This week I got a very well used little Optimus 100N, complete except for the globe. To my great disappointment, I immediately noticed that the found bottom was bulged out, so much that it wobbles on a flat surface. I was not aware that Optimus founts also suffer from this problem. My question is: Repair or replace? I suspect the best answer would be to replace the fount, in which case I would appreciate it if some kind soul with one for sale or trade would drop me a line.
Heat it up to about 350°F in the oven with the fuel cap off and the valve shut and the plastic knob off. Put the fuel cap on tightly and place in the freezer. Listen for the pop. If that doesn't work try again by pouring about a third of a fount of boiling water in the fount, cap tightly and put it in the freezer.
Hmm.. that temp is very close to the melting temp of the lead based solders that may have been used with the lamp.. just saying
You're right, I didn't think about soft solder being used. Cut that down to about 275° to be safe. Op might also use an automotive type hand vacuum pump to pop it back in.
@Rustytank , the bottom plate of the fount is designed with a slight outwards bulge, but with this one, the plate is deformed and the lead seam of the bottom plate has torn away all around the side wall. It looks to have been resoldered afterwards. The rim of the fount is made with an inwards curl, which captures the bottom plate. I don't think it is feasible to remove & refit or replace the bottom plate without effectively re-manufacturing the whole fount.
You could also try gently tapping it with a rubber or rawhide hammer. Or if you can locate a good tinsmith to consult about a proper repair or possibly making you a piece resembling a Coleman Parts safe to attach to the bottom so it sits level. Unless those lanterns are fairly common where you are a replacement fount could be hard to come by.
That's pretty unfortunate, @phaedrus42 . Even if you do managed to knock it back in a little, it'd re-bulge once its pressurized again. I've got this problem with one of my Petromax as well. The cause is what you've already mentioned. Meaning, the solder being partially torn off internally around the bottom rim. There had been people who are very skillful at repairing such items but there aren't many of them around these days. They are basically professional sheet metal craftsmen. They'd somehow undo the bottom lip around the rim quite effortlessly, re-shape the bottom plate and then resolder it back with near factory-perfect outcomes. They do use some sort of jig for re-folding back the bottom lip neatly. Unfortunately, I don't know any of them.
There's a Mennonite fella near me that can do it. Shipping would be cost prohibitive for you guys though.
The chances of finding an extra tank are very slim, so repair is the best option. I've never tried it but maybe clean the tank so the torn seam inside is spotless, then push the bulge back and heat the rim so the solder can re-flow inside.
I see that my Optimus 200P and 300P have flat bottom plates. Before I try to remove the bulged bottom plate I'll try to hammer concentric circles of ripples or corrugations into it and see what that does under pressure. The lamp now works and the fount does not leak, thanks to all the extra solder that the repairer applied under the lip.
The plan seems to have worked! I pumped up the fount to 1.5 bar after making the corrugations and the bottom popped into shape and stayed there. Then pumped to 2.5 bar and it stayed put. Reassembled and working:
