[Note: The Rhino was released between kits #31 and #32, but I’m including it now to keep it with the first Jansen kit.]
Otona no Kagaku – Mini-Rhinoceros, 3500 yen. The Animaris Rhinoceros is referred to as a “transport-style” beest, and the youtube video shows someone pulling it while a second could be riding inside. It’s one of the few of Theo Jansen’s beests that isn’t wind-powered. But it’s also one that actually has a practical purpose. The Rhino-Mini kit is a scaled-down version of the Rhino, measuring about 18 cm x 16 cm x 14 cm (7.1″ x 6.3″ x 5.5″). It’s made of light-weight plastic, but uses 2 small steel rods for holding the assembly together. The kit itself is wind-powered, with a little squirrel cage-style fan on top, but several of the suggested mods include replacing the fan with an electric fan or motor. My thought is that the life-sized version should be propelled by walking on a stairmaster in the main cab.
The only real mechanical difference between the mini-Strandbeest and the mini-Rhino is in the design of the legs. The theory behind the mechanics of the Jansen linkage is the same in both cases. The mini-Rhino has over 80 parts, and a recommended assembly time of 90 minutes. It took me a little longer than that because I wanted to remove the flash from the parts with a knife. All the pieces snap together so there’s no need for other tools. However, flash could conceivably rub against other moving parts, and I didn’t want to run the risk of having to disassemble the thing if it didn’t move smoothly (which was the problem I had with kit #30). The plastic is soft enough to be trimmed easily, but it’s still not something you want kids to do themselves. The instructions are pretty clear this time, and it’s pretty obvious what the order is for snapping the control rods to the crankshaft. Unlike with kit #30, the mini-Rhino walks unencumbered, although if you’re using a fan to spin the squirrel cage, there is an ideal attack angle involved. There’s also a separate drive rod for hand-powering the kit . The finished pieces don’t really fit together tightly, so you have to be careful about stripping the gears, or having the squirrel cage fan derail.
If you have some of the previous mooks, then the special mook is a little redundant, even though the material is all new. The first 16 pages are studies of the rhino animaris, the strandebeest and one or two of Theo’s latest concepts. This is followed by variations of the Rhino and examples of how the Jansen linkage can be put to use for artificial limbs. The next 8 pages are attempts at making robots based on snakes, tadpoles, lizards, cats and dogs. The Otaku Club section takes a look at Project Skeletonics, a group working on an exoskeleton; and a guy that makes robotic fish (more photos at hayashi). The suggested mods for the mini-rhino are to decorate it with fake barnacles, turn it into a horse-drawn cart, to make a mechanical wind-up crab with two of the legs, and to build an 8-arm cymbal-playing machine. The final article is the study of the movement of fossil creatures, and there’s a manga on the life of cockroaches (drawn by former Tezuka assistant and current director of the Suginami Animation Museum, Shinichi Suzuki). There’s also a one-page ad for a new “Sound Gadget” series of kits to come out from Gakken this Fall. Scheduled kits include the Udar, and the SX-150 Mark II (no prices, though. I’m assuming that the dedicated sound gadget series will allow Gakken to charge more, as with the premium theremin and the SX-150 synth.)
As always, the mook has a lot of nice pictures and some articles that introduce actual science concepts. However, this one does seem a little rushed, and a little lacking in historical content. At 3500 yen ($42 USD), it’s also at the top end of what I consider affordable. The mini-rhino is fun to watch, but just standing there waving a fan at it to make it go gets old fast. The ideal would be to put in a solar-powered motor and a couple switches and allow it to wander around the yard on its own. You can put it out in a parking lot on a windy day and scare the dogs, too, which is always good clean fun. But, I think it is a little lacking in replay value as-is.
One of the interesting things about the Gakken Otona no Kagaku “beest” kits is that with the Strandebeest, which is normally wind-driven, one of the suggested mods is to add a Japanino-driven motor to make it remote-controlled. While with the Rhinoceros, which is man-powered, the Gakken version uses a fan and there’s no suggestion in the attached mook for adding a motor. When I had my mini-Strandebeest, I tried adding a motor, but the movement of the legs was so stiff that the motor wouldn’t spin and the wires overheated. So, I was a little hesitant to buy the mini-rhino. Fortunately, the legs are geared down so much that the fan propels it with just a moderate breeze. Naturally, the next step was to figure out how to automate it.
I was able to find a small electric fan for 100 yen ($1.20 USD), which runs on 2 AA batteries. After a little experimenting, I came up with a mounting for it that consists of 4 thin sheets of cardboard glued together. If I was still in Akihabara I’d just get a sheet of perf board, but the cardboard, at least, is free. Also at the 100 Yen shop, I got a small package of nuts and bolts, and some tie-wraps. I hand-bored holes in the body of the kit for mounting the cardboard panel, and just tie-wrapped the fan battery casing and the motor in place. Luckily, the little white gear on the squirrel cage fan spindle turns out to fit on the motor spindle perfectly. One reason for mounting the motor on the panel, instead of hot gluing everything to the kit body is that it lets me switch between the motor and the squirrel fan as I like.
Initially, I wanted to mount the panel so that it brought both arms of the kit together a bit for added structural integrity, but this caused the gear threads to pull apart from each other and disengage. Seems that the kit was designed for the arms to be pushed apart instead. But, at that point I’d already drilled the holes on one side of the panel too close to the edge and the corners tore off. If I were to do this again, I’d go with the perf board and just slot the two far-end holes to make adjusting the arm tension (and gear spacing) easier. Another issue was that even with the gearing ratio as it is, the motor ran so fast that the legs thrashed about extremely hard and threatened to self-destruct. Because I don’t have access to a 1-battery holder, a soldering iron, or a potentiometer right now, I pulled out a good battery and replaced it with one that was nearly dead. Coupled with the extra workload associated with having to carry the motor, plastic case and batteries, the resulting walking speed is much more sedate and acceptable.
In summary, I give myself a B for the final product. It make not look all that great, but it works as well as I could hope for. If I had my Japanino, I’d get a second motor, split the mini-rhino in two, and turn it into a proper self-sufficient programmable robot. Maybe another day.