About six months ago I blogged about building an oil depot tank for the Lego railway. Six months later (and one MSc dissertation out the way) I have finally sorted out the missing roof and I'm quite pleased with the result.

Here's a picture of the tank getting 'plated up'. You can see the Technic frame holding the plates in place.

Now I needed a roof. It's hard to build in circles using Lego , but then I hit on an idea using 'A frame' pieces.

These enabled me to create a 'star' that fitted nicely resting on the uppermost circle of Technic rods.

My plan was then to fill in the gaps using plates. Easier said than done as the studs didn't line up on the rays of the star that were at 45 degree angles to each other. I tried several experiments with shaped roof plates.

And then tried to build it with offset plates that would only be connected to four of the rays. But this didn't work either.

So I went old school. I got a load of long Technic bricks and connected them sideways using black Technic connector pins. This creates an incredibly strong structure, like a sheet of bricks welded together.

I then plated over most of the Technic bricks, leaving a few exposed as I thought it gave a nice effect.

I was pleased with the complete structure. It looks round enough to work and is suitably imposing to look like a real industrial structure.

And here is what it look like in situ on a roundy-roundy loop lay out that I was mocking up in readiness for having a table to put the trains on.

I still need to create an unloading system and I want to put a ladder up it, but I've been a bit distracted by having the table and actually being able to set the trains up and get them running. More on that very soon!