I set myself a couple of goals for the session, the first was to get the smokebox door ring to fit in the smokebox barrel, the second was to assemble the cab.
Staring with the smokebox door ring, I had decided that filing it would be a complete pain and a last resort if I couldn’t work out how to hold it in the lathe to turn it down.
The amount of rim left after turning would be miniscule so no chance of griping it by that and being able to turn it. I didn’t have any material of a large enough diameter to make a mandrel so I decided to try holding it on the outside of the jaws. Because it’s white metal it would be really easy to distort or mark it. I cut a strip of aluminium drinks can to length so that it would wrap around the circumference of the inner ring but not overlap to throw it off centre. Once inserted I carefully opened the jaws until they were just gripping the part.
I started off by attempting to have it hard up against the jaws in an attempt to get it running concentric but the rivets on part of the ring prevent it from sitting flush so I had to move it away from the jaws and then use a pair of thin parallels inserted between the jaw and the face to ease it until I reduced the wobble to an acceptable level. Despite trying to get it perfectly flat on my glass sheet I wasn’t able to without damaging said rivets so I had to accept a little wobble.
I had the lathe running at about 100rpm or less, I set the carriage stop so that I wouldn’t inadvertently chop of the front rim and then moving in 0.050mm at a time I skimmed the rim at the back of the part. The first cut quickly proved that the outside of the part wasn’t completely circular either. I patiently took cuts until the rear rim was completely concentric, all the while checking the fit of the smokebox front after each cut.
In the end I took off a depth of 0.750mm which equates to 1.5mm overall. That would have been a killer with a file while attempting to keep it circular.
Having got that to fit successfully I turned my sight to the cab. I have never had something so simple be such a complete pain in the posterior to get together squarely. Today’s attempt was my third go at it, and it still took both sides being removed and refitted twice before I was satisfied that it fit as I thought it should. The problem is finding some part of it in between all the rivets and window frames inside that you can put a square against, to hold the sides at right angles to solder them.
Next, I spent some time with a spirit level adjusting the horn block screws to get the chassis/footplate to sit level.
Having the cab as a datum I can now see that the Firebox needs a slight trim where it goes over the rear splashers so that it will sit level. Once I have done that I need to sort out where the boiler is currently riding on the centre splashers. The problem here being that there isn’t a great deal of clearance between the wheels and the splashers so I think that I will have to cut into the boiler clothing to get it to seat. Once I have the boiler seated, I can consider what to remove from the saddle(s).
I will start by soldering the cab to the footplate and trimming the firebox…
PS just as I was posting this, I moved the loco from the photo area to my workbench and managed to drop the cab on the floor. Now the first job is to solder one of the cab sides back on….