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O’Shanassy’s Wharf was established in the late 1930’s on the southern shore of Luckless Bay by Shamus O’Shanassy, to service the small communities trying to scrap a living in the hills above the bay. With little space and in an area where the steep, pine covered slopes meet the water, all the wharf and piers had to be built on poles hammered into the sea floor. When planning this wharf, Shamus was able to buy third hand, two diminutive narrow gauge Porters and some rail, but alas, no turnouts. His solution to this dilemma was to home build a sector plate in the middle of the wharf to service the three spurs and the start of the mainline. Because of this configuration, both locomotives have to be used to shunt the wharf area. It is your job to try and switch the incoming cars to their required locations and to pick up the loaded cars so they can be dispatched to the small communities up the line. Good luck!!!


To be built sticking out of a simulated wooden shipping grate, this layout / diorama was primarily designed as an unusual switching problem, using the Bachmann Porters as the motive power. It was planned to be built in ‘O’ scale or 1/4” to the foot, and uses 16.5 mm gauge track (approximately 30 inches on a full size railroad). As can be seen in the diagram above there are no turnouts, only a sector plate which can move back and forwards to align with either of the pairs of sidings. Because of thisX’ track plan with the sector plate at the centre, two locomotives have to be used to switch the cars around the wharf. This adds the further problem of storing the other locomotive out of the way while the other does its required moves. Switching is done according to the card sequence located on the front of the layout.

All the required controls are located on the hand held controller seen opposite. Each of the four sidings off the sector plate can be isolated with a push button, however a locomotive will not move unless the sector plate is aligned to it. The push button in the middle of the X, when pushed will move the sector plate to its alternative position. Pressing the button again will move it back to its original position. The large knob is the locomotive speed control and when turned the green LED above it will glow brighter. Below this is the locomotive direction switch, with a centre off position.



The concept behind O’Shanassy’s Wharf called for a sector plate in the middle of the scene, which served three sidings and the incoming mainline (see layout drawing). The sidings/mainline are arranged in pairs with each pair aligned to each end of the sector plate.

For this concept to work, the sector plate had to be able to move back and forth between both the pairs of sidings/mainline time after time, and line up perfectly every time. Also, and most importantly, the control for this movement had to be simple and easy to operate and be located on the hand held controller.

Not very easy requirements to achieve. Aligning the sector plate could be achieved with adjustable stops, but how to control and stop the motor at the right spot could prove difficult. The solution came in the form of a split power supply, two micro switches and a single pole double throw push button switch and about three hours of drawing wiring diagrams.

The motor to be used to turn the sector plate is a 12 volt ‘Switchmaster’ motor. The one problem with this motor was at the full 12 volts it tended to try and over run the stops even though the micro switch had turned the power off to it. This would put pressure on the motor and gears. What was needed was a split power supply which I could control the voltage output. The solution – an old H&M ‘DUETTE” transformer with two controllers.

To obtain a controlled split power supply from this unit, turn the control knobs to forward, and with a multi-meter find out which of the two of power outlets on the back are the negative ones. Then bridge these two outlets. This becomes the common or zero voltage supply and is wired direct to the motor. Turn one of the front knobs to the reverse position. You can now adjust the forward and the reverse knobs to obtain the exact positive and negative voltage required. About 8 volts seems to work best for this application, but different motors may require different voltages. Trail and error is the only way of finding out.

The wiring diagrams above show how the system works and the sequences involved. The micro switches are used to cut the selected power (either +ve or –ve) when the moving arm hits it. When the arm moved from the other micro switch it opened the opposite power, which is then ready to move the arm back when the button is pushed again.


Thus, all you need to do to make the sector plate move back and forward is to simply the hit the push button, which is located on the hand held controller .