Some doubts about this Primus.

Discussion in 'Pressure Lamp Discussion Forum' started by MYN, Aug 25, 2018.

  1. MYN

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    @Nils Stephenson
    Here's the picture of the jet taken with the aid of a magnifying glass:
    20180914_205154.jpg
    Here's something else near the bottom rim of the fount: an inscription in a some language. Anyone's guess?

    1536931267356142397292.jpg Looks a little like Thai language. Not sure.
    Maybe the previous owner had a damaged 1050 vaporizer or valve which he or she could not find any spares, and happened to chance upon some old surplus 1020 and 1080 parts that could be fitted in, albeit with some effort?
    And here's an image of the flame taken after 20 minutes of burning.
    . 20180914_213657.jpg
     
    Last edited: Sep 14, 2018
  2. Carlsson

    Carlsson Sweden Admin/Founder Member

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    It's a 6145 jet, and that one would be correct for a Primus 1020 burner.
    A 1080 should have used 6147.
    They are interchangeable, though...
     
  3. MYN

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    @Carlsson
    Do you have any idea what's the size and thread pitch of a 6145 jet? And the size of the jet orifice?
    I might need to make one since there's no way I could get any spares around here.
     
  4. Titoo

    Titoo Subscriber

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    Hi MYN,
    You did a good job :thumbup:
    The cage is plated with tin.
    This lamp is slowly coming out of coma.
    The burner flame look good.
    It's soon light :D

    Regards,
    Titoo
     
  5. MYN

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    Thanks @Titoo for the kind words.
    I like the shape and appearance of some of these old Primus lanterns.
     
  6. Carlsson

    Carlsson Sweden Admin/Founder Member

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    Well, 300CP kerosene lamps usually use an orifice of around 0.20 mm, so that's most likely the jet size.
    The best matching thread gauge is the 0,7 mm. A 36 tpi gauge doesn't match as good, so I believe it is in mm.
    The diameter over the treads is 6,9 mm, so perhaps M7x0,7mm, which isn't a standard thread.
     
  7. MYN

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    That's not too good news for me. At best, I could get a die piece for M7 x 0.75 pitch. I know its a finer thread than a Petromax 350cp jet.
    And I'll need to get some micro drill bits for that too. I wonder if I could drill through straight enough:doh:.
     
  8. Carlsson

    Carlsson Sweden Admin/Founder Member

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    Yes, they often had a standard of their own, these manufacturers.
    0.75 mm does not match.
     
  9. MYN

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    Maybe I could still custom make it to 0.7mm in a local machine shop. They seem to be able to turn out any thread size on the lathe without a standard die.
     
  10. phaedrus42

    phaedrus42 Subscriber

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    From the flame colour and pattern it looks like your jet is still good. I've had very good results shrinking the jet size using a small pin punch which has a hollow dome on the tip.
    Also, the jets and needles are still available from Fogas in Sweden.
     
  11. MYN

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    Thanks @phaedrus42
    I'll check the site.
    That's the one and only Primus jet I have.
    I guess the only reason I'm trying to fabricate or make anything locally is that I've got no proper means for any online credit transfers that would otherwise enable me to buy the proper or original spare parts(if available) from abroad.
    I'll sort this out someday.
     
  12. Nils Stephenson

    Nils Stephenson Founder Member

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    Primus had their own thread size which was a good idea back when they were doing business, but is a pain in the but for us now. The thread is 7mm diameter and 35 tpi Whitworth thread. Nothing standard there. Luckily you can get new jets and cleaning needles from a couple of shops, Fogas being one of them. The jet size on the 6145 is 0.19mm.

    Btw, the cleaning needle thread is 2.1mm and 64 tpi Whitworth. Luckily a #2 UNF thread is close enough to use.
     
  13. Carlsson

    Carlsson Sweden Admin/Founder Member

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    Ah, yes, I was considering whitworth since that was a very common standard here in Sweden back then, but I couldn't find my gauge for that.
    And the "regular" inch gauges don't have 35 tpi. Only 34 and 36, and both were wrong for this thread.
     
