Gakken Mechamo Centipede
Review date: 25 May 2006 Last modified 03-Dec-2011.
There are two kinds of people in the world.
Some of them can look at this thing and not want it. Even when they're told that it's remote controlled via infra-red and fully manoeuvrable - forward, reverse, turns either way while going forward or backward, and pirouettes (turning on the spot).
And yes, its 32 legs move in smooth, hypnotic waves.
It's not terribly expensive, either. Not dirt cheap, but not particularly extravagant either, especially if you shop around.
Part of the reason for the low price is that you get to build it yourself, which is of course a feature, not a bug.
And yet - no interest, from some people.
I would like to invite those people to go away and do something else.
Right then.
What we're looking at here is Gakken's Mechamo Centipede. It's about 32 centimetres long (12.6 inches), and it weighs about 1140 grams (2.5 pounds) with batteries.
Like the two lesser beasties in the Mechamo range, the Centipede comes as a kit that you build yourself, and it's battery powered and self-propelled. The two other Mechamos are a "Crab" and an "Inchworm"; the crab only trundles back and forth, but the inchworm is manoeuvrable, and a bit cheaper than the Centipede.
The inchworm's turning system is a bit of a cheat - there's a point in its gait where its feet are up in the air, and then it pivots on a turnable plate sticking down from its tummy.
So the Centipede, which is truly and honestly both propelled and skid-steered by its legs, is clearly the choice of connoisseurs.
This is, of course, not really very much of a centipede, even though it's got long enough legs, and few enough of them, that it bears a slight resemblance to various of them, including the common-in-the-USA but nonetheless alarming house centipede.
(At this point I am, of course, duty bound to note that in the scary-but-harmless-common-household-arthropod stakes, Australia wins.)
This "Centipede" is really more of a millipede in the way it works - its feet move in simple little circles, and its legs are unarticulated.
The Mechamo Centipede has also recently become rather more widely known thanks to the unstinting efforts of one I-Wei Huang. He's made several steam powered... things. Most of them are radio controlled, almost all of them are self-propelled (the steam Armatron doesn't go anywhere...), and the ones that move can be entirely unfairly summed up as little steam engines grafted onto some sort of chassis that was expecting to be driven by an electric motor or two.
There is nothing, no matter how innocent, he will not pervert.
(He's also making a truly excellent looking
steam crab
steam crab, using two of the back-and-forth-only
Crab kits to make a twin-engine monster that
can turn corners. The similarly upcoming
spider looks as if it'll do the same thing
better, though.)
You don't have to go to these lengths, though. The standard Mechamo Centipede kit includes everything you need to build your aluminium insect (including a little wrench and screwdriver), and everything you need to run it except for six AA batteries (four for the Centipede, two for the IR remote control).
This review will be, by the standards of my other R/C gadget opuses, a bit short. I actually bought my Centipede just to build and play with by myself, and didn't intend to write about it, so I didn't take pictures of the construction process and all the little bits this time. If you want to see all sides of the box, you're out of luck.
Fortunately, the (not-so-) old trick of downloading and reading the manual before you buy the product is available to you. You can find the English instruction manual in Adobe Acrobat format here; the parts list is here.
(You can read entertainingly translated versions of Gakken's pages for the Centipede, Crab and Inchworm here, here and here, respectively. They've been in business for quite a while (Hey! I had the Tandy version of this!); they've re-released several kits, and the Mechamo series is apparently in some way related to some kits they were selling back in 1972. Some of their products are rather older designs, though; versions of these little automata have been around for centuries.)
Building it
There are a lot of places where a hobby kit manufacturer can go horribly wrong. If you just take something that's meant to be built on a production line and put the parts in a box, you can end up making your customers miserable. Parts that can be assembled the wrong way round, similar but different fasteners resulting in reamed holes and jammed screws, tiny components that're hard to find and easy to lose again, instructions that don't quite match the parts; the list goes on. People who build kits of all kinds - including plastic models and flat-pack furniture - will know what I'm talking about, here.
