My Coleman 237 was running a bit rich, and not as bright as a 500cp lamp should. I decided to give it a bit of a service. The first thing I noticed was a mud wasp nest in one side of the burner casing adjacent to the burner tube. With that out of the way, things got better with the light output, but still not quite right, so I pulled the generator off. It needed a good clean, but I also noted the distinct “bend to starboard”: I heated the end up and carefully pulled it back into shape. Light output is now fine! Cheers Tony
I've noticed this with one of my Coleman 242 lanterns; the generator was bent. I would assume the heat causes this.
I have noticed this bend on a few generators and sitting and looking at it, with the obligatory cup of coffee, I have come up with a possible cause. Sometime in the lamps’ previous lives they have been stripped, either to install a new generator or for cleaning. In the reassembly the alignment of the burner’s generator hole with the generator was not quite accurate enough. When tightening the burner down, because the generator is now to the side of the burner hole, it bends. How do I know this ....... I did it once on a 242B and it was quite easy to do. Of coarse there’s differential expansion caused by more heat on on side of the generator argument. However I’m not convinced that it would cause the pronounced banana effect. My reasoning is that the heat would conductively equalise thereby causing any slight bend to straighten. Just a thought. Cheers Pete
Peter I swapped it out with another that has a slight bend, and the one above is now cleaned of carbon and a spare. I’m using the 237 every night (along with a 236) at the moment (good light and warmth in the shed) so I’ll let you know how it goes. I’ve seen this kind of bend on a fair few old lanterns that have had a hard life. While I think bad alignment with the burner port might be a contributing factor, I think the heat from the mantle makes the brass sag after prolonged use. I’d be interested in others’ views. Cheers Tony
In my opinion, bad alignment does not help, but brass is a soft metal and is therefor very susceptible to changes of temperature.
@Tony Press now that’s a thought to contemplate, would a brass tube sag under considerable heat to one side? Or would the brass’s inherent thermal conductivity tend to equalise the heat. Forging temperature of a metal is the temperature at which a metal becomes substantially more soft, but is lower than the melting temperature. Bringing a metal to its forging temperature allows the metal's shape to be changed by applying a relatively small force, without creating cracks. The forging temperature of an alloy will lie between the temperatures of its component metals. For most metals, forging temperature will be approximately 70% of the melting temperature. Brass has a forging temperature of 815degC. (Ref Wikipedia) Many cups of coffee on this conundrum. Love it. Cheers Pete
Let’s conundrum away... I think I’ve got a Gloria 100 that I need to work on eventually that has a bent generator. I’ll keep this thread alive as I get to them. Tony
I've got a fair share of bent generators, for both the straight and Preston-looped types. There's also the pressure factor to be considered. So there's internal pressure from the heated fuel acting from the opposite side to the heat source. The brass's expansion is non-uniform. Be it laterally, longitudinally, etc. Probably more lateral displacement of the metal atoms on the mantle-side due to the heat Its more complex than this of course. For a simpler example, just try to heat a closed-ended brass tube with a propane torch on one side. Stop once its bent. The distortion is permanent. You'd get a banana too.