  14. MYN

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    Thanks @Nils Stephenson , @Carlsson
    Now I know it could be Whitworth. But 35tpi is going to proof tough here.
    I believe I can still obtain those 0.20 +/- 0.05mm drill bits around locally.

    I've been to Sweden(Storkholm and Sanviken) on a working trip more than a decade ago. My regrets that lanterns were not my interest back then. Otherwise, I could have net in a Primus or Optimus while being there.
     
  15. Carlsson

    Carlsson Sweden Admin/Founder Member

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    If you are serious about getting this lantern going, I can send you a jet.
    It may take a while for it to get to Malaysia, though, so if you are in a hurry and have access to a lathe, that would be the quickest.
    It's not hard to turn outer threads in brass on a lathe. It's the orifice that might be tricky. A small 0.19 mm drill-bit and extremely high rpm is what's needed.
    Then if the jet/nipple should be really correct, it's also a matter of having the correct taper inside it and above all; the actual length of the small orifice. I've seen an original drawing from Primus of a jet/nipple posted at some occasion, but I don't remember where or when. And strangely enough I can't find any file of it saved at my computer.
    I bet it was Nils who posted it long ago. Or possibly Bo Ryman.
     
  16. MYN

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    @Carlsson
    Thanks for the offer. I think its a little too troublesome to get a piece of jet to be sent all the way to Malaysia to me. Need not bother about that, Christer.
    I'll try the tricky option.
    Drilling a 0.19 or 0.20mm hole straight through could be a challenge too. I'll need to ensure that the drill chuck is true and non-wobbling as well.
    Perhaps I could approximate that the internal taper of the jet should snugly match that of its pricker similar to the conical plug of a needle valve.
    That'll be an interesting task by its own.
    I noticed there are some concentric 'rings' on the face of the jet extending upwards from the hexagonal side towards the flat upper part of the jet just before the orifice. That's unlike any other jets I've seen. I don't think these are critical anyway.
     
  17. MYN

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    Finally I've attached a mantle and the lantern worked out in low pressure(pic.1) and higher pressure(pic.2):
    20180917_200538.jpg 20180917_200646.jpg

    Its not without problems though.
    The pictures were taken during the initial 15-20 minutes after light up. After that, the light started to dim despite sufficient pressure and fuel.
    I operated the pricker wheel several times in case some dirt was clogging up the jet
    No avail.
    There was a growling noise, and I noticed that the mixing chamber(U-tube) was glowing red.
    I think the flame had been drawn-into the tube or the fuel-air mix had started to burn inside.
    I quickly relieved the pressure and shut off the lantern.
    Anyone has any ideas about what's causing this?
     
  18. Nils Stephenson

    Nils Stephenson Founder Member

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    The only thing I can think of at the moment is whether the ceramic flame spreader has come loose. Otherwise I'm at a bit of a loss as to why.
     
  19. phaedrus42

    phaedrus42 Subscriber

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    Myn, show us a close-up photo of the mantle when not burning please.
     
  20. phaedrus42

    phaedrus42 Subscriber

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    On closer inspection, I see there are two changes in diameter in the U-tube. Very interesting.
    These differences in diameter are not present on the 1020 U-tube.
     
  21. MYN

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    @Nils Stephenson
    I've checked the flame spreader. It was tight and there's some copper slip to ensure that too.

    @phaedrus42
    Perhaps the U-mixing tube belonged to a 1080?
     
  22. MYN

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    I removed the tube and pumped up the fount with the pricker up. Just to check that its not partially clogged( which might skew the fuel stream and reduce velocity somewhat). But nope. Its not clogged at all. The fuel stream was straight and sharp when I lowered the pricker.

    Then I thought: could it be that the mixing chamber was getting too hot under the hood?
    I re-assembled the lamp without the hood and gave it another try:
    20180917_224838.jpg
    Let's see how it goes without the hood.
     
  23. phaedrus42

    phaedrus42 Subscriber

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    You are probably correct, Myn, in which case the lamp should work just like any other 1080.
    I was wondering whether the mantle was big enough and whether there was any flame halo outside the mantle.
    I know that the 1020 likes a really big 500cp sock type mantle and that many 300-400cp round rosette type mantles, including the Butterfly brand mantles that are available here in South Africa, are too small when burned in.
     
