West Somerset Railway Association

The next job was to make and permanently insert the fitted bolts and nuts for the cylinder joint. The cylinder block was then taken off the ‘coffee table’ and turned over to stand on the floor upside down as seen in the photo. One of the extension frame blanks has been placed where it has to be fitted when after machining.

Each end of each cylinder bore 5 studs have to be fitted to reinforce the casting around the steam ports. Three of these studs are shown during manufacture – the one with the plain section to be fitted across a steam port. The ends are finished with square sections used to drive the studs into position when the squares are then cut off.

This photo. shows one cylinder end with the 5 studs in position and the ends dressed off. 3 can just be seen within the steam port and 2 between the cylinder bore and the steam chest below.

A close up view of the steam port showing the studs in position.

This photo shows one new extension frame plate on the milling machine preparatory to being set up for machining to size.

This photo shows the old extension frames which have been retained to act as patterns  for the machining. The new plates will be thicker to resist cracking and/or bending when 4561 is next in service.

Having set the cylinders up the first check made was that both castings were sitting flat on the ‘table’. This was done between each casting and the ‘table’ top using a feeler gauge which was 0.002” thick – i.e. two-thousandths of an inch.

These photos show the joint between the cylinders secured with temporary bolts. In the centre is the hand tool made to skim the casting surfaces around each bolt hole to ensure that the fitted bolt heads and nuts when inserted can be tightened evenly onto the casting surfaces.

A further alignment check was made using a straight edge across the cylinder end faces and the edges of the cylinder flanges. The straight edge is an 8 feet long steel bar which has been ground true over its length which is kept solely for this sort of work. This check was also done using feeler gauges to ensure there were no unacceptable gaps compared with the GWR standard tolerances for machined parts.

This photo shows one of the cylinder faces liberally coated with the jointing compound.

The two castings were rejoined on the ‘table’ and the same alignment checks made to confirm all was well before the bolts were tightened. The photo shows the cylinder flanges with bolts in place and evidence that the jointing compound has squeezed all around the joint

Machining of the surface table to form a level datum for assembling the cylinders has been completed and the resulting block mounted on a welded steel framework. It is now referred to as the ‘coffee table’ although it is considerably more substantial than these normally are!

Two photos that show the new cylinders having been set up on the ‘table’ with temporary nuts and bolts through the central flanges to hold the two castings steady. Once Ryan is satisfied that these are correctly aligned he will make and fit new fitted bolts for these flanges to hold the two cylinders together in service. Note that a small screw jack has been set up under each cylinder casting to take some of the weight to assist making any movements needed.

Work on the horn blocks and stays has now been completed and all have been fitted as can be seen in the photo. of the mainframe. This has enabled adjustment of the frame stands to leave clearance for the fitting of the spring hangers, two of which can be seen in position painted in light green primer.

In order to align the cylinders accurately they will be set up using a known level flat surface table with square sides to act as a datum base. This is shown in the photo.  under preparation on the horizontal milling machine where one side is being machined square.

Once the cylinders have been joined the next step is to fit 4561’s new extension frames and front bufferbeam. The two partially prepared extension pieces and the buffer plank have been brought into the workshop in readiness.

During October Ryan and Don visited the South Devon Railway at Buckfastleigh to discuss the possible needs for steel plates when work resumes on 4561’s boiler and firebox. These plates have now been delivered and are seen in Williton yard.

Ryan has made good progress with fitting the horn stays. This photo shows the RL Horn with its stay as fitted. The upright mating faces of the horn block and  horn stay are machined at an angle of 2 degrees from the vertical such that when the retaining nuts are tightened these faces become the register for locating the stay. A gap is left between the bottom horizontal face of the horn block and the matching face of the stay. This allows for adjustment when 4561 is in service should a stay show any signs of loosening under the pounding this part of the main frames have to sustain when the locomotive is working.

This photo shows how the upright faces of the stay are machined. The normally vertical spindle of the milling machine has been set over at the 2 degree angle to cut the stay face as it is traversed past the cutter. This is a separate operation for each of the 4 upright faces of the stay.

Here we can see the other 4 horn stays which, having been fitted and marked for each of their particular locations, have been put to one side pending the next operation. So far these stays have been fitted using one stud in each horn block but to complete the installation a second stud is required in each horn block,  i.e. a further 12 studs have to be made and fitted.