General view of the helix.
The helix from a slightly different angle, showing a train descending.
Closeup of the train descending the helix from the previous picture.
The helix is basically a standard “oval”, with the following differences:
The track goes round the helix twice, and continues, still climbing, along the straight by the fence until it passes the end of the helix and it levels off to continue up the garden towards Fiddlers Yard.
The supports are 6-foot fence posts, spaced 4 feet apart along the straights, and at 45° intervals around the curves.
Each fencepost has a 220 mm. bracket of 100 × 19 mm. softwood fixed on the outside, such that anything laid across the brackets is dead level. Then two half-metre lengths of 6 mm. threaded rod are fixed to the brackets, 180 mm. apart. Trackbed supports are then fixed to these threaded rods with nuts and “penny” washers, each one higher than its predecessor by 16 mm. if the track between them is straight or 12 mm. if it is curved. The incline works out at approximately 1 in 75 (1.333%), or slightly gentler.
The track base on the straights is 150 × 25 mm. planking, braced by 100 × 19 mm. planking, and on the curves it is basically two pieces of 25 mm. aluminium angle joined crosswise with 150 mm. lengths of redundant decking, and covered with 6 mm. plywood. This is covered by roofing felt as with everything else.
One circuit of the helix is approximately 33 feet, which is similar to the standard section-length of phases 1 and 2, so I decided to make each circuit of the helix an electrical section. The section breaks occur at the first helix fence post past the garden shed.
Click on any of the following pictures to see a larger version.
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General view of the helix. |
The helix from a slightly different angle, showing a train descending. |
Closeup of the train descending the helix from the previous picture. |
Copyright © 2000–2006 Jane Sullivan.