Hello ! Nice to meet you all, this is my first message here. I found a modified primus 71 (legs welded to the tank) and as you can see on the 2nd picture, the burner's bell has a "sliding shutter". Is it a common feature ? |imgRemoved| |imgRemoved| I guess its purpose is to vary the proportion of oxygen, am i right ? I must say that compared to an unmodified primus 71, it heats very moderately. So I wonder if it was modified to use another fuel..? Has someone an idea ?
Welcome. My old one has that feature along with the cap. Seems the metal tin, windscreen that it came with has burned out or unusable, hence the soldered on pot supports. Duane
It probably needs the wick taking out and a good clean out of the vaporizer. I bet that control knob gets hot!
Hi Nikos, welcome to CCS. Have a look at this thread: https://classiccampstoves.com/threads/16107 Best Regards, Kerophile.
I've a Radius # 43 here that's real close to having that mod done here, no tin and all to be had here. Murph
Nice looking modifications. On any of these self-pressurizing stoves with a weak flame, perhaps the first and easiest thing to check is the fuel cap gasket. If it is old and hardened, even the slightest leak can keep the stove from building good pressure.
Hi! Thanks for all the replies and links !! So, I got my answer. The sliding thing was made for the use of alcohol-petrol blend (Cleveland Discol) which explains the need of reducing the supply of air. Was it an original feature (1938 ? AC on the tank) or was it sold as individual part ? |imgRemoved| Actually, the flame is strong and blue. But doesn't heat as much as an other primus71 (coffee-test provided statement) Maybe the legs are simply to high ? Wick and fuel cap gasket are new. About the knob… I got 3 or 4 blisters before I decide to remove it. I wonder who had the idea of the burning knob !? Does it serve an other purpose ? About the welding of the legs, it's really well done. In the old time, was it common to have a stove/lamp repair shop at the corner of your street ?
That's a very interesting stove. Are the legs really welded? Do you mean soldered? Brazed? Maybe the person who modified the stove lost the regulating key? Seems odd to replace it with a knob, particularly a brass knob which would get very hot. Maybe they wore gloves or something? The pot supports don't look too high. Were you cooking outside? The wind might carry off some heat. Without the case, the stove is very exposed to wind. HJ
Hi Nikos, I believe the "adjustable bell" on our Pr.71s was an original fitting. Looking at your neat set-up I think you stove legs might be too short rather than too long. For the flame of a roarer burner to "breathe" and operate efficiently you need a gap of approx 16-19mm between top of the flame plate of the burner, and the base of the pan: https://classiccampstoves.com/posts/100141 Try out your stove with a spacer between the burner and pan to see if the boiling time is reduced. Best Regards, Kerophile.
I had not thought of that ! That's a very interesting formula and it seems that the legs are indeed too short... I am far from the primus now but I'll try as soon as I get back to my stoves and will let you know. Thanks !!