  24. MYN

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    @phaedrus42
    Here's the close-up view of the mantle unlit:
    20180918_001514.jpg
    Guess what? It was burning quite ok for an hour. Then I decided to put the hood/vent back onto it while its still burning.
    After about 25 minutes, a flame halo started to form outside the mantle and the symptom as before (dimming and growling sound) set in again. I didn't wait till the flames turn yellow or U-tube to glow red before shutting down the lantern.
    What could that indicate?
     
  25. phaedrus42

    phaedrus42 Subscriber

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    Your mantle looks more than good enough to my eyes. It is possible that the jet is a little worn. Have you tried turning up the pricker slowly so that it just interferes with the gas flow? If it suddenly burn brighter or whiter like that, it is a sign that the jet is oversize. See if a Petromax style 500cp needle will go through, without forcing it of course. If it does go through, you know the hole is too big. It can be shrunk without removing the jet with a medium size pin punch and small hammer and a lot of careful tapping and checking that the pricker can still pass through. I use a lamp with magnifier to see that the punch is centered.

    pin-punches.jpg

    On another note, the earlier 1020's had a cup shaped plate that fitted over the burner and may have shielded the mixing tube from some of the heat. They also had a cone shaped "inner hood" that shielded the mixing tube.
    The later 1020's did not have these.

    1020-1.jpg 1020-2.jpg 1020-3.jpg
     
  26. Nils Stephenson

    Nils Stephenson Founder Member

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    The hood on/off sounds interesting. Maybe that is why there was the extra hole in the intake tube.

    Anyway, It is possible you have a 1080 mixing tube, but that would mean that the non threaded end is just pushed into the top of the 1020 air tube. Here is a picture of a 1020 air tube beside a 1080 mixing tube.
    IMG_4191.jpg

    While checking this I discovered something else I didn't know. The mixing tube for a 980 and a 1080 are almost identical. The only difference is the length of the part of the tube above the jet. This gives a smaller gap on the 980. Here is a picture comparing the two. The 980 is on the left.
    IMG_4192.jpg
     
  27. ROBBO55

    ROBBO55 Subscriber

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    Myn, have you tried running the lantern with the extra hole uncovered? I think it will increase the air and make the fuel mixture leaner.
    I'd give it a go.
     
  28. MYN

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    Thank you for all your replies. This particular Primus hybrid is getting more intriguing than I've expected.

    @phaedrus42 ,
    I do not have a small pin punch that I could work on the jet if its really worn. Does not seem to be so because the initial light up was near perfect.
    The construction of the earlier 1020 is interesting, particularly the cone-shaped inner hood. Was there really reason to shield the mixing tube from the heating?
    I kind of suspect that the fuel-air mixture could have reached its auto-ignition temperature while its still in the U-tube.
    The kerosene I'm using here was contaminated with a lubricating oil. Maybe I replace that too.

    @Nils Stephenson , @ROBBO55 ,
    I will check if that's a 980 or 1080.
    Maybe there really was a reason for the extra hole being drilled into the air tube. I'll definitely uncover the hole to give it a try.
     
  29. MYN

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    There was one other thing I did not mention earlier. There was a pulsing phenomenon, which started after 10 minutes into the burn, where the fuel ìn the fount got quite hot and was accompanied by a noticeable flicker. I'm not sure if that could somehow reduce and increase (in a cyclical manner) the fuel flow to the burner cap at some point during the pulsation. I'm just guessing that the flame could possibly be drawn back into the U-tube during the instance of flow-reduction. And sustaining the flame within the tube doesn't seem too impossible, especially with the fact that its already very hot on that part.
     
  30. Nils Stephenson

    Nils Stephenson Founder Member

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    Primus obviously thought so from 1931 to 1954. From 1954 to 1956 they removed the inner cone and the extra plate on the burner (unnecessary expense?) and I havn't heard of any problems with these lamps.

    I have not experienced pulsing on any 1020, so that is a mystery. Is the loop on the vapouriser clean?
     

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