Primus 97 - the one in the middle - 'T' date stamp (1929)

Discussion in 'Primus No:97' started by presscall, Jan 10, 2014.

  1. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    You can see why I've referred to it as 'the one in middle'. Literally in this photo, but also because it combines features of a Primus 210 (1-pint fuel tank, pump knob style, pot rest legs) and a Primus 96 (burner)

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    My example was something of a 'no brainer' purchase off ebay - Christmas gift money to spend, £40 buy-it-now and seller's photos good enough to be sure it was a good and pretty much complete example, with just the primer fuel can added from my collection

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    Some minor issues to put right before fuelling up and firing it.

    A peculiar stack of pump cup washers

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    A user had supposed that the vapouriser-to-tank seal should be made using a leather washer, even though the in-tank lead washer was perfectly intact. They also reckoned that a gauze cap shoved into the jet end of the vapouriser and one parked in the tank end would do the job - presumably imagining the gauze inserts only had a filtering job to do and not that a proper roll of gauze was necessary as a thermal device to aid vapourisation

    1389391607-4.JPG


    To be expected, the fuel filler cap seal had become brittle over time and was replaced

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    Non-return valve equipped with a cork pip that had seen little use, judging by the fact that it wasn't indented in the way that one of its age in a well-used stove would be. I needn't have done, but I replaced it with a viton equivalent to be sure that I'd not have to service the NRV again in my lifetime

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    Primus quality components

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    Lively performer

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    Getting back to the Primus 210/Primus 96 comparison, the next couple of photos show the similarities and differences, the 210 pot rest legs a fraction longer than those on the 97 to compensate for the marginally taller burner on the former

    1389391676-11.JPG


    Offsetting the bulkier and heavier fuel tank, the 97 shares the 96's more modest thirst for fuel than that of a 210, thanks to their 0.23mm jet orifices being just a shade over half the surface area (π × radius squared) of that of the Primus 210's 0.32mm jet. Well, that's a potential for a more frugal fuel consumption, dependent on user restraint when pressurising the tank!

    1389391687-12.JPG


    Same sized fuel tank and same sized stove box, Primus 97 and 210, so it's got to be the Primus 96 if compactness stowed matters

    1389391698-13.JPG

    John
     
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  2. itchy

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    Nice presentation, as always.

    The pump cups puzzle me; can't see how they are all on there. It reminds me that I once got a stove on which there was a spare pump cup on the pump rod pointing the wrong way and just "floating" on the rod between the cup nut and the tumb end. Seemed like a reasonable place to store it.
     
  3. presscall

    presscall United Kingdom SotM Winner SotY Winner Subscriber

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    Yes, those pump cups puzzled me too, Itchy. Thing is, you know how there's got to be some movement of the pump cup/retainer on the pump rod so that air can pass through the gap on the 'pull' stroke? Well, the stack of two busted washers and an ok one took up the intended clearance, so it could never have worked efficiently, if at all, as a pump.

    That and the leather lipstick to tank sealing washer and the pristine state of the cork NRV pip - and the good condition of the stove as a whole for that matter - suggests it spent a number of years as a stove that outwitted its would-be user, who found it unfathomable to get going but didn't get around to passing it on to someone who could use it. Well, maybe!

    John
     
  4. Murph

    Murph United States Subscriber

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    Itchy, I've seen the same thing with the spare leather cup on my Coleman 520 stove.

    Murph
     
  5. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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    Hi John, lovely stove outfit and presentation. I don't have a Primus 97...yet, but I do have a Primus 210 from the same year as your "new" Pr.97 outfit (1929):

    https://classiccampstoves.com/threads/18231

    It was only in 1926 that the Pr.210 and Pr.96 acquired folding feet, before that date they were fixed.

    Your Christmas present should last a lot longer than a bottle of whisky or scarf.
    Best Regards,
    George.
     
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  6. mr optimus

    mr optimus United Kingdom Subscriber

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    Hi john brilliant documented comparison write up.
    I would love to have a rarer 97 in my collection, yet on another hand if I wanted a 1 pint collapsible, for its main purpose I would all ways choose the 210.
    As the 210 standard burner in my opinion more powerfull and with the extra surface are of the burner tubes easier to light especially out side.
    If a lipstick burner is pumped to quick it is easy to have a flare up, which I must admit I have done with the first stove I ever bought which was a 96.
    But as I say I would love one in my collection, a very nice fettle John, I have lost count the amount of filler cap washer's I have come across in my stoves and blowlamps, that have become so hard that I have chipped them out the filler cap with a old jewellers screwdriver.
    They become so hard they are more like Bakelite than rubber.
    I wonder how many flare ups the previous owner had with this stove, replacing the gauze roll with just a small piece thinking it is a filter.
    I am surprised the purpose of the gauze was not explained in the manufacturers instructions, being it played such a important role
     
  7. Doug L

    Doug L Subscriber

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    very nice John thx for sharing
     
  8. loco7stove

    loco7stove Subscriber

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    Hi John

    Very nice 97 8) :clap: :clap: :thumbup:

    Excellent presentation as usual , well done :clap: :clap: :clap: :thumbup: , i do love a 97 8) :thumbup: , & I must put mine in the ref gallery too :doh: :thumbup:

    Stu :D :thumbup:
     
  9. Doc Mark

    Doc Mark SotM Winner Subscriber

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    Morning, John,

    Excellent presentation, and what a wonderful stove is the 97! I've never seen one before, so seeing yours, and learning of its in's and out's, has been a real treat. Thanks for sharing this, and hearty congrats on having "made the right decision" in pushing the "BIN" button!! ;) :thumbup: :D :D Well done! Take care, and God Bless!

