Boomting!

There are disadvantages to living on several acres out in the country.

It's a long walk to the shops. Fast Internet can be a problem. If you're having a heart attack, the ambulance may come too late.

But on the other hand, there's this.

(I'm sure I've linked to videos of anvil shooting on previous occasions; hell, the pastime's even had its own TV special now. But if anything deserves a repost...)

Some might suggest that standard anvil patterns have a hollow in the bottom because it saves a little weight and a little money, and has no effect on the all-important hammer-bounciness of the top surface.

Others know the real reason.

More DIY noise

Further to yesterday's post about speakers:

Home-built speakers
(Image source: Flickr user Enrico Salad)

If you're looking for some reading matter to ease you into loudspeaker design and construction, do not buy Vance Dickason's famous, though now out of print, Loudspeaker Design Cookbook. Even getting a pirated PDF of it is not a great idea. This is because the Design Cookbook is for people who already know what they're doing - its subtitle is "Everything you Need to Become a Better Speaker Designer", emphasis mine. You're going to have to learn about Thiele/Small parameters and some other technical stuff at some point if you're building most kinds of multi-driver and ported loudspeaker, but there are several kinds of speaker you can build without doing anything beyond basic arithmetic.

There are a ton of books about speaker design, most of which I've never read, so maybe I'm about to suggest you go in a non-optimal direction. But the best book I have read on the subject is V.A. Capel's An Introduction to Loudspeakers and Enclosure Design, which is also out of print but can still be had cheaply on Amazon and on eBay (there are local Australian and UK sellers!UK sellers!).

An Introduction to Loudspeakers and Enclosure Design does what it says on the tin, and includes detailed instructions for building one of those single-cheap-driver transmission-line speakers I'm so keen on. If you build it according to the instructions you'll end up with a folded transmission line with ceramic-tile reflectors on the corners; I'm pretty sure just making the reflectors out of wood wouldn't significantly hurt performance.

Transmission-line speaker project
(Image source: Flickr user Moisturizing Tranquilizers)

You don't have to do all the extra woodwork required to make a transmission-line enclosure, though. A simple sealed box with one driver will do.

Single-driver loudspeakers
(Image source: Flickr user Milestoned); these speakers are the Visaton Solo 100s, one of those short-form kits where you have to make your own boxes.

There's a whole subsection of the audiophile world - both the empirical and the woo-woo side - devoted to single-driver speakers, and such a speaker is a really good option for your first speaker project.

Small home-built powered speakers
(Image source: Flickr user drosen7900)

A solidly constructed box with a single cheap driver can sound remarkably good, especially if the speakers are close to the listener, even though the response plot reports high treble and low bass are missing, presumed dead, and the midrange response looks like a Worms battlefield.

Loony-audiophile supply houses stand ready to relieve you of extraordinary amounts of money for Fostex or Tannoy drivers...

Home-built mini hi-fi
(Image source: Flickr user drosen7900. More about these speakers here.)

...but now that few people use CRT monitors and TVs, you can build your own computer or hi-fi/home-theatre speakers without even bothering to use magnetically shielded drivers. Any dirt-cheap paper-cone wideranges, or multi-driver round or oval car speakers (which are not strictly speaking single drivers, but can sound good just the same) will do.

And for your first project, all you need is a sealed box, the bigger the better, with one hole in the front that roughly fits a single driver. You will probably need to be able to solder, but not a lot of work is involved, and what work you do have to do can be quite sloppy and still give a perfectly functional result. (Think of it as the Roman Army knife of loudspeakers!)

Oh, and on the subject of very heavy speaker cabinets: What do you do if you've already got some speakers, but you want their cabinets to be less resonant?

Concrete speaker stand
(Image source: Flickr user Voxphoto)

Just cast your own speaker stands out of concrete, and bolt the speakers onto them!

DIY noise

Speaker kit

A commenter on yesterday's post about glass-fibre speaker-box lagging lamented that he can't get loudspeaker kits in the States.

