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Magic for the lazy

20 September 2008 — dan

This is a magic ring.

Here's a nice American man explaining it.

If you'd like to buy one, and/or see a nice English man explain it...

...the wonderful but expensive Grand Illusions stock it, for a mere three pounds plus delivery and possible VAT.

Many of the things Grand Illusions sells are very hard to find anywhere else, but this ring is not one of those things. I got mine for $AU8.99 delivered from this eBay seller. (Here they are on ebay.com, instead of ebay.com.au.)

They've got a lot of thumb-tips, too. With one of those and a good supply of chicken giblets, you could set yourself up with a nice little psychic surgery business!

Posted in Nerdery, Toys. 1 Comment »

Making tracks

19 September 2008 — dan

The most common limiting factor for makers of powered Lego tanks always used to be tracks.

The simplest Lego tracks were the one-piece rubber "Technic Tread Crawler" tracks that came with the Universal Motor Set. The rubber tracks fit all of those plastic-box pre-Technic motors, and they work well enough, within their limits.

I, like umpteen other kids lucky enough to have two motors, just stuck 'em together side by side with one driving a track on the left and one driving a track on the right and, with two battery boxes, then had myself a skid-steer machine.

(Which would never go quite straight, because the battery voltage and motor performance on either side never quite matched. But it was close enough for government work.)

The little rubber tracks were very limited, though. If you wanted less-power-sapping tracks of arbitrary length, you had to use the Technic Link Tread pieces.

The Link Treads were basically just Technic Link Chains with a broad bar attached to the top. They were small enough to mesh with standard Technic gears, which made them rather delicate. Not to mention a bit fiddly for even small fingers to snap together.

The Technic Link Treads weren't actually the first Lego chain/link pieces. That honour goes to Technic Link Chain Old, which was much sturdier because it meshed with the old big spiky gears. The spiky gears were replaced by the finer-toothed ones around 1980, though, because the old ones didn't mesh terribly well with each other, and couldn't be made small enough for intricate mechanisms. (The biggest ones might make a pretty nice scale waterwheel, though.)

Recently, Lego came out with some much beefier tracks to go with the cool new Power Functions line. (I was proud of my pneumatic 8851 Excavator, back in the day, but the all-electric 8294 Excavator, complete with linear actuators, knocks it into a cocked hat.)

The new tracks don't mesh with standard gears, so they need special driving wheels. But apart from that, they seem to be an excellent solution to the problem of making a tracked Lego vehicle that can traverse something more challenging than short-pile carpet.

But, via the excellent Technic Bricks, here's an even beefier solution.

Yep; that's a tank with treads made out of short, straight Technic "lift arm" pieces. Heck, you could probably make a clunkier version of these tracks out of good old studded beams.

This track design looks to be highly scalable, very strong, and easily repairable with cheap parts. And it doesn't need to crawl like this; you could probably drive these tracks quite fast, if you used a couple of the stronger motors.

Posted in Nerdery, Toys. 6 Comments »

Every uni student needs a siege engine

16 September 2008 — dan

Herewith, a letter I received yesterday:

As the all-knowing expert on model war machines (and the receiver of sponsorship from Backyard Artillery if I recall correctly?), I was wondering if you could recommend to me a catapult or trebuchet that is:

- Suitable for a beginner with fairly limited access to tools
- Suitable for someone who lives in a college at university (i.e. must be highly portable)
- Shippable by a method that will have it arrive by the 6th of October (the recipient's birthday)
- Not unreasonably expensive (I was thinking in the range of $80-$120, but if thats too little for something exciting, go higher)

Advice on where to get it would also be nice :)

Ed

Backyard Artillery is one of Ron Toms' numerous Web sites. He also runs Trebuchet.com and CatapultKits.com. Of his current models, I think the TK3 Model Trebuchet is the closest to the Tabletop Trebuchet I reviewed years ago. You might also like the smaller Desktop Trebuchet.

Unfortunately, though, the RLT sites don't offer international shipping any more, on account of the usual credit-card fraud BS.

(Ed didn't specifically say that he's buying a gift for someone in Australia, but I presumed he was, from his .au e-mail address. If the recipient is in the USA, by all means just go straight to trebuchet.com or catapultkits.com and pick whatever you want. And if you follow my affiliate links, I'll get a cut!)

I don't know of any companies in Australia that sell trebuchet kits (if you do, tell us all in the comments!), but fortunately, there are some dealers who'll ship Down Under.

Educational Innovations at teachersource.com, for instance. I've bought from them and I think delivery was pretty snappy; ordinary international air mail should make the cut for you, provided the package doesn't get held for examination by Customs or something (which it shouldn't, but sometimes they just do it at random to packages that don't look suspicious).

