If I were to attend a group helping people with addictions my introduction would sound something like this… Hi, my name is Luke; I’m addicted to making things. Any complex mechanical system that moves on its own steam (pardon the pun) will have me lost for hours solving the equations, then making the components and finally testing the system and optimising it, but I can stop any time I want.
I pitched a series of articles to Adendorff Machinery Mart, my preferred tool supplier, to show what is possible in a small workshop, and that complex mechanical systems can be made cost effectively if you are willing to dedicate the time. I’m sure by know you’re wondering what I’m on about. Simply put, I spend a large part of my free time doing model engineering, a hobby dedicated to making scale working models of machinery, etc. In my case, I enjoy live steam trains.
I often get asked if I make everything myself. The answer is a matter of perspective, but in short I don’t. I try to get as much of the plate work laser cut as possible; everything else is made from standard bar stock machined to whatever is called for. I do my own cast iron and bronze castings in a furnace I designed and built, using sand from the local river for the moulding. The series of articles will deal with some of that machining, casting, welding, soldering, tool and jig making needed to complete a 7¼ gauge Stirling 7 foot single, weighing roughly the dry weight of a 600cc superbike, but just over 1m long (without the tender).
Some background on the train
I sometimes get asked if the trains at the Rand Society of Model Engineers (RSME) are exact scale replicas of the larger locomotives, and none of the working scale models are. Generally, they are close, but some things don’t scale well and if they were made to scale the locomotive would never run. My model is based on one of Stirling’s famous single driver locomotives, no. 49 to be exact. It’s a bit of an odd one no. 49, because it was built to save a set of used large drive wheels which would otherwise be headed for the scrap pile. These wheels must have cost a fortune to make being 2.3m in diameter and forge welded! The loco ran from 1870-1902, and according to the records we have the 7 footers actually outperformed the more famous 8 footers, in terms of coal consumption and tractive effort. When these locos were made they were the fastest things on land reaching 80MPH, which is scary, considering the rudimentary braking systems of the day. Unfortunately, there’s not much technical information about these trains with most of the drawings destroyed during the Second World War, but with a few odd drawings and some pictures a decent model can be made. The locomotive consists of the engine, which consists of the boiler, cylinders, etc. and the tender, which stores the water and coal. Originally the engine didn’t have breaks fitted when they came out of Doncaster Works with the tender brake used for stopping. During braking trials in 1876, at a speed of 60mph, the stopping distance was 370m with the new and improved vacuum breaking system on the engine!
Starting with the frames
As mentioned, most of the complex plate work is laser cut; it works out cheaper than doing it yourself. Just bear in mind that you won’t get profiles more accurate than 0.2 mm and I prefer to have all hole centres engraved with a centre mark. I can then punch them and drill accurately using the Mac Afric bench type milling machine (EMILGH-032, 045 and 130) or the Mac Afric pedestal drill press (EDRILB-001 and 002). All simple or straight profiles under 1 mm are cut using the Mac Afric 3 in 1 sheet forming machine (ESHEET-100 and 132), and believe me when I say that machine has paid itself off a few times. A tip on using the guillotine part of the forming machine: the strap at the back is a reaction spring to help with the shearing action. If you find the machine pulls the plate between the blades instead of shearing, the strap isn’t set correctly and the bolt needs to be tightened.
With the laser items and a few standard angles machined to size the frame started to take shape. Solid rivets are cheap and available in sizes above 3 mm, for smaller than 3 mm, cheap (and I stress cheap) iron nails work well. I have a Mac Afric 190mm hammer action chisel set (AHAMMC-190), which I use with formers to do all the riveting. With that little setup the rivets become like butter and very neat heads can be formed.
For aligning the frames a piece of granite, found on the side of the road, serves as a good gauge plate. All frame plates and holes are checked that they are square, and line up using an engineer’s square. Initially the assembly can be held together with inexpensive MacAfric magnetic arrow welding squares (EAMAGW001). All holes are match drilled using a standard hand drill with the assembly held in place with MacAfric G-clamps (WCLAMG075 to 300). After every hole is drilled a bolt is inserted and tightened and the alignment rechecked to make sure nothing has moved. This takes some time but saves far more down the road. If this method is used and the holes are size for size for the bolts the frames will align perfectly every time after disassembly.
The tender frame was match drilled and aligned in a similar fashion, with far more rivets and angles. Clamping everything together before drilling was essential to get everything to line up properly. The buffers, which are the short plates at the end of the frames, were squared up on the milling machine to help with the frame assembly.
To clean all the edges a combination of hand files and an MacAfric air grinder kit (AGRIND001) with sanding tubes was used. This is how they did it on the larger locos and it just improves the look of the model without too much extra effort. In the good old days of train yards and enginemen, frames were modified using chisels and additions were made using a forge welding process. With the tools currently available we have it easy.
That pretty much sums up the assembly of the frame platework, the next article will touch on casting and machining of the various components needed to complete the frame and some woodwork to make the castings. Yep; woodwork is needed to make the patterns used in the casting process.
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