Making a pricker for a Petromax 900 “Little Baby”

Discussion in 'Fettling Forum' started by ROBBO55, Oct 10, 2020.

  1. ROBBO55

    ROBBO55 Subscriber

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    The wire pricker for this 900 Petromax 900 “Baby” is broken and as they are hard to find I decided to make a replacement.

    The brass section was made from a 3mm diameter round rod, cut 14.3mm long.
    Both ends are turned down to 2 mm diameter. One end 2.5mm long (pricker) and the other 3.5mm long (thread).
    Threaded with a M2 x 0.4 pitch metric thread.

    A hole was drilled in the pricker end 0.5mm diameter and about 4mm deep. I use 0.5mm because I am mot steady enough to drill a smaller hole (you might be).

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    I made a small section of brass rod (drilled and tapped M2) to hold the brass section whilst I ground the round bar into a triangle. I did this using a Dremel and a diamond grinding wheel. The size of the flats were not critical as long as the nominal 3mm diameter was maintained.

    Note: the inside of the nipple is 3mm diameter and I believe acts as a guide for the pricker. The triangular shape is to allow fuel past the pricker and for use of the Petromax pricker adjustment tool.

    3.JPG

    I used a 0.12mm diameter acupuncture needle for the pricker wire. For a new jet the wire might have to be reduced to 0.1 or 0.11 mm but in my case the needle slid nicely into the jet.

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    In this instance I used the aluminium handle on the acupuncture needle in the construction. I measured the depth of the hole I drilled in the brass and carefully removed the required section of the handle. Then reduced its diameter to 0.5mm and bent the end of the wire to stop it coming out.

    5.JPG

    Insert the pricker wire into the hole in the brass, it was a snug fit.

    6.JPG 7.JPG

    The crimping tool which gives a 1.5mm diameter swage.

    8.JPG

    Cleaned up and ready to cut the length of the wire to fit the jet.

    9.JPG

    Done

    10.jpg
     
  2. Tony Press

    Tony Press Australia Subscriber

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    Excellent work, Martin! :thumbup::thumbup::thumbup:

    Cheers

    Tony
     
  3. JEFF JOHNSON

    JEFF JOHNSON United Kingdom Subscriber

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    Great fettling!:thumbup::thumbup:
     
  4. presscall

    presscall United Kingdom Subscriber

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    @ROBBO55 Great work. I’m saving this thread for future reference.

    John
     
  5. ROBBO55

    ROBBO55 Subscriber

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  6. Darryl Durdin

    Darryl Durdin Australia Subscriber

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    @ROBBO55 , this is great detailed work well documented, good skill set.
    Well done
     
  7. WimVe

    WimVe Subscriber

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    Good engineering.
    Just an idea: would it be an idea to use a standard 150cp needle,
    cut off the round tip with needle remains and
    the drill a hole for the acupuncture needle,
    so that would go direct into the triangle shape px needle part ?

    I don't know if the thread of a 150 needle is the same as the 900 version but it would reduce a lot of work making the needle base part.
     
  8. ROBBO55

    ROBBO55 Subscriber

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    @Tony Press @Darryl Durdin

    Thanks gentleman

    @WimVe

    Thanks.
    Yes, converting a 150 needle could work. I believe they have the same 2mm thread , but I don't have one to know for sure.
    As you said the old steel wire would have to be removed otherwise the drill will be pushed off centre.
     
  9. Henry Plews

    Henry Plews Subscriber

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    If you're going to remove the wire, any needle (150, 250, 350 or 500) will do. I've noticed that on some needles, the wire is crimped into the brass better on some than on others. Using a pair of pliers, it may be possible to squeeze the brass carrier at ninety degrees to the crimp thus enabling the wire to be pulled out and a thinner one inserted.
     

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