Educational Innovations resell one of Ron Toms' kits; that'd probably suit you very nicely, but it's not cheap. Eighty US bucks for the kit, plus $US47.53 for delivery to Australia. Not peanuts, and a bit over your budget, but at least you ought to get it in plenty of time. And teachersource.com have lots of other cool stuff you might like.

You might also like to consider the kits ThinkGeek sell. You want the more expensive "Trebuchet Kit", not the cheaper "Catapult" one, which commits the cardinal sin of throwing from a cup on the end of the arm rather than from a sling.

(As I mentioned in the sidebar of the old trebuchet kit review, the cup-on-the-end "catapult" is the classic image of a medieval siege engine, but it's also mechanically stupid. All proper flingers actually used a sling, which allows the projectile to be hurled much faster than the end of the arm can move.)

ThinkGeek's international shipping fees are not low, either - more than the price of the kit, in this case, though the total is still well within your budget - but the regular DHL Express International delivery option is reliable and fast enough to make the cut for you. And the shipping's not too terrible if you add a few other lightweight items to the big thing you're buying; as with teachersource.com, you can easily build a small Emergency Present Pile out of ThinkGeek gear.

(See also HobbyLink Japan, who have tons of awesome stuff, much of which is not available anything like as cheaply, or at all, outside Japan. But don't see them now, because they don't have any siege engine kits.)

At this point, I started hunting on eBay, and found a couple of sellers with apparently identical treb kits for a reasonable price. Then I found the same thing on at catapultkits.com, which told me that this kit's from Pathfinders Design and Technology in Canada. Their trebuchet is a bit spindly, but that's because it's quite a nice scale model. And it's quite cheap. And Pathfinder even seem to offer international shipping - but when I entered dummy information to see how much the shipping actually cost (I just love how many sites make you do that...), I noticed that the "Country" box on the form is a text box, which doesn't seem to actually be taken into account when you click on through.

The Pathfinders site said shipping to Australia was a lousy nine bucks, for a grand total of $CA41.22. Which is great if it's true, but I'll bet you it's not.

If you're in Canada (or, surely, the USA...), though, Pathfinders look like an excellent source for cheap treb kits. They've got several other neat-looking products, too.

If ordering directly from Pathfinders doesn't work out, here and here are the eBay sellers I found that offerend the Pathfinders kit.

If it comes to that, it's actually not very difficult to make your own trebuchet, if you don't need something that can throw a bowling ball half a mile. Lego is very good for getting the hang of the concepts, and the basic simplicity of the idea - two A-frames, axle, throwing arm with sling at one end and weight at the other - means it's also not hard to knock one together from PVC pipe, or even authentic wood.

But a pile of plumbing and a book about siege engines is, I grant you, probably not the greatest of gifts.

(UPDATE: Murray Hill of 22AD Ancient & Medieval Artillery in New Zealand commented below. He isn't quite in the treb-kit business yet; at the moment he's just sending out free plans to school students, and making catapults himself for schools, now and then. But he just told me that he plans to "come up with a student friendly machine" quite soon. Check out his Web site, particularly the Shop section, for updates!)

Posted in Nerdery, Toys. 3 Comments »

News flash: Fuel cell even more forgettable than I thought!

9 September 2008 — dan

The other day, I concluded that the Medis 24-7 Power Pack fuel-cell gadget-charger wasn't a very interesting product, based on its specifications. The spec sheet didn't make it look as if the fuel cell could do anything you couldn't do with much cheaper conventional batteries.

I'm now indebted to blogger Techskeptic, a man after my own heart except less lazy. He, as he mentions in the comments for the original Medis post, actually bought some Medis power packs and tested them thoroughly.

The results are explained in great detail in Techskeptic's final testing report, replete with the kind of graphs that I only bother to make when I'm testing something completely hilarious.

Techskeptic tested three Medis Power Packs, and found that they actually managed to deliver only about nine to 13 watt-hours into real loads. Medis claim twenty watt-hours in their literature, and it's that figure on which I based my own unimpressed response.

So these things actually appear to be even worse than they seemed.

The lousy real-world performance could be due in part to Medis optimistically listing the amount of energy the fuel cell actually (sorta-kinda) delivers on the sticker, rather than the amount of energy that makes it out of the Power Pack, down the cable and into the device you're charging. There's a DC-to-DC converter, you see, that takes the very low output voltage of the fuel cell (less than one volt) and boosts it to a gadget-charging level. And that converter turned out to be only about 70% efficient at best. Into a one-watt load, it dropped to about 60%.

So Techskeptic concluded that the Medis device didn't even beat a pack of six alkaline AAs. Actually, you'd probably get better results than the fuel cell if you hooked a similar voltage-booster up to a single humble D battery.