In the mass-production world, it doesn't matter much if it takes a worker three tries to get it right. Kit buyers, on the other hand, usually only want to build one kit, and are both familiar with and annoyed by that feeling that now they know how to do it, but it's too late.
If you check out the above-linked instructions for the Centipede, though, you'll see that they bode well. And, I'm happy to say, Gakken have really paid attention to detail. I had no trouble at all assembling the kit with it sitting on my lap, just using the lid of the box next to me on the couch to hold the parts, and using only the included tools.
I kept noticing nice little touches.
There are, for instance, several aspects of a 32-legged walker that could make it a Big Pain to put together. Each of the 16 legs on each side of the Centipede needs to be driven by a crank with a particular angle between the input shaft and the output one - to put each leg in the right stage of the walk cycle compared with all of the others.
And one side of each crank has to be slightly bent, to engage the mechanism properly.
So the cranks are pre-assembled, and pre-bent. And each crank is numbered. And the places where the cranks go are numbered too. And the nines are underlined, on the #9 cranks and on their matching slots. You can still go wrong, but you have to really try.
If you're the kind of model builder who's really determined to build every part of the model then pre-assembled parts like this are going to disappoint you. I think you'd probably loosen your modelling ethics up a bit by the time you got your tenth crank angle wrong, though.
Every part of the Centipede that looks as if it can go in either way around can go in either way around, unless the instructions very clearly point out how to tell which way around the part should be. And the instructions don't just point this out the first time they mention that part; they remind you over and over later on.
There are also lots of spare small fasteners. It costs kit manufacturers very little to include 36 little screws when you only need 32, but some of them don't, resulting in carpet-grovelling if you drop just one of the tiny buggers.
The Mechamo kits are recommended for people aged 15 and up, but all of the above says to me that considerably younger kids should be able to put them together, adult supervision or no adult supervision. Kindergarten kids, no, but I could have built a Centipede well before high school, and I trained on Lego, not Meccano.
There are some reasons to keep smaller kids away from these kits, though.
It is, for a start, quite possible to get bitten severely by the Mechamo gear trains if you stick your finger in there. The motors these kits use are weedy, but there's a lot of gear reduction, all of those gears are metal, and they have no protective covers.
There are some sharp edges, too. The parts are all stamped metal, but they're very cleanly stamped out of aluminium, so this isn't the classic cheap-computer-case box-full-of-razors. Still, one side of every edge is sharp enough to draw blood if you bark your finger up against it hard enough.
How it works
The control and steering system for the Centipede is the same as that used by various radio controlled tanks. There's one motor for each side, and each motor can run independently of the other; result, steerability.
Instead of a simple sprocket pulling on a track, though, the Centipede has all those crank-driven legs.
A simple millipede-walker like this only needs to move its feet in circles, but that's still not totally straightforward, especially in an affordable model that uses simple bent-metal components and not luxury stuff like ball joints.
Each of the Centipede's legs has a two-way pivot at the inboard end, and hooks onto a drive crank roughly halfway along its length. This could be a real pain to put together, but once again the Gakken designers have made sure it isn't. The legs come with the inboard hinge already assembled (it's riveted together), so you only have to fix them in place with one screw; the crank hooks onto the leg with a simple peg through a hole, so no fastener's needed there.
The Centipede's remote control has a single thumb-joystick, which makes the control system intuitive. Personally, though, I prefer twin-stick control for skid-steer vehicles - just one fore-and-aft stick for each side.
Like an ordinary IR remote, the Mechamo one only uses any power when it's sending a signal, so it doesn't need an on/off switch.
(The Centipede itself doesn't flatten its batteries much if you leave it on by mistake either, by the way.
