February 2025

Due to Andrew's shift pattern, the February working party took place during the working week, from Monday through to Wednesday. Dave 1 and Dave 2 were also available, which meant that reasonable progress could be made.

The C2 has been invited to take part in the Ffestiniog Railway 70 gala in June, which will involve a cavalcade of locomotives on the Cob. The C2 last ran on the mainline in August 2023, and is still in running condition. However, back then we identified a problem with the length of the engine to tender drawbar.

Andrew had designed the length of the original engine to tender drawbar very carefully, considering the clearances between the engine and tender frames on various tight radius curves. But we had failed to realise that the cab overhangs the rear headstock of the engine by 5 inches. When we took the locomotive out of the C2 Shed, the front of the tender frames scuffed the rear of the wooden mock-up cab, indicating that there was less clearance than we had intended.

We had intended to make a longer engine to tender drawbar at some point in the future, but another invite out onto the mainline gives us a deadline to work to. Andrew therefore drew up a new drawbar, 5 inches longer than the original, and sent the drawing out to metal suppliers for quotes. Meanwhile, using the hydraulic press, Daves 1 and 2 pushed the bushes out of the original drawbar ready for re-use in the new one.

Dave 1 had been concerned that the regulator linkages were worn, as there seemed to be plenty of play in the 12mm pinned joints. He had proposed to ream the holes out to half inch diameter, and then make new larger diameter pins to fit. Dave 2 therefore measured the holes in the linkages and found that they were already over half inch diameter. A quick check of the drawings showed that the holes should be 13mm diameter, giving a clearance to the 12mm pins. Measuring the existing components showed that there was little wear, and that the play is no greater than intended. Panic over! That has saved us a bit of work.

One part which we knew would require repair is the regulator valve spindle. It has a threaded end, but the existing component has little thread remaining. Making a new component would be difficult because of the shape of the other end, so it was decided to cut the damaged section off, to weld a new part on, and then to re-machine the threaded end.

Dave 2 found an offcut of steel bar and turned it down until it was a little larger than the existing spindle. He cut off the damaged threaded part of the spindle, and turned weld preps into the ends of both parts. We will weld the parts together at the next working party so that Dave can re-machine the new end.

On Tuesday afternoon, Geoff completed his allocated tasks at Boston Lodge a couple of hours early and so kindly offered his services to the C2 Project. We have a number of components in the process of being painted, and we recently bought some new cans of paint. Geoff therefore applied paint to some of the primed components (mostly draincock operating linkages), and applied extra coats of paint to other components which needed it (lubricator drive brackets and radius rods). This provides corrosion protection for the components which have been cleaned.

To avoid wear, it is always important to align parts of the engine which move relative to each other. Some years ago we spent quite a lot of time measuring the cylinders and motion brackets with a laser, to ensure that we could align the slidebars with the cylinder centrelines. Andrew and Zoe have made packing pieces to be fitted at each end of the slidebars which will enable the slidebars to be fitted exactly where we want them.

The crossheads link the cylinders and connecting rods, and slide along the slidebars. As such, they need to bring together three major components very accurately. Deciding how to re-machine the crossheads, to keep the cylinders, crossheads and connecting rods all in alignment, is a taxing problem to which Andrew and Dave 1 turned their attention.

Measurement of the crossheads showed that the mounting faces for the top and bottom slippers were further apart than they should be. This would account for the packing pieces which we discovered when we took the engine apart.

There is also considerable wear of the little end bearing side faces. We will re-machine these faces to a greater than nominal dimension to ensure that they are flat. Inspection of the little end bearings shows that, by making the bearings over-length, it will be possible to restore the correct axial clearances. The extra material in the bearing side faces means that they can be machined to align the connecting rods without worrying too much about exact the position of the crosshead. That's one less variable to try and juggle with.

Dave 1 trawled through the log books in which we record all our measurements, and found the measurements that he and Paul had taken some years ago when checking the alignment of the cylinders and slidebars. Andrew also found a spreadsheet which Paul had used to calculate the slidebar packing from those measurements. Collating this information provided definitive dimensions for the relative lateral and vertical positions of the slidebars and cylinder centrelines.

At this point we know where everything wants to be relative to each other. But how to machine the crossheads and slippers to make sure the relative positions are achieved, given that there are no reliable datum faces on the crossheads? Keith was consulted and, as always, gave excellent advice. The plan we have come up with is to fit the bottom slipper and the piston rod into the crosshead, and to fit a temporary lengthened gudgeon pin into the little end bearing centres. Using the piston rod and temporary gudgeon pin as datums, the assembly can then be mounted squarely on a milling machine and the slot for the slidebar can be machined in the bottom slipper while in situ. This will ensure that the slidebar slot is correctly aligned with the piston rod, the latter of which coincides with the cylinder centreline. The top slipper will have to me machined separately, but this can be done by taking measurements relative to the bottom slipper. If it all sounds rather complicated, you can understand why it took Andrew and Dave 1 a couple of days to get their heads around it!

With a plan now devised, during a spell of welcome sunshine Dave 2 took the crossheads and their keeps outside and used wire wheels and a flap wheel to remove corrosion and scuff marks. The components look a lot neater now. Andrew and Dave 1 looked at the drawings to understand what fixings (fitted bolts, set screws, studs and castle nuts) would be required for the crosshead overhaul.

Andrew also investigated material costs for the slippers. The drawings show them to be made of bronze, but this is prohibitively expensive. Keith pointed out that all the Ffestiniog and Welsh Highland Railway locomotives have whitemetalled crosshead slippers. After further discussion in the pub one evening with Matt, we therefore propose to make slippers from brass, with pockets machined into them to take whitemetal linings.

Although Andrew and Dave spent most of the three days taking measurements and studying drawings rather than cutting metal, remaking the drawbar is now in progress and we now have a very clear plan for overhaul of the crossheads. The latter was something that had been worrying us, but we now feel quite confident about it. Thank you to Keith and Matt for their very valuable advice.