He is wrong. There are definitely speaker-kit sellers in the States. Probably quite a few of them, given the much larger market. (Australian population: 23 million. US population: 314 million.)

I think the biggest name in US speaker kits (do feel free to correct me in the comments) is Parts Express, mostly under their in-house "Dayton" brand. There was a Dayton driver...

Dayton bass driver

...in the kit subwoofer I reviewed.

Parts Express sell everything you need to make speakers of your own design, and have a reasonable selection of kits, too. Their speaker-kit listing is here; prices are quite good, especially given that most of the kits have enclosures that are veneered or otherwise nicely finished.

Parts Express speaker kit

This super-cheap Parts Express kit comes with only bare plywood boxes, but it's two little 2-way speakers for $US128 with free US delivery! For some reason the kit lacks binding posts and wire, but you can get those for a few bucks more; if you're really pinching pennies, buy those parts on eBay from China.

(Oddly, absolutely nobody seems to sell speaker kits on eBay. I wonder if that's because of the awkwardness of shipping all that wood.)

Note that these little speakers aren't really "bookshelf" speakers, because they have a port on the back, and if you plug the port by pushing it up against a wall, your bass will go away. You certainly can put them on a bookshelf, but you can't push them all the way in like a book.

This Parts Express kit is expensive...

Crazy-looking speakers

...and regrettably also out of stock, but how can you not want them!?

Back here in Australia, the inventively named "The Loud Speaker Kit", makers of all the kit speakers I've reviewed, is now out of business. I'm not an authority on other Australian speaker-kit places, but I know of a few.

Peninsula Home Theatre have some rather expensive options (their prices are per speaker, not per pair...), but the drivers are high-quality and the boxes are very nicely finished.

Omnidirectional kit speakers

Decibel Hi-Fi's omnidirectional kit speakers look fun too, but are a bit expensive.

Danish Sound Technology have kits, but you have to contact them for prices, which is not a good sign.

Fountek kit speaker

The Fountek "Signature Series" kits look good for the money, though.

ER Audio has electrostatic-speaker kits, which are all very expensive, but that's because electrostatic loudspeakers are awesome. (They're hideously incompatible with cats and small children, though.)

VAF Research sell kit versions of at least some of their speakers, too, but they're very high-end so their kits cost thousands as well.

At one time or another I think all of the Australian chain electronics stores - Altronics, Dick Smith, Jaycar and possibly even Tandy (Radio Shack in the States, amalgamated with Dick Smith now in Australia) - have offered speaker kits. At the moment I think only Jaycar have them, and they've only got one.

Jaycar kit-speaker electronics

These electronics plus these cabinets give you...

Jaycar kit speaker

...some very nice European-driver loudspeakers for $AU698 all up, which is quite good value.

You could save a little by only buying the electronics and building your own cabinets. Many "speaker kit" dealers work this way - they sell "short form" kits, giving you everything but the boxes. In Australia, people who sell these kinds of kits include Soundlabs Group and Stones Sound Studio, the latter dealer continuing the proud association between... untidy... Web-site design and audiophile woo-woo. (They also sell the Fountek kits mentioned above.)

Making your own enclosures isn't actually all that hard, by the way; I did it when I was a teenager. If you're a DIYer without a table saw, you just go to a place that sells wood-sheet products and get them to cut some MDF to size for you. Note that they will probably only do cuts all the way across the sheet (or what remains of the sheet after previous cuts), so it can be a bit of a puzzle to get all the parts you want out of the minimum number of sheets. This lets you have unusual finishes on your speakers, though; any material you can use for a kitchen counter, for instance, you can use for a speaker.

Anyway, you get the panels made, then assemble the boxes at home with simple screws 'n' glue and ugly butt joints (proper woodworkers of course use mitre joints). You can jigsaw the holes for the drivers; it doesn't matter if the holes aren't perfectly round, because the driver surround will cover them.

(When I was about 15, I cut my own box panels freehand with a jigsaw from a sheet of super-cheap particle board, and then plugged the gaps where the wood didn't quite touch with Blu-Tack!)

