Rebuilding a Radius No. 42 burner

Discussion in 'Fettling Forum' started by Tony Press, Aug 7, 2017.

  1. Tony Press

    Tony Press Australia Subscriber

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    Inspired by the work of @presscall rebuilding a burner for his Optimus No. 80 here, I decided to tackle a Radius burner from a No. 42 that was almost identical in its injuries.

    Unfortunately I don"t have a photo of the mess it was in when I got it, but it looked just like John's. The riser tube to the burner had been twisted open and had a gash about 1.5cm long in it.




    Here is the top of the burner after I cut off the broken tube.
    IMG_2788.jpg


    Here is the tank with the riser tube cut off flush with the top of the tank boss.
    IMG_2787.jpg


    My first move was to braze an outside tube of brass to the top of the burner with 40:60 silver:brass rod:

    IMG_3008.jpg

    Rough enough for the bush.
    IMG_3009.jpg

    I then cut it short so that I could now braze a new riser tube inside the remaining brass tube.
    IMG_3010.jpg

    IMG_3012.jpg


    IMG_3013.jpg


    After brazing.
    IMG_3015.jpg

    IMG_3016.jpg


    Before I attempted to then braze the riser tube into the tank, I cleaned it up a bit with a Dremel and some fine emery paper so they it looked acceptable. I treated it with dilute sulphur acid to make sure it was free of flux inside and out.
    IMG_3035.jpg

    The riser tube needed to be the correct height above the tank (measured off another Radius No. 42) and penetrate about 6mm into the tank itself.


    I had to remove the remnant of the old riser tube. I did this with a tap - gently until the remnant poking into the tank fell out.
    IMG_3018.jpg


    I cleaned the tank surface where it was to take the riser tube.
    IMG_3024.jpg


    I applied flux to both the tank surface and the burner tube and set hung the burner from wire so that it sat at the right height.
    IMG_3036.jpg


    Brazed into position.
    IMG_3037.jpg



    It was here that I discovered something I didn't know:

    The threaded filler in the bottom of the tank is soft-soldered in place. It developed a couple of holes when I brazed the burner in to place so I had to run a bit of solder around it.

    IMG_3039.jpg

    Felt pen to stop the solder running.
    IMG_3040.jpg

    Before cleaning up the solder with a Dremel.
    IMG_3042.jpg



    So, now I'm quite happy with the general appearance of the repair and the soundness of all the components:

    IMG_3041.jpg

    IMG_3043.jpg



    I then gave the whole stove a good clean on the inside to make sure there was no residual flux or other foreign material.

    I used some of @Trojandog's graphite sheet for the packing box; and I made a lead washer for the filler cap in the base of the tank. I used an second hand, but clean, wick from a Primus No. 71.

    NOTE: this stove does not have an SRV (unless you think the filler cap arrangement would work...)


    The first test burn was a great start.
    IMG_3058.jpg


    I did have a bit of trouble with black particles accumulating in the burner tube and had to start and clean and restart the stove about 6 times before the particles eventually disappeared. I suspect they may have been burned bits of flux or other artefacts of the fettling process. I also had to resurface the tip of the control spindle to make it seal properly when closed.

    It's running well now.
    IMG_3073.jpg




    I'm still working on the tin that the stove came with, so I'll post in the Reference Gallery later this week.


    Cheers

    Tony
     
    Last edited: Aug 7, 2017
  2. Metropolitantrout

    Metropolitantrout Subscriber

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    Mighty fine work and write up! Jerry
     
  3. Robert Bruce

    Robert Bruce SotM Winner Subscriber

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    Well you do like a challenge , it looks the goods now. I am sure the box will come up as good. Well done !

    Cheers
    Rob
     
  4. shueilung.2008

    shueilung.2008 Subscriber

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    @Tony Press

    Great work!

    Congratulations! :clap: Another Old Lady standing again thanks to your efforts!

    Enrique
     
  5. Murph

    Murph United States Subscriber

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    Damn nice workmanship!

    Next time, get a copper phosphorus brazing rod, no flux needed!

    Murph
     
  6. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    @Tony Press
    Great work Tony.

    Couple of questions.

    You used a tap to remove the stub of riser tube in the tank. I take it that the stub was silbrazed in there (that discussion we had, brazed or tapped!) and as well as gripping the stub the tap weakened the bond? Couldn't the stub have been drilled out?

    The threaded boss for the filler cap was soldered in place as you say. How about the seam between base and the rest of the tank? I guess that was brazed, or it would have been disrupted too.

    John
     
  7. Tony Press

    Tony Press Australia Subscriber

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    @Murph

    I have seven lifetimes supply of 40% silver...