(Little kits to make that sort of converter, usually to allow you to replace low-capacity 9V batteries with beefier but lower-voltage cells, have been around for ages. Here's one that'll boost the output of two cells to 9V; I'm sure I've seen single-cell versions as well, but can't find one right now.)

So Medis' numbers would appear to be, at best, sort of like the old gross horsepower measurements that told you how much power a nude engine - no transmission, no air filter, no exhaust system, no alternator, no nothin' - on a test-stand once managed to deliver. This did not have very much to do with the amount of power that would make it to the rear wheels of a car powered by the same model of engine.

Posted in Electricity, Nerdery. 4 Comments »

Yet more SupCom destruction-orgy eye-candy

30 August 2008 — dan

This video - self-effacing announcement post here, 261Mb high-definition version here - features pretty much all of the new units in the current version of Supreme Commander, which is pretty neat by itself, especially in the HD version.

But it also rips off the Megadeth Duke Nukem theme, recently featured in an incredibly moronic Duke Nukem trailer. Which, for those out of the loop, was just a clip-art slideshow from older Duke Nukem games.

But it had pretty great music.

So here that music is, along with something far better to look at.

Posted in Games, Nerdery. 1 Comment »

Thank you for coming in and being so time-consuming, Blathers.

25 August 2008 — dan

Now that I know that Stephen Fry owns a pink Nintendo DS, I cannot help but visualise him playing Animal Crossing: Wild World and writing exceedingly genteel letters of apology to teddy bears.

While wearing reading glasses.

(Actually, I think it'd be funnier if he were running around pwning n00bs in Halo 3.
m3g4d3aTh: "Fag!"
JeevesMelchett: "I really don't think that's relevant.")

Posted in Games, Nerdery, Strange Tales. 2 Comments »

Further Freudian illumination

22 August 2008 — dan

The 85-watt compact fluorescent lamp I wrote about almost two years ago now still works fine. (Though the eBay seller I bought it from has vanished.)

But that lamp now looks a little... weedy.

This monster has a power rating - the actual power it draws, not the "equivalent" power that an incandesent bulb would have to draw to output the same amount of light - of two hundred and fifty watts.

(I found it in the eBay store of "DigiMate3". As sometimes happens on eBay, this store has a twin with all the same products, called CNW International.)

This lamp's output, in incandescent-equivalent terms, has to be something like 1200 watts. Since it's got the simple out-and-back design that doesn't get in its own way as much as a more compact (but in this case baroquely complex) spiral, I wouldn't be surprised if it actually shines as bright as three 500-watt halogen floodlights.

My 85W lamp lights the room it's in to about 205 lux, measuring on top of the spare bed that I use for most of my product photography. That's about half the brightness of outdoor light at sunrise or sunset on a clear day. This thing'd probably manage an easy 600 lux all by itself.

A few of these lamps would probably make fantastic workroom or warehouse lights. You could probably even power them from a normal domestic lighting circuit - many normal light sockets can deliver 250 watts safely, especially if they don't also have to cope with a 250-watt incandescent filament blasting away six inches away from the socket's plastic parts.

(You couldn't directly install these lamps in a normal light-bulb socket, because they use the big E39/E40 "Mogul" version of the Edison-screw fitting, rather than the bayonet fitting that's normal here in Australia or the "medium" Edison screw that most US light bulbs use. They're also obviously too heavy to dangle from a poor innocent domestic bulb socket, even if they'd otherwise fit; you can get simple screw-in medium-to-mogul adapters, but they don't magically make the bulb weightless. It wouldn't be a big deal to whip up a home-made luminaire to fit these lamps, though. You might even not electrocute yourself.)

You could even use these things as photo lights, though their colour rendering probably isn't all that great. The seller claims a Colour Rendering Index of 80, which ain't that bad, but might not be accurate.

I think most people who buy this things intend to use them as hydroponic grow-lights, though. I've written about this area of human endeavour before.

(Just think how much electricity would be saved if marijuana were legal, so people could grow it in their garden, instead of in their garage...)

Here's a hydroponic company being a bit sniffy about these "unbranded" lamps, which do indeed seem to be inferior to their similar...

...but even bigger product.

If you've found a CFL that's bigger still, do tell us in the comments.

UPDATE: It took some doing, but I managed to come up with something much more ridiculous than this bulb.

Posted in Electricity, Nerdery, Toys. 12 Comments »

From the "ball-bearing motor" file

19 August 2008 — dan

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":

Make Some "Liquid Nitrogen" - Awesome video clips here

Posted in Hacks, Nerdery, Science. 6 Comments »

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