Graham Goodchild demonstrates that a simple home-made device can bring operational interest to your layout – and provide a fun hobby project.
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Graham Goodchild shows how a simple device can add modelling interest.
One feature frequently seen on a layout is a level crossing. The gates on an old style of gated crossing, for example, can be made to swing open and closed by installing servos such as the ‘Peco Smart Switch’, whereby the hinge side of each gate is attached to the output shaft on its corresponding servo. It is also feasible for all the gates on a single or double-track level crossing to be operated by connecting the gates together via lever-type linkages to a single servo.
The level crossing described here is for automating a modern style crossing by adapting an ‘N’ gauge plastic kit produced by Ratio. ‘OO’ gauge and ‘HO’ scale barrier crossings produced by Ratio and Peco are equally suited to automation by using the same method. At the heart of the crossing is
a multi-ratio geared motor that powers a cam to raise and lower a hinged platform which, in turn, pushes and lowers the barrier arms via wire linkages. Gear ratios on the motor’s gearbox can be adjusted by removing or adding certain cogs.
With the motor connected to a 3V power supply the barriers will operate in prototypical fashion, with all the cogs in place. Apart from the geared motor, other items required are a switch and battery holder to fit two 1.5V AA batteries, screws and a wiring harness, styrene sheet, metal hinge, lead shot fishing weights, piano-wire, metal collar with fastening screw (the type of collar used to retain undercarriage wheels on axles of model aircraft). The collar is used to fasten the barrier operating cam onto the output shaft of the geared motor. The level crossing base, motor mount and operating cam are constructed from 3mm (⅛in) plywood and 6mm (¼in) thick balsawood.
Small, ball-like lead shot fishing weights (available from your local angling supplier) are attached to the tail ends of each wire linkage, allowing the barrier arms to lower by gravity. They also provide a smooth bearing on the cam-operated hinged platform that, as it rises, pushes all four barrier linkages upwards, thus raising the barriers simultaneously.
All of the components used here are cheap and freely available from hobby, craft and technology outlets. It provides an interesting practical challenge and a pleasant way to spend a few evenings. Adding automated layout features brings an element of fun to a layout and can be rather addictive. You’ll soon be looking around your layout, wondering what can be motorised next!
Working level crossing barriers add plenty of interest to a layout. It’s possible to fashion a cheap automation system using simple materials and a little ingenuity.
The static barrier arms on this ‘N’ gauge plastic kit can be remotely controlled using a geared electric motor and pianowire linkages. Only the pivoting barrier arms in the plastic kit require modifying, by drilling a small hole in the barriers to accept the linkages.
ASSEMBLY PLAN
This diagram shows the principal dimensions and component layout for motorising Peco’s ‘N’ gauge barrier crossing.
1
The crossing base was cut from 3mm plywood. The base must accommodate both tracks and road ramps, adding a small margin around the edges to allow for mounting the crossing flush with the surface of the layout baseboard.
3
For the barrier linkages, cut four lengths of 21-gauge piano wire to approximately 50mm in length. Bend the ends of the linkages at right angles using pliers and hook them into the pre-drilled holes in the barriers.
2
Each barrier consists of a front and rear section, which are glued together leaving a gap between them. Drill a 0.8mm hole through the rear section at a position 5mm from the barrier pivot point for the piano-wire linkages.
4
Glue to the linkage ends to prevent them from slipping out of the barriers, ensuring the linkages move freely. Assemble all four posts and temporarily position them, marking where the linkages will pass through the base.
5
Drill four 1.6mm holes at a slight angle through the base where previously marked and pass the linkages through the holes. Then fix each barrier into the crossing base.
6
Create a hinged barrier platform from 1.6mm styrene sheet, which should cover the positions of the four protruding piano wire linkages on the underside of the plywood crossing base. Attach one half of a metal hinge to the styrene platform with nuts and bolts.
15
The completed crossing is mounted in a cut-out section of the baseboard as shown in this underside view. The crossing sits flush with the baseboard surface. Laying and connecting the adjoining track with rail clips will secure the crossing in place. Alternatively, dropper wires can be soldered to the track ends to ensure electrical conductivity and the wires routed through holes drilled in the baseboard. This method is particularly useful for quickly removing the crossing without disturbing adjoining track.
10
A pair of dividers was used to discern the diameter of a semi-circular cam. To minimize the size of the cam, a strip of 6mm balsa, which engages with the cam, is glued to the underside of the leading edge of the hinged styrene platform.
9
Screw the geared motor onto a 3mm plywood base, the same thickness as the base of the crossing. Each end of the base is screwed onto two side supports which are cut from 6mm balsawood glued to the underside of the crossing base.
7
The remaining half of the hinge is attached to a balsawood block which, in turn, is glued to the underside of the plywood crossing base. Movement of the barriers with their corresponding linkages is checked by raising and lowering the hinged platform by hand.
8
Cut the wire linkages to length and attach lead shot fishing weights, using pliers to fasten them. The weights allow the barriers to lower by gravity and provide a smooth bearing on the cam-operated hinged platform, enabling all barriers to operate simultaneously.
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After installing the motor unit to the level crossing base, the wires were connected to the motor terminals, battery pack and operating switch. The switch to operate the barriers can be located in any convenient position.
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Balsa cement is smeared around the edges of the cam and balsawood strip on the hinged barrier platform and allowed to cure before lightly sanding smooth. This seals the wood’s grain and provides a hardened bearing surface.
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A prototype cam was made from card initially, turning it by hand to test the barrier movements. When happy with the operation of the barriers, the card was used as a template for cutting the operating cam from 6mm balsa.
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A metal collar, fixed to the balsa cam with cyanoacrylate glue, fastens the cam onto the gearbox output shaft.