Building a small loco is best,I found,divided into chunks. "Achievement periods"Is I think the official term.
The chassis frames were joined at each end by an anngle steel buffer/drag beam,and braced in the middle by a frame stay. Generally called the pump stay,because thats where the water pump is mounted.But before erection the axle slots had the hornguides riveted on and opened out to size to take the axleboxes.At this point you admired the chassis and tried *not* to think too hard about what was still left to do. The next stage was the rolling chassis.This is great fun because you now have the thing on wheels,and can play at puffer trains with it uip and down the bench.
Now the job changes nature completely.Up to now,its all been machining and fitting,to quite close tolerances.But we need a boiler.And thats a big hammer job in sheet copper,which needs annealing every half minute(or so it seems).And the formers for the tubplates and backhead(BACKhead,Bill,not blackhead) No-one I know actually *likes* boilermaking.The whole thing is put together using silver solder,and then pressure tested hydraulically to 1 1/2 times working pressure.Mine had a pinhole leak so small the jet of water couldnt be seen.In the barrel joint.This was eventually located,and wiped with HMP soft (lead)solder.You then cart the thing along to the club,and the poor sap who has got the job of testing boilers for the insurance does it all over again with the club test kit.Passed,you get a boiler certificate with no start date on it.You "activate" the thing when you've finished the engine and want to steam it.Then it last two years,and you get the boiler tested on the loco to 1 1/2 X pressure.(The original teat should have read TWICE working pressure. After another two years,the bloody thing has to come*off* the engine and go through the whole rigmarole again. A better method would be,as in full size work,to test the boiler only after so many *hours* steaming.It only needs the builder/owner to keep a little log book.I doubt whether my engine has done eight hours steaming all told, in the two years I ran it regularly.
When you've eventually finished the boiler,mated it to the smokebox,and grubbed around inside the smokebox to make good the superheater fittings.....ah yes,the superheater. This,basically is a long pipe,or pipes,that steam taken from the boiler is fed along,back towards the fire.The pipe,or element(s) are housed in large diameter firetubes. This dries and superheats the steam,necessitating the aforementioned oil pump,because a displacement lubricator doesnt work too well with superheated steam.
In passing,I said I only bought the horncheeks and pressure gauge.I lied.I also bought the piston rings.The cylinder is 1" bore X 1 1/2" stroke.The rings are cast iron,hardly Land Rover size!
Well,now you've got an engine all but its platework and tanks, which have to hold water.I HATE platework,but managed it,and then you've got to *paint* the thing.Which is where I got my brushwork practice.