Primus/Optimus 535 tank recoating

Discussion in 'Fettling Forum' started by Kalle, Apr 7, 2017.

  1. Kalle

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    Dear fellow Stovies,

    I wanted to restore the original brass coating on all three of my 535's that has more or less tarnished away but my search for similar looking varnish has for a long time been in vain.

    Finally I decided to try to put together such a concoction myself. After some thinking I placed an order for brass flake powder ("Messing Pulver Flaky") from evilbay and picked up a 2-component polyurethane varnish from a local retail store ("Biltema").

    First I mixed a quantity of brass powder with thinner, then added component A and mixed well. Having a paint gun ready I then mixed in the component B and then sprayed it on. Based on experimenting I found the following recipe give satisfactory results :

    * 15 grams PU component "A"
    * 3,8 grams PU component "B"
    * 8,0 grams Brass flake powder
    * 2,5 grams PU varnish thinner

    The setup :
    recoat.jpg

    I attached the tank to my coil winding machine which has an inverter driven motor to it, set it rotating at low speed (ca. 10 rpm) and then sprayed on the coating. I noticed this coating has to be sprayed from quite a great distance away with a much of air. I did two coatings on two consecutive days and the process took around 5 minutes per run. NOTICE: This has to be done outside well protected; the powder will get everywhere!

    I am very happy with the results. It has a bit lighter tone to it than the original, but it may age over time. It could probably be aged in an oven with modest temperatures.

    I wish you find this useful. -K
     
    Last edited: Apr 7, 2017
  2. Afterburner

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    Was there some kind of coating originally? I have one 535 and it doesn't have any coating, just plain brass (that could be polished if 'the look' doesn't please...)
     
  3. Kalle

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    On this "Primus" one I did there definitely was one which I believe was an original. I am not sure though, of the two more tarnished "Optimus" versions I acquired before; back then I did not realize to check for it before I cleaned them up (but I assumed they had...) . Here is another thread referring to the subject: https://classiccampstoves.com/threads/primus-535.9878/
     
  4. Kalle

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  5. Jack Enright

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    That's a very neat job, Kalle!
     
  6. Kalle

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    Thank you, Jack! To my eyes the coating rhymes with white enamel better than plain brass so I'm going to give the remaining two the same treatment. I went through several pictures of both makes of 535's and some seem to have the coating while the others not. Would be nice to know the history behind it.
     
  7. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    @Kalle
    A very classy and resourceful restoration. Making up your own paint and rotating the tank (on a coil winder?) was a touch of genius. It paid off, the effect is superb.

    John
     
  8. Kalle

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    Thank you, John! Yes I built the contraption originally as a coil winder. For safety reasons (line voltage involved) I do not wish to go into further detail, but basically it is just a 1:10 gear AC motor plus a VSD inverter on a plywood chassis. Now here lies is a risk I unfortunately did not realize earlier: Varnish vapour is highly flammable. Using anything other than AC (=brushless) motor like a cordless drill having sparking carbon brushes, would probably be dangerous. An assisting stovie rotating the tank by hand would be the safest alternative.
     
  9. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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    Hi @Kalle . Clockwork is the answer!
    Best Regards,
    Kerophile.
     
  10. Kalle

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    @kerophile , Now That would be old-school! (made me think of a gramophone I have..)
     
  11. Afterburner

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    Water wheel would also work and fire wise it's safe. :lol:
     
  12. phaedrus42

    phaedrus42 Subscriber

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    Get with the 21st century, you guys; two words: Stepper Motor :lol::lol:

    A beautiful result, Kalle! Thanks for sharing the technique.
     
  13. Kalle

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    An update. The second tank in the row was very denty. Perfect option would have been to unsolder the joint in the middle, hammer out the dents and then put the thing back together. But as I was going to paint the tank anyway, I figured out a less arduous one. Having first shaked the tank with acetone, followed with alcohol and then thoroughly with hot water (to remove slightest fuel remains!) I simply filled up dents with tin/lead solder using a mapp torch. After filing and sanding the patches down I soda-blasted the thing on the machine to remove traces of rosin and soldering paste. Here is a picture after the blasting. I already painted it too, but it evidently will have to be sanded and re-coated few times to completely fade out the patches.

    dent_repair.jpg
     
  14. Jack Enright

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    [-X

    Who let this philistine join?
    ;)

    Jack
     
  15. Jack Enright

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    Good 'thinking outside the box', Kalle - I've seen the same technique used in car repair shops, where a dent was in a place very difficult to repair by panel beating. Once the paint was done as you describe, you couldn't see where the original dent was at all.

    Best regards,
    Jack
     
  16. phaedrus42

    phaedrus42 Subscriber

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    I've used the lead fill technique with fair success on lamp founts. I found that it is easy to underestimate the diameter of the dent and have had to resolder a few to get the curve to blend in perfectly where the lead/brass transition is. If you get that part right, your repair will be invisible under the paint and last better than other filler materials.
     
  17. Kalle

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    @phaedrus42 , That's correct! I had to learn it by trial and error. That was quite surprising. The diameter of tinned area has to have roughly twice (or even over) the diameter of a dent seen by eyes. Having learned that, I found it easier to start tinning from the far perimeter first and then proceeding towards centre.
     
  18. phaedrus42

    phaedrus42 Subscriber

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    The old school panel beaters use a vixen flat file for filing away the excess lead. It works quite fast and does not clog. The other good trick I learned in another thread here is to draw a circle with a permanent marker felt tip pen around the filling area to stop the molten lead running away. Works like a dam wall:)

    file_vixen_flat_lg.jpg

    -Phil
     
  19. Kalle

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    Hi, just got 2nd tank finished. Thanks for your suggestion @phaedrus42 it would have been much more easier with that kind of fileO:) Ordinary file clogged up quite severely. But here is a picture, it turned out quite nice after two consecutive coatings. Between the coatings I sanded it with 600 sand paper. I found out that the coating can be greatly improved by polishing it carefully 4...5 hours after spraying with lint-free polishing cloth (these were Turtlewax -brand). The surface was still soft in that point. Note the burner nuts and air pump flange has to be protected with masking tape during coating, here I have already removed them. -K
    2nd_tank_finished.jpg
     
    Last edited: Apr 22, 2017