The following stock turntable was produced by the Aberdeen Modern O Gauge Group for their layout Strathdon. The principles described can be adapted to suit a range of sizes for different layouts.

To provide storage at each end of the layout there are two large rotating stock turntables. The dimensions of the turntables can be varied to suit individual requirements but in the case of Strathdon the frame is 2750mm long by 900mm wide and the rotating decks are 2450mm long by 900mm wide. Each deck can take 10 roads. An earlier design 600mm wide could carry 6 roads.

The general construction details are shown in Figure 1. The mainframe is made from 50mm by 25mm timber with cross-bearers from the same material. Slots for the leg units are similar to those of the main layout boards and are located at each end and in the centre. The latter is to compensate for the additional weight of the rolling stock. Diagonal braces fitted with flush mounts complete the supporting unit. A 2750mm by 900mm sheet of 15mm plastic faced chipboard (Contiplas or similar) is glued and screwed to the base. A second sheet of the same material, 2750mm by 900mm, is clamped to the first and, by means of intersecting lines, the centre point of the rotating deck can be located and drilled 10mm through both sheets for the centre pivot hole. Because our turntables are only connected at one end the pivot hole is slightly offset from the true centre to give a longer lead onto the table.


Figure 1. General arrangement of the rotating stock turntable.

A bolt with a 1200mm length of string attached is dropped into the pivot hole and, with a pencil held at the outer end, the curved ends of the rotating deck can be marked off. The second sheet is then unclamped, lifted clear and cut along the pencilled curves with an electric jigsaw. The rotating deck is replaced on its pivot and the surplus end pieces are glued and screwed on top of the first sheet of plastic faced chipboard to align with the surface of the rotating deck. It may necessary to sand the curved edges of the rotating deck and make minor adjustments but the deck should revolve freely, assisted by the occasional application of furniture polish as a lubricant.

On the original six track turntable the 10mm bolt arrangement was quite satisfactory but the heavier ten track version caused the hole to become enlarged. This was overcome by reinforcing the pivot holes with two pieces of machined steel plate with central sleeves which were recessed into the plastic faced chipboard (Figure 2).


Figure 2. Turntable pivot assembly.

The vertical sides of the rotating decks are made from 18mm thick by 100mm high strips of blockboard. It is advantageous to slightly plane and shape the lower edge of the blockboard strip so that it is 100mm high in the centre but 97mm at each end. When screwed and glued to the rotating deck, the slight shaping will make the deck rotate even more smoothly. At each end of the deck stock safety guard rails made from 50mm by 25mm timber are fitted to the blockboard strips. They are arranged to swivel from the vertical to the horizontal to prevent stock from overshooting the outer end of the track. At one end of the turntable base along the centreline a length of single track is attached. From this point it becomes a matter of aligning the tracks on the rotating deck. We managed to attach ten tracks with the ends curved to allow smooth alignment to the single entry track but the curves on tracks 1 and 10 are quite tight.

With the rotating deck removed, two steel ball catches are recessed into the lower sheet of plastic faced chipboard, 50mm from the end of the entry track and in line with the two rails. Dropper wires from the incoming rails are bonded to the lower ends of the ball catch units, one wire being diverted via a recessed push-to-make button. Drilled through from the lower face of the rotating deck, brass screws are inserted which are long enough to emerge through the rotating deck adjacent to each rail. A bonding wire is led from each screw to its adjacent rail so that current is passed from the entry track via the ball catches to the screws and thence the rails of the appropriate track only when it is lined up with the entry track and the push button is pressed. Figure 3 shows the system schematically.


Figure 3. Schematic of the electrical connections.

A slip bolt is placed alongside the entry track on the main frame. A slip bolt eyelet is placed alongside every track on the turntable to guarantee the physical alignment of the tracks. With one eyelet per track at each end this is a total of 20 eyelets. The track can be rail soldered to copper-clad printed circuit board sleepers spaced at 100mm intervals as appearance is not too important. The entry rails and the ends of all the turntable tracks are fitted with check rails to give smooth passage over the joints and make derailments almost unknown.

This article was originally supplied by Robert Humphry, Michael Ogston and Tom Simpsom of the Aberdeen Modern O Gauge Group, and was published in the Gauge O Guild Manual. It was adapted for the GOGWiki by Nick Baines.