Now No.2 is more or less a rolling chassis - I was thinking about a name - and this is it.....
The Rev Brian Favell is (obviously) my father, and although he has been an Engineer, Designer and Parent, he is first, foremost, and last, a Priest.
Dad designed 'Alice' - the Bagnall that has proved so very successful - and she has been a credit to him..... (if this loco doesn't work - it's my fault...!)
Dad had high standards when it came to up-bringing, and therefore used to take us regularly to the Hilton Valley Railway in the Midlands. Aidan and I were also encouraged to build our own model layouts - mine inevitably narrow-gauge and Aidan invariably standard. We always had ideas and ambitions beyond our capabilities - but instead of telling us not to be silly or unreasonable, poor Dad spent much of his spare time rescuing our half built (and in trouble) projects. It was a really useful learning opportunity......
....showing 'Alice' and 'The Priest' to the same scale as a size comparison!
WHEELS
My poor, long-suffering Father, who I had talked into doing a bit more machining, kindly delivered the last pair of driving wheels for No 2 recently, and I welded them to their 50mm dia. plain axles the next day. Purists may suggest that this approach is verging of criminal – and that I should machine shoulders on this that and the other, with interference fits etc., however, I can achieve the same sort of accuracy this way, I can sling the whole wheelset onto the lathe for re-profiling when necessary, and if major surgery is required, I can simply chop through the axle and replace it (being plain 50mm dia. bar). You will see in the photo that I use three identical spacers (of the back-to-back dimension) to ensure that the wheels remain true and parallel at all times. One wheel is fully welded first, and only then, the second wheel is tacked and welded. This ensures that there is only one lot of contraction to consider – if both wheels are tacked before welding, the back-to-back dimension will turn out measurably smaller than it should be. The spacers are then tapped out after welding.
wheelset ready for welding
CYLINDERS
I managed to buy one metre of seamless 4” I.D. tube for the cylinder liners instead of the usual 6 metre length (probably an unrepeatable bargain!), chopped it off slightly oversize, and set about facing the ends on the lathe. This meant there was about 1½” in the chuck, and around 8” overhang. This was fine for facing, but proved a real problem when it came to reducing the diameter on the ends, causing the lathe to chatter badly. This was cured by Dad’s suggestion of using the lathe tool upside-down, and running the machine backwards. This really transformed the operation, making the job very easy and straightforward.
The next job was to draw out the various components that I needed for the rest of the cylinder fabrication – i.e. end plates, valve face, valve chest (being slide valve) and valve chest cover.
Talking to Parker Steel – our steel stockholder we use at work, I found that they would laser cut plates up to 20mm thick, and would flame cut anything over this. It transpired that the cutting tolerances for laser were plus or minus 0.2mm (apparently) and for flame cutting, plus or minus 1-2mm. Because the assembly is to be welded, I hoped to keep distortion to a minimum by using as thick a plate as I could – therefore I ordered the cylinder end plates from 25mm thick, with a circular cut out to fit the machined cylinder liner. The valve chest I ordered to be flame cut from 50mm plate, and the valve face to be laser cut from 20mm plate.
After faxing Parker Steel with the (dimensioned) drawings, they phoned me up to explain that they had a problem with the valve faces. One of the points of this exercise was to minimise machining (as well as cost) and to streamline the build process as much as I could, and therefore I wanted to have the steam ports laser cut into the plate rather than have to machine them myself….. It transpired that with the steam port being rectangular slots of 12.5mm x 62mm, with bridges between ports of the same dimension, they felt that heat dissipation would be insufficient during the cutting process. We therefore negotiated a reduction of thickness to 15mm plate – the thickest I could persuade them to cut the ports in! Whilst I was at it, I ordered 6 fly-cranks to be supplied cut from 40mm plate. The total bill was under £220 for 3cwt of unique profiles – not so very much more than the raw materials would have cost me.
