I was approached by soneone to service his older Optimus 111 stove and he then brought to me a brand new Optimus 111 which has a leaky burner. On closer inspection I can see that the brazed or hard soldered joint around the central tube had melted and sprung a few leaks. There is considerable splatter of molten brazing inside the inner burner cap. Has anyone else here ever encountered this? Any thoughts on why/how it happened? And most importantly, what is the best way to repair it and prevent this melt-down from happening again? Thanks, -Phil
Hi @phaedrus42 . It is possible that an inexperienced user managed to get the silent burner stove operating in under-burn, not realised what had happened, and allowed it to continue running. The later outer burner caps were made of heat-resistant steel and did not burn through like earlier brass and mild steel varieties. Once the burner head reached the melting-point of the braze metal used, the burner would have started to dis-assemble (fall-apart). The stove would be under pressure, so any braze subject to fuel pressure would likely blow-out as molten braze droplets. Once pressure decreased sufficiently the stove would likely shut-off. However the whole event would be very exciting and probably scary! I’ll let one of my CCS stove friends give you the repair instructions..... Best Regards, Kerophile.
Is this a 111C? Don't have one myself but I remember hearing that there were occasional problems with the Cobra burner. Is it possible that someone tried a repair of a crack and managed to do additional damage?
https://classiccampstoves.com/threads/which-111-have-i-got.15499/ https://classiccampstoves.com/threads/optimus-no-111c.874/
It is quite likely underburn as the owner is not technically proficient with these stoves. He bought it brand new and says that the problem occurred (one of) the first times he lit it. Perhaps he was more familiar with the roarer burner. The stove is not marked 111C, only the stamped Optimus with an unreadably faint number and the instruction sheet pasted inside the lid mentions not to use petrol, for health reasons. There seems to be no other damage to the burner and I'm sure with the correct heat grade hard solder/braze/silbraze it would be quick and easy to repair. Question is, how hot does the burner get in normal operation and what type brazing rod to use.
Hi @phaedrus42 Others have successfuly repaired burners using high silver content brazing alloy. You will also need the matching flux. In the UK Johnson Matthey make the Easiflo range of these silver brazes. These brazes are very fluid and penetrate cracks and joints well, but they are not gap-filling so you need close fitting joints. These silver-based brazes tend to have lower melting points than copper based brazes but that is good when you have existing joints in the same assembly that you don’t want to melt when making the repair. In normal stove service they should be fine, but as with the manufacturer’s original braze if you have under-burn, all bets are off. Best Regards, Kerophile.
Found it! So if the burner will never reach about 600C in normal use, the standard Easi-flo 2 will do the trick...
Hi @phaedrus42 , If you read through this old thread you will see reference to use of these alloys. https://classiccampstoves.com/threads/pump-tube-nrv-assembly.14028/ Best Regards, Kerophile.
The same happened to mine, exact same model. I had it repaired by a workshop working with A/C and cooling for cars, they soldered it with silver braze. As to the root cause, I suspect that Optimus/Katadyn offshored production to a supplier who found the specified solder too expensive in the long run and changed to a solder that was too soft. Possibly without discussing with Optimus. Possibly long after Optimus themselves had completed their evaluation of the prototypes, preseries samples and early production from the supplier. Pure speculation of course. When doing the repair, be careful with the top flange and the top tube, they are very thin and soft, yet a lot of heat is needed to heat up the heavy base part. When soldering the thin parts can easily melt, which happened to mine. One of the holes is now bigger and flame slightly assymetric.
@phaedrus42 Phil It should be reparable with: 1. Correct grade silver solder rod (your Easy-flo will do the job) and correct flux. 2. A MAPP torch. 3. Cleanliness is a must. 4. Keep heat at the point to be brazed. 5. Let it cool slowly. Cheers Tony
The issue of leaks in that type of Optimus burner have featured on CCS before, in the post HERE, with a suggestion that manufacturing deficiencies were responsible. John
I had a former expert here repair the leak in my 111C around the tube there. Can't say it was a crack, more like a spot that was not soldered correctly. Duane
Sorry for the late response; my internet was off for almost a whole day. Thank you all very much for your suggestions, links and expertise. I'm quite confident of doing the repair now that I know that the normal silver solder I use for other repairs will work in this case too.
