The Helix Part II …
As mentioned in the previous helix post, I am basically following the design and construction techniques from this article in Model Railroad Hobbyist. It starts on page 61.
Rather than repeating what the article says, I will just explain what I have done, as things have gone a little differently.
Firstly, a template was made from 3mm ply for the helix segments. As my helix is only single track compared to double track in the article, I made my segments 90mm wide. I also made my segments as one-eighth of a circle to maximise what I could fit on an 8’ x 4’ sheet of 6mm ply with minimum waste. The helix requires 80 of these segments, 16 per level. As mentioned in the article, these get laminated together to form a roadbed of 12mm thickness which should be very strong and not require any splice plates. Splice plates have the disadvantage of reducing the clearance between levels.
The picture above shows eleven segments laid out on a piece of the 6mm ply. Three 8’ x 4’ sheets were purchased. As I could fit 33 segments on each sheet, these would give me plenty of room for the 80 required with some ply left over for possible entry and exit segments.
Once all the segments were cut out with a jigsaw, they were cleaned up with some sandpaper.
A lot of thought went into the next stage which was how to assemble the first helix layer. My situation differed from the article in that I could not just lay the segments out on the benchwork and go from there. There were obstacles in the way, namely the steel post and the already built benchwork.
So, it was decided to lay the segments out on the floor and glue them together.
Once the first layer was laid out, the next layer was glued to the top, with the segments overlapping by 50%. Using clamps to hold the segments whilst the glue dried was not an option, as I didn’t really want to disturb the segments in lifting them to install clamps. Small screws were used instead. These would be removed once the glue dried. During the process, measurements across the diameter were checked to see that I was in fact making a circle!
As mentioned in the article, the last overlapping segment was omitted at this stage. This was done, in my case at least, to enable this first level to be manipulated into the layout around the steel post etc.
During this time of cutting out helix segments, I also commenced work on the next section of benchwork to support the helix and the next section of spline heading towards Ardglen.
Another two I-beams were utilised again for the main supports with another L-girder wall constructed on top.
Now came time for locating the first helix layer in place. With Andrew’s assistance, we managed to get it in and around the steel post, but could not manipulate it around the wall ‘studs’ on the main peninsula. Three of these had to be removed to allow the helix to be moved into place. These were replaced later.
The final position of the helix was checked against the drawings and numerous measurements taken to get in in the right spot. It was then temporarily clamped in position.
The next stage was to construct ‘footings’ for the vertical risers which would support the helix structure. Referring to the article, this will be made from 2×1 DAR with notches cut about 12mm into the edge, spaced at the required separation distance.
Simple L-girders were made from scrap 3×1 and 2×1 in eight locations around the circumference, spaced evenly.
The above shots show the helix in position and the riser supports. There will be a 2×1 notched riser each side of the helix and they will be screwed to the 2×1 on which the helix is resting at the moment. Note that this first layer will be about seven inches higher that it is now. The bottom layer is around 49 inches elevation. Where it sits now gives me a solid base to construct the remaining four layers and to lay the track as I go. I am currently waiting on a shipment of PECO code 75 flex track from the UK before I can proceed any further. Flex track seemed to me to be the easiest method of laying track in the helix rather than using my handbuilt track method. The plan is to lay track on the first level, then construct the next level from the segments, lay the track on that level and so on. More on this later.
Cheers for now.