Some switchless remotes, mind you, really ought to have a switch. The radio transmitter for this cool thing is power-switchless; leave a battery in it, though, and it'll run it dead flat. And it's one of those old-style consumer R/C toys with a bunch of AAs in the car and a 9V battery for the transmitter, not a modern all-AA job like the Centipede. Don't let me stop you from buying one, though.)
For all this simplicity, though, I found the Centipede a bit difficult to just drive in a straight line. If you don't push the stick exactly forward, one or the other side will tend to cut out. And it took more pressure to make the stick work than seemed sensible, too. A little kid might have real problems.
The weirdness of the controller was explained when I looked inside it.
I was expecting to find four little switches in a plus-sign layout - one for forward, one for backward, and one each for left and right, with two possible pressure levels for the turn switches.
Instead, I found this. Four single-pressure switches in an X configuration, not a plus-sign one.
Clockwise from top left, they're right-legs-forward, left-legs-forward, right-legs-backward, left-legs-backward. Moving the stick forward presses the top two, backward presses the bottom two, and directly to either side both on that side, giving a pirouette. Moving the stick to either side with a bit of a forward or backward bias presses only one button on that side, giving the old-tank-style braked turn.
(Many tracked vehicles, past and present, can't pirouette; they just try to drive forward or backward, and you use a brake and/or a clutch to remove drive from one side to execute a turn. Agricultural tractors have separate brakes for each rear wheel, for similar reasons.)
Once you know how the control switches are laid out, it becomes easier to drive the Centipede. You don't actually need much pressure to trigger these little rubber-dome switches; you just need to know where they are. A lighter touch with more accuracy makes the driving simpler.
Not that this thing's particularly thrilling to drive. With fresh batteries, the Centipede storms along at about 0.4 kilometres per hour. Battery life permitting, it'll take an hour to cover the quarter-mile. Even a DigiQ tank can outdistance it. So if you're racing anything faster than a Walkie Bits tortoise, you're going to lose.
The Centipede is less likely to be fazed by stuff it runs over than most small, slow remote controlled gadgets - its little legs move like oars, not like wheels, it's got no axles for hairs to wind around, and no tracks to throw. So it can handle grass and carpet quite well. And it's a more stable chassis than a Roboraptor. But that's about all you can say for its all-terrain talents.
That, of course, is not the point. It's the look of it in motion, not the speed or precision of that motion, that matters.
So, I hear you ask, what does it look like in motion?
I'm glad you asked.
Using a digital video camera which currently has a retail value of, oh, maybe $20, I've captured some thrilling vision of the Centipede in action.
Here it is trundling up, turning and trundling away again. Here it is just passing by. Here it is on its back, pathetically waving its legs in the air. And, my personal favourite, here it is passing very, very close to the camera.
When I shot all of these videos, by the way, there were no fewer than three cats in the room. You don't see them in the clips because the Centipede causes their tiny brains to seize up. It's not fast enough to be really scary; it has, indeed, certain food/toy qualities. But they still elect to observe it from a safe distance.
Your own pet/Centipede interactions may vary.
Fiddling
The Centipede's two battery boxes, and its remote control, both have battery doors held on by a captive screw. This stops kids from removing and losing the door and/or the batteries, which is good, but makes battery changes more onerous. You're not likely to be swapping Centipede batteries all that often, though, unless you start a racing league or something.
It would, by the way, be pathetically easy to convert the Centipede to run from a rechargeable battery pack. Just using NiMH AAs in the standard battery boxes will make the robo-bug even slower (the Centipede doesn't draw enough power to suck alkalines down to match the lower terminal voltage of NiMH cells), but the standard R/C trick of running low current four-alkaline devices from five rechargeables should work perfectly.
There are lots of five-cell pack configurations that'd fit into the Centipede's long and skinny spine tray. I think five sub-C cells in a nose-to-tail row would be favourite. Cheap old NiCd sub-Cs (a use for that old Tamiya six cell stick pack with one dead cell!) will give you around the same run time as alkalines; modern high capacity NiMH sub-Cs may give you as much as twice the run time.
