Good evening folks...I am hoping to tap into the collective wisdom here. I was refurbishing the fuel cap on an Optimus 8R, replacing the fuel cap gasket and pip because I couldn't remember if I had replaced them and the stove just doesn't seem to run with as much power as I'd expect. Long story short, after replacing the cap gasket, I set about removing the pip setscrew (whatever that part is called) with a penta-key. I didn't use any solvent or heat to loosen any potential locking compound (probably my first mistake) and decided to just try to remove the screw with the pentakey. It took some force, but the set screw popped loose. However, while I was removing the screw to get at the pip holder, I noticed a crack at one of angles of the SRV setscrew. Hopefully that can be seen on the pictures below: Now I have a dilemma - although it was no problem to replace the pip and reuse the setscrew to load the pip-holder spring, I'm not sure if this crack poses a safety issue or not. It doesn't seem to have cracked down into the threaded part of the setscrew. So my question is - has anyone else ever encountered a cracked SRV setscrew like this? Any thoughts on whether this crack poses a safety issue? It doesn't seem like it would affect the ability of the SRV to vent pressure, and it doesn't seem like it would be loaded in a way that could cause it to fail during operation, but I'd really appreciate any feedback from those more experienced than I - particularly since this is a safety-related component. I could simply buy another fuel filler cap but those are getting pricey nowadays, so if I can keep using the cap I'd like to. I've never seen the setscrew sold individually either - as far as I can tell it doesn't have a separate Optimus part number, and I'm guessing Optimus didn't want people messing around with the SRV anyway. Any thoughts are appreciated. Many thanks to all those here who have shared their wisdom on my other questions...every successful fettle just makes the next one that much more tempting. Thanks!
I’m not an expert by any means but some thoughts are pressure test it to see if it leaks, braze it to repair the crack or make or have made a new one, maybe with a hex(Allen) fitting.
If the safety release valve is working properly you are fine; but the SRV will be hard to service unless the crack is fixed. Also, double check to make sure the crack does not extend down through the threads. Tony
It would worry me enough to just replace the whole fuel cap. If they're still available is the question... NOS is not that 'new' anymore and Seals and SRV pips probably need replacement even on spares.
If that true... Welding that cracked surface And add extra "ring" fitted inner diameter on cracked part and weld it Rinng stops cracking wrench hole
So, just an update...I decided it was better to be safe than sorry and ordered new (old) cap. However, I decided to try my hand at soldering the crack because I have never soldered anything other than electronics (and that poorly). I found the following (old) solder and flux in my plumbing tools drawer: I cleaned up the pip screw, applied some flux around the crack, stuck a tiny scrap of solder to the crack, and heated the setscrew with a butane microtorch. It seemed like the solder didn't want to flow, even when the setscrew was red hot, but I eventually decided that it had filled the crack and that the excess solder "blob" was simply not flowing on the unfluxed area. I let it cool down, then filed, wirebrushed, and sanded the excess solder and oxidation. It looked like a reasonably clean repair to my uncalibrated eyeballs...the following shows the soldered screw from the back of the crack and the front of the crack: Feeling quite pleased with myself, I reinstalled the setscrew. I wanted to tighten to the same depth that it was when I removed it initially - i.e., so that the top thread was barely showing - when, with a sound that I am getting used to, I heard a crack. I tried to loosen and heard another crack. The net result is below: I suspect this is an example of what Tony was referring to - continuing to stress the setscrew, even with a (possibly poorly) soldered joint, was too much for it and it eventually failed. I think that gieorgijewski was right: I suspect a reinforcing ring would have been a much more robust support than a soldered joint. And so ended my weekend setscrew soldering saga. Hopefully someone somewhere can learn something from my experience. If a Level 0 fettler can recognize an old stove, a Level 1 fettler can light an old stove, a Level 2 fettler can fix gaskets on an old stove, and a Level 3 fettler can undertake structural repairs on an old stove...I'm still firmly at Level 2 . Although this was an unsuccessful repair, it was successful in that it gave me a chance to start developing new skills. And I have plenty of other stoves to keep practicing on.... Just to end on a positive note - and also to include a flame shot - the picture below shows the other stove I've been working on this weekend, that started out with a very weak orangish flame and ended up boiling a pint of water in 5 min... It's good to have some successes to stay motivated after the failures. Thanks for reading!
@Peregrinans Great job you made of the soldering, but I doubt that the crack was of any consequence. As @Tony Press was alluding to, the only time the integrity of that screw may matter is if force were needed to unscrew it (if thread lock had been applied) at some time in the future to replace the release valve ‘pip’ seal. It might then fracture along the crack and the ‘soft’ solder you’ve used with its moderate shear strength wouldn’t prevent that happening. ‘Hard’ solder (silbraze) would handle the torsional force applied to it by a penta-key in breaking the thread lock solution bond. But, hey, that’s of no consequence to the function of the SRV and there’d be little prospect of the screw disintegrating if no thread lock or a low-strength one were used. No thread lock isn’t unreasonable, the spring compression having a locking effect to prevent the screw from creeping loose. John
Thanks John! I think you (and others) are right about the initial crack. I'm probably just cautious by nature, and sometimes I just can't stop myself from fixing things that aren't clearly broken. And it usually turns out the way it did this weekend, where I "fix" things until they are well and truly broken . At least I got some soldering practice in. Sounds like I need to find a project to let me learn how to silver braze. Also appreciate your perspective about the need (or lack thereof) for threadlocking the SRV pip setscrews. I've decided *not* to routinely threadlock when I replace SRV pips, reasoning that it seems unlikely to creep loose, but if it did, with reasonable care I'd notice if the setscrew was slowly backing itself out and could tighten it back down. Appreciate it!
