Loco about Locos

Just by way of a change, some pics of my finished locos - not me driving! This is a 5 in gauge B1. And this is my A3 Pacific, again in 5 in gauge.

I then turned, bored and reamed the valve chest (sorry, no pics of this) and cut the two recessed passages where the ports were to go, using a parting of tool. Then the ports were drilled and filed all the way through. Accuracy is very important here. The valve chest is to be a light press fit into the cylinder - the end parts of the valve chest stick out of the cylinder, and their o.d. is not critical to the thou. So I turned this part down until it would just pass into its bore in the main casting - then withdrew the tool by a thou (diameter) and cut a bit more. I tried it against the cylinder casting, and checked that it wouldn't enter the bore. I actually went over the surface with some very fine abrasive nylon (like panscrubs) to keep the interference fit to a minimum. The problem is that there is very little metal at the valve area, and it can easily collapse if the press fit is too great. (I've heard it suggested that a sliding fit and loctite might be better - as ret...

The cylinders on this loco are gunmetal. Simply because that's what came with the bits I bought! I much prefer gunmetal anyway. I don't run my locos a lot, and worry that cast iron cylinders will rust. The other side of the coin is that you can use conventional piston rings with CI cylinders. The first thing I did was to make up the boring bars. Mine were cross drilled bar, of as big a diameter as could pass through the cast bore - within reason. I have quite a few carbide drills intended for drilling glass fibre printed circuit boards. They do have their uses -but are very fragile. They all have a 3mm shank, which is ideal for making small cutters. They're easily ground using a diamond wheel (but nothing else will do !) The tip is held in the boring bar by one grubscrew which presses on the shank of the cutter, and another grubscrew behind it, which is also used to control the advance of the cutter. I needed to make more than one cutter with different lengths, or a ...

I started with a set of frames which had already been made. I was going to say - which saved a lot of sawing - but in fact I would probably have cut them in the mill. The important thing is that the two blanks are riveted together and treat as a pair until complete. As I had no idea how mine had been done, I started with dimensional checks. I soon found that the axle box spacing was marginally different (of the order of 20 thou) from one side to the other. And the horn slots had been finished individually and were different (hence the axle box spacing). Apart from that, they seemed ok. I set the frames on parallels standing on a surface table. The structure was not truly parallel, with a rock of at least 1/16 in in one corner. I slackened fixings and kept rechecking, until I found that the central cross braces were the cause of the problem - one was a few thou out of parallel. I milled a few thou off to make it truly parallel, and made up a shim (only 5 thou) to keep the spacing correc...

What I started with was a set of frames with hornblocks fitted, and wheels turned. So I'm afraid I've no construction details for these. Except for quartering the wheels. You can do this either with a jig,or in the lathe. I've used both methods - a jig works well. Most books and drawings show jigs which are specific to one model, which is not brilliant. Since then, I have seen a general one detailed, which is a far beter idea. I've also quartered wheels in the lathe, which is what I chose to do this time. Two sets of wheels were already assembled and quartered, but, when I checked them, both were different ! The object is to set the two wheels on an axle at 90 Deg to each other -usually, the right leads on British locos. Having said that, the really critical thing about quatering is not the exact angle, but is that all the wheelsets on the loco must be set at EXACTLY the same angle. This is because the wheel relationships are locked by the coupling rods, and any diffe...

One of my serious interests is model engineering. I've built steam locomotives in 5 inch gauge, and also in gauge 1. Interest in the hobby seems to have grown quite a lot in the last few years - certainly my local model engineering society is a lot busier. Several people I've spoken to have expressed an interest in building a loco. These days, sadly, most of the college based courses are no longer running making it harder to start from scratch. I have just started building a 3 1/2 inch gauge loco and thought I would keep a journal of my progress. I thought if I set up a blog perhaps it might help someone else to get going. I will share some notes and photographs documenting my progress. Hopefully my blog will promote discussion with like minded people. The loco I am building is a GWR Hall (3 1/2" gauge). Its an LBSC design: the construction looks typical of lots of locos, so the construction notes should transfer to other locos. Truth to tell, I bought it at a...