Hi! There. Does anyone give me the said information for me? I've wondered that the cracks of the fount could be triggered by the thickness of brass fount also. However I've found hardly the information of thickness through web. Help me, please.
This might help with the Tilley question. It is necessary to use some judgement but at a guess 1.5mm thick? Tilley Guardsman font base ballooning Link seems to point rather late in the thread. Scroll up to see the pictures in post #14
Thanks, JonD. The photos linked at your reply are quite helpful for me. By the way, I'd like to know the factual thickness. Might the thickness be less than 1.5mm? For the further reply. Thanks.
@Ernest Kimm If it’s an X246 (not 246B) I do not think thickness of the brass has anything to do with stress cracks. It could be quality of the batch of brass, or some chemical injury after manufacture. I haven’t dissected an X246 (yet) but here is a cutaway: Tilley X246 Cutaway (early 1950s) Best regards Tony
I would have thought older Tilley's would have used materials in imperial measurements so 1/16th of an inch? .. perhaps if someone has a scrap font they could measure... Martin
Thanks Tony, The photos you linked are too much informative. Furthermore I agree on you opinion about the thickness of brass would be not a big deal with the stress crack. Definitely the quality of the batch would be.
The nice thing about Tony's photos is they show the better method of assembly of the tank bottom that is less prone to bulging under pressure. @Tony Press @Ernest Kimm
With regards to the base plate soldering, at the bialaddin 300x, the base edge is downward, not upward like the above pic, and is held by wall folding. Might the base plate be prone to bulge even there is under internal seam soldering. Is it proper understanding that prone to bulge would be prone to occur the stress cracks at the rim of bialaddin 300x?
Any (slight) deformation of the bottom, as a result of various pressures in the tank, will relay forces on the rim. So this might contribute for cracks to appear in theory. However, the main cause for stress cracks is the lack of annealing after the tank was pressed. Without it, the stresses in the brass as a result of the considerable shaping remain and will make themselves seen in time. I think for a mass produced item it is quite easy to overlook the annealing process for certain batches of tanks. Hence the stress cracks are seen at random, meaning not all the lamps of one particular model (300X seems prominent) have this ailment.
Seems AGM and Akron must have had this annealing problem. They seem to turn up more than Coleman, Petromax or Bialaddin with stress cracks.
You could try to measure the edge of the folded rim at the bottom of the fount if its accessible. That should be approximately the thickness of the fount wall too. I think it'll be less than 1.5mm. Anyway, thickness is not the cause for stress cracks. Besides improper or absence of annealling, stress cracks could also be initiated from de-zinfication of brass in the presence of ammonia or some of their compounds. The zinc in the brass would be preferentially corroded, leaving the copper behind. The loss of zinc in the presence of ammonia extend into the material rather than just on the surface. Rather different from the corrosion due to acids.
Thanks for your deep insights on this issue, Meijer. The more production could have occured in the more stress cracks, as you mentioned. I agreed that not special model issue but use of frequencies.
Thanks, Myn. That a reasonable points which I missed. Beside of thickness of the brass fount, yes, what you mentioned would be a good explanation for me. Thanks again.
If you happen to clean a very dirty fount with an alkaline degreaser, such as lye/sodium hydroxide solutions, do not leave it in the solution for too long. Alkalis would corrode zinc from the brass quickly, leaving voids. That would be prone to stress cracks later, especially when pressurized.
Thanks, Myn, for your kind comments, even at the condition of alkalies. I'll keep the same in my memory.
