OK, did a simple experiment and perhaps it doesn't tell the whole story but it's pretty clear. First of all, I don't have a Svea123R, I only have a plane Jane 123 so no needle. But I did lite her up tonight where it's dark and the results were plain to see. The jet of liquid fuel comes out of the jet, rises approximately 1/2" then vapourizes, and burns for the last 1/4" before it hits the burner plate. Perhaps it actually hits the burner plate and bounces down that 1/4" while burning before it escapes out the top around the edges of the burner bell. I stuck a wooden toothpick into the spray of fuel droplets, and although it did disrupt the flow and cause a bit of chaos inside the burning chamber, it didn't burn the tip of the toothpick. My conclusion is....When the spray of fuel droplets is heated to quite hot but still capable of holding the tank comfortably, it is squirted out the jet, and when it comes in close contact with the burner plate it bursts into flame. I'd love it if someone could do that on their Svea 123 R and report back if the same thing happens, especially with the cleaning needle part way up. It couldn't be all the way up or it would probably extinguish the flame. Any takers? Stan
Does anybody have access to an infrared thermal camera, and can take actual temperature readings? Yonadav
Interesting concept the slow destruction of the needle. Its been rumoured to happen on brass stoves but Ive never see a photo of an eroded needle. Colman stoves use the same mechanism to control the needle as they do to control simmer so there needle is always in the fuel flow while simmering unyet they dont suffer from needle failure. If it does happen it happens so slowly that it isnt realy an issue. In any case simmering on a 123r is better achieved by turning the key the other way towards off. The real problem with the needle is that it can wear the jet but even this takes forever. As colectors we tend to gravitate towards old well used stoves which is why we see these problems. Some of the stoves with these problems have probably worked as hard as we ever have
Morning, Gents, I would like to stress that there is a difference between the Swedish designs, and those from Coleman, and because of that, Coleman does use the cleaning needle to regulate fuel flow, whilst the SVEA/8R/99/, etc., do not. To me, and this is just my opinion, if the company which makes the stove did not manufacture it so that the cleaning needle regulates the flow of fuel, I most certainly would NOT try to use it that way. Others may, of course, do whatever they wish to do. Just sayin'..... Take care, and God Bless! Every Good Wish, Doc
You are right Doc, the Coleman stoves (with the exception of the Solus) are very different designs from the Optimus, Svea, Primus type stoves when it comes to the principles behind vapourizing the fuel. Primus even mentions this in their website. They state that their stove's system, when used with clean fuel, won't gunk up the system. They say that generators that are heated before the fuel exits the tip, (like the Coleman system) are a system, they say, that could result in carbon and other tars plugging up both the generator and tip. This says to me that Optimus/Primus/Svea type fuel systems have less heat at the tip. Something that reassures me I won't have to worry about tips and jets wearing because of heat. Now tips will always wear from over zealous cleaning and/or fuel that has some form of granular pollutants in them, but fuel cleanliness is a whole different topic. Stan
Hey, Magikbus, Thanks for the shout back. In truth, what it tells ME is not to do it with the Primus/Optimus/SVEA stoves! I've seen far more gunked and carboned up burners from those stoves, than I have with Coleman stoves. In fact, the only such problems with Coleman were caused when the stove owners used the wrong fuels with stoves that were never designed to burn them, for the most part. However, I've seen tons of Swedish burners coked-up and carboned on the inside, and that was just from use, not improper fuel. But, to say again, you may choose to do whatever you wish. Just saying that's my long experience with both types of stoves, with few exceptions. For what it's worth.... Take care, and God Bless! Every Good Wish, Doc
Greetings All, I believe the needles on Coleman stoves do erode. It may be as Geeves suggests that it happens slower but I've seen model 400's that had no flame control and operated at full blast because the needle had shortened significantly. My belief is the more simmering you do the quicker it'll erode. The earlier model 400 and 508 both had needle control levers that Coleman did away with on the later models of these series making the fuel flow valve the only way to regulate flame size. Ray
Hi, If I may comment on the issue of whether or not to use the needle as a flame regulator: Primus and Optimus specifically advise against this, for example in the instructions for the Optimus 8R: https://classiccampstoves.com/threads/271 and the Optimus No.22B and 111B: https://classiccampstoves.com/threads/275 I reckon they did this for a reason, probably their experience with the early "self-cleaning" burners, which had cleaning needles, that also acted as a flame regulator. The needles wore away and subsequently a needle valve was adopted for the regulator function. It seems likely that if a needle alone could act as both jet cleaner and regulator, the Manufacturers would have been delighted to avoid the cost and complexity of incorporating an additional item, the needle valve, into the burner. As to the mechanism of jet degradation; It does not need to be heat, or heat alone. It is possible to get ablation, or wear of needles and jets by the effect of high velocity liquids and vapours alone. If you also have heat present, the wear rates increase considerably. It is a science in its own right, with perhaps degradation of atomisers and injector nozzles being the most widely studied subject. If anyone wants to regulate their stove by using the cleaning needle rather than the installed regulator valve, I guess that is their business. However they are doing this against the specific instructions of the Manufacturer, and shouldn't be surprised if the "Adults" did know best. Long live the Experimentalists! Best Regards, Kerophile.
Hey Stan, I see things differently. Reviewing jet temperature first, Let's start with classic kero stoves, with a four tube roarer burner. The hottest place in that burner will be the burner head, where fuel vaporization takes place. The four brass tubes will be almost as hot, and the jet a little bit less. Now, the self pressurizers white gas stoves (123, 8R et al) do not have a fuel tube in the flame. The hottest place is obviously the flame plate (glowing red hot), together with the upper half of the burner bell. Due to the excellent heat conduction of brass, that intense heat flows down the brass into the jet and the vaporizer underneath it, so those parts also get VERY hot (enough to vaporize the fuel). That's why use of the cleaning needle to regulate the flame in these burners in not such a good idea. On the other hand, they all have a conical valve, capable of doing a moderate job of fuel flow regulation. Coleman stoves are a different story. The part that sits in the flame is the central part of the generator, made of rather thin brass, so less capacity for heat transfer. The jet in all Colemans is at the far end of the generator, inside an air mixing chamber, away from the flame. Thus the Coleman jet is much less hot than on the previous two, allowing for use of the needle to regulate the flame without risk of burning the needle. And now to gunking of burner innards. The primary cause of excessive gunking in classic kero stove is that kerosene, as sold, is not "pure", and contains various other stuff that tends to accumulate in the very hot burner head. White gas, used in the 123 et al, is much cleaner, and therefore there will be less gunk due to its burning. The trouble comes when an owner switches to the dirtier car gas. Coleman fuel is even cleaner than typical white gas, and therefore the Coleman generators have rather long lives (unless again a user burns unleaded gas in them). My two cents on this subject... Yonadav
No, vapourisation is a physical change and doesn't require either oxygen, or any other substance - just a high enough temperature and sufficient heat energy to provide the latent heat of vapourisation. What is being emitted from the jet is a stream of fuel molecules, not droplets.
Sorry, I didn't make myself clear. I wasn't saying that the Oxygen was required to change the state of the fuel from minute droplets, into a vapourous state. The oxygen is however required to ignite the fuel vapour (into flame) when a high enough temperature is provided. The process of converting the liquid (droplets) into vapour is what takes energy, and that sucks up heat energy effectively (what we call) cooling the stream down. It's the same principle as when your sweat evapourates and cools you down. Sorry for any misunderstanding. Stan
However, vaporization of the fuel happens inside the "vaporizer" tube, underneath the jet. That's where the fuel boils and turns into gas state, taking heat energy from the hot brass tube (not from the air). What comes out of the jet is a "cloud" of fuel vapor, not droplets. You do have fuel droplets in Coleman stoves during the primeless ignition state, where a mix of fuel and air comes out of the still cold generator.
Cheap drugstore reading glasses don't deal with astigmatism, only myopia. With one replacement lens as well my readers are not the same prescription in each eye and are expensive bifocals. So whilst I have a spare pair they are not sacrificial enough to be tossed in a rucksack! Cheers, Graham.
Anyhow, I've enjoyed this discussion, learned a few things, done an experiment I wouldn't have thought of myself, and really want to thank everyone who participated. Just to be clear, I wouldn't think of trying to tell anyone how to use their stoves against their will, anymore than I'd allow anyone to tell me how to use mine against my will. That's just not how it works. Ain't this a great forum, eh? Stan in the great white North (well, it will be soon anyway)
Hi demonfurby, I have the same "problem" as you: the Optimus 123 R does not perform well with regard to simmering. When turning towards "off" the flame becomes yellow - apparently the speed of the gas flow becomes too low in order to create a blue flame. When pushing the cleaning needle partly into the jet (or close to it) the flame becomes very small and blue. A perfect simmering, but apparently not the recommended way. Pics here: https://classiccampstoves.com/posts/27814 I am still guessing that the jet orifice is too big with the new Optimus 123 R: too yellow flames (too much fuel?) when burning full power, and blue flames on low power only when the jet orifice is being minimised by the cleaning needle pushed upwards. Regards,Philipp
Magikbus, Once the 123 is hot and running well, the fuel exits the jet as a vapor, not an aerosol. The phase transition and necessary heat transfer that results in vaporization of the liquid fuel occurs in the vaporizer of the stove prior to mixing with air. However, the process you describe is seen upon the exciting process of starting a Coleman 530 (see recent posts related to that).
lastnight i test the svea again and pulled the needle back out, it simmers quite well i did notice that the needle was slightly bent it may have been impeding the flow of fuel thought id pass along the info
This thread is more than 10 yrs. old now, but perhaps this is interesting: on the website of Katadyn they write about the Svea 123r: “A built-in cleaning needle helps you keep the flame burning and that pot of nourishment simmering.” Am I reading this correctly and are they actually recommending to “simmer with the needle”, contrary to received wisdom?