Taking the further step of building your own speakers from scratch isn't that hard, either, especially if you build simple sealed boxes. Doing it entirely yourself is also the only way to get some unusual speaker designs, like corner-loaded horns and transmission lines, at an affordable price.

Transmission lines are one of my favourite loudspeaker types. You make a tall hollow square wooden tube, or reduce the size by folding the tube and putting periscope-type sound-reflecting angled pieces on the corners. The drivers go at the top in the front, there's a port at the bottom at the back, with lagging material all the way down the tube so very little sound actually makes it out of the back. Even if the driver you use is a paper-cone widerange from a junkyard car, the result will often be quite startlingly good, even though the frequency-response plot will look dreadful.

There's no good way to get low bass out of this design without making it really big, though - I once made some folded transmission lines with eight-inch whizzer-cone wideranges in them, and they still didn't have really low bass, but were serious pieces of furniture. So if that matters to you and you don't want the speakers to dominate the room a bit, you'll need a subwoofer as well.

Building your own cabinets also lets you massively over-build the cabinets, for near-zero panel resonance. The easiest way is to use super-thick wood and many braces inside, but you can also make a double-walled design filled with sand, cement or even lead shot, or line the panels with lead sheet. Many super-expensive speakers have cabinets like this, but retailers hate them; do-it-yourself lets you have super-cabinets with affordably-priced drivers in them.

I'm sure some readers know of other speaker-kit outfits; I only mentioned Parts Express in the States, but I'm sure there are more options there and in other countries. I invite people living elsewhere to comment.

And heck, we don't even have to be talking about only kit speakers. Do tell if you know of pre-built speakers that offer similar value for money, like those white-van speakers sold for fair prices on eBay I wrote about a while ago.

More knives and stabbing weapons

A reader writes:

I have little background knowledge of knives and even less experience with sharpening. I recently did some googling of your older articles to learn a bit more about these topics.

[Except for the Miyabi 613 review I put up the other day...

Big eff-off shiny knife

...and this piece, I haven't actually written much about knives and sharpening. These three reviews don't really talk about it. -Dan]

I'm in the market for some solid kitchen knives. It looks like buying some used Global knives on eBay might be a good way to get some high quality steel. I would likely purchase the CRKT Slide Sharp (based on your recommendation) and attempt to learn to sharpen. The other possibility is a ceramic knife, since these kitchen knives shouldn't ever be prone to "abuse". Which would you recommend?

More interestingly, though, I'm looking to purchase an every-day-carry foldable knife for my Dad. He has a long history of buying $20 pocket knives and shortly destroying them. He uses them to pry, chisel, stab, cut, and occasionally as a makeshift screwdriver. I've done some brief research on the topic and heard some names like "Strider" tossed around. I'm OK with spending some decent money to get a knife that will withstand this sort of abuse (and ideally have a warranty of some type). What would you recommend in this situation?

Kendell

Yes, used famous-brand kitchen knives are a good idea, provided they haven't already been sharpened down to nothing, or hideously abused. (See also, old cast-iron pots and pans. Very tough, and quite non-stick too, when properly seasoned.)

If you're going to be using the knives a lot then you might want to try a few different types, though. Not only are there umpteen blade styles, but some people prefer Global's unusual seamless ovoid handles, some like traditional Western handles that're a riveted sandwich with a full tang in the middle, and some people prefer the circular traditional Japanese handles.

If you're buying used knives that you're probably going to have to sharpen before you use them, though, you should practice on a cheap knife or three before assaulting a nice one. Yes, it is possible for a complete amateur to to screw up even when using a guide jig, and the faster a given sharpening system works, the faster you can screw up.

The Slide Sharp jig is pretty close to foolproof, but because it's based on ceramic "crock sticks", it's no good for sharpening a really blunt blade. It'll do it eventually, but it's much better to start with a cheap coarse stone to put something approximating an edge on the blade.

