Background
To provide music for my silent automata, some time ago I carelessly knocked up The Music Man. This isn’t an automata, you just push one of his teeth and 60 seconds of cheerful fairground organ music are played. The pupils in his eyes are actually the openings for the loudspeaker, driven by an off-the-shelf audio recorder/playback module. Each of the five teeth plays a different tune. I then thought that this actually turned out to be quite a happy character, so I decided to reuse the idea in something that actually moves.
For the movement I thought that I would place him bareback on a rocking horse, carefully balancing on one leg, as if cantering around the ring in a circus. A rocking horse has the advantage of staying put as well as being something of a curious, historic toy. Horses may once have dominated the streets in our cities, making them obvious subjects for childrens’ toys. These days you are just as likely to see a unicorn as a horse clip-clopping its way through central Berlin.
Making
I used a pencil compass to draw two arcs for the rails. The central dowel is to keep the horse in place in the centre of the box.
The base has two hemicircles with vertical slots to accommodate the central dowel. As the horse rocks the central dowel moves up and down as you can see in the video. The slot is for the pusher rod.
The horse’s body is made of three pieces of plywood and a wooden egg for the head, pinned together with 3 mm dowel, making it easier to cut a hole in the middle for the mechanism.
I originally thought that a lead weight would keep the rider standing on the horse’s back upright as the horse rocked to and fro. This proved more difficult than I thought, so I gave up that idea and linked the small robot figure to the pusher rod instead.
The operating lever uses hinges made from 1.5 mm brass rods.
The End Result
The horse rocks very nicely, but I’m not really happy with the movement of the robot. I would prefer the robot to respond more to the movement of the horse , as if it were human, trying to maintain its balance. Maybe some day I will have another go, using this as a reference, perhaps returning to my lead weight idea to see if that improves things. The setting is fine; the idea of a mechanical man trying bare-back riding on a rocking horse is satisfyingly whimsical.
Video
Link to video https://www.youtube.com/watch?v=NE_BAbGzjkY
Download
The image files can be downloaded here https://www.wordwise.de/Rocking_Robot_Archive.zip