    Every Good Wish,
    Mark
     
  10. SMolson

    SMolson Subscriber

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    Hi John - Thanks for the great presentation. I've noticed regarding tin sizes (L) that the 210 and the 97 do differ, the 210 being larger (19 x 14 x 9.5 cm) versus 97 (17 x 13 x 8.5 cm). Same goes for the Sport (SP) version of course. Tin sizes in my experience also depend on year of manufacture within the same model grouping as do their paint jobs and construction (clasp/no clasp).
    The 97's are fine and handsome stoves with good fuel consumption as you've mentioned and will support groups of 2's adequately in terms of meal prep. Comparing them with the 210, in my experience, the 210s are a slightly more safer stove to use on account of the fixed burner plate. The burner plate on the 97s (like the 96, 100, 200, etc) if jostled sufficiently (or tipped) can shift position which will result in an unequal flame pattern or a nice jet of flame if dislodged completely. There was also a 2-piece silent damper version (like that for a 100) that would fit these 96/97-sized burner bells.
     
  11. kaw550red

    kaw550red RIP

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    Hi John

    The 97s are interesting but you have to remember that the heat output directly relates to the amount of fuel burnt.

    As you say the jet is 0.23 mm as against the 210 0.32 mm jet. There is no need to calculate the area of each jet. The area of similar shaped items is proportional to the square of the like dimension. In this case it is the diameter of the jet. As the 210 passes 1.94 as much fuel as the 97 it also produces almost twice as much heat.

    In my youth I extensively used 96s and Optimus 80s both of which had 0.23 mm jets. They were ok in summer but a ruddy nuisance in winter in sub zero temperatures as they did not produce sufficient heat to boil water. The problem was that the heat loss from the water at higher temperatures equalled the heat that the stove produced. You got the water to a temperature where the heat input equalled the heat loss and the water stuck at that temperature no matter how long you heated it.

    Food takes a given amount of heat to cook it and a low output stove does not necessarily save fuel. It simply means that it takes longer to cook food

    If you use a 210 you will get sufficient heat to boil water in sub zero temperatures but you can also turn the stove down and save fuel in that way

    Regards Bryan
     
  12. SMolson

    SMolson Subscriber

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    You're probably aware of this, but many of the early Primus and Optimus burner bells (< 1930) were lacking the little flange/rim that jutted out at the the top inside of the tube where it slides over the vaporizer tube. This ring prevented the burner bell from sliding further down the vaporizer tube during operation (from heat). As a result, those missing this rim would often get stuck (slide down the vap tube) during prolonged operation of the stove. This movement may only be a mm or so but it's enough to hold it tight enough that hand pressure will not dislodge them. There's a posting here on using small metal shims (cut from thin-aluminum pop/beer cans) that can be used to help prevent slippage on such burner bells. Using the shim they may still get stuck but firm hand pressure (no tools) will pull them apart. When the burner bell slides down the vap tube the distance between burner plate and orifice becomes smaller which will result in a yellowed flame (poor combustion).

    I've received 3 such stoves with burners bells that have slid down their vap tubes (2 x Primus 96 + Optimus 100) and were stuck hard (plus 1 I did myself before discovering the issue). One of these (96) had the vap tube sticking a good 5 mm into the burner bell. They can be dislodged by using propane torch on affected area and holding it upside down over a bucket of water (wet rag remnant wrapped around solder on vap tube/bolt to prevent it melting). The burner bell will either slip off itself after 5 minutes or so (depending on torch/flame strength and size of vap tube/how badly its stuck) or try dropping it into water once she's sufficiently red hot if gravity doesn't do it for you. This procedure is also posted in the forum.

    I don't know whether it's the same case with other manufaturer's pre-1930 vap tube/burner bells (e.g. Svea, Radius, Enders, etc).
     
  13. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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  14. SMolson

    SMolson Subscriber

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    Post describing methods to remove a stuck/slipped burner bell: https://classiccampstoves.com/threads/24277

    Heating with a propane torch worked in all my cases. I tie back the spirit dish with a strip of rag soaked in water, tight to the bolt. This also helps expose more of the vaporizer tube and creates a workable gap.

    edit: I hadn't seen the link you posted Kerophile, there was another discussing the shims that I read.
     
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