C2 Project News

February 2024

Working Party report from February 2024

In our second working party of 2024, production of components was in full swing with 4 machines running simultaneously at one point. Two lathes, one milling machine and one radial arm drill!
Fuel for the working party from local cake baker CelEmmabrations (Click here)

Precision machining

We all know that steam locomotive technology is normally considered quite crude. Locomotives will still work even when they are completely worn out, although obviously they work better when everything is new and tolerances are as intended. However, some parts will always require tight tolerances to ensure that they fit correctly.
The reverser weighshaft cranks pins need to be a press fit into the holes in the cranks, to stop them falling out. Make the pin too big and it will be impossible to push it in. Make it too small and it will not hold itself in place. On Friday, Dave 1 therefore set out to make the three reverser weighshaft crank pins (one for the operating rod and two for the lifting links). It took a couple of days to make the pins, as we were working at the limits of accuracy of the lathes at Boston Lodge, but eventually all three pins were made within the specified tolerance bands.
Stainless steel pins for reverser weighshaft cranks.
While Dave was doing this, Andrew recommenced work on the slidebar packers. Dave had made one of them last year, but it was unfinished. The thickness of the packers is important, to ensure the slidebars will be aligned with the cylinder bores. But there is an added complication. The slidebars are held in place with fitted bolts, but the holes in the motion brackets are oversize (due to wear). Pushing a bush into the oversize hole is unlikely to be successful, since pushing the fitted bolt in will likely push the bush out again! The bush has therefore been made integral with the packer. Therefore, not only does the thickness of the packer need to be machined precisely, so do the inside and outside diameters of the integral bush. Again, it took time to achieve the required tolerances, but Andrew managed it. Final task was to cut the edges off, to make the packers square. A hand held slitting disk seemed very crude for this operation, but resulted in quite acceptable results.
Slide bar packers
Chris and Erle joined us on Saturday and Sunday. Chris set about repairing the holes in the draincock linkages. These holes were worn, often oval, and so have been reamed to a larger diameter. This will allow us to fit plastic bushes, which we hope will reduce wear in future. If nothing else, plastic bushes will be easier to replace should wear occur.
The draincock operating rods are in a vulnerable position underneath the cylinders, and our originals look as though they've been knocked about on numerous occasions. Chris therefore started to make replacement operating rods. Each rod comprises a steel bar with an eye on the end, and two notches which line up with the drain cocks themselves. Rather than try and forge the eyes, as the original drawings suggest, Chris cut eyes from 10mm steel plate and Andrew welded them onto the rods.
Preparing to weld on the "eyes on the new drain cock operating rods.
The old drain cock operating rods (top) are battered and twisted. The new rods (below) after welding on the new eyes. These then required forming to shape and drilling.
After a little fettling, the eyes look very neat. Next task will be to measure the drain cock positions (we're not assuming they are exactly to drawing!) and make notches in the draincock operating rods at the appropriate positions. We'll do this once the rest of the mechanism is assembled to ensure that all four draincocks open at the same time.
Forming the eyes in the drain cock operating rods.
Eyes formed in the drain cock operating rods
Old and new drain cock operating rods.
Erle continued work on the reverser baseplate. Andrew helped him move the block of steel to the machine shop, and Erle set it up on the Wanderer milling machine. Machining the baseplate out of solid is not a quick process, and generated an impressive amount of swarf, but Erle is making good progress. It has occurred to him that some of the bolt-on parts of the reverser could be made integral with the baseplate since it is being machined from solid. This sounds like a good idea as it will reduce the amount of steel to be removed, and will likely end up with a stronger component.
Milling the new reverser baseplate out of solid.
The old reverser baseplate is a pressing.
Old and new (partly made) reverser baseplates side by side.
After a good weekend of making things, Andrew and Dave stayed on an extra day. Monday was spent on lighter duties, ordering tools and components (new expansion links, fitted bolts, plastic bushes, etc.), and planning the next working party. Having completed most of the tasks we had planned at the previous working party, we have now re-filled the whiteboard with new jobs for the next one. Drawings, material and tools should all be available, thereby hopefully avoiding any delays.
Andrew and Dave couldn't resist getting their hands dirty though. A minor task which was required was to identify the thread in the holes in the draincock weighshaft bearings. These holes are a Chinese adaption, to accept grease nipples (good idea!), so do not appear on the original drawings. After a bit of trial and error with a thread gauge, the thread was identified as 1/4 inch BSP. Suitable grease nipples were quickly located, and after the threads were cleaned, the grease nipples fitted. This showed up a problem with a couple of the bearings; the grease nipple interferes with the shaft inside. We'll have to make some small spacers to avoid this.
The next planned working party will be at Easter when we hope to make more pins and collars for the motion and draincock linkages. Sometimes it seems as though there is an infinite list of things to make, but we are working our way through them.
Nice enough to sit outside and eat your lunch in February.
Easter 2024