I made a start on the conrods after the Christmas break. I
hadn't been in the workshop for a fortnight and the first few days were spent fitting the cylinders, brackets,
crossheads and slide. Very time consuming.
I think the lazer cutter was at its limit at 12mm thick,
because the edges will need a lot of work to clean them up. I had anticipated this and allowed for it.
The photo shows how I set up the first rod for milling the sides, which is a cut 2mm deep. This leaves
me with an 8mm thickness between, the original being 1/4".I should have blocked up one end as the curved
edge now slopes! Must be the Christmas break. I shan't make that mistake on the other five.
Its all very well getting things lazer cut, but there is a lot of work to clean up the resulting edge.
The close up photo shows just how deep the grooves left by the cutter are. This rough edge also suffers
from having a thin, hardened skin, which blunts the cutters quite quickly! Having said that, a lot of time
has been saved and the lazer cutting firm supplied the steel too.
It takes quite a lot of physical effort to finish the rods to any reasonable standard. It
also takes its toll on files! But once through the hard skin, the steel will produce a nice finish after
going through various grades of emery and polish. This is a time consuming job. The bushes are phos bronze
and of the split variety, press fitted into the rods. I didn't have any luck finding the size of bush
commercially, without paying a hefty minimum fee; hence the phos bronze.
The gudgeon pin can't be fitted
as a one piece job without taking off the crosshead as there isn't enough clearance between the crosshead
and the wheel. Not really practical, as this would upset the piston setting,
so I've made it in two parts using a cap head countersunk on the inside with half the pin and then the
other half from the front. By doing up the nut, it also tightens the caphead. The crack between aids oil
distribution. Instead of case hardening as on the original, I've used EN8.
The whole lot has been assembled, but as I've only done the one side, I haven't been able to set the piston
position as the wheels won't turn smoothly until the rods are fitted to the other side. Now that it's
assembled, I can't think why I thought it necessary to reduce the size of the rear coupling rod where it
pivots with the previous one. All that work was a waste of time, and I could have had a larger diameter
connecting pin. Hindsight is wonderful.
Although there isn't much to show on this month's page, I did
have a fortnight off over Christmas and the rest of this month will be spent doing exactly the same to the
other side of the loco.