Loco about Locos

I decided that I didn't want to cut holes in any of the plates until I'd formed the firebox wrappers - so I started on those next. One way to form them is to make a wooden template and beat the annealed copper around them. Or you can form the sheet using bars of the appropriate diameter, which was the way I chose to go ( not being an enthusiastic woodworker !) Once annealed, the copper is incredibly soft, and needs little more than hand pressure to start to form it. I used various formers, as the pictures show. This firebox has a combination of inside and outside curves (most do) which makes it arkward. I just bent a bit at a time, checking against the flanged plates. A good fit is important, as silver solder has no gap filling properties. When the copper stops bending easily, its time to re-anneal. It took me five or six heats to get the inner firebox wrapper to my liking - less for the outer. Incidentally, I deliberately left the sheets oversize; putting lots of bends and f

I know several model engineers who wouldn't touch boiler making - it's not for everyone. You need several sources of heat - a lot of it, somewhere safe to work, and you need to be aware that - unlike most aspects of model engineering, it is possible to get into a situation where all your work - and expensive materials - are irrecoverably scrapped. I've got to say, I like the challenge, and satisfaction that its 'all my own work'. Then there's the lack of waiting time. Whilst its also true that there's a significant cost saving, this is definately not a good reason for doing it. I bought a kit of materials from Reeves- this comprises all the copper sheet, bar and tubes. You really do need to have the correct materials, all in good condition, and, these days, of traceable quality. Copper is interesting to work with. After annealing, its amazingly soft, and can easily be shaped - until it reaches a point where it work hardens. Its then time to stop and re-anne

The frames were already cut out, saving a bit of sawing. I checked that all dimensions were correct, and cut out the buffer beam and drag beam, from angle section. It never seems to be truely square, which shows up on the insides, when the angle fixings are mounted. So i lightly milled them all over, which got rid of the mill scale at the same time. Also the angle sections to lock it all together. I clamped the angle iron in place, and drilled through from the fames. Only then, I marked of the length of these pieces, taking the dimension from the frames rather than from the drawings - at least this way, they all fit accurately. I worked on a surface table, checking that all was square as I went along. For the horn blocks, I milled the mounting surfaces to size, and riveted them to the frames, slightly overlapping the horn openings. then milled the horn gaps to size - if they were milled to size before fitting. This makes sure that the horn slots are accurate and truly square. If I'

I've been trying to buy a panel saw (sheet saw?) for some time, but have been told that they havn't been made for many years. I was lent one a year or two ago, and found it much better for cutting large sheets of brass than the jigsaw I had been using. As I can't just buy one, I took an old wood saw, and ground off the cutting points. I then made up brackets to mount a fine-toothed 12 inch hacksaw blade, and drilled the saw blade to suit (A solid carbide drill goes straight through the saw steel) It might look a bit odd - but it works. Its as easy as can be to cut a straight line right through a 4 ft by 2 ft brass sheet. I might get round to tidying the saw up - the real thing is styled like a tenon saw without the tenon. And there seems to be no need for a blade tensioner because of the way the saw works.

I initially assembled the linkage with all the joints unpinned, so I could check that it all fitted and could move freely without any obstructions. Disaster!!! The angles that some parts of the motion were moving through were clearly wrong. The pendulum levers - which support the expansion link, and the link hangers were both visibly wrong. I checked all the components against the drawings - and discovered that the weighshaft -which supports the link hangers had been located in the wrong place on the frames- a dimension of 13/32 on the drawing had been set out as 13/16 in. (Actually, by the original maker of the frames -but I was supposed to have checked it). Everything else was correct - but -adding up the various dimensions on the drawing showed that the centres for the link hanger brackets were in fact wrong -by 1/8 in. Still, it made me read up and understand how Stephenson link gear is designed. To make matters worse, I'd drilled all the mounting holes around both items,and th

The Hall uses Stephenson link gear mounted internally between the frames, and the cylinders have piston valves. Most of the valve gear components are straightforeward to make, although the eccentric strap might be worth a comment. The first step was to machine up a bit of bar to 1 1/8 diameter, with a lead that was a few thou less - as a go/ no-go gauge, and also for use as a jig. To machine up the eccentric,(from a casting), I sawed it in two, to form the two halves of the strap, then milled the surfaces square. I used a fine hacksaw blade, and was careful to mill off the least possible metal. Then I silver soldered the cut halves together again, and set up in the 4 jaw to bore the eccentric. (To set up work in a 4 jaw chuck, I use a dial gauge mounted on a tool holder, and TWO chuck keys on opposing jaws. This let me move the work together with the clamped up pair of jaws - much quicker and easier. A simple jig made sure that all four eccentric links were the same length.