I have a Petromax 827 250CP, and my centerplate is rusted badly. Does a 122 centerplate from a 829/500cp also fit the 827? I can't find a centerplate that is specifically offered for the 827 whereas ones for the 829 are cheap and everywhere. And I also saw a 126 'protection plate': What does this plate exactly protect? And does it also fit my 827? (it's sold as a 829 accesory). I plan to retrofit my 827 with a methalated spirits cup.
No that won’t fit the size is different the plate holds the top of your lamp attached to the tank by the center screw
There is the idea that in the situation that the mantle breaks, and you get a flame directly down and nobody is around to notice all these thing: that THEN when ll these things happen at the same moment in time, there is a change that the center bolt get unsoldered. Only the military after ww2 had these kind of failure analyses or saftety ideas and mounted these protection plates on the NATO/BW lanterns. The first plate is the one that keeps the globe cage on the tank the second one is a gizmo (in my eyes).
Thanks Wim. That protection plate does sound a bit like a gimmick. If the centerscrewhole getting unsoldered was a real risk and would cause fires, you'd think that at some point the standard design would be fitted with a protection for that over it's 100 year production run. I'll probably order the 122 centerplate anyway. If it doesn't fit the 827, I may be able to reduce it's diameter a little bit. In most pictures the diameter looks very close. I know the 829 has a bigger cage with larger glas and larger top hood, but the bottom seems to flair out more than on the 827, so the diameter there might not be so much different.
In fact, the difference in diameter isn't very much: 84.5 mm for the 250 HK size and 88.5 mm for the 350/500 HK size (or 92.3 mm for the 300 HK size) outer diameter of the rim. A problem could be the inner diameter (which sits inside the globe cage): 73.3 mm for the 250 HK size and 79.5 mm for the 300/350/500 HK size. If you cut down the bigger center plates it might have a very small rim of only 2.5 mm around, and may sit above the indent of the globe cage. Better to search for spares, e. g. from the Swiss military, who had the 250 HK size globe cages combined with the larger 350/500 HK tanks (lantern type called 821/523). From left to right: older 300 HK centerplate, new 350/500 HK centerplate, 250 HK Swiss centerplate.
I would remove rust from the centring bottom #122 and leave it as is. All Petromax lanterns manufactured in Germany had a centring bottom #122 of iron . The lanterns of different brands made in Portugal at Hipolito ,which also included the Petromax brand ,all had centring bottoms #122 made of brass.This is also a striking distinguishing feature. I use the heat shield#126 on the 829B lanterns from 1958 to 1960 that are equipped with petrol carburetors . And I also use it as protection for lanterns that have been soldered onto the top of the tank.
yeah I'll probably do that. This is how it was after cleaning (with alkaline electrlytic cleaner), so some rust is already gone, it was worse (to the eye at least): This is after using some scotchbrite and having it soaked in a light hydrochloric acid. Most of the red rust seems gone, but the pitting is very deep and some red rust pockets remain: The deep pitting is not something you can polish away (within acceptable means), rust pitting is usually way deeper than some scratches. I could sandblast/beadblast it, but then the surface texture changes considerably, giving again a very different look/feel. I might nickelplate it to get an even colour and get some rust protection. Maybe I'll treat it with phosphoric acid too to convert the last small red rust pockets in iron(III)oxide. Although giving it a light oiling afterwards will also fill that deep pitting, sealing it from additional red rust...
The original center plate of your Petromax 827 still is in not-too-bad condition despite rusting. It isn't even half as badly corroded as some of the pieces on my 826. I'm still using them despite the conditions. I believe you can get all the rust out including the last traces in the pitted areas if you leave it for a couple of days in citric acid. Whatever subsequent treatments is up to your means. Anyway, the outcome after the rust removal and treatments looks pretty good.
Since the centrepiece of a Petromax 250HK or an 827 is rather hard to come by these days, you might want to check if you provide the actual dimensions to any local metal smith or machine shop. For a reasonable fee, they might be able to make several new ones as spares for future projects. The original is a stamped-out and nickel-plated piece. Stamping requires dedicated heavy machines. The local smiths would likely produce a replica using different means.
True, it's patina and the rest of the lamp also isn't perfect. A new centerplate might look too obvious shiny and perfect. The diluted HCL and some inbetween scrubbing with some scotchbrite did the trick pretty good. I nickelplated it and it now looks pretty good. Of course the pitting remains, but the pitted areas are now nickelcoloured and not the gray steel colour. This is how I have it now: The pitted areas will always seem a bit darker in most lighting conditions because of the shadows, there is no mirror effect. But inside the pitted areas, it seems that the nickelplating also took hold. The colour is the same and it's now of course again somewhat protected against further corrosion. Closeup: I think having them re-made in small numbers will be extremely expensive.
@GuidoK It does look good now. The pits are already there and it would be a lot work to re-build the surface with metal. Not sure if that is even feasible...for instance, with sil-braze, smoothing, finishing and then finally re-plate. I believe so. I could not imagine how can that be machined on a lathe or milled out. The only efficient way is by stamping it out. That would require hydraulic stamps and specially-shaped jigs/moulds
Normally the part would be sandblasted, sanded, tankplated with a thick layer of copper (preferably coppercyanide as that has the best filling capabilities and good adhesion, but cyanides are difficult these days in the EU), then sanded/polished and then nickelplated. This is usually how corroded/damaged chrome parts etc on classic cars etc are done. But I'm not gonna go that route . The lamp isn't perfect.
I'm sure you'd prefer it to look matching in age and overall appearance to the rest of the lantern. Would love to get my hands on some copper cyanides someday I guess that'd be a little elusive here in my location as well.