    Cheers

    Tony
     
  8. Tony Press

    Tony Press Australia Subscriber

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    @presscall

    I used the tap rather than a drill so that I could make sure it was always centred and didn't drift to one side.

    My conclusion on whether the tube was threaded or not is that it was NOT threaded and had been brazed in place.

    As to the bottom plate of the stove, I've been pondering that myself - I suspect it might be soft soldered... I will investigate in the morning when there is more daylight.

    Cheers

    Tony
     
  9. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    @Tony Press
    Thanks Tony, makes sense to use a tap for that reason.

    I'll await your findings on the base seam. With Primus and Optimus equivalents brazing that seam (at least the examples I've encountered) I wonder if there's good reason for Radius using soft solder. I'm thinking a safety pressure release function.

    The other makes have a soldered pin (early Primus 71) or filler cap mounted safety release valve. That era of Radius has neither. A soldered base seam and filler cap boss would at least 'let go' somewhere along a solder joint at some point and dump fuel ground-ward if the stove overheated.

    John
     
  10. Tony Press

    Tony Press Australia Subscriber

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    @presscall

    As I said above, I thought the pressure release theory might be why the filler assembly was soldered.

    Mmmm... I'll have to go out now and get the stove...


    Tony
     
  11. Tony Press

    Tony Press Australia Subscriber

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    @presscall

    Having taken my knife to the seam, I conclude that it is soft solder.

    IMG_3093.jpg


    Cheers

    Tony
     
  12. shagratork

    shagratork United Kingdom Moderator, R.I.P. Subscriber

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  13. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    So you did Tony. Plausible reason it was soldered.
     
  14. Tony Press

    Tony Press Australia Subscriber

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    @presscall & @shagratork

    The difference between having an SRV above the fuel, even if it's a 'weak link' like a soldered pin, is that it will first release gas to relieve pressure. Having a week joint at the bottom of the stove, under the fuel, means liquid gasoline running all over the place.

    Cheers

    Tony
     
  15. shagratork

    shagratork United Kingdom Moderator, R.I.P. Subscriber

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    As you have already done a lot of work on this stove, you could add a soldered pin safety device.
    That would mean drilling a small hole in the top of the tank, but at least it would be safer to use.
     
  16. Tony Press

    Tony Press Australia Subscriber

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    @shagratork

    But, in order to make sure the safety pin worked before the filler cap or the base did, wouldn't I have to de-solder them and braze them back in place...:?:

    I expect it's very unlikely that it will ever fail anyway.

    Cheers

    Tony
     
  17. shagratork

    shagratork United Kingdom Moderator, R.I.P. Subscriber

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    Good point Tony. My thinking was that the pip would be closer to the heat source and would melt first, but there are probably flaws in that assumption.
    As it happens, like you I would be happy to use the stove as it is. I don't use these small petrol stoves much. I used to use my 123 a lot and never had the SRV blow.
     
  18. Jeopardy

    Jeopardy Subscriber

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    Fine outcome from an excellent job.
    For a moment I thought you had forgotten about the wick.. until your last picture reminded me that you had the option to add it through the filler port on the base.
    Regards
    John
     
  19. OMC

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    Tony,
    I appreciate all your efforts sharing your 42 and the repair process.
    As to failure points on 42, here is a 42 that was close to bursting. Credit to SMolson.
    Radius_42_opt.jpg
    It shows tank expansion top and bottom while seams and joints held.

    It's been so long I can't recall source but my impression is the concave bottom is stronger than flat and also does allow bottom to expand providing a level of safety. That and tanks formed with integral primer cup similarly also allow for expansion on top. I've seen other tank bottom/top expand similarly.

    If one were distracted or less attentive to a hot gasoline camp stove.
    Prior to a tank rupture, one might:
    hear: noise while tank is distorting
    and
    see entire stove move and at a glance note it is no longer upright.

    In that same post geeves shares that he has seen a stove of same style that did explode. That failure point happen to be the rizer which separated from the tank and was blown-off with a big bang.
    thanks omc
     
    Last edited: Aug 8, 2017
  20. Face scrape 2001

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    Yes, running out at explosive speeds!

    I think I can confirm soft solder joins under, but I couldn't begin to guess why.
    I've got a Radius 42 too, I bought it in 1984 for $4.00 AUD, had been used about four times, judging by the deterioration of the tinwork's paint over the next few uses.

    It had a fibre washer on the refill screw cap, but after thirty some years it was starting to leak, so I replaced it with a nitrile O ring, so far so good.

    I've bought and used five litres of fuel now over the years, and either the stove is changing or the fuel is no longer as volatile as it was 33 years ago.
    What have you used to clean it's jets?