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It was New Year's day 2016. I had finished the build of a VS Class for the RMWeb "Build a Loco" the previous day. I was now thinking about beginning to test it, and had dusted down and set up my (as yet very basic) test track.

 

However, on an impulse I picked up an entirely different loco. This was a GNR(I) S Class 4-4-0 which I had been building in fits and starts over the past few years. It is the kit produced by Studio Scale Models, though this particular example dates from the Terry MacDermott era when it was TMD models. It was an eBay purchase, in an unstarted state, several years ago. It is about 90% complete, but there was a problem. I had decided to fit working inside motion, for which I adapted the 4F motion produced by Brassmasters.This is fairly close to what is found in an S (though not an S2) - Stephenson's gear, 2 pairs of slidebars for each crosshead, valves driven by rocker shafts. It was my first attempt at building inside motion and was certainly a learning experience. All seemed (eventually) to go well until I finally connected up the motion. The loco, which up to then had ran OK, developed a discernable jerk when running at low speed. This was incredibly annoying at the time; it was barely present, but just enough to make slow running unnaceptable. I tried various tweaks, but to no avail.

Reluctantly, I set the S Class aside as I needed to get on with building the VS. I would return to it at some point in the future, but had more or less resigned myself to having to replace the inside motion. The plan was to build up a new set from another set of Brassmasters etches, then swop this with the existing motion, which could then be dismantled and fixed at leisure. Fortunately, I did not get around to doing this.

Back to New Years Day and my impulse which said "let's just give the S another go before I start testing the VS". So I set up the S on the rollers and turned on the power. There was still a very slight jerk with every revolution of the wheels. The tight spot, or whatever it was, had not magically disappeared. So no surprise there, then. However, I left it running and went and made a coffee.

On return, it was still merrily running on the rollers, but was I imagining things or was it running just a little freer than it had been? It definitely was, I thought, so I left it running. Over an hour or so the running gradually improved, until the proceedings were interrupted by an ominous clunk, and the loco stopping dead. Closer inspection revealed that the two rear crankpin nuts had worked loose, and the rods had come off the crankpins as a result. It wasn't a big deal as they had only been retained at that stage with a tiny dab of superglue.

This left the driving wheels (and the motion) disconnected from the trailing wheels, so I was able to turn the drivers round by hand to see if I could find the tight spot. To my surprise, there wasn't one. Everything was silky smooth and revolved perfectly.  Somewhat puzzled, I reattached the coupling rods to the rear wheels, then slackened off the grub screw to the final gear (so that the rear wheels would also rotate by hand). It quickly became apparent where the problem was. The clearances are very tight between the coupling rods and the insides of the splashers. On one side, the rod was just touching the splasher at one point. I'm guessing that without the inside valve gear coupled up to the front axle, the motor was powerful enough to overcome any resistance from the rod touching the splasher, but with the motion engaged, there was then enough additional resistance to produce the jerky running I observed.

So, off with the loco body, and a small file was used to file away a little more metal from the inside of the splashers. Once reassembled, testing revealed that the tight spot had gone, and the loco would now run right down to a crawl. A result! - and one which gives me, at long last, a working S Class. By the end of the day a few minor tweaks had it running successfully end to end on the test track. There are still a few minor details need to be added to the body, at which point it can be declared complete. I am just very glad that I did not dismantle the motion!

 

Alan

 

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?...GNR(I) S Class 4-4-0 which I had been building in fits and starts over the past few years. It is the kit produced by Studio Scale Models, though this particular example dates from the Terry MacDermott era when it was TMD models. It was an eBay purchase, in an unstarted state, ....

For anyone contemplating building the "S" for themselves, the kit now sold by SSM is still the TMD one, and the etches still bear the old TMD marks. No change there. Mine also came out of eBay, but with no instructions, so SSM e-mailed a new set to me. Des's style of instruction leaflet tends to be a bit clearer than the TMD original, but could be better as regards identifying individual parts.

 

I didn't think the Brassmasters 4F parts were "right", so chose to do the inside motion the hard way, with proper cranks and eccentrics (the ones in the Martin Finney 2721/Dean Goods are a very close match in shape and throw) and rods from various sources, including a Finney T9). Motion drawings were provided by the RPSI's Peter Scott, and IRRS's Richard McLachlan.

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 Mine also came out of eBay, but with no instructions, so SSM e-mailed a new set to me.

The TMD period instructions which I have are very reminiscent of the instructions from the old Jidenco kits (same era) There are two or three typed pages of instructions describing in words how to build the model and in what order. There are line drawings, and a map of where numbered parts are on the etch. You do have to read the text very carefully to avoid making mistakes.

 

This particular kit was missing the castings when I first got it, but happily Des was able to supply a full set for it.

 

I didn't think the Brassmasters 4F parts were "right", so chose to do the inside motion the hard way, with proper cranks and eccentrics (the ones in the Martin Finney 2721/Dean Goods are a very close match in shape and throw) and rods from various sources, including a Finney T9). Motion drawings were provided by the RPSI's Peter Scott, and IRRS's Richard McLachlan.

Like yourself, I obtained copies of Dundalk drawings from Richard recently. They cover the motion of the S and the S2 classes and date from the time the valves were modified to long travel. Comparing the S class motion to the Brassmasters etches, they are pretty much identical. The main differences I can see are:

 

1) The S Class motion bracket is concave at the top, whereas the 4F is straight across. One of the finishing off jobs to do is to solder two little triangles of metal on top of the motion bracket to make it the correct shape.

 

2) The 4F has two massive stuffing boxes (at least that's what I assume they are) at the rear of the piston valves. The S class has no such fitting. Brassmasters represent them with a pair of whitemetal castings so it is easy to leave them out.

 

Brassmasters employed a crafty deception with the crank axle, of course.  It's actually a plain axle with cams, rather than cranks, and some "simulated cranks" to complete the illusion. This is somewhat simpler to construct than a real crank axle, and once fitted in the loco you do not notice. I have seen a few Brassmasters 4Fs that have been built to P4 standards. The motion is fairly visible but looks totally convincing - unless you happen to be in between the frames with a stereo microscope! On the S class the motion is less visible, behind the deeper frames and the larger driving wheel splashers.

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I'm still thinking about the best way to do this but haven't yet come to a conclusion. I did lining on a 1915 U class a while back, using commercially available lining transfers. It was hard work as some of the curves are not available in double (ie white/ black / white) lining form on the sheets.

 

On the S Class the lining is particularly intricate around the splashers and sub splashers - lots of flowing curves. I'd love to say I was going to do it all freehand using a bow pen, but having the skill is some way off. I have managed to put some single yellow lines on coaches using a bow pen, which is a start, I suppose.

 

Alan

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Doesn't SSM produce a lining and numbering sheet?

Indeed they do. I have some of these transfers and using them is one of the options. A minus point I've encountered is that they are printed (at least the example I had was) on a solid block of backing sheet. It was necessary to carefully trim round the edge of the lines with a sharp blade so that the lining fitted onto the splashers, or wherever.

SSM also produce equivalent transfers for the U Class. These did not exist at the time I was initially doing mine, although I subsequently used some from the SSM sheet to replace the corner lining on the tender sides and rear. What I had used originally (SMS transfers, if I remember rightly) did not look right (white lines too thick, black band too thin) .

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