The reason for choosing a Helix

Very early on in the design process, I established that my layout would be built on two levels. I required a way of getting trains from the lower level to the top level and vice versa. To reduce strain on a train's motor and to allow for longer trains, I wanted to ensure a gentle gradient was created.
The first option investigated to transverse from one level to the other was via a straight run. The height difference between the two levels was approximately 400mm. I worked out that I needed an absolute minimum height of 80mm clearance for all railway stock. (I based this conclusion on the height of existing Hornby incline peers which elevate the track to 80mm high.) I decided that a 100mm incline would be sufficient to allow for any structural support that will be created for the incline surface.

Figure 1

Based on a 7% incline, I calculated that 1.5 meters of track would be needed for every 100mm of height gained. Therefore, to achieve the required 400mm height between the levels, a 6 meter long incline would be required. If I designed the incline this way, then more than half of the space around the room would be taken up with the incline.
Whilst researching other peoples multi-level layouts, I found that most of the people who had a multi-level layout, had used a helix in their designs. This use of a helix appears to be the most efficient way to achieve an incline without vast amounts of layout space being taken up.

The Style of Helix

I have set aside a 1.2 meter square in the corner of my bench work to accommodate the helix. The helix would have two circular tracks using second and third radius curves, thus giving me an "up" and a "down" line at the same time. This is something that I picked up from someone else's web site saying that it can take quite a while for trains to emerge from the helix. Doubling up the track would not take up much more space than a single track. Another important criteria I wanted was to ensure that I could have access to each level of the helix from the inside. This would facilitate access to any derailments that might occur.

How NOT to do it...!

Having decided on a helix design for my layout I started thinking of how I was going to construct it. I tried creating a hexagon design, as this is very efficient for cutting out of a straight piece of wood.

Figure 2

Using a 4x2 sheet (as shown in figure 2.a) the shaded bits are the waste cuts. Once cut out, the pieces tessellate together to form a rough circle. See figure 2.b. This idea was very efficient on the amount of wood required but fell short on the design front. When I prototyped this method, I found that edges did not line up once an incline was formed. The different levels/angles caused by the edges would mean that you would have to distort each piece. The design works great on the flat, but does not work on an incline. Therefore, resort to 'Plan B'!

The Final Design

I produced a couple more prototypes using cardboard and quickly came to the conclusion that the only way you can achieve a helix is via a circular path.

The design I came up with is to create half circles in hardboard and then glue them back to back in quarter intervals. This was it produces a stronger support and a continuous circle in a spiral.

Figure 3

Cut lots of half circles as shown in figure (3a). Place the first cut board down as shown in (3b), then glue the next piece rotated round a quarter of a turn as shown in figure (3c). A couple of optional bits that can be done are as follows:-
Using strips of decorators gap filling tape (this can be painted over) can be placed over each of the joints. This will act as additional strengthening and help hide any gaps when each piece is joined together. The edges can also be taped to hide any glue that might have seeped out during the lamination process. Very occasionally, if the wood is slightly warped or the piece is not completely flat when it is being laminated, you end up with a slight gap between the pieces. This can be hidden by the use of tape applied to the edges should it be required. In my case and probably like most, the helix is going to be hidden from view, therefore this may not be an issue.

The supports for the helix surface are constructed using adjustable shelf fixings, which so happen to have 10mm spacing. Each of the shelf fixing tabs needs a hole drilled in the centre of the tab. This is so that strips of wood, cut to 250mm wide can be screwed to the tabs. These strips of wood act as a platform for the helix surface to sit on. There will be a platform at 0, 45, 90, 135, 180, 225, 270, 315 degrees around the circle. This spacing allows for 10mm per 45 revolution, thus giving 80mm height.

A recalculation based on 10 revolutions....
0, 36, 72, 108, 144, 180, 216, 252, 288, and 324 degrees.