A nicely patinated old Lux stove with a Lux-burner still mounted. The logotype indicates 1906 or later, and I assume that it was made before the stove production was acquired by Optimus in 1914. Sorry for the crummy pictures. These were some old photos I just found on the computer, and didn't feel like making a new arrangement.
Amazing how the stove structure remained practically the same during 100 years of production. (We do have all those fancy multi-fuel camping stoves of today, but stoves that look identical to this "LUX No.1" are still being manufactured in several countries to this day.) BTW - what is this lug sticking out of the tank under the "T" of "patent"? Is it a safety valve? Yonadav
Hi Yonadav. That lug is the NRV. Or rather a part of it. Some early stove and lanterns used this instead of the regular ones we're used to at the bottom of the pump tube. At the bottom of the pump tube here, there is just a thin tubing soldered, nothing else. The other end of this tubing is attached to the outside accessible NRV under that dome nut. If I unscrew that little dome nut, I get access to the seat, the spring and the cup, all very similar to the one you will find inside "the regular" NRV's. The seat is more or less the protruding tubing. Outside this seat, and under it, there are a couple of slots that allow the air to enter the tank when the valve is forced from it's seat by the compressed air.
Interesting! They simply put the NRV on the outside of the tank, so it will be easily accessible for repair, at the cost of another screw-cap and seal.
Yep. Pretty much so. I don't really fancy this construction. I think it makes things a bit more difficult than needed. They are working fine on some other stuff I have, but this actual stove needs some major fettling, and that's only because of this arrangement... The tubing between the pump and the NRV has a leak somewhere, so I have to desolder the pump tube to fix this. That's a very easy job normally, but here I also have to desolder the whole NRV at the opposite side in order to get the entire assembly out of the tank! I'll save that to the autumn.
I don't think lack of reliability is the reason for having this outer NRV. The "normal" NRV that we are used to had been around for a long time before this stove, but probably prevented to use by others by the 1896 Primus patent. (Primus actually had a dispute with Optimus in 1906 regarding this.) I think that Lux used both NRV versions parallel at some time, but I have no idea when they got the right to use the "Primus type". Must have been before the 20 years patent protection time had run out.
