Calbourne - 5" gauge boiler

[Kim]

That certainly is beautiful work!  I can only hope to approximate the excellent work you are doing here 

Kim

[springcrocus]

Thank you, gentlemen, for your kind words and encouragement. The job is made much easier by having two torches available and much of the credit goes to my mate Wilf (not a member here, AFAIK).
Rich, I loved that beam engine you made out of odd-ball bits. Proper engineering. I'm trying to convince Wilf to team up with me to design and  produce a steam-punk loco which could be great fun as a joint project.

Regards, Steve

[FKreider]

I'd forgotten to spigot the two 22mm tubes so a pair of small clamps stopped them falling into the firebox.

Hi Steve, can you clarify what you mean by "spigot" the tubes? I'm not understanding what keeps them from falling down into the firebox during the soldering, I see the two that are clamped which makes sense but all the others I'm not sure about.

[springcrocus]

I'd forgotten to spigot the two 22mm tubes so a pair of small clamps stopped them falling into the firebox.

Hi Steve, can you clarify what you mean by "spigot" the tubes? I'm not understanding what keeps them from falling down into the firebox during the soldering, I see the two that are clamped which makes sense but all the others I'm not sure about.

Hello Frank,

Go back to post 6 on page 1 and one of the pictures shows the tubes resting in the holes and one with a spigot on the end. What I do is force a bung into one end of each tube so that it expands about six to ten thou, then skim it back down to nominal size. When placed in it's hole, it rests on the turned shoulder. It doesn't matter that the tube is now thinner because it is enclosed by the tubeplate and the silver solder makes it a solid lump.

Regards, Steve

[springcrocus]

It was now time to start bringing the two sub-assemblies together and one of the first jobs was to machine the firehole into the backhead because that helps to position the firebox correctly. Luckily, it's a circular firehole rather than an oval one which requires a lot more work to get a snug fit. This is 1.1/2" diameter.



The tube support was modified so that it fitted the barrel correctly and the tubes, which had become squashed together, were reworked to their correct positions. The firebox assembly was loaded to the barrel and the backhead placed into position.



The firebox was clamped to the throatplate and the backhead with packing pieces and adjusted until square. After the next picture was taken, a small clamp was used through the firehole to keep the backhead tight to the firehole ring. The rule under the dome ring ensures the barrel is parallel to the table.



Then the backhead fixing points were drilled and tapped 6BA, all done freehand with a pistol drill or hand-drill.

With this complete, the firebox assembly was removed, the backhead put back in place and the positions of the stay holes marked out. All the stays are on a 9/16" grid and will be made using 1/8" copper rivets except for four extra ones which I've added to the backhead and the ones that will replace the girder stays on the crown. These will be 3/16" diameter. While I had it disassembled, I also dressed the inside end of the barrel back to the throatplate.



The first holes I drilled were the front throatplate and I was able to use a homemade drill that I cobbled together when doing the Allchin boiler. However, because of distance and clearance issues, I had to remove the backhead to get it to work. It's a 1/8" diameter drill silver-soldered into a length of 1/4" diameter mild steel rod.



Because the backhead was out, I drilled that freehand on the drill, using the MDF former as support while centre-popping and drilling. Then it was bolted back into the outer wrapper to provide support while doing the side holes. Three rows of holes are within the curve of the wrapper but I want them square in the firebox so I did these on the mill with a slot drill instead. Although the grid was there to guide me, I actually used the DRO to position them.



The boiler was reassembled, still using the tube support at the front, and the base of the firebox centralized in the wrapper. I made a couple of screws to fit the blowdown bushes and used these to keep things in place. Then I started the laborious process of drilling all the stay holes in the firebox.



They were all done with a pistol drill and a rivet dropped in to test the hole as I completed each one. This is not how they will be soldered; the heads will be on the inside and the outer tails dressed back to clear the frames. The four holes that are unfilled in the backhead will have 3/16" rivets instead and I will drill and tap these 8BA, keeping the holes blind. They will be used to fix the plate for the firehole door and rails.



That just left the crown stay holes to be drilled and these needed to be inclined so that they spread the spacing correctly on the top of the firebox but not interfere with the bushes. A large vee-block was set up on the mill and the assembly clamped to it at an angle of 12 degrees. The holes in the wrapper were made using a 3/16" slot drill but the holes in the firebox crown were very carefully spotted with a 3/16" drill because of deflection. They were then drilled through with a 4.4mm drill followed by a 3/16" reamer.



Because the stays are from 3/16" dia copper rod, the spacing can be increased to 11/16" but I chose to use a spacing of 5/8" for extra support. This next picture shows how the crown stays are spaced in the firebox.



