May 2025

This year's May working party fell just after the May Day bank holiday weekend. However since Andrew and Dave 2 were available on the bank holiday weekend, they held an additional working party prior to the planned event.

Andrew spent most of the bank holiday weekend milling the internal faces of the little end bearing interfaces on the crossheads. This was not an easy task, as the faces are deep within the crosshead castings and so required very light cuts using the side of a long end-mill. The two faces on each crosshead are now perpendicular to the axis of the little end bearing and are parallel to each other. Although further apart than they should be (due to wear), we can compensate for this by making the little end bearings a bit wider.

Andrew found a few moments to weld the new end of the regulator valve spindle on. This allowed Dave 2 to complete the machining of it, including cutting a new thread on the end. Andrew also welded the yaw damper brackets to the new drawbar.

Dave 2 turned, milled, drilled and tapped a special nut for the regulator valve spindle. He made this to the original drawings, to replace the conventional nut and stack of washers which were fitted when we bought the locomotive.

The working party proper started on Thursday; a spectacularly sunny day without a cloud in the sky. It seemed a shame to be working indoors in such weather, so Andrew and Dave 1 took the decision to move the locomotive out of the C2 Shed. This required a couple of wagons to be shunted out of the way first, but it didn't take long before the C2 was basking in the sunshine.

Firstly, Dave 1 and Andy carried out a test fitting of the new engine to tender drawbar. The yaw damper brackets are slightly different to those on the old drawbar, so we wanted to check everything still fitted correctly. As expected, everything fitted well.

Andy then transferred the drawbar to a slate wagon on an adjacent siding. After cleaning it with white spirit, he applied a coat of primer. Thanks to the excellent paint drying weather, he was able to apply a coat of paint to the drawbar during the afternoon.

We believed that we were ready to fit the slidebars, having completed all the packing pieces and fitted bolts. Dave 1 therefore took a look around the area on the locomotive to which the slidebars fit, to check if there were any jobs which would be easier done without the slidebars in place.

The cylinder end covers have recesses in them into which insulation can be fitted. This keeps the cylinders warm when the locomotive is in operation, preventing excessive steam condensation within them. Because each rear cylinder cover has a piston rod passing through it, the insulation is held in place by pairs of cladding sheets. It seemed logical to fit all of these parts before the slidebars were fitted.

Andrew spoke to Jake about insulation, and an offcut was found which would provide us with sufficient material to fill all four cylinder end covers. Jake also provided us with a handful of short M8 screws which we would need to fit the cladding.

Dave 1 discovered the original rear cylinder cover cladding sheets on a pallet in the C2 Shed. They were in fairly good condition, having been painted at some point in the past, but some corrosion was beginning to reappear. A few minutes with a wire wheel removed the offending corrosion.

Andy applied primer to the cladding sheets where Dave had wire wheeled them. With the weather so warm the primer was dry within an hour, and so Andy was able to apply a coat of paint to them a short while later.

The centre part of each cylinder is covered by insulation and cladding but the ends are not. The cylinders had been painted in an orange corrosion resisting paint (which has worked very well) but which would look very odd if visible on the finished engine. Andrew therefore found some heat resistant black paint and applied it to the ends of the cylinders; another job rather easier without the slidebars in place.

With the paint on the inside faces of the rear cylinder cover cladding sheets now dry, Andrew packed the recesses in the rear cylinder covers with insulation and Dave 1 screwed the cladding sheets into place. After a wipe round with white spirit to remove any grease, Dave 1 applied primer and then paint to the outer faces of the cladding sheets to offer them some protection against corrosion. The speed with which the primer dried was a godsend, which allowed the job to proceed rapidly.

A few weeks previously, Dave 1 found a box of studs which he suspected were for the cylinder covers (we have fitted the rear cylinder covers, but not the front ones). A check of our records confirmed this and also identified that the box contained the studs required to fit the front of the slidebars to the cylinder rear covers. Dave 1 and Andrew therefore fitted these studs into place.

We left the C2 outside the C2 Shed overnight, as there was no chance of rain. By Friday afternoon, all the minor tasks had been completed and were really were ready to fit the slidebars. First to go on was the Fireman's side.

The rear packing piece is a top-hat section, which fits into a hole in the motion bracket. In the morning Dave 1 had discovered, to his consternation, that this was a somewhat loose fit even though it had been machined carefully to be an interference fit. Dave couldn't remember it being so loose before, which seemed odd. By the time we came to fit the packing piece it had become an interference fit again, and needed to be driven into the hole with a mallet. For an explanation we needed to look at the position of the sun. In the morning it was on the Fireman's side of the locomotive, warming and expanding the motion bracket on that side. By the afternoon the sun had moved round to the Driver's side and the motion bracket (and hole) had returned to it's original dimensions. It's amazing how much difference a little bit of heat can make.

The fitted bolt was still a little tight in the slidebar, so Dave 1 placed the bolt in a lathe and used some emery paper to reduce the diameter by a tiny amount. Andrew carried the slidebar to the machine shop so that we could check the bolt against it. Once the bolt showed signs of starting to fit into the hole it was deemed to be a suitable size. Back at the locomotive, the fitted bolt was knocked into the slidebar with a mallet; a perfect fit.

