Chassis
Laying out the frames
After the ashpan the instructions start laying out the frames and the beam compensation. This is one of the small deviations I have made in the kit, preferring to go for sprung compensation in the form of Continuous Springy Beam (CSB).
Continuous Springy Beam
The first task was to layout the frames with the multitude of frame spacers to try and visualize what room I had and to work out if it was feasible to fit the spring wire for CSB. In laying it out like this I suddenly realised that I could use one of the frame spacers as one of the pivot points for the spring wire. It was one of the rear spacers around the motor mount, so the distance from this frame to the rear driving axle fixed one of the dimensions on the CSB plot. With a little help from contributors on RMWeb I ended up with the following diagram for the CSB pivot points.
Where the dimensions worked out as
a = 19.5mm
b = 28.25mm
c = 30.5mm
d = 20.25mm
The ashpan needed a slot cut in the edges near the frame to allow the spring wire to pass through and a couple of the frame spacers needed small slots cutout to allow the spring wire room to move.
Roller Bearings
The second modification to the kit can be seen in the above photographs, the fitting of roller bearings to the driving axles. This was prompted by an article in MRJ by Tony Reynalds. Again I worked out there was just enough room to bore out the axleboxes and fit roller bearings to the main axles. There are commercial roller bearing axleboxes which I dare say could be used as a replacement. However for scratchbuilding loco's, whilst not essential, a lathe is extremely useful. So I used a mini-lathe for this modification. I fashioned a D-bit boring tool from a short length of silver steel. A short length at the end was filed flat so not surprisingly the end profile is a D shape. This was then hardened by heating it to a cherry red colour and then quenching in an oil bath. The tip was then cleaned with a bit of steel wool to make the steel colour visible. As it stands the tip of the steel is very hard but this means it is also brittle, and sharp severe cuts may chip the tip of the steel so before use it is tempered slightly. This is done by gently heating the steel, as it gets heated the steel changes colour from a pale straw to a dark blue colour. The colour is a very accurate indicator of the temperature in the steel. For working with brass we just need to heat it up to a pale yellow / straw colour and then leave it to cool. Once we have one that we can mount it in the lathe.
The axlebox being square is mounted in a 4-jaw chuck on the lathe. To help the centering of the axlebox I put an axle in tailstock on the lathe and used this to hold the axlebox whilst tightening up the jaws.
Once happy that the axlebox was running true the centre is bored out to accept the roller bearing. The distance across the flats on the square axlebox is the same as the diameter of the roller bearings so the last bit is taken very carefully. The brass axlebox spreads slightly as the wall gets thinner and thinner, until you get to the point where there is just 4 corners to hold in the bearing.
Finally once bored out for the roller bearing don't forget to bore out the remaining axlebox bearing to clear the axle. There is no point fitting roller bearings if the steel axles are still rubbing against the brass bearing.
Frame Assembly
So laying out the frames and 14 frame spacers are layed out. The brackets for the CSB are soldered to the frames. The ashpan is showing the cutout required to clear the spring wire. 
Most of the spacers will only fit one way so you can't really go wrong, the only couple that needed care was the large X frame with the etched writing on, I wasn't sure how much of this would be visible under the boiler so I made sure this faced downwards and the the other one was the bolster attachment frame for the front pony truck. The slot and tabs allows it to mounted either way round, the attachment holes should be towards the rear and this matches up with the side frames. All the spacers are soldered to one frame.
Once soldered up the majority of tabs all have to filed off, half a dozen need to be left to mount the etched rivet overlays later so I circled these with a marker pen so that I wouldn't get carried away and file them all off. The vertical frame is part of the motor mounting system.
Once the tabs were removed the thin etched overlays for the frames were soldered on. They are held in place with a few tabs and then worked around the edge soldering them together. The remaining tabs were then cleaned up and a small splasher is soldered over the rear driving wheel position. Finally to get an idea of what it looks like the obligatory photo with driving wheels fitted.
