Let’s get 4561 rolling

2nd April 2021

Front footplate brackets and angles recovered from the old frames have been prepared ready to be fitted to the new behind the front buffer beam. Included are the front footsteps.

Fitting of the brake and spring gear is being progressed. This is a check fitting of a brake hanger and cross beam (below frame plate) to check that all parts are available. Either side of the hanger firmly bolted to the frame plate are the ‘J’ brackets (light green) from which the coupled wheel springs will be suspended in due course.

Safety chains are to be fitted to the brake beams in case of breakage in service for which the bolts are being made.

When the extension frames were assembled some fitted bolts and nuts were omitted from the front pony truck pivot. The remaining 6 bolts and nuts have now been made.

Items are gradually being fitted to the leading buffer beam now it is in place. The rectangular hole needed in the centre for the front coupling has been finished to size and the coupling  hook inserted. Hung in the hook is part of the screw coupling linkage which is being refurbished. The pipe flange alongside is the leading end of 4561’s steam train heating pipe to be. The small item next to the buffer is part of the bracket on which the leading vacuum brake hose is to be secured when 4561 is hauling a train in traffic.


With the main horn block sets in place in each frame plate it is critical that the gaps between each pair are finished to known sizes to ensure the correct tolerances when the axleboxes are fitted. Not only must they be a known distance apart but in line across and square to the frames; and in line along each side parallel to the locomotive’s centre line. The horn faces are ground to final sizes to ensure they are smooth, flat and parallel.

For this work the workshop team has developed the multi-fit horn guide grinding machine seen in the photograph mounted between a pair of horn blocks and in use to grind their respective faces. The machine’s capabilities have been checked and confirmed to give good results on some other locomotive work that Williton Works has been involved with.


12th March 2021

Steady progress is being maintained on the frames with the front buffer beam (now fully drilled) bolted into position and the buffers fitted having been overhauled. These mask the work done on completing the fitting of the front dragbox and the leading pony truck centre. Yet to be done to the buffer beam are drilling the hole for the front steam heat train pipe and completion of the cutting of the rectangular hole in the centre ready for fitting the front coupling hook.

To reinforce the ends of the buffer beam outside the frames, brackets are fitted between this and each main frame plate. These were on hand but have been found not to comply with the design drawings so are being replaced with correct versions, thanks to Bob Meanley being able to provide a copy of the appropriate drawing.

The incorrect buffer beam brackets awaiting their fate.

23rd February 2021

Having completed the assembly of the extension frames and cylinders with all the bolts fitted and tightened down the opportunity was taken to try the pony truck in position to confirm clearances would allow truck to swing adequately. Although the extension frames were thicker their profiles should have been unchanged but the lower bends at the front of the cylinders were more generous than desired. The photo shows this bend on LH frame highlighted to show lack of clearance from pony truck (light green).

The spare metal was removed by hand grinding both LH and RH frames to the required shape.

The next step was to try the complete extension frame assembly (which was still upside down) in position in the main frames. Using the shop overhead crane it was first lifted over to a clear section of the shop floor :-

With care it was lowered down to the floor resting on the back of the extension frames :-

These photos show the top of the smokebox saddle and the cylinders. By care in lowering and moving the crane away from the camera the whole assembly was slowly turned over to rest on the bottom of the cylinders on the floor. This allowed the crane slings to be adjusted for the next lift.

The second photo shows the assembly having been lowered into position within 4561’s main frames.

Nuts and bolts through the main and extension frames behind the cylinders and a frame stand to support the front of the frames enabled the assembly to be levelled and the crane slings removed. To judge appearances the opportunity was then taken to put 4561’s smokebox on its saddle.

19th February 2021

With the extension frames and racking stretcher finally fitted in position on the cylinder block it was necessary to make and fit all the bolts and nuts needed for security. This photo shows the work in progress.

At this stage the racking stretcher plate has been bolted to the cylinder block with the corner angles either side bolted through their respective extension frames. The remaining extension frame bolts are being inserted and when fully driven in will be secured with the nuts that can be seen ready in the centre of the stretcher.

When a batch of fitted nuts and bolts is required it is usual to cut lengths of bar steel as blanks as in this photo. These can then be machined to cut and form the screw threads to fine limits depending on the type of fit required. Ideally the bar steel is supplied as a hexagon shape the size needed.

This photo shows a typical set up for a bolt being machined in a screw-cutting centre lathe. The head of the bolt is held in the rotating lathe chuck on the left, the other end of the bolt blank being supported on the tailstock centre. In between the cutting tool mounted on the lathe saddle tool post is traversing to the left as it profiles the shank of the bolt.

With the extension frame assembly almost complete attention has turned to the leading pony truck. The frame transverse assembly seen is to straddle the leading wheelset being ‘steered’ by the two arms to the left. In checking the condition of the main securing bolts these were found to be worn out and are being replaced. A reject bolt is seen on the RH arm with its replacement in the frame above.

A close-up of the defective bolt. It can be seen that the screw thread is severely worn and not capable of providing a strong fastening with its companion nut when fitted and tightened.


Having corrected the pony truck frame the opportunity was taken of setting it up in position in the main frame assembly as shown. It will be seen how the rear ‘steering arms’ are coupled to a pivot block mounted on the front horizontal frame stretcher.  This block needs to be securely mounted to withstand the shocks in will experience when 4561 is in traffic.


When examined this block was found to contain badly worn bolt holes and signs of previous repairs symptomatic of having been allowed to remain in service with loose bolts. The mounting face is seen in the photo. and shows the variations in sizes of the four corner bolt holes. For rectification this block has therefore been sent to specialist welders experienced in the recovery of old cast iron castings. These holes will be filled in before being re-drilled the correct size in the right places.

25th January 2021

Looking back at the lockdown challenge from a couple of weeks ago:-

The central hole is where the piston rod will go. The hole to the left in the back cover is where the anti-compression valve (cylinder safety valve) will be fitted to the outside; the hole in the cylinder wall is where the cylinder cock (cylinder drain valve) will be fitted outside when 4561 is assembled.

Having completed the milling of the frame extensions the inner end of one is shown where any rough edges or machining marks have been finished off by dressing (de-burring or removing sharp corners from) the plate edges and around the bolt holes.

Each plate was then set up on the vertical milling machine in order to spot face a number of the bolt holes to a common depth for when each extension frame is bolted to its associated main frame plate. This is to compensate for having increased the extension frame thickness in order to minimise the possibility of cracking in service while maintaining adequate clearances between the fixing nuts and bolts and the leading pony truck.

This photo. shows the fully machined LH frame extension in position on the cylinder block. It can be seen that it is supported on the underside of the smokebox saddle and butted up against, and to be bolted to the back of the cylinder casting. The spot faced holes may be clearly seen.

A view taken from behind the assembly shows the profile that was machined on the inner end of the LH frame extension. This has been done to ensure adequate clearances are left between the frame extensions when finally assembled to accommodate 4561’s leading sandbox between the frames.

With the machining of both plates completed both are now in place in the cylinder block in order to check clearances and to confirm the dimensions between them for manufacture of the racking plate.

This is a horizontal frame stretcher to be fitted tightly between the frame extensions and bolted to the underside of the cylinder to provide reinforcement of the joint between the two cylinder castings and assist rigidity of 4561’s main frame assembly at the front where high stresses will have to be endured in operational  service.

This photo shows the racking plate in position fitted between the frame extensions in order to mark out and drill the bolt holes between it and the cylinder castings.