Andrew found that the front packing piece, which fits around the two studs on the cylinder end casting, was slightly too narrow. Since Zoe had made the packing precisely to drawing, it seems likely that the two bolts are spaced slightly farther apart than they ought to be. This was confirmed when we tried to place the slidebar over the studs; it was an extremely tight fit and would not locate properly.

Both front packing piece and the holes in the slidebar received attention from a file (elbow grease provided by Andrew). Only a fraction of a millimetre of material needed to be removed before these parts fitted, even if there was still no lateral clearance around the studs.

With the front of the slidebar located on the two studs on the cylinder rear cover, the fitted bolt at the rear of the slidebar was knocked into the packing piece fitted to the motion bracket. We don't yet have the castle nuts we need, so normal nuts were used as a temporary measure to hold the slidebar in place. It had taken us most of the afternoon, but the first slidebar was on.

The following morning attention moved to the Driver's side. Dave 1 noted that the front packing piece fitted around the studs much better than it had on the Fireman's side, and did not require any adjustment.

The diameter of the fitted bolt was again marginally reduced with emery paper, to start it fitting in the slidebar. This time, back at the locomotive, the front of the slidebar was lowered onto the studs, the fitted bolt was knocked into the rear packing piece in the motion bracket, and the nuts screwed on to hold everything in place. It only took about 15 minutes!

Erle spent Thursday and Friday working on the C2 with us. We are making the new reverser handle from stainless steel, so Erle machined a bar of that material down to size to form the lever which is fixed to the latching wheel. Being a hard material, it took a while to machine it, but Erle achieved an excellent finish.

The lever needs a joggle in it, to clear the reverser latch. Andrew helped Erle bend the lever, using a gas torch to heat the metal. Although we had been warned of the difficulties of bending stainless steel, Erle and Andrew took a cautious approach and managed to form the lever without too much trouble.

Erle then continued work on the reverser lever, drilling holes for the fixings. On Saturday and Sunday he transferred to Dinas, to work on the NG15. Such is the demand for his excellent machining abilities!

With the slidebars progressing well, it won't be long before we are wanting to fit the crossheads. Andrew has finished the machining on the crosshead castings, but spent a few hours cleaning out the oil ports. He also started cleaning up some of the components (little end bearing pin retaining straps, oil pipes, etc.) which will be bolted on to the crossheads.

While Andrew fettled the crossheads, Dave 1 measured the little end bearing interfaces in the connecting rods. A check against the Polish drawings showed that these interfaces are to the original design, so we now know the basic dimensions we need to make the new little end bearings to. Dave 1 also managed to apply a second coat of paint to the drawbar.

Andrew and Dave 1 put together a list of fixings we will need for the crossheads. There are six fitted bolts required, which we will probably outsource to a CNC machining company. There are also quite a number of studs to a wide variety of dimensions. Given that there are no more than four each of most of them, it is doubtful if it will be efficient to get them made by CNC. Current thoughts are, therefore, that we will have a go at making our own studs for the crossheads.

More castle nuts are required for the crossheads. We can order these when we order those for the slidebars.

The weather forecast for Sunday showed a slight chance of rain, so on Saturday evening we shunted the C2 back into the shed. Apart from a few drops on Sunday night, no rain materialised though.

By Sunday, the heat was becoming a little oppressive, so Dave 1 and Andrew took things a little easier. Having fitted the slidebars, we wanted to double check their alignment relative to the cylinder bores. Vertically, we are quite confident that the slidebars are aligned, as we carried out some very careful measurement to decide the packing thicknesses. However, there is (or ought to be) some lateral adjustment possible, so the lateral alignment needed rechecking.

Dave 1 found the piston gland bushes and X shaped cylinder centre locators made by Alan. They had suffered some light corrosion, so required brief attention with a wire wheel. Andrew then removed the cylinder front blanking plates and fitted the cylinder centre locators.

The piston gland bushes and cylinder centre locators are designed to hold 25mm diameter stainless steel rods on the cylinder centrelines. The stainless steel rods we have are not long enough to run the full length of the slidebars, so we found a longer length of 25mm steel bar in the Works and used that instead. The weight of the bar will cause it to sag, thereby making vertical measurements inaccurate. But we were only interested in lateral measurements, so this is not a problem. Any lack of straightness of the bar can be compensated for by taking two sets of measurements, rotating the bar by 180 degrees between each set and averaging the results.

We started by considering the Fireman's side slidebar. Multiple measurements were taken and fed into a spreadsheet. This showed that the slidebar was almost perfectly parallel to the cylinder centreline. This is rather fortunate since the slidebar was a very tight fit on the studs, thus making lateral adjustment difficult.

Measurement of the Driver's side slidebar indicated that it was not quite so well aligned, with a 1.5mm lateral difference over the working length of the slidebar (approximately 520mm). Previous measurements suggested that this would be the case, so we are getting consistent results. Since the Driver's side slidebar was a clearance fit (as it should be) over the studs at the front, the first approach was to loosen the nuts and knock the front end of the slidebar sideways with a mallet. A quick re-measure suggested that this had improved the situation, with the misalignment reduced to 1.2mm; still more than we want though. Further adjustment with the mallet may be possible, or we may have to file the sides of the holes in the slidebar a little to get the alignment within what we consider acceptable limits; something we will attend to at the next working party.

In conclusion, we made some good visible progress at this working party. The slidebars are on, the crossheads are well under way, and much paint was applied.