So go to the dollar store and get yourself a cheap coarse stone or some suspiciously cheap alleged diamond cards, and the cheapest knives they've got that are actually physically functional. This mainly just means the knives need to have a a proper tang - steel extending from the blade - down the middle of the handle, not just some dinky glue joint; I don't know what the cheapie-stores are like where you live, but the one in my town doesn't have any really worthless knives. You'll probably find Western-style kitchen knives in a discount store, and quite often also small knives and cleavers using the single-sided Japanese chisel grind.

The only thing really wrong with super-cheap knives, provided they have a proper tang, is that they'll go blunt faster than a fancy knife. But that means they're faster to sharpen, too, and it also means you can just chuck them in the dishwasher and not worry about them maybe bouncing against a glass and denting the edge. "Oh no, my two-dollar knife is dented."

(Update: To make sure the above claims remain true of, at least, my local Go-Lo, I just bought a boning knife with a six-inch blade there, for $AU2.49. Full tang, good handle, and a good factory edge everywhere but on the tip, which is a common problem for cheap knives and easily remedied. All in all a perfectly satisfactory piece of cutlery even without touching up the tip, for marginally more than the price of a McDonald's cheeseburger.

Update 2: After about a year of use and numerous trips through the dishwasher, it's become apparent that the "rivets" holding the handle onto this super-cheap knife are just disks of metal glued onto the side of the handle. One has fallen off. So there's glue holding the handle and blade together, instead of real rivets, but it's still holding on fine. It'd be easy to re-attach the handle "scales" to the sides of the blade if they ever do come loose. Here's an illustrated article about the handle of a knife with real rivets, in case you're wondering what I'm talking about.

There were four-knife sets there too, including a full-sized carving knife, for less than $AU10. If I were a penniless student kitting out the share-house kitchen, I'd just get those knives and one cheap sharpening stone; job done, for a third of the price of one Wüsthof paring knife.)

You can get off-brand knives of decent quality quite cheaply, too. I like the ones Aldi supermarkets sometimes sell along with their other limited-time loss-leader products; their santoku-type knives have a good thin profile and those little hollows in the sides of the blade to stop sliced food sticking to the knife, and you can get a small one and a medium one for less than $US10. You may be able to find similar bargains in kitchen-gear or department stores, if the salespeople don't manage to steer you towards higher-margin European brands.

If you sprinkle a few carefully-chosen search terms on eBay, you can find quite a few decent-looking and cheap kitchen knives there, too.

Ceramic knives can now be had cheaply from the usual crapvendors (and Aldi!). I don't know how good the edge is on the off-brand ones, though, and they're basically unsharpenable even with diamond abrasive (you have to send the brand-name ones back to the factory for re-sharpening). So if you get a bad one it's going to stay bad forever. But if you get a decent one and don't use it to pry the lids off paint cans, in domestic use it'll probably last you many years. (I wouldn't be surprised if advanced materials, over the next decade or three, made knife-sharpening a thing of the past.)

I actively enjoy keeping steel knives sharp, so I haven't bothered to buy any ceramic ones. The only ceramic blade in this house is the one on my Kyocera scraper, which is an interesting tool; the ultra-hard blade hasn't visibly worn in years of use, and you can use it to scrape just about anything off just about anything else. If I were buying ceramic knives, I'd just start with the best-reviewed ones on DealExtreme or whereever. There are some pretty cheap ones on Amazon, too. (Note that the brightly-coloured super-cheap Komachi knives are actually steel with a low-friction plastic coating, not ceramic.)

The one other piece of advice I have for the kitchen-knife novice - not that I'm very far above novice status myself - is that you should never use a sharp knife on a glass cutting board, ceramic plate or stone tabletop. Cutting on a metal surface isn't a great idea, either. Glass cutting boards are wonderfully hygienic, and they're fine for cutting cheese on with a blunt knife, and they're also OK for the average domestic chef, because the average domestic chef has nothing but blunt knives anyway. Glass cutting boards might even be all right with ceramic knives, though I doubt it. They'll definitely instantly fold over the edge of a sharp steel knife, though. Use wooden or plastic cutting boards instead; plastic is the more hygienic.

On to the subject of your knife-torturing father.

