Building a viaduct for my garden

27 March 2023
Steve Howard creates a bespoke viaduct for his 16mm scale line, that looks great, and includes important safety features.

Most of the track in my garden is at ground level, however, because it is on a slope, some of it runs along the top of low brick walls. Where these walls become too high or obtrusive, the solid wall is broken up with various viaducts. The largest of these is the subject of this article. Hopefully, the pictures are fairly self-explanatory as to its construction.

The piers are three hole bricks set on end in the wall and are sitting on a single course of brick in the ground on a 2in bed of mortar. The arches are semi-circular clay ridge tiles used for roof capping. Each tile was sliced into 3 sections, each 4 ins wide, using a 9 in angle grinder. These were cemented in place on top of the brick pillars.

Finally, topped with a cement bed to bring the track base to the correct height to match the adjoining wall. The in-fill between the arches was cast in cement, initially contained using Plastikard stone sheets stuck to the sides of the arches with silicone sealant. Before filling with cement, the sheets were first rubbed with oil as a release agent to prevent the cement from sticking to them. When set, the sheets were removed leaving a stone-embossed pattern in the cement. The track was fixed down with brass countersunk screws and small rawlplugs drilled into the top concrete surface. This was then all painted with a dirty matt black enamel paint.

The walkway supports were made from 11.5 mm wide aluminium strips purchased from the local DIY store. These were cut to 8" in length and were glued in place using an external waterproof glue in a cartridge gun.

The webbing between the sleepers on the Peco G45 track was cut to allow the sleeper spacing to be adjusted to allow the walkway supports to be evenly distributed along the length of the viaduct. The ends of the aluminium strips were drilled with a 6BA clearance hole to take the handrail stanchions.

1/4" wide Plastikard angle strip was glued to the deck to contain the track ballast.

Ballast was a mixture of 5 parts sharp sand, 1 part O scale granite ballast and 1 part cement. This was applied with a small trowel and cleaned off the sleeper tops and rail sides with an old toothbrush and screwdriver before the cement had set.

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Handrail stanchions were made from some spare lengths of Peco SM32 rail. These stanchions were 2in high and drilled with 2 x 2mm holes to take the horizontal wires. The top end was rounded slightly and the bottom end filed to produce a tongue that fitted into the slot of a brass 6BA screw.

As I only have two hands, the problem was how to make the stanchions vertical by correctly aligning the rail to the 6ba screw whilst it was being soldered. This was achieved by using a jig made from a piece of wood and held in the vice. The rail stanchion was inserted one end and the 6BA bolt the other and it held the two in alignment whilst they were soldered together.

The stanchions were secured in place on the aluminium strips with 6BA nuts. The horizontal rails were made from galvanised garden wire sold on a roll at garden centres. This is usually a roll of about 4" in diameter and when unrolled, is anything but straight. The only way to straighten this out is to stretch it.

To do this, one end was secured around the base of a tree and the other end to the front towing hook of my van. The van was slowly reversed until the wire snapped, stretching and straightening it in the process. The stanchions were threaded onto this and then secured in the horizontal supports with 6BA nuts. The handrail and stanchions were painted with gloss black paint.

The walkway boards were cut 10mm x 3mm pine wooden strips from the local hobby shop. These were left soaking in a tray of some old creosote I had in the back of the shed. This is now banned, but there are modern-day equivalents. After being left in the sun to dry for a few days, they were glued in place. It remains to be seen as to how long these survive the elements before needing to be replaced, but at £6 for about 15m, this is a fairly cheap and easy exercise.


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