New Petromax owner - couple of questions please if I may

Many many thanks to Jeff and yourself as well as all the other members taking their time and patience to answer these questions. It's worth knowing that my mechanical knowledge and understanding is pretty good. I rebuild engines and differentials just for fun. Things being tight, sealed, on the right way around etc can be taken as read I feel.

In terms of pressure, there is certainly plenty of pressure in there. I have a Geniol stove with the same gauge and I know how much pumping that takes. I have pumped this lantern a little more and it's making no difference. I am concerned that it seems to be full bore after only 1/4 turn suggesting that the next 1/4 isn't doing anything at all in increasing the fuel flow? It's more or less either on or off. As I said, it's burning very cleanly with no visible vapour at all from the jet (I wish my other kero toys worked that well). There's no spitting, hissing, flaring or anything like that.

I shall keep implementing your advice and with a bit of luck we might hit lucky. I don't have a.45 cal brush anymore after the hand in, but I do have a .44!

Stunned that it might be from the 60's. I figured it would be fairly newish. No markings at all in terms of anything unique, no.

 

Has the mantle formed very close to the vapouriser?
It's best if it does, because that keeps the vapouriser hotter and therefor the paraffin vapourises properly.

 

I dont think that it being open after 1/4 turn is relevant. However it will be a product of the length of the lower part of the rod. You could adjust (shorten) it a little to remove it from the equation if you feel it relevant. I have found that all lamps have individual quirks.

 

No, the top isn't on straight! Too hot to move it

Pretty close Jeff yes. Not quite touching.. But I've just had another fettle and fired it up. I found (again) that the air gap had dropped from 14mm to much less. it seems to have a problem staying clamped. So I reset that. Then I pumped it up a bit more as you suggested. Quote a lot of pumping! And when I lit is I got some unusual flaring. Very bright actually then it settled. I'd say it is brighter. Getting much harder to look at directly, so I think we're on the right track. Little by little

 

It might be helpful if you post some pictures of the lantern operating with the lower-than-desirable intensity.
Some Petromax and clones would light up brighter or cleaner if the air gap between the jet and the inlet of the mixer J-tube is adjusted higher than the norminal 14.2mm. You can always try with 15, 16, 17 or 18mm to see if that makes any difference in brightness. I sometimes adjust in this manner to slightly improve the air draw.
The paddle in the J-tube would have more effect if you keep the air gap distance closer to the norminal 14.2mm but would hardly have any effects on the mixing if you increase the distance beyond a certain point.

 

Makes sense MYN thank you. I have posted a picture of it buring at less than desired performance - previous post scrolling up. That's about the best I have had it. Showing it duller than that can be imagined I think. I shall try messing with the gap again.

 

I think that looks pretty bright!

 

I see, Chris. It doesn't appear to be burning rich(from the picture). Have you checked that its getting a full-flow of fuel? I've had a similar problem in the past with partially clogged jets and vaporizer. There was just sufficient flow to produce only half to two-thirds of the maximum output. On other times, I had the foot valve inside the fount that was not fully opened when I lowered the pricker needle/rod. That was due to the lower part of the rod was too far from the pip of the foot valve when the needle was in the 'up' position. In another case, the upper pricker rod was not adjusted correctly (too high up) and the needle was actually partially obstructing the fuel path when it was lowered.

 

Here's a question following on from MYNs thoughts. The range to which I can raise and lower the tube is very limited. Lowest is limited by the air paddle screw head which won't pass through the fixture and highest is limited by the ceramic socket fitting hitting this little cross support inside. I can't believe that the manufacturer would make it so that it was bent like this. Thing is that if it's not bent then I can't achieve 14mm at all. So it's been bent but to bend it much further would see the J tube binding no it. Something feels a little odd here chaps. It does look like the bent tab is pushing the J tube slightly off centre when I tighten the clamp screw above.

 

MYN, I have had exactly those thoughts. The pricker is adjusted so that it just appears above the jet - .5 mm perhaps. you can feel it but barely see it. Any less and it wouldn't do anything. Lowered it does fully clear the jet, yes. I have checked that dimension. As to the bottom part of the rod, might it not be allowing full fuel - ahh, that I don't know. I can tell you that with the valve wheel at 12 O'Clock, it's off. But at 1 minute past it starts to flow so there's only the smallest of clearances there. Any longer and it wouldn't close.