No folding knife can be anything like as strong as a fixed-blade knife for levering and prying and such. Some fancy folders are a lot stronger than you'd expect, but it's just not possible to make a hinge that's as tough as a piece of solid metal.

(If you're in an emergency situation and have to pry something with a folding knife, then you'll often be successful; usually the blade will break before the pivot does. There's a good chance you'll ruin the pivot before anything actually breaks, though, so your folder won't fold any more.)

That said, there are indeed quite a few surprisingly tough folders. Kershaw's "Zero Tolerance" line, for instance, pretty much won't break unless you're really actively trying to break them:

The street price for the knives in that video is pretty high, though. Alleged "Zero Tolerance" knives go quite cheaply on eBay; I suspect most of them are knockoffs.

That's not necessarily a disaster, though. Just because the steel's cheaper and the machining's less precise doesn't mean a knife will be easy to break. The only knockoff knives I'm really leery about are liner-locks and their relatives the frame locks. These must be made precisely, with hard steel in the right places, or they may close on your hand during a push-cut.

(If in doubt, open the knife, turn it over and, with your fingers out of the closing path of the blade, smack the back of the blade sharply on the edge of a table. A lousy liner- or frame-lock knife, or a good one that's old and badly worn, will close when you do this.)

The "Strider" brand you mention is known for making very beefy knives that're probably about as strong...

...as a folder that fits in a pocket can possibly be (you name it, and someone on YouTube will be obsessing over it!), but I don't know anything more about them than that. Strider also make fixed-blades, which is really what you've got to get if you want to get as close as possible to indestructibility. Umpteen companies make different versions of the single-edged fixed-blade "combat knife"; a small one of those would suit your dad, if he doesn't have to have a folder.

If he must have a folder, I'm torn between suggesting some expensive chunky US-made "tactical" folder that preferably didn't hit too many branches when it fell out of the Mall Ninja tree, or just a hatful of cheap Chinese folders. Abuse will kill any folding knife eventually; if it only cost eight dollars in the first place, though, who cares?

You can also get cheap Chinese knockoffs of every oddball folding-knife innovation, which is a cheap way to make a fun little collection of things that'll make you bleed when you play with them while drunk.

(A gold-medal example of this is knockoffs of the Kershaw External Toggle, most of which copy the entertaining mechanism very well, but are smaller than the real thing. Here's one that isn't too tiny. There's a simple, safe way to open and close this sort of knife, and a flashy, dangerous way involving flicking the protruding lever with your thumb. The smaller the E.T. clone, the more it hungers to bisect your thumbnail.)

Columbia River Knife and Tool, makers of the abovementioned Slide Sharp kit, are known for their range of folding knives that open and close in peculiar ways. My own everyday pocket knife is a CRKT Rollock (now discontinued). Like many novelty folders, the Rollock doesn't really work any better than a normal folding knife - actually, it's slightly prone to close unexpectedly, or try to open in your pocket, and it's definitely not going to win any abuse-tolerance prizes. But it's cool, with no mall-ninja ballistic carbon-fibre tactical BS.

If you find something on eBay that's described as a CRKT or Spyderco or Strider or some other big-brand knife, and looks just like it, but costs a fifth as much, it's a knockoff. Some knockoffs are crap, many - often the ones that don't try to look exactly like a given big-brand knife - look and feel fine, and some are almost indistinguishable from the real thing.

I review an excellent example from the obviously-a-knockoff category, here; it shares only its general shape with the Boker original, and is an excellent tool for the money. I also once bought a couple of knockoff CRKT Glide Locks on eBay. They look exactly like the real thing, but one of them fell apart in a week.

It also occurs to me that a person who keeps abusing a knife by using it as some other kind of tool could, perhaps, be in the market for a multi-tool. I think the toughest of the Leatherman/Gerber-type plier-multitools is the SOG PowerLock, and there are of course many others. SOG also just released the PowerDuo, a plier-type tool with a full-size knife blade.

