Hi, I have recently been working with a Primus No.1S:or stove from 1939 (AD19) and noted that the tank seemed more curvaceous than usual.... Is it my age Doctor? Should I worry? I have therefore taken some photos of other paraffin stoves for comparison and to get a second ( and third, fourth etc) opinion: First, here is the Primus 1S:or from 1939: Now we have a Primus 5S;or from 1949 (AN1): Here is a shot of them side-by-side, with my curvaceous 1S:or on the right: Next I have included an Optimus 45 in the set, as I have always considered this stove one of the shapliest in the business: I'm not imagining it, am I? It is a genuine effect isn't it? Best Regards from a worried Kerophile.
Nice Stoves Kerophile... I'm thinking the first version of the Sor tooling was a bit different to the 'standard' tooling. I haven't really looked closely but I reckon the top 1/2 of a No5 tank is a pressing and is not a spun item. So it make sense that if Primus were retooling for the Sor versions without the filler recess that the first version of the tank could be a differing profile???? One way to tell might be to find another Sor from the same year.. if it has the same profile it's tooling generated if not the over pumping might be the cause.... either that or it's a copy What the workshops of Asia do today for LV handbags they might have doen then for primus stoves??? Either way nice stoves and as always an interesting problem..... Cheers john
Hi Paul,that was my concern at first but the shaping is perhaps too symmetrical, and as Robert says the burner to pan-holder distance is about right..... The stove operates very well anyway! More suggestions welcome. Best Regards, George.
Well, Primus No.1S:or is clearly the "bustier" of the stoves (a real Dolly Parton ), while the Optimus 45 is slimmer in the "hips". It all depends on your preferences, though both are very nice. ....Arch
I still prefer the 45 on looks 8) The 1:Sor has round shoulders, a bit of a belly and less sharpness than the younger one. Hey, it sounds like me . And it's a year younger than me too
Greetings gents, 1. A wild guess might be that the stove tank was formed in a first die with a large radius to the forming plug making very rounded corners on the tank, to avoid tearing the brass on entry into the mold mounted on the press, and that the second die which then sharpens the corners on a second press operation may not have been used on the subject 1939 stove. Keep in mind this is a wild guess, but items like model 96 vapo tubes (as an example of progressive forming) most likely were made in 3 or more press operations, in a progressive manner, gradually elongating a pot like shape of the first press operation and eventually taking what started as a disk of thin steel and turning it into the shape of a lipstick tube. sharp corner stove tanks may have required similar manufacturing processes to get the sharp corner on the tank body. 2. For a reference timeline when George's stove was made In 1939: !n August 1939 Hitler signed a non aggression pact with Russia, and in September rolled into Poland. I believe this is also the year when England declared war. 3. Metals or at least the quality materials needed for the type brass used for stove tank forming may have been in scarce supply whilst Europe was in turmoil in 1939, and the forming shape might have been altered because the available materials at the time did not make for easy forming of the sharp corner. I too like the 45 style tanks for their beauty more than a model 5 or model 1, but the 1 and 5 are still great stoves. I think Kerophile has a very rare stove. Regards, Doug
An interesting observation & one that's probably going to have to be resolved by finding the same models from the same year. Catalogue listings for the model tend to be illustrated by the non S:or model. Looks to me like a pressure pop-out even with the burner height issue. The S:or was thinner gauge brass than the standard model so would likely be more prone to deformation under excess pressure - I'm not that hot on the physics of this. All over-pressure deformations I've seen have been even. The curve of the tank from the vertical around to the top looks unnatural to me - the turn on the edge looks uneven, but that could just be the reflection. If it has blown out would the volume inside the tank not be greater than normal? Maybe a comparison could be done with a regular shaped one. The volumes for the model don't vary over that period from the info I've seen.
If it has blown out the riser tube would no longer reach the bottom of the tank and a rather large amount of fuel would be left in the tank when the stove has burned out. This can be tested I think.
