit of a black art to be honest!
@chocki , hi there and welcome, the pulsing, follow @ROBBO55 directions, clean and clear, your j tube may not have anything to do with it. Your generator, imagine your fuel it is under pressure as it gets heated then super heated into gas vapour there is more pressure inside the generator the expansion pushes in both directions gas vapour out fuel back down the generator so creating a continuous cycle of out with the hot vapour in with the cooler fuel, if you look at the burning mantle safely of any lantern they all have a pulse. Chinese petromax copy can be a little contrary . Follow the above comments I hope this may help
Thanks for the replies. I spoke to the helpful people at base-camp whom said the straight sided type of J tube has been around for quite a while and is not just a Chinese cost saving exercise. A venturi like this is normally to help draw in air then there should be a gradual opening out where the fuel air mixture can mix thoroughly, so the original design by petromax wouldn't have been that brilliant anyway, they were on the right track, just never quite got it 100% correct. I guess if I want a steady no pulse lamp I should pack in kerosene and get a (Am I even allowed to mention this on this forum? ) gas lamp. OK I will go and whip myself to within an inch of my life and wash my mouth out with C2 paraffin for mentioning such a heinous thing on here. Awaiting my seal kits etc from base-camp, order placed yesterday. 2 more 4 ltr plastic bottles of C1 paraffin bought today and a jerry can to transfer it into, I read the shelf life of the plastic pre-packs can be as little as a year, whereas stored in a metal fuel container it can even be up to 10 years, dont know how much truth there is in this, but I feel a lot better getting a good 20 Ltr jerry can for all my paraffin.
I've got an early fifties petromax which had a pulsing problem. Cleaned out the vaporizer as best I could, still pulsed a bit so followed advice that I read on here and wrapped copper wire about a mil thick around the pricker rod and now it's as smooth as silk. Some good advice above. As for the kero, I just buy 20 litre drums of it. Cheers
Made a copper coil from 1.5 / 6 mm wire, wrapped around a 3.2 mm terminal screwdriver, held in a battery drill and wound to give about 7mm spacing between the coils, this fits nicely in the tube between the join for the upper part of the vapouriser and below the hole for the vapouriser loop, still allows the needle rod to move up and down and fitted this to my Chinese PX. Has made no difference at all. Oh well, back to the drawing board. The lamp works well, just has this slight pulsing about 1.75 Hz which gets slower as the pressure drops, but I'm an engineer who's motto is, if it ain't broke, it doesn't have enough features yet!. I know there are those who would say, if it's working, leave it alone, but there is always room for improvement.
So tried increasing the gap today, no real improvement, so then tried closing it to the 250CP gap on the setting tool and this has quietened the pulsing right down, hardly any present now. I do wonder if this is because it is a new jet, and maybe the hole is just a little on the small side, I don't think the lamp is actually putting out 500CP, but until I get my old PX going, I have nothing to compare it against.
Hey, glad it's behaving itself better. I've fitted copper coils to all my Chinese Petromax clones... It seems to help most of them but not all. Sometimes the pulsing dissapates when they've been running for a while, probably temperature and thermal mass related.
I removed the copper coil as it was causing reduced output of the light compared to a lamp with no coil fitted. Both lamps now shine about the same brightness.
