Second boiler

[Steamup]

This will be my second boiler build the first was a multi tube vertical design which I was just about able to manage.
This will be a little more challenging. I am unsure if the boiler tubes and end plates should be soldered first or should I do it all in one hit?

 

[GWRdriver]

Steamup,
It appears to me there will certainly be two, and potentially three heats.

I would suggest soldering the cross tubes into the lower flue first, I think you have no choice actually, and insure generous fillets of solder on both side of the flue tube. I strongly suggest you pressure test this assembly to insure the cross-tube solder joints are sound. Leaving this to visual inspection can sometimes come back to bite you in the bum (Don't ask me how I know this) and can't be repaired without a great deal of time and effort.

I would then solder everything else except the end closure plate at one go. My practice is apply plenty of flux and preheat to bake (not boil) away the water in the flux so that it doesn't bubble and spatter or run when things get very hot. I can't tell from what I see if the closure plate needs to be soldered in but if so that would be your third heat.

If I have somehow misinterpreted the assembly sequence please set me straight.

 

[Steamup]

Very helpful thanks for that. Would the bushes be soldered in first?

 

[GWRdriver]

Would the bushes be soldered in first?

Probably not. Unless there is a specific reason they can't be, bushings are typically soldered in when you do the main heat.

 

[Steamup]

Thanks for that.
Mark

 

[KBC]

Mark,
As Harry says ,hydraulic test the fire tube before soldering in, it is very important.
When I make boilers with the fire tube having cross tubes I leave the tube a little bit longer and soft solder plates to the ends with one of the plates having a 1/4 x 32 t.p.i fitting to take the test gear.
When proven you can then cut the tube to length without having to clean off the soft solder.
Another tip is to drill holes with a small C/Sink on the outside of the shell to take copper rivets thro' the shell and the end plates which holds the assembly in position while soldering, a touch of the solder on the outside of the shell fills the C/Sink and you can then flush off.

First pic shows the copper rivets that I use as pegs.
Second pic after brazing

Best of luck , this is the weather to solder up a boiler, keeps the shop nice and warm.

George.

 

[Steamup]

Great photos, I had came to the same conclusion regarding the fire tube glad yoe confirmed my idea to temp. soft solder end plates.

 

[GWRdriver]

Since over time I've built a large number of boilers for small (Ga1) loco and marine builders, many of which have flues with cross-tubes, I devised a somewhat quicker method of plugging my flues for testing. I turned a pair of brass plugs to an east fit into the flue ID (a set for each tube size I use) which end up looking very much like the bushing in the sketch I recently posted. The plugs are then grooved for O-rings to suit the tube ID and I drill and tap one of the plugs from the side for the test pump water connection. I then clamp the assembled flue and plugs in such a way that the plugs are held securely in, usually with just a C-clamp, and connect the water line. Placing the water line connection in the side of the plug allows me to clamp the plugs over their ends. This is quite quick and clean and seals positively against any test pressure.

I've attached a photo which should explain.