Despite wanting this thing to 'be quick to make' I hit an early snag - all is revealed below...

One of the key features of this design is that the track will go inside the frame, rather than sitting on top of the frame per the conventional approach. This means:

• no underboard wiring, point motors etc (a false bottom could be added - but this is meant to be quick and simple)
  
• no track pins - unless it doubles as a bed of nails!
  

Assembly tolerances must be quite tight, as even small errors will cause running problems across board joins in N. My joinery is not the best, so this aspect was daunting

Here are some of the box parts carefully cut to size and smoothed down:

I did consider halving or even dovetailing the joints, but 14mm isn't much to work with, so I chickened out. A skilled carpenter would do it properly.

One half of the box glued and pinned and screwed:

On starting the second half, it was clear something was wrong. The longest side piece was bowed by about 2mm at the centre - despite carefully selecting timber when buying, rejecting badly knotted pieces and so on. The remaining offcuts I had weren't suitable, so how to un-bow a piece of timber?

In fact, it's pretty straightforward for short-ish pieces. Add moisture on the concave side of the bow, then clamp so that an opposite bow is applied. I used a kettle (steam, woo!), a piece of kitchen towel, and a folded plastic bag to retain the moisture, and stuck the whole lot in a vice between two rigid battens for about a day. Then let it all slowly dry out - hopefully straight! If this seems a right ol' palaver, well yes it was, but those odd mm might compromise the result - derailing isn't the sort of test I had in mind!

Whilst waiting - two days - there was time to obtain suitable hinges and catches. And also decided to add triangular fillets to strengthen the middle hinge supports.

The second half of the box was then finally glued, pinned and screwed. When dry, the hinges were fitted - proving quite fiddly to align and fix all the pieces:

- these pics highlight inaccurate chiselling! But at last things are taking shape:

Of course, when the box is closed, there is a large gap at the hinge end. This must be covered so that rail ends etc are not damaged in store or transit, but easily removed to enable the two halves to butt together when open. My intended solution is to use a piece of ply/mdf/sheet stuff attached with velcro - with perhaps a couple of cross bearers to act as feet. I'll work out that detail later...