1933/4 Optimus No.10 - puzzler.

Discussion in 'Optimus No:10' started by igh371, Nov 18, 2015.

  1. igh371

    igh371 SotM Winner Subscriber

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    DSC03390.JPG

    There is only one reason for posting this stove here, and that is that I cannot explain what it is or why it exists. A 3-leg 2 pint Optimus No.10 is nowhere to be found listed in any of the catalogues currently to be found in the library. BUT IT CLEARLY DOES EXIST.
    All of the visible features place it as being from the 1920s.
    But all of the visible features bar one make it identical, as far as I can see, to a standard Optimus No.1 of that period. So why is it given the model number '10'? What am I missing? The only feature not common to the No.1s that I can see is the dimpled spirit cup with auto-light flame leader (part no.293a in the 1929 catalogue). OK so those are normally found on silent burners, and in fact are pretty pointless on a 'roarer', but that surely isn't sufficient to give it a new model number even if it is original. What am I missing? [​IMG] Why is this a '10'? when was it made? and why?

    DSC03393.JPG DSC03394.JPG DSC03391.JPG DSC03395.JPG DSC03401.JPG DSC03402.JPG DSC03403.JPG DSC03409.JPG DSC03405.JPG

    DSC03408.JPG
     
  2. shagratork

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

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    Hi Ian

    You are nearly right, but the Optimus No.10 does appear in one place (only one!) in our catalogues section.
    Have a look here in this 1933 brochure.
     
  3. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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    Hi Ian, following Trevor's link and the logic of stove-makers competition, the Op. 10 was a higher power version of the Op. 5 stove.

    It shares a burner with the larger Op. 25 but has the same tank as the Op. 5.

    It is possible that a standard Op. 5 or Op.1 burner was added later to your Op. 10 tank, thereby reducing its power to an Op.1or 5 stove. This certainly happened to Pr. 10 Stoves when the larger burners became unobtainable.

    Best Regards,
    George.
     
    Last edited: Nov 18, 2015
  4. igh371

    igh371 SotM Winner Subscriber

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    All makes sense now! CCS at its best :thumbup:

    Curiosity satisfied.

    Now the next problem: what am I going to do with it? :-k
     
  5. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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    Last edited: Nov 18, 2015
  6. Tony Press

    Tony Press Australia Subscriber

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    Mmmm... I like a mystery.

    So the Optimus 10 appears with the 4, 5s, 25 and 35 displayed with a silent burner and the long 'leader' (thanks, Ian).

    I've no idea what that means...

    Tony
     
  7. igh371

    igh371 SotM Winner Subscriber

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    Actually, I have to be honest, it was Christer who drew my attention to the correct terminology here. Still manage to learn something new every day :D
    Ian.
     
  8. Jeopardy

    Jeopardy Subscriber

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    Hi Ian,
    I have a pilot lighter that came with one of my 1 pint roarer and it makes it easier to light the main burner at the end of priming. Without one, if you leave it too late before pumping at the end of priming there is a chance that the meths will burn out and you end up scrabbling around for the matches. With one the pilot light continues burning up at the burner height for a few seconds so even if you forget to close the air screw (as I have been known to do) you have time to put that right and still get a successful ignition. Far from useless in my experience.
    Best regards
    John
     
  9. igh371

    igh371 SotM Winner Subscriber

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    Hi @Jeopardy, totally agree about the value of the little reserve of lighter spirit in the spirit ring dimple on certain Svea and Optimus stoves. The point I was making, however, is that on those stoves the raised leader is superfluous with roarer burners. The dimple reserve alone is sufficient to do the job you describe for 'roarers' as there is no issue of underburning as there is with silent burners. Consequently both of those 2 manufacturers provided 2 types of auto-lighting dimpled spirit rings, one with the leader for silent burners and one without for roarers (both nicely illustrated on this parts page). The tubular wick containing pilot lighter used by Primus and some British manufacturers is of course a completely different story all together.
    In the case of this rare Optimus 10 model the 'leader' type auto-lighter is another clue to the fact that it would originally have been fitted with a large size silent burner, as Shagratork and Kerophile worked out above; it was the out of place later substitute roarer burner which had led me off up a wrong track.
    Ian
     
  10. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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  11. Spiritburner

    Spiritburner Admin SotM Winner Subscriber

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    Here you go chaps - from 1934. Looks like it was introduced around this time from the description. This isn't on CCS yet but will be shortly as I've just completed the scan of the stove section. It's a bit delicate!

    opt10_1934.JPG
     
  12. Tony Press

    Tony Press Australia Subscriber

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    @Spiritburner

    Excellent detective work. That's what is great about CSS/CPL.