If you want the knife to be the main tool with other stuff less important, then a hollow-handled fixed-blade "survival knife" could be a good idea. The hollow handle doesn't have to have matches and tinder and fishing line in it, after all; you can pack other tools, like a real screwdriver for instance, in there.

The overwhelming majority of hollow-handle knives are garbage, because they have no tang to speak of and just glue connecting the blade to the handle. Until recently the only good options in this field were expensive models forged out of one piece of steel, but now the overgrown teenagers at Cold Steel have made the Survival Edge, which is big enough to be useful without being so large that it's a ridiculous Rambo knife, and whose plastic handle is moulded around the short tang of the knife.

The plastic-handle idea still sounds as if it'd be breakable, but...

...that does not seem to be the case. It's the thick end of fifty US bucks delivered, but comes with a polymer sheath and sharpening doodad, and if the above video can be believed, will probably last approximately forever.

The Survival Edge is also new enough that none of the ones on eBay should be knockoffs.

Yet.

One LED, two LED, red LED, blue LED

A reader writes:

Myself and a friend were just reading Big Clive's "Hack your solar garden lights", and we are unsure how he came to those amp readings and the conclusion that two LEDs use less amps than one.

LED brightness comparison

I am assuming we are just missing something, could you please enlighten us?

Daniel

To oversimplify, two LEDs in series have more resistance, so less current flows. But halving the current passing through an LED doesn't necessarily halve its brightness. Standard high-brightness 5mm LEDs generally have a 20-milliamp current draw on the spec sheet, but will glow from much less, and may be considerably more efficient at small currents.

The reason why this is an oversimplification is that LEDs, unlike incandescent-filament lamps, aren't just a relatively simple resistive device.

(And the "relatively" is in that sentence because not even tungsten-filament bulbs are completely straightforward. They have, for instance, a much lower resistance when cold than when operating. And reducing the power of a filament bulb will generally give you a reduction in apparent brightness that's greater than the reduction in power, because the filament will be cooler and more of its output will be down in the invisible infrared. LEDs, in contrast, only know how to make one colour, even when they're only barely creating a tiny spark of light. This is the case for white LEDs too, because to date all of those are actually blue LEDs with a phosphor coating that turns some of the blue light into other colours.)

Instead of being resistors, Light Emitting Diodes are, yes, diodes, with a constant voltage drop across them at a given temperature. But when they're lit they get warmer, causing them to pass more current and glow brighter and get warmer again, which can rapidly lead to destructive thermal runaway unless the LED is restrained in some way, by for instance limiting the source voltage so the LED will just never be able to get hot enough. Or, more commonly, by limiting the maximum possible current.

You can see how this can get complicated. (Power-supply design in general is a surprisingly tricky field.) Just running LEDs from a simple DC source via current-limiting resistors can be a bit complex; proper efficient LED drivers that deliver a set current no matter what LED you plug into them are more complicated again. (The drivers in garden lights are elegant, but like the "joule thief", not actually very efficient.)

Don't let all this put you off monkeying with garden lights, though; as Clive says, they're both easy to modify and so cheap that it doesn't matter if you wreck something. Just add some of the incredibly cheap high-brightness LEDs you can get nowadays (which I mentioned the other day), and you can make all sorts of decorative, and even useful, solar LED lights for close to no money at all.

DIY plastic update!

If you're not in Australia, and not interested in polycaprolactone, this post is not for you.

Regarding that second criterion, though, I think pretty much everyone should be interested in polycaprolactone. I'd actually go so far as to say that every home should have some, even if you're not at all "handy". Just put it in that kitchen drawer with the screwdriver, the hammer, the dried-up epoxy and the random screws and washers.

Well, put it there when you've finished playing with it, anyway.

As I explained in this rambling 2010 post about the construction of...

Home-made laser pointer

...this, um, thing, polycaprolactone (which is sold under several easier-to-remember brand names) is a remarkable substance.

