C2 Project News

November 2022

Progress with the Cab, Cylinders and Turbogenerator

Our November working party was a week earlier than normal, owing to a planned power outage on our normal weekend. As usual, it lasted longer than just the weekend, with Andrew arriving on Wednesday and Erle on Thursday, being joined by Paul from Friday and Helen and Dave 2 from Saturday. Erle continued his work on the turbogenerator, while the rest of us worked on aspects of the cab floor and cylinder covers.
Starting with the Turbogenerator, Erle had fitted all 110 of the newly-cast blades to the turbine disc, and prepared the turbine band which was curved from a laser-cut perforated strip. The joint in the band needed welding together, a job requiring some expertise as it's just two short joints and possibly one shot at getting it right. We decided this was best done by an expert so consulted Bob the coded welder on the works staff, and he's done a lovely job. The next stage is to rivet over the head of the Turbine Blades, and dress the weld to minimise imbalance of the turbine rotor.
The TIG-welded joint in the turbine retaining band
The new Governor Centrifugal Weights have now completed their milling on the Bridgeport and Wanderer machines. The shape of these is very complex and required numerous machining operations with different fixtures, but they are now complete. The next step is to get them surface hardened. They closely match the originals in size, shape and weight, except that they're not rusty and broken!
Stages in machining the complex shape of the turbine governor weights.
Stages in machining the complex shape of the turbine governor weights.
Stages in machining the complex shape of the turbine governor weights.
The completed governor weights, compared to the damaged originals
Governor installed on the turbine disc.
The next stage on the loco chassis is the slidebars, crossheads and pistons. These rely on the rear cylinder covers being fitted, so we decided to do a trial fit. In due course we will need to order new studs, so Paul measured up the existing ones and compared them to the drawings - as usual there isn't a exact match and we may need to adjust some dimensions slightly to suit our needs. Paul then selected the studs in better condition and Dave 2 cleaned these up for temporary re-use. Dave 2 also cleaned all the mating faces, inserted the studs and trial-fitted the cylinder covers. This all sounds straightforward but there are a lot of holes and studs to deal with!
Trial fitting of the piston into the bore from the front
We also wanted to ensure that the piston and rod could be fitted via the cylinder front cover with the rear cover in place. We didn't anticipate problems but it was worth checking as the clearances here have changed as a consequence of the re-gauging and new front bufferbeam.
Andrew arrived on the Wednesday afternoon to make an early start with the aim of fabricating the new cab floor. Because of the restrictions of the FR loading gauge, the locomotive cab must be returned to that of a narrow cab, the like of which was fitted to this locomotive prior to 1999 in China. Andrew spent a few days measuring out the components from steel stock angle, carefully setting them out and then welding them together as can be seen in the following pictures.
Andrew has set out the basic cab floor frame to tack weld it together. This was then offered up to the loco frames to ensure that it was correct. Remember, measure twice, cut once!
Welding in the intermediate ribs which will support the floorboards.
The cab floor outer frame trial-fitted to the loco frame after tack welding.
The completed cab floor frame placed in position.
Rob and Norman, two of our friendly wood workers in the carriage works, have kindly offered to construct us a mock-up cab made of ply. This will enable us to finalise the cab layout, sightlines and gauging clearances in the new year.
Providing access to the cab floor are the steps. We had stored these when dismantling the loco, but they were pretty rough. Both had been badly bent, probably after colliding with something, and one had a weld repair that was terrible in alignment, strength and appearance. I wish I'd taken a photo of them before we started! But I have found some photos showing them when we loaded the loco at Dahuichang - see below.

We're well aware that a lot of parts of this loco are ending up in the scrap skip, so if we have a chance to re-use original components we like to take it. We decided the cab steps were worth the effort to refurbish although it might well have been easier to make new.
Helen and Paul straighten the cab steps with by localised heating with the oxy-acetylene.
The refurbished original cab steps.
Here is the cab floor in place on the loco frames. The floor boards will be placed over this frame. Note one of the original cab steps, temporarily clamped in place.
Helen started the work by cleaning up the rusty parts with wire wheel and flap-disc, and then Paul assisted with straightening by heating the bent parts while Helen realigned them. This had to be done in several different planes, and one was so banana-shaped that we cut the step from the stirrup and straightened them separately. The terrible weld repair was cut and realigned properly, and Andrew re-welded it with a good quality weld in the right place. We'll give them a final clean and paint at the next working party and then they'll be ready to re-attach to the cab floor frame. There will be one subtle difference - for clearance reasons we will attach them to the inside of the frame angle rather than the outside.
We all think that the original boiler, cleaned and painted, looks rather glorious mounted on the locomotive chassis once again. Sadly, making it look nice isn't enough to satisfy the boiler insurers, so we are still in need of a new boiler. However, progress is being made to that end.
We are often asked "Who is going to make the new boiler for you?". The answer is "We haven't decided yet". You may be surprised to read that this isn't due to procrastination within the C2 Project, but is because before we place an order for the new boiler we need to get the design approved first.
Paul and Dave have both spent a considerable amount of time carrying out and checking design calculations for the boiler. But this is rather too similar to their day jobs to be enjoyable, and we have a disadvantage that we do not currently have a relationship with the boiler approvals organisation. Therefore the C2 Project have subcontracted the work to Jon Whalley, the FfWHR's Chief Engineer. Jon has designed and got approval for all the recent FfWHR locomotive boilers, and has good contacts with the boiler insurers, so is in an ideal position to be able to help us. With the C2 Project's consent, Jon has raised an order with British Engineering to start the process of getting the boiler design approved, and has initiated discussions with them. This has led to a number of aspects of the existing boiler design being queried. Some are easy to alter, others less so.
Locomotive boiler design is something of a "black art" and the applicable standards were developed in the era of the slide rule rather than detailed stress modelling. There is a need for compromise between strength to withstand the pressure, and flexibility to cope with thermal expansion. Corrosion, erosion and fracture mechanics are also important. Some designs work well and some don't, sometimes without anyone really understanding why. History tells us that making quite minor changes can potentially have a big impact on boiler performance or reliability, and for this reason the C2 Project want to make as few changes as possible to the proven boiler design.
One of the problems which the C2 Project face is that the boiler is not of typical British design. So when the boiler insurer says "I don't like the look of that feature", is that because it is a badly designed feature or is it just because it is different to most previous boilers seen in Britain? These are the discussions which are beginning to take place. In some areas, a minor change to manufacturing processes will resolve compliance issues. For example, in recent years the type of fillet-welded stays used on the C2 has come to be favoured over the J-prep welds specified in the old British standards, so it is possible for preferred designs to evolve in the light of experience.
Our next working party will be over the Christmas period, and we have published our intended dates for 2023 too - please see the sidebar menu.
In the meantime, here are a couple of old photos recently purchased by Paul, showing C2s in their natural environment of a Chinese Forestry Railway:
Yabuli Forestry Railway 06 hauls a train of logs and brushwood in 1998. Photographer unknown, original slide purchased by Paul.
Yabuli Forestry Railway C2-161 at the stabling point in 1998. We believe this is Harbin works number 161. If so, it was built in 1963, the last loco of Harbin's first (large) batch of C2s. New C2 production at Harbin resumed in 1975. Photographer unknown, original slide purchased by Paul.
News Archive 
October 2022