I have returned to my Hydra.
I have found this kit rather harder to build than the apparently similar Lomac-L from the same manufacturer because the angles for the deck set out on the top edges of the frames do not match up with the grooves for the deck etched into the curb rails.
Trying to compensate for too many things at the same time and using an awful lot of solder in the process I had ended up with a gentle lateral curve along the length of the first frame. The offset was about 1 mm so not enough to notice with the model on the layout but really annoying when looking underneath. I ended up taking the torch to all the gusset plates and the frames and rebuilding them.
Happy again I continued to ignore the sequence of assembly suggested in the instructions and added as many brass detail parts as I could.
This photo shows the re-worked frame. At least the parts were pre-tinned. The second curb rail went on easily.
The half-etched areas above the buffer locations had bulged upwards under the heat of the torch so I ground these down a bit.
I now had enough space to let the plates for vehicle wheels to sit flat. The support brackets for these went on next and so did the reinforcing plates for the couplers.
Now I really had to add the second side frame.
The error is a gap of most of 0.5 mm along the frame/deck joint except at the two ends of the frame. It seemed sensible to tack the frame at the centre and work outwards so I soldered on a strip of fret to give myself a foundation to work from.
And then, well I just added the wheels in their bearings. This was so easy, yet I had been anxious about these since I started. There is loads of space to manoeuvre the wheels and their bearings, and the model sat flat on the track at the first attempt.
This stage always seems like a threshold to me, it is the moment when a build goes from being an assembly of parts which still might get consigned to the bin, to the essence of a model railway wagon. I soldered the second side frame up solid (with more scrap fret to save solder), and the model is now "a wagon".