Three days later, this lot arrived in sacks….
The cylinder end plates were very nice, and accurate enough, but unfortunately had the locating holes for cylinders at about 118mm diameter – the lower end of the tolerance- so I’ve has to open the holes out to the 120mm I’d already machined the liners to. (I didn’t really want to machine the liners down further, wanting to preserve the maximum possible thickness to discourage contraction when the liners are welded in). With hind sight, I would have reduced the plate thickness to 20mm and had them laser cut for the accuracy, enabling the pieces to truly slot together requiring no fitting. I’m sure that 20mm would still be quite thick enough to stay straight as end plates… oh well!
The valve faces were delightful. Being laser cut for accuracy, they use a better quality steel with a much better surface than you get with the flame cut profiles. The ports are all cut accurately, and the plates require no attention other than the drilling and tapping necessary for the valve chest studs. A real success!
dry run of cylinder assembly. One valve chest still needs machining.
The valve chests themselves however, were not quite so clean. Being flame cut from 50mm plate, the cut isn’t quite true to 90 degrees – not a real problem as valve gland surfaces will be machined anyway. Of more import was that the (uncut) surfaces were of black plate, with varying degrees of scale on them. This clearly would not provide a steam-tight surface, and so these did require work. First of all, I drilled and tapped an M10 thread into the centre of each side of the chests (making sure I avoided the through holes for the studs) and bolted on a bit of 40 x 40 x 5 angle, thereby enabling me to bolt the whole chest onto the lathe face-plate. These drillings can later be used for lubrication points etc.. It was then a really quick and simple exercise to face off both sides, leaving the chests and cover plates ready to be drilled for the mounting studs. At this point, the next job is to weld on some RHS (rolled hollow section) to create the exhaust passage, and then to weld the whole cylinder assembly together. With the amount of welding that I have to do, it is only reasonable to expect some distortion (probably on the hitherto flat valve face) and a lot of stressing within the assembly. I therefore propose to ‘normalize’ the unit by shoving the whole thing in the gas oven for a day. This will help everything return to ‘normal’ – relieving the stress, and will ensure that if I do have to machine the valve face, that it will stay put after the process!
I reckon that even with this fuss, fabricating the cylinders will have been significantly quicker and cheaper than using the more conventional cast-iron approach. If however, I was using piston valves, the process is really simple – requiring only the tubes of the right size, and the two (pre-cut) endplates, with either machined or fabricated steam passages.
On a completely different subject, I was faced with having to make 11 metres of (accurate) cuts on open mesh flooring for a show we are putting on at work. The only way I had available to do the job (‘cos you can’t get this stuff sheared to size) was to use a 9” angle grinder – nasty, unsociable and dangerous (and not very accurate). I then recalled that about two years ago I had been sent a flyer (from B.O.C.) for a circular saw designed to cut mild steel. We made a phone call, and this machine was delivered next morning (£199 plus VAT for the Evolution 180, and £299 for the Evolution 230). It has been brilliant! (see photo) Very quick, accurate, and much safer (still noisy). It cuts without cutting oils or fluids, and our machine (the 230) is capable of cutting 18mm thick plate, or 80mm RHS. I wonder if we can cut point blades and stock rails with this…..
Much later...
Following a significant break of a year ………… I finally got round to welding in the steam passages (the exhaust already having been done). Needless to say I couldn’t remember for the life of me how I had planned to do it, so I stood round it for ten minutes waiting for inspiration. It came in the form of 50 x 50 x 6 angle, which with a very small amount of profiling neatly in-filled the corner – leaving a ½” gap for the passage – and welded to the existing exhaust and to the cylinder itself. One has to be very careful planning this sort of thing, as you have to get the welding torch to the whole joint successfully – therefore you can’t have an acute angle to the joint, as the head of the torch won’t go in………
The exhaust passage is already in, waiting for the steam passages...
