baggo wrote: ↑Sun Aug 08, 2021 11:46 am
When I was watching your video on fitting the boiler tubes and end plates I was thinking 'that's an awful lot of clearance for the solder'. Personally, I would never use the recommended clearances as I think they are far too big. So long as the tubes etc. are a sliding fit into the respective hole then the solder will penetrate the joint with no problems. The thicker the solder in the joint then the more prone it will be to crack due to differential cooling. Also some solders are not very good at gap filling. I've no experience of the Harris solders though as in the UK we tend to use Johnson Matthey or Cup Alloys solders.
That's helpful, thank you! I will aim for less clearance next time. People say up to 6 thou is acceptable but that sounded like a crazy amount of open air to me, so I was aiming for 1-3. All the books and articles warn of too little clearance being the death knell, but now I wonder about that advice.
baggo wrote: ↑Sun Aug 08, 2021 11:46 am
Have you tried wrapping the outside of the boiler with a thermal blanket to stop it cooling down so quickly after the soldering? (Wrap it around the boiler before soldering). That may help to prevent cracking of the joints due to too rapid cooling.
I did indeed. I kept it in the hearth and wrapped up to cool it as slowly as possible, just in case.
baggo wrote: ↑Sun Aug 08, 2021 11:46 am
If you do have to start again (and I hope that you don't) consider soldering in the bushes first with a higher melting point solder. Those joints then shouldn't be affected by the subsequent heating to do the rest with your 56% solder.
The bushings were actually okay- they seemed to be far enough away, down on the middle of shell, that I had no trouble with them leaking or needing multiple repairs.
baggo wrote: ↑Sun Aug 08, 2021 11:46 am
There is another way to seal the leaks but ONLY if the boiler is structurally sound. That is to caulk the leaks with a high melting point soft solder such as Comsol. That melts at about 305°C so won't involve reheating the boiler to such a high temperature. It does tend to be frowned upon over here nowadays by some people (usually those that have never built a boiler) but it's a perfectly safe and valid way to fix a leak (in my opinion anyway). You do then have to be more careful about the water level in the boiler and not let it get too low.
Yah, I did actually do that for one stubborn leak on my previous boiler, but I really wanted to do this one the "right" way. Here's what I get for that! My last hail mary will likely be to swage the tubes real firmly then reflow solder one more time to caulk. I know swaging-and-caulking is also frowned upon these days, but at least it would be silver-solder caulking.
baggo wrote: ↑Sun Aug 08, 2021 11:46 am
Don't give up and good luck with it.
Thank you! The encouraging words I've gotten from people really do help. You advice is greatly appreciated also.