    Any ideas how the burner is "more powerful"?

    Cheers

    Tony
     
  13. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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    Hi, in the case of the Primus equivalent stove:

    The No.10 stove uses a bigger burner ( No.4140) than the No.5 stove.

    I estimate that the 4140 burner has a maximum heat output of about 3.4kW, or 11600BTU/h.

    This is about 20% more than a Primus No.5 stove burner.
     
  14. brassnipplekey

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    Christer . Ian .Tony....& contributors ..The usual suspects.. Good morning. George .& even the mods and a scan from Ross.
    cheersmedears ..the nuances and twiddles of it all :-).
    C.C.S... What an education ..cheers.
    Nomenclature ... the naming of things
    ' leader' with reference to stovey things = ? ?? .
    A n other 'new one on me' (nothing new there... were all still learning).....
    ......the thin plate tonguey thingy that sits above the sump of the priming annular ?
    ' Leading' the flame in an intended direction.. that says it..!
    perfect.
    bang on for me .
    Does what it says on the tin .
    Obviously other folks around here spend hours captivated ?Hr's...by the brochures , documents,information & Etc.on/around stoves + ++ here.CCS..What a resource /trove.
    1933/4 opti no 10 ? What an interesting stove :-)..
    nuances and twiddly bits raise the unavoidable nerd in me ....
    bstrd stoves buggaroid compfuser..... one linky leads to the next linky...
    oops ...2 or so well spent hours.
    Supper time.
    Nick
     
  15. shagratork

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

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    Hi Nick, nice to hear from you.
    Yes it is an exiting thread with so many unusual information items.
    I knew of an optimus No.10 but had never seen one for real or in a photograph.
    Ian has a real rare gem!
     
  16. Tony Press

    Tony Press Australia Subscriber

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    @kerophile

    What is the jet size in the nipple of the Optimus 4140 burner?

    And can anyone post a photo of the standard Primus No.5 burner next to an Optimus 4140 (or equivalent)?

    I'm with Nick: there is much to learn here.

    Cheers

    Tony
     
  17. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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  18. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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    j
     
  19. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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    Hi, according to the Primus Burner chart in the CCS Library:

    the #4139 burner as used on No.5 stoves uses a jet #4390 with two flats on the head. The appropriate cleaning needle (pricker) is #4605

    the #4140 burner, as used on No.2, No.25, and No.10 stoves uses jet #4392, the head of which is hexagonal in shape. The recommended cleaning needle is #4605

    the small roarer burner used on a Primus No.210 stove also uses this same #4605 pricker.


    Although Primus do not publish aperture diameters for their jets, I believe we can assume that the three burners listed above all utilise a 0.32mm diameter aperture.

    At first sight it might seem surprising that three stoves with very different maximum heat outputs, say 1.9kW for the Pr.210, 2.8kW for the No.5, and perhaps 3.9kW for the Pr.10, could share the same jet aperture diameter.
    However, jet aperture is only one factor in determining maximum heat output.

    Back in Jan 2013, CCS member Grigory discussed the factors in a Post on Op.8R stoves, which was so interesting that I made a note in my notebook at the time.

    Stove Power depends on four things ( for a given fuel type):

    1. Jet diameter
    2. Pressure
    3. Pre-mixing capacity, and
    4. Vapour production capacity

    The first and second factors give mass flux of fuel through the nozzle. The third factor means all fuel thrown out by the nozzle is mixed with air in the correct proportion. Point 4 means that all fuel thrown out and pre-mixed can be vaporised inside the stove burner.

    Here is a link to a Pr,10 in a 1933/4 Catalogue:

    https://classiccampstoves.com/attachments/1248824971-004-jpg.98218/

    I have never seen one of these combined windshields/heat-shields in the flesh.

    Best Regards,
    Kerophile.
     
  20. Tony Press

    Tony Press Australia Subscriber

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