Yes PB, it's certainly a bit brighter. Yesterday it was orange

 

The tab is pretty thin and bends easily. Its supposed to be straight though. You might want to check that the length of the J-tube had not been shortened previously. Sometimes they might be, due to someone sawing off a part of the threaded end. Mine certainly can be adjusted more than 14 or 15mm without bending the tab. In any case, its not absolutely necessary to screw the adapter/flame spreader which is holding the ceramic burner cap all the way to the last thread of the J-tube. You can get more clearance-lenght on the tube by not screwing all the way. Some copper antiseize compound can be used on the threads to prevent loosening of the assembly after a few heat-cool cycles.
You can always check if you're getting a full fuel flow by removing the inner hood and burner assembly, pumping up and lowering the needle as usual. There should be a strong, straight and sharp jet of fuel stream shooting upwards to a 'considerable height'.
I forgot to mention: there could also be a tiny screen located at the bottom of the footvalve at the fuel intake point. Sometimes, it could get sludged or clogged up too.

 

All good stuff. Yes there's a jet that could take your eye out. There's nothing wrong with that. I did check and clean the gauze on the pick up. All good. OK I shall look at unscrewing the cap holder out a bit. The J tube is so low that the clamp is trying to hold on the bend in effect rather than on the straight section.

 

If the J-tube is off-center, the output can be negatively affected too.

 

Like what's been mentioned before, the mantle sometimes makes considerable difference in perceived brightness. Thoriated-types usually glow 'whiter' and appear brighter to the eyes.(not necessary haviñg a higher lumen output, though).

 

Gotcha. We're getting there.

 

I have found - admittedly on a sample of "one" - replacement Pmax J tubes shorter than older ones. I was going to put a new one on my Pmax but the new replacement was shorter on the threaded side, so I kept the old one.
Not related to your current issue but If the lower rod is so close to the bottom valve then as it heats up after protracted use and expands it may prevent it closing ? - just a thought.
And one last suggestion - put a lumen app on your smartphone ? - I think they are not far off what you might get from a proper lux meter but in any case you can measure your improvements.

 

I might have to go old school on the lumen thing. If I can see the door to get out of my garage than it's bright enough ha ha. Don't think the rod expansion thing is something I'm experiencing. These things get raging hot don't they! I've left it running and it still turns off perfectly.
Interesting about the J tube though. I shall be fiddling with that when I've finished today for sure

 

It's working fairly well in the photo, try leaving it running for a couple of hours, sometimes that helps.

 

For refererence; photos of similar age/condition to yours; top photo genuine mantle and daytime. Scroll down for night time photo with thorium mantle.
Petromax 829 500CP Rapid money shot

 

Well that was interesting. I took the mantle off and pulled the J tube. I flattened the little tab out and did a minor reshape on the tube itself. it went together better and this time I backed off the ceramic holder. I was able to set a slightly bigger air gap and when I came to screw the holder on, it came to rest against the tab but because it's springy, it held the holder nicely without the need to put anything on the threads. Like it was supposed to do that?

OK so let's get a new mantle in there and have a go

 

Well I am typing this by lantern light folks. I'm sure there are some tiny tweaks left for optimal performance but here's the result. It's quieter and brighter. It actually lights a room now. So we got there.

A million thanks for the patience and guidance. Now where did I put that stove ......

 

Proper job. You must be pleased.

 

relieved more than anything, yes

 

That's good news!

 

Well - treat yourself to a spirit cup. The rapid heater can hammer the glass after a while - especially if the shield is a little off. And it is a little more civilised IMHO

 

OK I might do that

 

Well it looks great to me from the picture. No idea how it appeared in the real.
You might want to adjust the mixer tube paddle. Every lantern differs a little. I remember having an odd one that seemed to get brighter with the paddle adjusted to the horizontal position instead of the usual vertical.
Your lantern looks like its from the 1960s(telling from the design features). But those usually have a 4-digit code stamped at the bottom plate of the fount. Earlier ones have hand scratches that I believe could be the date of production. Some have nothing, just a plain bottom.

 

Yes, I'll play with the normal adjustments like the height and paddle to see if I can fine tune it at all. But for now it's mission accomplished. Going to be a nice addition to the cooking / lighting collection. I really bought it on a whim, with no real need at all. The price dropped and I jumped in. It came in a wooden box which you can buy but it's pretty new. Certainly not from the 1960's. I looked them up and they're around £40 on their own so I figure I got a bargain. I'm now stocked with spares, funnel and tools. Just need a camping destination now.

 

The mix paddle is there to to that: mixing the air/fuel more or less.
My suspicion is that it also create sound.

The fixture of the J-tube is a less wel thought construction:
1) it tends to get loose by the changes in heat.
2) the screw end can be pointed and to long and make a dent in the tube. The clamp should do the trick not the screw head.

 

Good points Wim. I agree, the heating and cooling of the J tube was almost certainly leading to it becoming loose because it was clamping on the curved section. It seems better now I have been able to raise the tube's height. The assembly is now being held by upward pressure to by the spring tab just above the ceramic holder.

Noise, possibly so, but I have not experienced that when turning the damper / paddle
My clamp does have a nice flat plate so the screw isn't touching the J tube but yes it could certainly damage the tube if it was simply a plain screw.