Calbourne - 5" gauge boiler

[Kim]

Very neatly done, Steve!  That's a lot of rivets/stays to get soldered! 
I really appreciate all the detail you're providing here on how you did the setup for soldering.  Thank you!

Kim

[springcrocus]

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?

It was only a thou or so; enough to jam those rivets but not enough to affect the following operations. I just push a drill or reamer back through each pair of holes prior to inserting each stay and the solder fills any tiny gap.

Regards Steve

[vtsteam]

Again, very fine work!, Steve I, like the others really appreciate the detail, fine photos, and careful explanations. 

[Mike R]

I appreciate all this detail as I'm getting ready for these steps on a Martin Evans designed 5" Springbok B1 I've picked up as a running chassis needing the boiler built (and a bit more..).  Just waiting for the garage to thaw out enough to be able to go solder! 

[MJM460]

Hi Steve, this is truly a masterclass in boiler construction.  Thanks for the excellent detailed photos and write up.  Very much appreciated.

MJM460

[ddmckee54]

It was only a thou or so; enough to jam those rivets but not enough to affect the following operations. I just push a drill or reamer back through each pair of holes prior to inserting each stay and the solder fills any tiny gap.

I was wondering about that, and whether or not you would have to enlarge the holes to the next larger size rivet.

[springcrocus]

Sorry if anyone caught the antics of a few moments ago. The forum software is definitely a bit quirky in places, especially when trying to edit on the fly. 

 The next lot of stays were soldered into place and preparation for this took the best part of two hours because of the difficulty getting solder rings on the deepest stays. I haven't bothered to write this up fully because it's just a repeat of the previous but the next three pictures show our progress. The first one shows a view into the waterspace where it can be seen that solder has flowed through the joints. Ignore the apparent gap between the backplate and the wrapper, it's a trick of the light.


The next one is a view of the outside. Don Young's drawing shows the expansion support bracket screwed to the side but I've chosen to solder it with the stays coming through. I suspect his idea was an afterthought.



The last one shows a view inside the firebox with all the rivet heads neatly soldered. It was easier to get the heat in this time because we didn't need to use the backhead as a support, the box already being held firmly by the throatplate stays.



The stays on the other side of the firebox were done next, a repeat of the previous work. I did, however, take a photo of the boiler in the hearth just before lighting the torches. The cyclone burner was used to heat the inside of the firebox and the normal burner fed heat into the water space from the back.



I also meant to show this earlier on. Because we were throwing a lot of heat into the firebox, I made a steel plate to cover the tube ends and give them a bit of protection. The thin wall of these makes them more vunerable to overheating, leading to a damaged joint. A length of M6 stainless steel studding passes through one of the flues to keep it in place and the rod can be drawn out through the firehole if the nut gets jammed at the firebox end. It gets removed before pickling because I've found that the steel contaminates the citric acid, so I keep a separate tub for mixed metals and try to keep my main dip-tank clean.



We revisited two stays that didn't look quite good enough. Rather than risk having a leak later on, it was worth resoldering now whilst access was much easier. Then we fitted all the crown stays, which replace the girder stays that Don Young had specified on the drawing. I made these from 3/16" diameter copper rod because rivets of the required length were not available. After parting off, one end of each was gently hammered over to form a mushroom head. A close-fitting washer protects the collet and limits the spread of the copper.



This is how they look inside the firebox. The stay spacing is greater than on the sides because the larger stay sizes allow for a larger grid pattern but the dimensions used reflect those in the Australian boiler code for these sizes of material and operating pressure. They are also superior to the girder stays because of the stronger through-joint compared to the butt-joint of a girder stay. Although it looks like a couple of the stays are a bit bare of solder, they have formed a good joint.



One unusual thing were the four additional stays that I've added around the firehole. I wasn't happy with what was shown on the drawing and these additional stays perform a dual function. These are 3/16" diameter copper rivets that have had the heads thinned down, then cut to length and the core drilled and tapped 8BA and will be used to fix the firehole door panel to. The unusual bit is that I've opted to solder them to the firebox now, rather than when the backhead goes on because they would have been extremely difficult to get to later on. This next photo shows them in place.



With it all cleaned up, here is a view through the crown before the backhead goes on. The angled stays are to allow enough room for the regulator tube to pass freely through, with the blower and air-brake hollow stays passing by on the outward sides. Also, the firehole door fixing points can be more clearly seen.



And this final picture shows the backhead offered up for fit, and showing the regulator bush which has been soldered into place with 40% silver solder. The four backhead rivets are nice and soft so easy to align. Once the backhead is soldered up, they will be trimmed back to flush and the thread re-tapped. By doing it this way, I don't have the risk of trying to drill a blind hole in the rivet and/or breaking a tap in there at the last moment.



This may not be how the old-school boiler-makers would have done things but that doesn't mean we are doing it wrong, just differently. These cadmium-free solders are completely different to the old stuff and new methods can be adopted to suit the new materials.

Regards, Steve

[PJPickard]

This is great and thanks for posting! I have two similar boilers to make in the future. One thing I may have missed in your explanation is what is "correction fluid" and what does it do?

