North Sunderland Manning Wardle "Bamburgh" scratchbuildOne of the signature locos of the North Sunderland line was the Manning Wardle "Class L altered". It arrived on the line in 1898, was overhauled and modified in 1934, and was life expired in September 1947, having been run into the ground.
The loco has had to be scratchbuilt, as it was a one-off, so no kit exists. The build presents a number of challenges. First up, here's what I'm aiming at:
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Below are some notes on methods for the ideal reader suffering from the ideal insomnia...
Saddle tank A drawing of the loco appeared in MRJ number 8, and a dimensioned sketch in Wright's book
The North Sunderland Railway. The latter confirms that the radii on the former are wrong. Head-on photos confirm Wright is, well, right. The challenge here was to get the tank wrapper curved in a deep, crisp and even way. I was at pains to avoid the uneven rolling I often see on saddle tanks of all shapes and sizes. This was the method I used - a plasticard former to the right size and radii, over which the 10 thou brass wrapper could be draped and bent. The former takes an evening to make - far less than the time for the previous three failed wrappers, and the year of despair that punctuated the failures. Ideally, I should have covered the former in Milliput to smooth out the "steps" between plasticard layers, as these did leave a slight imprint on the brass; however, that was easily sanded out.
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Here's the finished tank:
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Frames Although no kit exists for the Class L altered, RT Models do produce a chassis kit for a Class K, which has the same wheelbase. Unfortunately, the frame profile is wrong for Bamburgh, so new frames have to be scratchbuilt in 15 thou N/S:
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In theory, I should get some inside valve gear from the kit too, though even if I could work out the instructions, it's fouling the CSB anchor points at the moment. What the kit does give me, though, are rods etched to modern levels of accuracy,
from which (and not
with which - see the FINE RUNNING thread) to set the hornguides. However, the rods are overetched, with the part that should make the knuckle etched away, meaning that they cannot be jointed on the knuckle and instead have to be jointed on the centre crankpin, with a cosmetic knuckle added later. Not ideal....
To set up the hornguides, I used my "gauges", again mentioned in the FINE RUNNING thread. Initially, these were set between the HL hornguide backing: for each hornguide, I measured the width of the backing (5.45-5.49mm), averaged it, then subtracted that from the rod centres and made my gauges:
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I tack-solder the hornguides on one side only, in case any adjustment is needed. I clearly hadn't tacked one well enough and it came adrift. When I repositioned it, I used Dave Bradwell's recommendation and made a new gauge, which I positioned between the hornways, rather than between the backing plates, in order to "cut out the middle man", as Dave put it.
Brakes Again, in theory, the kit should provide some brake parts. However, Bamburgh had hangers of a different pattern to the K:
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So some work had to be done to adapt the ones in the kit - a ten-thou overlay to the hangers, shaped to the correct profile, with the original holes used as drilling guides. Hopefully they won't (all) de-solder when I connect them to the pull rods etc...
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Fittings I'd initially hoped I'd be able to use some of the castings from the K class kit, but unfortunately the chimney was too spindly and the s.box door too small. I have, however, got the tank filler and the spring castings from RT models - though the leading support on the front two springs will need altering. Name and number plates are from Planet Industrials.
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For the really important fittings though, I had to resort to a friend in a high place with grown-up tools. I commissioned Jeremy Suter to turn the chimney, s.box door and splashers for me using his lathe-thingy:
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I need to add the flange, straps and dart to the door. I have a plan for a jig that will help me position the straps - a piece of N/S or brass the same width as the straps are apart, curved to the profile of the door, and bolted through the dart hole while the straps are glued or soldered on.
