Overhaul update
The SMF working party met on Wednesday this week instead of the usual Thursday to trial – and hopefully permanently – fit the connecting rods after checking clearances.
In the boiler shop, we had noticed the previous week that riveting the foundation ring was underway on the right side, and that some side stays had been fitted.
In December, the same had been done to the left side, with some more stays fitted to the right.
Also soon to be final riveted is the firehole door, with some bolts removed to reveal the holes.
The smokebox still stands in the workshop, but now in a proper colour.
The main focus of the day was the assembly of the connecting rods on to the engine, and this shows the method of positioning these heavy items; we started on the left side. The LMS helpfully provided a lifting ring below the running plate from which the chain blocks could be hung, while the pump trolley was an additional precaution, but useful to allow the rod to slide as needed in the fore and aft direction.
Using the chain block to lift the rod, the little end is already sitting on the lower slide bar.
The big end entered on the crank pin...
... and pushed fully home. The return crank was then fitted and the retaining nuts tightened.
This showed a problem at the little end, which would not align with its recess in the crosshead.
The return crank was again removed and examined as there was no clearance between it and the connecting rod bush, and the reason found. Note the lip surrounding the bright contact face.
The return crank for the right side has no such lip. This is an original as fitted to the engine in 1934; the other side crank was not with the engine at Barry and was replaced by one from a Black Five. Apparently, the LMS modified the design, and it will be necessary to modify the bush and / or return crank to make them work.
The left side could not proceed, so the rod was removed and attention transferred to the right side. The methodology now established, all was aligned to push the big end on to the crank pin.
This was as far as it could be persuaded to go. A measure with the micrometres revealed that there was no clearance between the internal diameter of the bush and the external diameter of the pin.
Reversion was made to former craftsmanship methodology of using a spoon scraper to remove excess white metal from inside the bush.
Here was see the surface part way through the process.
The job was completed by fine honing with a rotary abrasive. Once fitted, the clearances between the bush’s outer face in the connecting rod and return crank were considered inadequate and the rod removed andtaken to the milling machine to increase this to one sixteenth of an inch. With all the clearances corrected, it should be possible to assemble the connecting rods before the new year starts.