[springcrocus]

This is great and thanks for posting! I have two similar boilers to make in the future. One thing I may have missed in your explanation is what is "correction fluid" and what does it do?

Tippex, although I use the cheap generic alternatives (see picture 6 in post #25). It's a very efficient, high-temperature, paint-on masking tape. I always paint it into the threads of any bushes prior to soldering to protect the thread from stray solder. Painted around a bush or alongside a seam, it also contains the solder and flux within bounds, preventing those ugly run that sometimes occur.

Regards, Steve

[vtsteam]

I feel very repetitive, but I'm just going to have to say it over again, Steve, as long as you keep posting these pics and descriptions....it's a fabulous job, including any corrections to work done, and modifications, which are just as interesting and a truly great read! 

[PJPickard]

Steve,

Thanks for explanation of the correction fluid, I may have to get some!

[crueby]

Steve,

Thanks for explanation of the correction fluid, I may have to get some!

It also works great for when you have a clamp or jig near the joint that you dont want to solder to the part - put a layer on the jig/clamp, let it dry, then assemble.

Make sure you get the type of fluid that is volatiles based, not water based. If it smells like solvent and dries quick its the right stuff. Here in the US the Wite-Out brand is the same thing as he used.

[springcrocus]

It's impossible to make the gauge glass arrangement look anything like the prototype and still function properly and the backhead of the model only bears a passing resemblance to the full-sized "Calbourne", anyway. The upper bush is the one that causes the problems and Don Young drew up a flimsy bracket with a couple of bits of tube soldered together that looks awful. My effort doesn't look any better but is a fair bit stronger.



To allow for replacement of the complete gauge glass assembly I made a bush from hexagon bronze, drilled and tapped 1/4" x 40 tpi the same as the fixed lower bush, and soldered a short length of 1/4" diameter thick-walled copper tube to it with 40% (high temp) silver solder. The backhead was clamped to an angle plate and a matching hole made with a 3/16" diameter slot drill. Then the upper bush assembly was set in the hole using a spacing gauge to set both height and orientation.



I've chosen hexagon material because I will be able to support the bush with a spanner when I tighten up the top fitting. The lower bush has also been soldered in with 40% solder, as will be the fitting-to-backhead joint. That way, I should have no problems when it comes to closing the boiler.



Although it looks a bit silly at the moment, once the cab front is in place, it will blend into the background. The drawing shows the position of the upper bush suspended in mid-air.



This is the completed assembly temporarily set into the boiler. A small notch has been cut to allow the backhead to sit in the correct position but there is still plenty of flange available for soldering at final assembly.



The next job was to get the front tubeplate soldered into position. I took extra care with this, starting with a good half-hour in the pickle followed by a clean rinse. Flux was painted onto each tube-end, the barrel wall, the rim of the tubeplate and into all the holes. then the tubeplate was eased down into position, coming to rest on the turned shoulder in the barrel. Solder rings, made from 1mm diameter rod, were placed over each of the tubes and 1.5mm rod cut and bent to fit the gulley around the perimeter. I didn't take a picture of the layout prior to silver-soldering so I've borrowed a picture from my Allchin file to illustrate things.



It took a little while to align the tubes because I missed a trick when I bored the barrel. I should have relieved the front section by an extra five thou and this would have allowed the tubeplate to wobble about a bit easier. Lesson learned for next time. On my first boiler, I made some tube pegs to aid alignment but that had thirty-two tubes that needed aligning.



I then built a hearth around the boiler, enclosing as much as possible but leaving the firebox open at the bottom and also the dome-hole. It's important to get the whole boiler up to temperature rather than just the area around the tubeplate because, for the first time, I'm closing a loop. The barrel and the tubes need to expand at the same rate, be joined by the solder at the tubeplate and then contract at the same rate. Otherwise, there is a risk of one or more of the tubes cracking it's joint at either top or bottom. To keep some heat at the bottom, a lower-power butane torch was set up as shown, although this picture is borrowed from the Allchin file as well.



Wilf and I swapped torches with me using the the cyclone nozzle to add heat into the firebox and through the dome-hole while Wilf used a normal burner to heat the outside of the barrel, with just the occasional foray to the inside. As we got close to temperature, we concentrated on getting the perimeter solder to go first with lots of heat to the outside and to the underside of the tubeplate. Soon after that flashed, the tube rings started to go and Wilf moved his flame to the inside of the barrel but keeping it directed to the barrel wall. Once all the solder had gone, we quickly covered the boiler over with more blocks to slow the cooling. It took about three-quarters of an hour before I could handle the boiler and then it was placed in the pickle for an hour. This is the result.



However, once I laid it flat on the bench, I spotted this.



OH S**T!!. I'd burnt through one of the tubes. Time for a break and to take stock.

Regards, Steve

[Admiral_dk]

Commiserations - such a beautiful solder result  - just to discover that things went wrong elsewhere   :'(

I guess that you got quite a bit of work ahead, just to take things enough apart, to be able to change the dammaged part ....

Best wishes

Per

[Kim]

Ouch! That has got to hurt!     
Very sorry to see that! 

Kim