We Need More Heat!

Whilst soldering the smokebox end of the boiler was reasonably straightforward, soldering the boiler to the cab was an absolute nightmare, although I did get there in the end and without any burnt fingers. Positioning the boiler was reasonably easy as there is a nice hole for the whistle that makes sure I know where the top is, and then it slots into a half etched ring on the cab front, and there are three little tabs on the end which further slot into holes on the cab front. The problem was that I just couldn't get enough heat into the joins to solder it in place.

As you can see I did eventually get it soldered on but not without having to find a different source of heat. When I used the soldering iron the solder paste would run but not melt, and the solid solder would melt into a blob but I couldn't get it to flow. Both issues were caused because I couldn't get the solder hot enough as the heat is pulled away into the rest of the brass that makes up the cab and boiler rather than staying close to the tip of the soldering iron where I want it. The solution was to switch tools to something with a bit more heat.

As you can see from the photo I own two gas torches. I've tried using the large cooks one before and managed to burn a whole through a brass part, so my plan was to use the small modellling torch instead. Unfortunately the small torch is useless. I had no problems filling it with gaz but couldn't get it to light properly. With the valve open the gaz was coming out and would light if I held a match in front of it, but it wouldn't stay lit when you removed the match. No idea what's wrong with it as although it's been in my toolbox for a while this was the first time I'd actually tried using it. So with more than a little trepedation I used the large cooks torch instead.

With the parts held gently in place, using a mixture of masking tape and coffee stirrers, I added some solder paste and then gently wafted the flame over the joint. Within no time at all the paste melted, flowed, and formed a nice joint. It's difficult to get the larger flame into odd places but I think I'll be using the torch again in the future for cases like this. Although I might see if I can find a smaller modelling torch that actually works.

Just as a final photo here is the mess I made on the inside of the boiler when trying to use the soldering iron. As you can see the solder turned into a blob but I just couldn't get it to flow and form a join. Anyway it was a useful lesson to learn that I can use the torch to make these kinds of joint if I need to.

Still some cleaning up of the joint to do before I move on, but I think that is the hardest part of the body built quite successfully.