Science toys

July 12, 2003 8:54 PM

Self-built science toys. Too much fun with the world around you. I'm making the Binaca cannon first thing tomorrow.
posted by skyscraper (14 comments total)

i'm going to make a hydrogen bomb.
posted by birdherder at 10:14 PM on July 12, 2003

I like the gauss rifle, but I think I'd rather make a rail gun.
posted by Civil_Disobedient at 12:09 AM on July 13, 2003

On the cheap laser communication? Count me in. I wonder if I can transmit ethernet with four lasers.
posted by skallas at 2:00 AM on July 13, 2003

I used to love those little steamboats.
posted by Pretty_Generic at 4:33 AM on July 13, 2003

This is going to ruin my plans for yardwork today. Great site.
posted by TedW at 8:17 AM on July 13, 2003

Note the bianca cannon is touchy -- you have to get just the right mix of air and bianca (or, actually, to sound all geekly, the proper stochimetric mixture of oxygen and isobutane/isopropyl alcohol.) This can be surprisingly hard to do. You can cut out the bottom of one film can, and tape it to another, whole can (without lid,) making a double-height can, this is much, much easier to get to fire, but because of the added mass, doesn't go as far unless you hit that perfect mixture. Use the minimum of tape to connect them.

Oh, and the regular flavor works much better than the spearmint -- more isobutane, less isopropyl alcohol, is my guess, but I haven't sprayed any into a mass chromatograph, so I can't be certain.

Inspired by a friend, I built one that uses a disposable camera flash unit that, instead of firing a very large arc through a xenon filled tube, fires a shorter arc through air, and I use that to ignite the propellent. It works amazingly well, and with a 250uF, 250V capacitor storing the charge, it makes an amazingly nasty zap all by itself.

ObWarning: Kids, voltage and capacitance can provide a nasty shock. If you don't understand why, and don't know how to discharge large capacitors safely, don't play with this until you learn how. If you do know, you can often beg a couple of disposable camera bodies off of photo shops that develop the film, just buy one and tear it apart, or find them at various surplus shops.

Having noted that, as far as big caps go, 250V 220uF isn't that big. It will, however, bite you, so be careful. Learn habits that will let you play with serious capacitors later.

As to homebuilt toys and mad science, I have to give due credit to Bill Beaty's website. It looks simple, but just keep digging. Bill's greatest weakness is his greatest strength -- he thinks like a 10 year old (with a solid college level background in science.) So, there's some crackpottery there -- but it's fun crackpottery, and there's bunches and bunches of fun things. He's the reason I have a Van de Graaf, and, by Ghugle, you should have one too!

(last minute add. Spell Check wasn't particularly helpful here, and no, "b2b" is not a good replacement for "250V".)
posted by eriko at 8:54 AM on July 13, 2003

Oh, Civil_Disobedient, don't diss that ruler Gauss rifle until you've tried it. I started with the 4 NdFeB magnets, and was amazed how fast that last ball bearing flies out. I kept adding magnets, at 7, I could shatter glass across the table.

At 8, the force was too much for the sintered magnet, which shattered (NdFeB magnets are very, very brittle.) I'm thinking a belt of steel around the magnet -- the question is how much force will I lose?

Various surplus shops have these magnets for cheap (Just Google up "surplus shops" and find one locally, if you want to walk down and play with them first.)

Things to remember. 1) even small ones are powerful -- I have ones that are smaller than a dime, about twice as thick -- and lift two pounds easy. 2) These things will trash your credit cards in no time flat. 3) If you sit these next to a monitor, you'll magnetize the screen, which means you'll live with the weird colors forever (the weak degaussing coils in most monitors won't fix this.) 4) If you have two large ones, and they get close, they *will* jump together. If your finger is in the way, this can really, really hurt. If you finger isn't in the way, they can shatter from the force.

Given that, go play.
posted by eriko at 9:08 AM on July 13, 2003

Neat. Very neat.
posted by insulglass at 9:36 AM on July 13, 2003

Don't forget, everyone, fire is conductive. Remember when playing with spark gaps and explosives.
posted by Civil_Disobedient at 11:12 AM on July 13, 2003

*cough*

You would never do these things because the result, when done exactly wrong, is a total flameover of the fuel/air mix inside the bottle that sends it (literally) rocketing away, probably faster than you can turn your head to track it, and certainly louder than you want to hear. MUCH louder. A tremendous high volume and high pitched wooshing/hissing noise, probably no more than two feet from your ear, were you foolish enough totally disregard what I said and do what I told you not to do. Under these conditions, the bottle behaves like a rubber balloon on steroids releasing it's air. Fuck steroids: like a balloon with lightning up its ass, a HARD balloon with lightning up its ass.

Yes, it hit somebody. In the head. Well, more like the face. Yes, there was a lot of blood, and stitches, too.

Oh, and be sure not to flush the bottle with water between each flight.

posted by NortonDC at 2:58 PM on July 13, 2003

I want a Tesla howitzer.
posted by troutfishing at 7:02 PM on July 13, 2003

Skallas, you can transmit ethernet (old-fashioned "slow" ethernet) with one laser pretty darn easily. The trick is to get the existing ethernet hardware to do a lot of the analogue work for you.
posted by hattifattener at 7:13 PM on July 13, 2003

RE the binaca cannon: great fun. I built one a few months ago. The trick to getting the mixture to work perfectly: spray exactly one burst into the bottle, put it on the cap, and then WAIT ten minutes or so. Works spectacularly every time. Apparently it has a better chance to evaporate.

Also, if it doesn't work, don't confidently tap the ignition ten minutes later to demonstrate its failure to work. That surprised me big time.
posted by mmoncur at 10:21 PM on July 13, 2003

I want to build a vacuum pump. No, I won't tell you what for.

mmoncur, I had the same experience with a skyrocket once (before they banned fun stuff like fireworks sold from the local newsagent). Take it from me, once they are lit, they will fire - it just takes a while sometimes. Being hit in the face with one is not my idea of a fun way to spend a few microseconds.
posted by dg at 10:54 PM on July 13, 2003