It can be moulded like rather sticky, see-through clay when hot (its melting point is about 60°C, but it's comfortable to handle at quite high temperatures, thanks to low thermal conductivity). When it cools, it turns into a smooth opaque white plastic about as strong, and tough, and easy to shape with other tools, as nylon. You can use it to do anything you could do with nylon, except of course withstand temperatures above 60°C.

And, unlike Sugru and various other putties and clays, polycaprolactone is reusable - just heat it up again. It'll also last forever on the shelf, and isn't even toxic, unless you set it on fire and inhale deeply.

You need hot water to soften polycaprolactone, but that's the only thing remotely dangerous or difficult about this stuff. Any child old enough to boil water without supervision can use polycaprolactone to make, fix or modify things. Because you can reuse it as much as you like, polycaprolactone is also an excellent do-it-yourself material for klutzy adults.

I spent a while in the 2010 post talking about where to find polycaprolactone, and what it cost. At the time, it wasn't hard to find the stuff here in Australia, but it was a bit expensive.

Now one Peter Edmunds, the proprietor of plastimake.com, is selling polycaprolactone locally for good prices.

Plastimake-branded polycaprolactone comes as the same white granules as pretty much every other brand. ("Friendly Plastic"-branded polycaprolactone is rather more expensive, but can be had in numerous colours and finishes.) As I write this, there are only two package sizes available from Plastimake; a hundred grams is $AU10 including delivery anywhere in the country, and 800-gram jars are $AU30, plus a flat fee of $AU10 delivery for as many jars as you like. They accept PayPal or credit cards for payment.

(Plastimake sell on eBay as well. Prices are the same.)

For comparison, Jaycar are still selling Polymorph-branded polycaprolactone in Australia. Their pricing starts at $AU11.50 for 100 grams - plus delivery, if you're buying mail-order - and drops to $AU8.95 per hundred grams if you're buying a kilo or more.

So if you're building your own Plastic Pal Who's Fun to Be With and want four kilos of the stuff - which is quite a lot, because polycaprolactone is only slightly denser than water - Jaycar will relieve you of $AU368 including road-freight delivery, versus only $160 delivered from Plastimake.

The UK eBay dealer (on ebay.com, on ebay.co.uk) that I recommended in the last post is still selling Polymorph-branded polycaprolactone, too. A kilo from them is £15.10 (about $AU23, as I write this) plus international delivery, which currently isn't specified for this largest size. If four one-kilo bags cost the same to send to Australia as four kilos worth of their 750-gram bags, though, the delivered price for four kilos would be about a hundred quid, or $AU153.

So Plastimake are ahead by a bit for small amounts - and if you've never played with polycaprolactone before, a hundred-gram bag will be plenty to give you the idea - and they charge about the same for large amounts delivered to Australian customers as the best eBay dealer I've found.

(If you want to place a really big order, you can also contact Plastimake for a further discount.)

Plastimake have a good site, too. In addition to the usual simple instructions, there's a big page of example projects, containing the various simple repair projects you'd expect, plus...

Polycaprolactone fishing-rod eyelets

...eyelets for a rustic fishing rod...

Polycaprolactone Monkey headband

...an item of headwear which many Australians will recognise...

Polycaprolactone roses

...some quite impressive sculptures...

Polycaprolactone salami cap

...and that most prosaic of all kitchen accessories, the form-fitted salami cap.

Plastimake also have a page of techniques, including colouring the plastic (as seen in the rose sculpture), making thin sheets, and alternative heating techniques.

Plastimake are brand new, so I suppose it's possible that Peter Edmunds will turn out to take your money and run, or something. Presuming he is not a rip-off artist or crazy person, though, there's really no excuse any more for Australians to remain polycaprolactone-less.

The stuff really is very fun, very useful and very easy to work with, and it tremendously appeals to the large penny-pinching lobe of my brain. It'll never go stale or dry out, and if you drill or carve something you've made out of it, you can collect and reuse even tiny shavings.

Highly recommended.

Clang!

A reader writes:

Following on from your tweet yesterday, and this awesome dude you also tweeted about, I've been watching a lot of more or less realistic sword fights on YouTube.

Something occurred to me, though. If you're armored all over, including gauntlets, how can you hold a sword?