Question: I think I have clearances worked out for the splashers, but could do with some confirmation from those more experienced in such things. The wheel centres are 7mm below the top of the frames. Half a wheel (over flanges) is 7.32mm. Given that the footplate is 10-thou thick, that seems to put the tops of the flanges level with the top of the footplate - which the blurry reproduction of the GA in Wright seems to confirm. That means that my splashers are only there to provide clearance for upward movement. Now John Bateson recommends 0.67mm movement distance plus the thickness of the splasher top (0.3mm), which seems to suggest my splashers should be 1mm high - seemingly confirmed by the MRJ drawing, though this is in 7mm, and doesn't quote dimensions. I also have the 5 thou base to the splashers that would act as a get-out-of-jail-free card, giving me an extra 0.17mm above the flanges. Does that sound enough? Have I calculated correctly?
Wheels This is where the real fun starts. The MW wheels made by Gibson don't capture the look of the wheels on Bamburgh. They have 1/8th axles, which makes the centre bosses too big, and the balance weights are in the wrong place / of the wrong pattern. So as I'd done on the Y7 (further up in this thread), I used tender/bogie wheels, which give me a 2mm axle, and, aided and abetted by Dave, converted them to driving wheels using some cranks he etched for me.
Before I could fit the cranks, though, I had to fit the balance weights. Because these are flush with the tops of the spokes, rather than the wheel rims, I had to remove the rims; I could then fill (Devcon, then Milliput) and sand the faces of the wheel flat, before re-fitting the tyres. The wheels were then ready for the etched cranks, but first these latter needed the crankpins fitting.
The crankpin - or rather the bushes - are 1.52 (more on this below) brass tube soldered into the crank etches using a piece of tufnol with a hole drilled through it with the bench drill (to ensure verticality); the crankpin-bush-to-be is then held in that hole in the tufnol during soldering. Also added at the soldering stage were flanges/collars where the crankpin tube meets the crank etches. These are to space the rod off the wheel face; on a Gibson bush they are 0.25mm, so I made some from slivers of 2.0mm tube filed down to 10 thou using a piece of 10 thou as a filing "stop".
The crankpin bushes could then be filed to length: the rods were placed on the crankpins, topped by a piece of 5 thou and filed down; the 5 thou is to allow the rods some possibility of movement, so that the crankpin nut does not come into contact with them. Next will be the crankpin proper. For these on the Y7 I cut the head off a Gibson crankpin screw and glue it into my crankpin tube - this gives me something steel to screw the Gibson crankpin nut on to. The screw is a tiny bit loose (0.92 in a 1.00 hole) but this doesn't matter as the rods are not touching it but instead rotating on the tube/bush.
The cranks were then glued on to the wheel faces with Devcon Home. On the first two I positioned them using the axle, whereas on later ones I used a shaped cocktail stick. After 6 minutes the Devcon allows fine-positioning, for which I use strong magnification.
As said, the crankpin tubes are 1.52. I had two tubes nominally 1.5 in diameter. The other one was 1.47. I used the 1.52 as I know that the 1.6 drills that come in those Microbox sets are actually 1.56 or 1.57, depending on which side of the bed the vernier gets out of, and when the rods are drilled to 1.56/1.57 it offers the perfect clearance between them and the crankpin. I'm waiting for a motor and gearbox before I fully wheel up the chassis, but initial tests /sightings (John Brighton) suggest all the dimensions have worked out well and the rods will turn first time without binding or fettling - the result I've always had with my gauges.
Here are the parts for the wheels, with rejected Gibson MW bottom left, disassembled wheel top left, tufnol jig far right, finished wheel in the centre and crankpin tube and collar in there somewhere.
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This one shows the crankpin collars - slivers of 2.00 tube soldered to PCB - being filed down to the 10 thou "stop" or "gauge" to the side. It took a whole afternoon - most of it cleaning the solder off the collars afterwards; there must be a better way!
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Here are the crankpin bushes being filed down with the rods and the 5 thou filing "stop" in place:
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That's it. I'm nearly done with the nasty stuff. Soon it will be time for the pipes and injectors and the Roscoe valve and the Westinghouse pump, and I'll be able to enjoy my hobby once again...
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