heavy angle cut and weld prepared to form the passages
10mm bar to form the passage sides
one side welded
...only just fits on the mill...
after welding and machiningThis gave me the bulk of the steam passages, but with no sides. Instead of carefully profiling a bit of plate as side in-fills, which would then need ‘V’ prepping for welding, I very simply cut off short lengths of 8mm dia black steel bar (bought from B & Q), bend them to a right angle, dropped them in and – voila – buzz round them with the welder – instant steam tight passages.
all welding finished!By this time, the deflection of the valve face (which of course should be perfectly flat) was over 2mm at the centre – just as I had thought. Now, I also know that when you machine a surface that has been abused as much as I have abused the valve face, it can distort during the cutting process – thereby ruining it completely. Taking my own advice, I stuffed each cylinder in the oven at Gas Mark 9 for 24 hours in order to stress relieve them.
I have a wife second to none. How many partners would get home after a hard days work, ask “What’s that smell?” and still be perfectly relaxed when told that instead of the evenings supper, it was merely a half hundredweight block of fabricated cylinder that was going to be in there all night? (The smell was due to the fact that I had forgotten to clean all the oil off……).
normalising in the oven for 24hours!
A day later, I took the cylinder out of the oven (it took 3 hours to cool down) and bolted it down on the slide of my mill/drill. This machine is a wonderful drill, and a lousy mill – owing to the fact that it has no draw-bar – thus allowing the cutter to fall out and ruin the job. I had to use this one, and not the Herbert, as the area to be machined was 7”x 9” and the Herbert only had a travel of 5” maximum. The Arbarboga – or whatever it’s called – itself only had a maximum travel of 6”, but by using a 40mm dia cutter, I was able to get over the whole surface. Honestly, by the time I’d finished, it felt like I’d had to mill a whole kitchen table…. The plus side was that the valve face didn’t move a fraction. It may be that it wouldn’t have done anyway, but I like to think that it was the cooking. Of course, if I had been making cylinders with piston valves, I wouldn’t have had to go through this as the two tubes would have been self supporting, incurring no relevant distortion – but having said that, it has been no more onerous than machining up a casting. Incidentally, I know of a few locos that have suffered from valve trouble – and they have all had piston valves.
Cylinders now awaiting pistons and valves
1st June '05
I've been working this last year in a new job, and had little time for anything....
First thing I've had a play with recently is the fly cranks which I had flame cut so long ago.........
I have very carefully set them up on my old mill/drill, and drilled them out to 50mm diameter - I've never drilled holes that big before -
It actually went quite well, working my way up size - wise. It is however crucially important that the drills are correctly sharpened - drilling 2% oversize here would be enough to cause serious problems. I made sure by having my 50mm drill professionally sharpened (on a jig) at a cost of £15 or so - but subsequently Aidan explained how I could make a jig / test stand myself to ensure accuracy - I'll have to explain it in the future.
Still, the drilling went well, and I then proceded to jig up and drill the cranks for the M12 clamping bolt. This was entirely straight forward apart from the depth of hole required (it all needs to be drilled from one side..)
The first obvious problem was the need to lengthen the drill as a whole - easily achieved by simply taking some steel bar, chucking it in the lathe, using the drill to be lengthened to drill a 20mm bore in the end, taking it all out, reversing the drill and putting the shank into the (accurately) drilled hole, and tacking it there with the welder. It almost takes longer to say than to do.....
The next problem was that the flutes on the drill were still too short - so when I had drilled to a depth of about about three inches, the swarf would no longer clear, and I had to keep with drawing the drill and cleaning it out - slow and laborious.
Tapping the M12 thread for the clamping bolt was a real treat, as last year I had picked up a second-hand tapping head from the Great Dorset for £25... and it works brilliantly! (with spiral fluted taps, of course)
The next job was to slot the balance side to enable the clamping bolt to do its job. For this, I used a nine inch angle grinder with the 'plasma' cutting discs. They are very fine discs 1.5mm or so thick which will cut through stupid thicknesses (like 40mm fly cranks) with comparative ease.
