"The worst problem is that the spindle of the regulator valve is about 10mm higher than the spindle in the side of the smokebox, so I had to tilt the regulator valve down to point towards it as shown in the top right of the photograph. It will need a connecting piece with a fair amount of angular freedom to connect the two, and I'm doubtful as to how well this linkage is going to work."
I had a similar problem with one of my locos and it was solved with a 6mm "round end" allen key and corresponding high tensile steel cap screw. I managed to affix the suitably shortened cap screw to the reg. spindle with a stainless steel bar bent in a U shape and drilled through the uprights of the 'U' with lock nuts inside the 'U'.
(Hope that makes sense)
Then I machined the allen key down to form the smokebox spindle, obviously with the 'rounded' end of the allen key mating with the cap srew head. All a bit simplified but it did work and still does.
The beauty of it is you get the angular freedom you need without any slack, just as it would were you to use the key to get at a screw at an awkward angle.
Thanks, that sounds an excellent idea. I'll need to sort this problem out soon and Modelworks have shown no sign of producing the missing part, so I was planning to fabricate some sort of universal joint if they don't come up with something soon. The spindle through the side of the smokebox is 5mm diameter and about 40mm long - I don't know if it's possible to get hold of a cap-head screw with a long plain 5mm shank that I could adapt to fit, silver-soldering a stub of allen key into the head? I don't have the facilities to turn a 5mm shank on a larger allen key. Alternatively I can probably silver-solder a U-shaped arm onto each fitting and fit a disc between the arms to form a crude universal joint.
It's true I did have to turn the allen key down to suit the smokebox gland box, leaving the required length protruding inside the smokebox to sink firmly into the cap screw head.
Your disc idea sounds intriguing but I can't picture the joint like that myself. I would have thought if you angle your regulator spindle to point down a few degrees so it intersects with the horizontal sitting smokebox spindle around half way. Then assuming you can secure the cap screw to the reg. spindle (my reg. valve had a threaded spindle and nut to secure the lever), whether silver solder (problems with the ptfe in the valve burning?) or lock nut, the allen key head should mate with the cap screw at the point of intersection. Of course, there is a limit to the angle...