All that remained was to dismantle everything and deburr all the holes. There are still a couple of holes to sort out in the backhead for the water gauge but this can be done later.



Regards, Steve

[RReid]

I'm enjoying watching this boiler come together very much, Steve. Both the write-up and the work itself are first rate!

[Dave Otto]

Beautiful work Steve, I'm enjoying this!

Dave

[tghs]

great work!!! taking lots of mental notes for future work..

[flying fox]

Greetings Steve, great work with the boiler, well done for demonstrating that you can make your own boiler.  One small comment, I think one of your photos showed the stays (Rivets) with their heads outside, is that how you are going to solder them?  I think with heads inside the stay ends exposed to the fire get more protection from the extra metal in the formed rivet head, and easier to trim.
Shows I look at you pictures anyway
Regards
Brian Baker

[wagnmkr]

Thank You for the excellent photos and explanation. Now I understand more about the building of a boiler.

[springcrocus]

 Thanks, guys, for the kind words. 

Greetings Steve, great work with the boiler, well done for demonstrating that you can make your own boiler.  One small comment, I think one of your photos showed the stays (Rivets) with their heads outside, is that how you are going to solder them?  I think with heads inside the stay ends exposed to the fire get more protection from the extra metal in the formed rivet head, and easier to trim.
Shows I look at you pictures anyway
Regards
Brian Baker

Indeed, Brian, but did you spot the text cunningly placed between the pictures to - er, fox  the unwary? 
 
Regards, Steve

[springcrocus]

Sixty or so silver solder rings were made on the lathe by winding 1mm rod onto a 2.9mm drill, similar to winding home-made springs.





I also modified a pair of surgical forceps to hold the rings by grinding small, longitudinal grooves in the jaws and thinning them down to 5mm. That is so they can lowered down the gap between the inner and outer while a copper rivet is pushed through each ring.



The two halves of the boiler were assembled using the backhead to get the firebox in the correct position and pushing a couple of rivets through some of the side holes for additional alignment. Starting with the lowest row, a 1/8" drill was passed through the first pair of holes to check clearance, then flux was painted in with a tiny brush. Wilf held a solder ring in the water space in line with the hole using the special forceps. I fluxed up a rivet, pushed it through from inside the firebox and gently tapped it fully home. On the outside, a pair of flat-faced cutters were used to indent the rivet...



... and raise a burr, keeping it in place, then a second ring was placed on the outside of the rivet and more flux added. This was repeated until the first row was complete, even more flux added, and the procedure repeated until all the rivets were in. This is part-way through the second row.



With all fifteen rivets in place, we fluxed up all the nearest seams that had previously been soldered and checked that all the solder rings were sitting down flat. The packing piece in the next picture is to make sure the gap doesn't close during soldering - there's not much chance of recovering from it if the inner moves relative to the outer. Then it was set up in the hearth.



Blocks were placed all round and another one on top to cut down heat-loss although the dome bush was left clear to allow burnt gases to escape. The gaps to the sides are there for one of the burners to heat the outer wrapper while the other one applies heat to the inside of the firebox. The whole thing is built up on a workmate so that we have a comfortable working height.



The heat-up took about ten minutes and we kept applying heat until the last solder ring flashed, the outside ones furthest from the foundation ring taking the longest because it was difficult to get the heat down the water-space. I was using a fairly slim nozzle on my burner to produce a narrow flame while Wilf was using a cyclone burner to apply the heat inside the firebox. The biggest problem we found in the past was starving the burner of air when working into an enclosed space and a cyclone nozzle overcomes that. After cooling and pickling in citric acid, this shows how the solder has pulled through to the inside.



All fifteen rivet heads have a nice fillet around them.

It's not so easy to see the down into the water space but the solder has gone from the outside without forming puddles around any rivet tails so I'm happy that we have good penetration. However, the rivet at top right in the next picture doesn't appear to have a perfect seal so I will put another solder ring on there and give it another heat-up.



And I learnt another lesson today: don't use copper rivets to aid alignment! During the heat-up, they softened and sagged a little giving me the devil's own job to get them out. One had to be cut and punched through. I shall use steel another time.

Regards, Steve

[simplyloco]

As neat as a well known lady boilersmith would produce, if not better!
John

[ddmckee54]

If the copper rivets that you were using for alignment on the sides softened and sagged, won't all the holes on the firebox sides be misaligned now?

[flying fox]

Greeting Steve, only look at the pictures, can't read!
Now I am going to earth.
regards
Brian B