Opting to build a series of modules depicting the branch line I always intended rolling stock to be able to move between them. The only issue was how to do it. I don’t have space for staging so I decided to build a fixture called a ‘cassette’ to store, assemble and move trains between modules. I first read about cassettes in one of Iain Rice’s books on small layouts and always thought that they were good way to save┬áspace and store trains. The underlying concept is of two aluminium corner bars mounted on a wooden deck which join to the layout at a docking point. The three main components are a cassette, a dock and a cradle. Here are some images of the design and construction process:

I used SketchUp to design the basic cassette. It uses aluminum angle bars (4ft long) screwed down to 1/2 inch solid pine board. It has handles to help lift it and it has drawbridge handles at the ends to keep trains from rolling off while being moved.
The hardest part of the design to figure out was how to connect the cassette to the layout. I decided to make something I called a ”cradle”. It took several iterations of the design to get right. Eventually I designed it to attach to a dock to into which the cassette sits and this prevents any sideways movement.
Power comes into the cradle from two connectors and a shaft that connects with power plates on the upper surface.

Power plates on the cassette touch the power plates on the cradle.

I took me a while to gather all the materials and parts. I have to build another one soon so I’ll publish a proper building diary with parts listed for anyone who wants to have a go themselves.
After failing miserably to make handles from aluminum I eventually turned to Shapeways and had them 3D printed.
And here’s the final result. It actually came together pretty quickly although I definitely had to scrap one earlier version.

It is designed to hold the local freight which is really the only train that will move between modules.
I added an upper ridge to the cradle to stop upwards movement of the cassette.
I had Shapeways print the cradles for me. I can have as many duplicates made as I need. The Town module will need three.
The cassette has a tight fit with the cradle to prevent vertical and horizontal movement.
The cradle is fitted to the dock area. It is where the most care needs to be taken to make sure things line up and trains don’t derail.

I added power plates to the cradle. Shapeways printed the holes for me but the plastic is easy to drill through if necessary.
This is a test to power the cradle and the cassette.

The train ran though without any hitches.
I added docks and cradles to both ends and so trains can enter and exit as planned.