One of my No 1 seniors has almost the same deformed shape as Kerophiles, and i always assumed that it was caused by overpumping. I think i will take a check when I come home regarding hight of the burner and also if the pickup tube are to high from the bottom.
Hi Everyone, thanks for your comments and suggestions. I have now done some more work and took some additional photos today. I have collected together a group of eight Primus stoves, being either 5S:or or 1S:or models, manufactured during the period 1933 to 1955. The Primus 1S:or stoves had roarer burners, whereas the 5S:or models were fitted with silent burners. On the right hand side in the above photo we have the curvaceous Primus 1S:or from 1939 (AD19). On the left is a 1937 (AB3) Primus 1S:or for comparison. In the photo above we have the curvaceous 1939 Primus 1S:or on the left, and a 1939 (AD30) Primus 5S:or in the centre. Above we have a "Blown" stove recovered from the donor ward. This is a 1933 (X21) Primus 5S:or stove. In the centre we have another 1933 (X16) Primus 5S:or, with a good tank. On the right is a Primus 1S:or marked AB3, giving a date of 1937. Finally I have lined up the "normal" Primus 1S:or from 1937 (on the left), with the curvaceous 1939 Primus 1S:or. You will note that the top of the tank appears to sit considerably higher in the curvaceous stove. I took measurements and whereas the "normal" 1S:or is 100mm from the ground at the highest point on the tank, the curvaceous one is 110mm Conclusion: 1. Those who diagnosed a "Blown" tank are most probably correct. I am sure if I had followed the advice to check the dip-leg I would have found this raised as well. Thanks again for your input. Aren't stoves fascinating? Best Regards, Kerophile.
Very interesting ! I have not seen a blown stove before but it does make sense . Thanks for making the photo comparisons and braving the cold to do so. I noticed you don't yet have much snow. We may have received some of your's by mistake over here in Northeast US. Happy holidays everyone................... Best Regards, Doug
I note your use of "accession" numbers George. I have a similar system but now number them underneath when I caught the wife reading the numbered labels . . . .
A real lineup of portly ladies there, George! Let's see those sveldt 1.75s parade down the runway sometime!
Hi Doug, we have't had snow this week, What you see in the photos is "Hoar frost", I think that is how you spell it...... The ice crystals form on all surfaces and can built up quite a coating. It has been bright today but the temperature never rose above freezing. If you got our snow delivery by mistake please hold onto it. Thanks. Hi Keith, "Accession numbers", I thought I was the only one old enough to use such terms...You obviously spent too much time hanging around libraries and librarians. My wife has not so far commented on the number of stoves. I hide them under the house! Ed, it would be good to have a "salute" of Op45s...or Svea 106s. I will bear it in mind. Of course I could also light them up and go for the World record. Best Regards, Kerophile.
hello kerophile, i was wondering if you have any idea how so much pressure was built up in that stove? is it possible to pump it that much, or is it from too much heat built up on top of a lot of pumping? i am surprised that a solder joint didnt let go as it must take a lot of pressure to blow the tank out like that . just curios, brian.
Hi Brian, it should be possible to do the calculation, but the geometry is fairly complex as the tank is a short cylinder and well supported by the rolled and soldered circumferential seams, and the soldered stove legs. If you have a "full" load of fuel and a relatively small air-space the limit on the pressure you can achieve in the tank is determined by the back-pressure acting on the air-pump. If we plugged the jet and put an pressure gauge on the filler cap we could do the experiment! If you then light the stove, the pressure can increase substantially due to radiant heat from the burner increasing the pressure of the air and the fuel held in the tank. There is no pressure release valve on these kerosene stoves, so in practice the pressure could rise until a washer or solder seam ruptures, and releases fuel and air....or the fuel is simply consumed. Although undesirable, this example of over-pressurisation has shown just how robust and forgiving the solder joints on these brass stoves are, since this stove still operates well, with no suggestion of leakage. On close examination the solder joint on the legs to tank seam have started to tear at the top of the tank, but the legs are still firmly attached and all other joints appear un-damaged. Best Regards, Kerophile.
