Hello All, An aquaintance of mine is in the process of bringing back a Primus 1050 into working condition. He mentions a blue top but has not mentioned a letter on the bottom (yet). However, the NRV needs replacement and it appears it has a greater diameter on the threads than the regular NRV common with most lamps and stoves. The first question then is, if this is an odd deviation Primus implemented for whatever reason? Typical for a gasoline model? The second question is where to get such a replacement. Mike
Same acqaintance got in touch with someone in Denmark who will order said NRV with Fogas.se as they seem to carry this model. As to why this NRV is bigger in diameter on the threads than the standard model we all know still is not clear. While the item now seems available, perhaps someone could confirm this different size has something to do with a close-off feature? Mike
It is because the 1050/1051 is a coleman gas lantern and has a different NRV and pump rod for that. It is a safer way to do it for that fuel
That is what I thought as well, but thank your for the confirmation. This acquaintance has not had a chance to operate it and this is new for him. I will pass on the information. Mike
I had intended to answer this post, but got distracted and forgot about it. As discussed the 1050/1051 NRV is a larger diameter. I have not found a logical reason for it, but that's the way it is. The pump on the 981/1081 uses a similar locking feature and still has the normal size NRV. The only added feature on the 1050/1051 NRV is that the pip holder has a rod extending from the back which goes through the spring and the hole in the end of the NRV. I can only imagine that this is to ensure pip holder does not tilt and get jammed. Also as said, Fogas in Sweden still have the part listed on their website.
Thank you Nils for your response. So this is yet another odd variety Primus is known for? Like different threads for their applied needles? Anyway, you do confirm one is on the right track with Fogas.se But you make an interesting statement here: the locking feature on a 981 pomp in relation with the NRV. The only locking feature on my AD (1939) lamp is a coarse thread on the pump rod and in the pump cap that has to my mind no relation with the NRV. It is an extern feature to secure the pump rod and knob. So far I have been thinking about an NRV for the 1050 lamp that is a tap also, closing off the pump tube internally when done pumping, as on a Coleman lamp. That construction - again, in my mind - could possibly necessitate a larger diameter valve. The arrangement as illustrated here merely prevents a pump rod to come out, something regarded as important as several makers of that time had some kind of arrangement to lock the pump knob into place. It does nothing as to close off the possible passage of fuel should the standard NRV fail. My 981 from 1938 - supposedly the first year this model excisted - does not have this feature, by the way.
The positive closing feature on the 1051 and 981 is in the end of the pump rod. There should be a conical section that sticks out past the thread for the pump washer nut. When the pump knob is screwed down, this conical part seals into the hole of the NRV. I'm at work so can't take any photos at the moment.
Aha; I think I can imagine what that does look like. But no such feature on the pump rods I have, nor is there any conical recess in the NRV's. One does wonder why Primus applied this on a strict paraffin lamp, unless alcohol was in mind. After all, alcohol is not a fuel you want to spill from a burning lamp either. Thanks again Nils.
Just my thoughts. Perhaps the larger diametre nrv was also meant to prevent anyone from mistakenly using one that's meant for kerosene-fueled lanterns? I think the air inlet hole for kero-type nrvs would not have the conical tapered seat to accommodate the conical point at the end of the pump rod. The positive shut-off might not work with a kero nrv.
I see what you are driving at: no NRV without a positive shut-off should be installed in a petrol fuelled lamp. That would make sense, even if that would depend on a pumprod with that conical extension, upper thread and a pump cap with mating threads to press the cones shut. All of those can easily swapped with the other (kerosene) lamps. It would be more fool proof had Primus enlarged on pumptube and cap, plus a thicker pumprod as well to prevent interchanging. But even today, with many appliances more thougt out and foolproof, the real safety lies with those owners with fundamental knowledge. Good thinking and common sense still rule and should be applied especially with volatile fuels.
Here is a picture of the pump rod end from the 1051. Not the best photo, but hopefully it shows the details. It is a very flat cone. The hole in the NRV has the normal sharp edges, no matching conical shape. With the flexibility of the pump leather as far as centering goes, the cone should seal on the hole edges. The 981 and 1081 should have the same idea, but with the standard NRV.
Well Nils, I learn still everyday! Thank you for the picture which is clear enough. It is thanks to you I am now aware of this, that in my case, has no bearing other than on knowlege. Both the 981's will stay as they are, without that cone end on the pump rod. Regards, Mike
