The New Layout - Cassettes

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As the layout is end-to-end, the fiddle yard (off-scene staging area) system is central to the whole concept. The simplest option is to have a length of track on which the trains are manually assembled. However, this is tedious and the constant handling of rolling stock takes a toll on paint and details. Suppose we could pick up the whole train as one unit, turn it around or replace it with another train? This can be achieved by using "cassettes".  The idea of using cassettes was first explained in the UK model press by Chris Pendlenton, in Model Railway Journal, Issue 27 back in 1988. The concept quick caught on and many layouts use the idea.  Personally, although it has advantages, in larger scales and for longer trains in N scale, the cassettes can sometimes be a bit unwieldy. Here on this layout, it's not so, the length of a cassette is only 200mm which is very easy to pick up and turn around with one hand, even with Nn3 rolling stock on it.
Click on the pictures to get a larger image in a new window
Click on the image to get a larger view (opens in a new window) So what actually is a "cassette"? Simply, it's a piece of wood on which is fixed two lengths of 12mm (½") aluminium angle. The angle strips are set to gauge using whatever method is convenient. In my case, I use the gauge blocks which I use in tracklaying. The wood is MDF, 6mm thick, the same material used for the basebaord surface.  It's a nice stable material which is easy to cut accurately. The MDF is left slightly larger than the pieces of angle.
Click on the image to get a larger view (opens in a new window) Here's a close view of the cassette. The most important thing is to cut the lengths of aluminium angle accurately so the ends are absolutely square and of identical lengths. What I do is initially cut slightly over size by about 1mm and file down to scribe marks. A little slow, but time spent here makes life easier later on. The aluminium is glued to the MDF using a contact adhesive and also pinned. Once firmly set, the MDF is trimmed exactly to the size of the aluminium.

Click on the image to get a larger view (opens in a new window) To align and locate the cassettes, plastic fixing blocks are used. These are nicely square and of a convenient size. Each side of the cassette is gently sanded until it drops into the 4 blocks with about 5 thou' clearance either side (the thickness of a piece of thin paper). It's very important that the cassette moves freely, any "stiction" might lead to stock being derail as the cassette gets jerked about. To match the height of the aluminium angle to the eventual rail height, a strip of plastic sheet is glued in between the blocks.

Check that each cassette drops in and lifts out nicely. I found it useful to just shave the edges of the fixing blocks as each one had a minute burr left over from the moulding process.

Click on the image to get a larger view (opens in a new window) A closer look at the plastic locating blocks...
Click on the image to get a larger view (opens in a new window) ...and now with the cassette in place.
Click on the image to get a larger view (opens in a new window) Here's how it looks with the end screens in place. Note there is still plenty of room for a couple of other cassettes in the fiddle yard area.
Click on the image to get a larger view (opens in a new window) 2 cassettes, with and without stock. The vertical sides of the angle provide a decent amount of protection, while the 12mm size allows room for getting in to rail the stock easily.
Ariel view of the cassettes. After each cassette has been assembled and sanded to size, the aluminium is polished and degreased.
Here we see the end view of a cassette. As I said before, it's important to get the ends and sides square. Because the whole area is uncluttered, it's very easy to get stock "railed" onto the aluminium.
This shows how easy each unit is to pick up. Granted, I'm using quite a short train length, but larger units should be quite feasible in Nn3, which shows the advantage of the scale. Units of 600mm (2 feet) would be about the largest I would attempt to use. For longer trains, cassettes could be linked up in the staging area.

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