Ok, the new shelves are in, and I have a load of wood ready to make the framework per my design:
As I want to make some proper joints, I need a few tools - a wood saw and power drill are a good start, but a back saw of some sort would help. I think it was a tenon saw I bought.
I also went on a little diversion here, spending most of one morning re-organising my tools into a tote-style tool bag, and putting screws and nails into separate compartments. I'd be worried about OCD if it didn't pay off by making things easier to find, but it does, so that's fine :-)
Anyway, the frame starts with the outside edges of a cuboid:
The edges resting on the floor are basically there to hold the four uprights in the corners, each of which have been cut at the bottom so they fit over the skirting board.
The corner joints at the top are a sort of combination of mitre and lap joints. Not the most accurate mitres ever, but the overall sizes lock it in place:
With the outer edges done, I make lap joints on the four uprights, facing the front and back of the cupboard. These are inset with horizontals going from side to side, which in turn have lap joints and corresponding horizontals going front to back.
To space the drawers from the sides, and for more vertical strength, additional vertical colums are created between the front horizontals, to be kept in place with dowels.
Most of this is in the sketches on the right side of this bit of paper:
Not very well described, but it's late, and I have a video of me on a dry-run putting it together that might show it in a comprehensible manner, in which case I'll post it. Update: Here's the video.
Here are all the framework parts ready to be set in place:
And here they are in place, with dowels, glue, and just a couple of screws to make sure it doesn't move:
I haven't mentioned the two uprights in the middle before; they're screwed to the front-back horizontals, and should stop the drawers fishtailing (as well as giving more vertical strength).
A closer view:
Note the horizontals going front to back are slightly inside the verticals - they will be supporting the drawers.
Inevitably, this produced plenty of spare wood and off-cuts - hopefully I'll have use for some of them over the rest of the build, and eventually the remainder can go in someone's BBQ, chiminea, or something:
Next up - drawers...