Wouldn't covering your whole hand with metal make it really easy for the sword to just slip out, or twist so you're whacking people instead of cutting them? How did/does that work?

Juan

Gauntlets were, and are, not steel gloves. They cover the back of the hand and wrist, which is the part your enemy can actually hit, not the gripping surface on the inside. Sturdy gloves were usually standard equipment too; they went along with all of the other padding and covering that went under and over your armour, to help soak up the shock of impacts and stop your mail from ripping your nipples off.

There were many kinds of armour gauntlets, some of which probably had plates and/or mail permanently attached to a glove. And there may actually have been full-coverage metal gauntlets, for some reason, too; many odd kinds of armour have been made, and many of the most impressive pieces were for display or ceremonial purposes, and so didn't need to be practical.

(Whenever you start talking about this stuff you tend to end up with a giant comments-thread argument among a bunch of people who know an awful lot about historical weaponry, or think they do because they've read a lot of Dungeons and Dragons sourcebooks.)

But, in general, gauntlet armour was for the backs of the hands.

Today, most things called "gauntlets" are whole tough gloves - motorcycle gauntlets, welding gauntlets, et cetera. They'd probably work well as undergloves for armour.

(The abovementioned Nikolas Lloyd's site has a page about armour he's made, but he's only done mail and hoplite armour. But on the mail page he uses the term "preventing over-much beflapment", and that should be good enough for anyone.)

July 4th handicrafts

'Tis the season for my ancient sparkler-bombs page to suddenly get a lot more traffic, as the great American combination of patriotism, capitalism and pyromania reaches its annual peak.

If you're wondering what sort of bomb we're talking about here, this video should fill you in. It was grabbed from elderly videotape by my friend Mark. Note the commentary and a brief ceiling-scorching appearance from a person who somewhat resembles me, but is much younger and thinner and has an annoying reedy voice.

(WD-40 cans don't do that any more. They probably still do if you put a little pile of thermite on top of them, though. This concludes the Extremely Dangerous Suggestions portion of this blog post.)

So, on the subject of Sparkler "Bombs" That Do Not Actually Go Bang, here's a letter I got a while ago:

I am considering building a sparkler "bomb" for the upcoming July 4th holiday here in the US. In the course of my research on how to safely construct one, I came across some other pages stating that sparklers without magnesium were substandard and would not produce the desired effect. These pages were directions for actual enclosed bombs but I was wondering if you had tried the magnesium-less sparklers in the course of your experimentation for the "fwoosh" version and whether there was a noticeable difference if you had.

The reason why I am asking is because the only sparklers I can find around here that are made with wire do not have magnesium and the ones that do are on wooden sticks.

MAV

My answer:

I think most of the combustion energy of a sparkler comes from the oxidiser-fuel combination - generally something like potassium nitrate plus dextrin, with optional extra carbon, sulfur, sawdust or whatever. The stuff that makes the actual sparks contributes relatively little to the combustion.

The spark composition obviously does contribute a lot to the great vertical whoosh of sparks you get from the standard, safe sparkler "bomb", though, so it's possible that less-sparky sparklers will make much the same noise, and much the same amount of heat, but be rather less exciting to watch.

(I've never tried wood-stick sparklers for this job either. They might work OK, if bound together with coat-hanger wire or something, but I don't know.)

It's tempting to spice up the combustion with, say, a dollop of aluminium powder such as you can buy from some paint suppliers. This might actually work well, but note that flammable metal powders can "self-confine", in which the metal chaotically melts even as it burns, causing small-to-medium explosions. That sort of thing could make a sparkler bomb significantly less safe.

Honestly, I think any sparkler that sparks reasonably well, even if it's a bit less impressive than the classic bright-white-sparks aluminium/magnesium type, should work. It's easy enough to do a small-scale test, though; make a mini-bomb of only 100-odd sparklers, and see what it does. It'll burn much slower than a bigger bomb (a full-sized sparkler bomb has a burn time of only about one second), but should still demonstrate the principle.