Hexworthy represents the terminus of a preserved railway, and should have the facilities of one, which often include a kids' playground. I had left space and a removable base for this at the end of the car park behind the station. After looking at what was available I settled on this plastic kit marketed by Gaugemaster as OO, although it's actually a Faller HO scale kit. To be fair, there's little visible difference in the size of the play equipment.
Now the thing is I thought a static playground would look a bit dull. This might be a daft idea, but I wanted movement in the playground. I was inspired by the book "Industrial and mechanised modelling" by Dave Rowe in which a number of animated layout features are described, including a swing hung from a tree branch.
I started with the swing, partly because it looked tricky. I replaced the top bar with one cut from plastic tube into which a brass tube fitted perfectly, and was able to rotate within it. I had thought of using a brass outer tube too but I had to cut slots in it for the swing "ropes" which would be much more difficult in brass, and because plastic could be attached to the supports with solvent.
I cut grooves across the brass tube so I could drill them for the "ropes", which are 0.5mm wire and soldered into the tube (it's easier to drill in a groove than the outside of a cylinder). The end of the tube had a piece of brass fret with a hole in one end soldered on as a crank. The brass tube slots into the plastic tube and is able to rotate with the swing ropes moving through an arc via the lateral slots. A small piece of microstrip across one of the lateral slots prevents the assembly coming back out. Similar wire "ropes" for the static swing (one moving is enough!) were glued into holes in the plastic tube, the wires and crank were blackened and swing seats were then added from plasticard.
The swing supports are from the kit and assembled with the replacement top bar, the moving swing is operated by the crank on the end of the top bar. The easiest way to fix the uprights rigidly was to glue to a plastic base with solvent, the base is attached to the wooden playground base with contact adhesive. Another brass tube is superglued up the rear support through which passes a blackened springy steel wire, after a flexible arc this passes through the hole in the crank. Moving this wire up and down through the tube moves the swing, the arc and springiness of the wire (it might be a guitar string or left over from wire-in-tube point control) allows for the crank hole movement being an arc rather than linear.
I had toyed with the idea of using servos driven by a Raspberry Pi, Pico, or similar microprocessor. This approach would have great potential here and might simplify the drive, but would be a whole new area of learning for me and could become a bit of a rabbit hole. Plus, I had a couple of cheap motors with gearboxes and a load of gears and shafts - the gears left over from motorising the turntable on Southon Yard. So, here we have a crank arrangement to turn the rotary motion from the motor (seen far left) into sinusoidal linear motion of the operating wire.
The brass arm is pivoted (right) and has a slot made from a loop of 1mm brass wire (left), a track pin moving in a circular motion (attached off-centre to the gear - the teeth are not used) moves the slotted arm up and down. After some experimentation the thinner arm branching off is used to move the wire, the arm has three holes and the wire has a couple of bends to allow adjustment with pliers.
The drive unit is simply made from lengths of timber, quite small section, and designed to fit below the playground sub-base. Here it is seen inverted, the motor is glued in place with a couple of screws to stop any twist, and hangs down into the baseboard void. The arm driving the swing is on the far end. There are gears on the inner of the left side which step down the speed to the crank. With the motors running on 3V the output shaft rotates in 2 seconds, so the gears step down 2:1 for the swing to take 4 seconds, which is what Dave Rowe had calculated for his swing, and seems about right.
My Dremel in its drill stand came in very useful in making the mechanism. I clamped the two pieces of wood together and drilled 2mm holes in two corners. Cut-down shafts were fitted in these ensuring the wood stayed aligned while I drilled the other carefully marked-out holes, the drill stand ensuring they were straight and parallel. The wood pieces were then spaced apart using longer shafts through the corner holes, holes for rotating shafts were opened out slightly. The two wood pieces spaced apart ensure shafts stay aligned and parallel when rotating, allow reducing gears between them, and as will be seen in the next instalment, allow drive to another item a little distance from the swing.
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