I see that there have been 1883 views of this thread, so time for another update.
Andrew from Wizard Models has been very helpful (as always!) in helping me understand the castings for the hopper door control gear. You may remember this picture, where I highlighted the two different casting shapes that were in my kits.
The castings on the bottom right are the correct ones. The triangular part to the left of the bracket represents the semi-circular plates that lock the door open. Geoff Kent mentions adding these in his MRJ article, so the 51L moulds must've been updated at some point to better represent this. New castings arrived very quickly in the post.
I still felt, though, that the two plates need to be included. These were marked out on a 3mm x 0.25mm strip of nickel silver from the useful Palantine Models etch
. I guesstimated the curved part to be 2.6mm tall, 3.5mm wide and a radius of 4mm seems to work ok. There is a lug at the top, which I made 0.5mm square.
These were roughed out with jeweller's snips and then filed to shape. The castings have a very pronounced draft, so I used a curved scalpel blade to scrape this back a bit so that the plates would stand vertically. The new plates could then be Loctite'd in place. The photo attempts to show the marked out plates, the draft of the castings, and a finished unit.
Holding such small pieces to shape them accurately is always a challenge. Seeing the lines to file to is even more so. By adjusting my vice to hold the parts at a comfortable attitude and arranged to catch the light, the filing process wasn't too bad. I even managed to avoid feeding the carpet monster on this occasion.
One further point about these castings: they are intended to be fixed to the underside of the wagon top-plate such that the bracket assembly pokes up into the holes in the top-plate. Before fixing, cut about 3mm from each end of the bar, otherwise this will impede the bearing carriers. As I've moved the spring position 1mm further away from the wagon floor than intended, this would just impede the spring movement. If built as designed, the ends of the beams will try to occupy the same space as the tops of the bearing carriers. This is pretty obvious, but not called out directly in the instructions.