I will not be relying soley on the bolt, but when I've confirmed the quartering, I will drill and pin the axle / crank interface to ensure everything stays put!
One fly crank bolted to axle (no crank pin as yet...)
They are cut from 12mm plate, more than six feet long, plus add ons behind the back-head and weigh quite a lot.
The bill for mainframes, font buffer beam, rear drag beam etc. comes to around £500 plus VAT - the frames being £150 or so each. At first sight, it seems a lot - but when you have to lift them you can appreciate there is a significant amount of material there......
In an effort to economise, I asked for a price without all the holes (for horn guides, Bufferbeam mountings, coupling mountings etc.) and was told that all the holes only added £30 or so to the bill! I therefore had all the holes I could done! Accuracy is assured, and it saves so much work - all I have to do is get some 40 x 40 angle, drill that to match the frames - and the carcass will be there. An interesting point to note is that although the centre driver guide holes are round, the trailing and leading holes I've had cut as slots (at no extra cost - but a real pain to do by hand!) - this is so I can adjust the horn guides easily for any wear or inaccuracy in the rods.
I still need to organise some stretchers (12mm plate still bends.......), weld on spring hangers, make the horn guides and away we go!
Just to prove the frames are really there...
'The Priest' is now very much a rolling chassis with suspension
8th November
I've been grabbing a few bits of time here and there, and the result is a rolling chassis, with cylinders and motion brackets attached.
Erecting the frames was really no trouble - it was helped by my having had bolt holes cut in when the frames where profiled. However,
I did find that there was a little ridge on the inside of the holes, where the cutting process started and finished. This was
quite enough to damage the tip of the drill as I was piloting through - especially as the cutting process had hardened the surface.....
The cure for this would have been to have made the holes around 12.3mm instead of 12mm. Non the less, it didn't slow me down much - just a few extra trips to the grinder to touch up the cutting edge (incidentally, Aidan showed my how to grind a large drill so it'll cut straight through without piloting - extremely useful when mounting cylinders and bracketry).
One interesting point is how flexible the frames are (or were). I would have thought that at 12mm thick, they would be absolutely rigid - but no - they were relatively floppy....
however, some 50 x 50 x 6 angle bolted down the top edge, and a couple of stretchers welded in have sorted them.
The 'Horn Guides' are fairly self explanatory, the only trick being a modicum of accuracy, and ensuring the drilling is square, and not diving off to the side. The spring beams are exactly as they look,
with cut-down bolts welded to the ends to take the (temporary) springs.
The pony truck pivot is a weld-on three-point linkage link from an agricultural source, and this gives me full articulation for about a fiver. This is welded to a stretcher immediately in front of the leading driver.
The method of conducting the weight down to the pony truck had me thinking for some time, as there are so many options - all quite valid. In the end, I went for an unsprung plate (all the springing done at the axle box) in the same way that Exmoor do. I then added a couple of grease nipples to help it along....
I had the motion Brackets profiled from 15mm plate in my usual way - these were expensive at around £75 each, but the coupling rod blanks (25mm plate) came out at £12 each for the large ones and £9.50 each for the shorter ones - you win some - you lose some....
I chose to weld on a bolting flange to the brackets from 40 x 10 flat, V prepping and welding from both sides at the highest ampage I have available (220A) to ensure that they weren't going to drop off. These were then clamped in position (measuring twice and drilling once..) and
drilled through M12, and bolted. I had taken care to ensure that the bolting flange was welded on at 90 degrees (as near as I could), and once each bracket was welded on, I fine tuned it with a sledge hammer to get it exactly right.
Not model engineering, I suppose.
This sounds horribly crude, but in fact it is effective, really quite controllable, one of the few ways of shifting 15mm plate, and no one was looking anyway.
Click here to return to home page