I would have mentioned this earlier, but the excellent Illusion Sciences blog went over its Google Pages hosting quota, so I couldn't snag myself a copy of the SWF file to host on my own site.
Now the blog's back, so here it is:
Brilliant, huh?
More info at Illusion Sciences.
UPDATE: Here's a nifty HTML5 version of the same illusion, as per caerphoto's comment below.
The Phoenix spider-bot I mentioned earlier this year is now available as a (rather expensive) kit!
The kit costs $US949.99 ex shipping, which would be outrageous if all you got were the mechanical parts and R/C gear. But you also get a pre-programmed microcontroller that ties the bot's actions together, allowing you to control it with a wireless PlayStation controller, which is also included.
So it's not a Crabfu-type "robo-puppet", where leg movement is tied directly to stick movement. It's more like a normal radio-controlled walker, but with far more freedom of motion, including a variety of gaits.
And it can still play with boxes.
I never go camping, we have very reliable gas for cooking, and there are several overdue reviews I should be working on.
So I, naturally, just made a little camp stove, after reading about it on Cool Tools.
It's called the Super Cat, because it's made from a small cat-food tin. Since this household goes through small cat-food tins so rapidly that I really should have made some sort of belt-feed system for them by now, the raw materials were not difficult to procure.
And all you have to do to make a Super Cat is poke some holes in said tin.
That's it. You're done.
And it really does work. Mine worked perfectly first try, getting three cups of water from 15°C to a rolling boil in about seven minutes, which is when it ran out of its first shot-glass of methylated spirits (denatured alcohol) fuel. It won't work that well if there's a breeze or it's colder, but a couple of cups quickly boiled per shot of fuel ought to be possible in all sorts of real-world situations.
It's not the safest possible cooker, of course. It'd be easy to set your camp-site, or yourself, on fire if the little tin fell over or the pot on top overbalanced. (You should rest the pot on three rocks, or make a support out of coat-hanger wire or something.) And there's no heat adjustment - it runs full blast for several minutes, then goes out.
But if you're going to cook with an improvised naked-flame device, going with alcohol for fuel is not a bad idea. It doesn't burn hot enough to instantly cook you if you get some of it on you, and you can extinguish it easily with water.
Then again, the flame's invisible in sunlight, which can be a little risky. If you see someone crash a methanol-fueled racing car then leap out and start dancing around and screaming, he may not just be angry.
But c'mon, whaddaya want from a cooker you can make in fifteen minutes by candle-light with only a nail for a tool?
As I mentioned in my old piece about rare-earth magnets, there's a little cocktail-party physics demo I like to do.
(The deal is, I drink some cocktails, and then I do the demos.)
This demo shows magnetic eddy-current braking down the inside of a conductive tube. I take a length of aluminium tube, roll a plastic ball down it to demonstrate that it contains no gimmicks, and then drop a little rare-earth magnet down the tube.
You can hear the magnet going ting-ting-ting down the tube, but it takes a surprisingly long time to come out the other end. When I do this trick with a magnet that fits the tube quite closely, it takes about 30 seconds before it comes out. The plastic pellet takes only about 0.6 seconds.
You can also demonstrate magnetic braking with a chunk of copper and a decent-sized rare-earth magnet. If you slide the magnet up and down the copper, there's an oily feeling of resistance that gets stronger the faster you move the magnet. It fades away to nothing as the movement speed drops, though, which is why magnetic braking is such a great way to get precision balance scales to settle.
A more dramatic demonstration is to use a horizontal spinning disk of non-ferromagnetic, highly-conductive metal, preferably copper. It'll grab and throw a strong magnet that you bring close to it.
(More boringly, you can just use the magnet to slow down a less ferocious disk.)
In theory, you could even use this principle to achieve magnetic levitation. All you'd need would be two copper cylinders in the oh-so-safe "mangle" configuration, spinning like crazy around their long axes. Then a strong enough magnet could be suspended by the Lenz's Law eddy-current effect between and above the cylinders.
You'd have to be out of your freakin' mind to make such a thing, of course.
I give you: The one, the only, Bill Beaty. (More videos here.)
(Via. I should have noticed this when it was new, more than a year ago, but I didn't. I presume that in the intervening time at least one crank has decided that this, at last, must be the secret of antigravity/perpetual motion/free beer.)
Oh, and before someone asks me what a ball-bearing motor is: It's this.
And herewith, a more recent BillB video, partly just to get him a few MetaCafe hits (the older vids, like the one above, are on YouTube), and partly for "it's like cryogenic napalm":
Pretty much every time a new update appears in the Evil Mad Scientist Laboratories RSS feed, I am reminded of my own hateful indolence and miserable lack of talent.
Windell and Lenore have really outdone themselves this time, though.
(I think the next kit I get around to building will actually be a ThingamaKIT. If, that is, you don't count the trapezoidal loudspeakers and giant box of medieval wood from Ron Toms that've been awaiting my attention for lo, these many months.)
The latest CrabFu robot-made-out-of-servos is...
...the robot fish out of water.
A reader who'd noticed my affection for "the hideous, terrifying combination of polycaprolactone and robotics" just pointed me to...
...XRobots' Android 10. Which is, I think, not entirely unlike what you'd see in the workshop of a necromancer. Especially if he'd read a book about tensegrity lately.
Next project: Polycaprolactone Sedlec Ossuary, please!