You could probably also hot-rod the Centipede with another volt or two, but don't come crying to me if you blow up the receiver.
Of course, it needn't be the end of the world if you do. It'd be easy to run the Centipede from normal radio control gear. A couple of standard reversible speed controllers (even the old mechanical kind) and an inexpensive stick radio (as long as it's not so inexpensive that you can't set it up with two fore-and-aft sticks) would get you rolling again, and then you'd be able to drive the motors a lot harder, or swap them out for beefier units. The motor geartrain terminates in one simple shaft, which is why it's so (relatively) easy to convert a Centipede to steam power. Various other power sources would work too.
(The first person to create a Centipede powered by two hamsters in exercise wheels gets a gold star.)
Eye candy
I put up some desktop-background-sized pics of the Centipede on my front page a while ago; they've scrolled off the end now, so here they are again.
Plain 768-pixel-high version here; 960-pixel-high here, 1024 here, 1200 here. Arty faded version 768 pixels high here, 960 here, 1024 here, 1200 here.
Buying one
Beautifully packaged, well designed, well documented Japanese hobby stuff can reasonably be expected to be fairly expensive in Japan and ridiculously expensive everywhere else.
And you can, indeed, pay quite a bit of money for Mechamo kits. Edmund Scientific (purveyors of some fine gadgets I've talked about before), for instance, sell the Centipede for $US159.95 plus $US15.50 shipping, in the USA. Hit eBay and you can push that down to $US120 or so, ex shipping.
Forget, utterly, all such shopping around. Buy your Gakken gear from HobbyLink Japan.
They sell the Centipede for 5700 yen, plus about 4700 yen for delivery outside Japan (because the Centipede box is not tiny, and HLJ add good extra packaging around the standard box).
As I write this, 10,400 yen is about $US95 or $AU122, which is so much better than the best other prices that it's not even funny.
The only down side to this is that HLJ generally run pretty close to the wind, stock-wise, on account of how they stock an incredible amount of essentially useless stuff and don't want to end up sitting on thousands of units of things that nobody wants.
As I write this, HLJ have Centipedes to sell; a couple of weeks ago, they didn't. Their stock control system is pretty nifty, though, and for un-rare items like the Centipede you're unlikely to have to wait long.
And, unlike many dealers, HLJ don't take your money now for goods to be shipped at some point in the future, even if you choose to pay via PayPal.
Yes, I have received free stuff from HLJ in the past, but I have bought plenty more stuff from them as well. This is not a paid advertisement.
Overall
If the Mechamo Centipede came pre-assembled, it'd still be pretty nifty, but not as good as it is. If you can't see why that is, then you're one of those people I told not to read this review.
If you just build it, play with it a bit, then put it on display, a Mechamo Centipede will have been well worth what you paid if you had it mailed to you from Japan; it'll be ridiculously good value if you bought it in Japan, though one of these in a holiday-maker's suitcase may or may not cause the airport security screeners to utterly freak out.
If you feel like building something on a skid-steer chassis, though, and wheels or tracks just don't tickle your fancy, I assure you that a Mechamo Centipede will.
Be warned, though; it may well lead to harder drugs - or at least a heavy Gakken habit. They've got a quite impressive array of new vaguely educational doodads; all of them are, like the Centipede, cheaper than you'd think, for what you get.
(Once again, HLJ seem to be the price leader. Would you rather pay $US65, or $US22?)
Personally, I think I can restrict myself to just the Centipede for now. But I should mention that I've already bought another Centipede, to put on the present pile and, in time, dispense to some suitably deserving friend.
(I also got a few of these, which are quite useful little holders for parts and soldering and such, but whose primary appeal is that, as you can see if you look closely at the box, they're called "Mr Almighty Clips II". The first version was, presumably, insufficiently almighty.)
Highly recommended.
