I've been trying to work on my B5 for the last few days. Nothing is ever easy....

Having finally succeeded with the coupled wheels.... getting me this far

I turned attention to the valvegear and bogie. Ah. Oh buggar.

The bogie needs to be drawn in toward the coupled wheels by a good 8mm or so. Unfortunately I couldn't pull the link bar in to this degree (I managed it on the C5 only by cutting it and drilling a new hole, which managed to wreck one of my dremel drills), so I took it off entirely. I drilled the hole through the cylinder block necessary to fit it, and then began to think. A-ha! Parts of a 2P in the spares box- I found a screw just the right size and a spring. I turned the B12 bogie upside down and sat the spring in the circular hole in the bottom of it. I then slid the screw through the bogie, screwed the cylinder block onto it, and then screwed that onto the little metal lip on the B12 chassis, getting me this far

Problem is that I now find that the clearances are too tight for it to go on anything but the very gentlest of curves! Thinking back to the C5 I remember now having to file down the inside faces of the cylinders and the bottom of the chassis block. Wish I'd remembered that before putting it all together....