Small Change, and Other Physics Fun 310
fishy jew writes "Ever want an easy way to make your 'small change' even smaller? Well, Bert Hickman has it - mix a home-brewed machine, 6.5 kiloJoules, and 100,000 Amps of current! On his website, he has descriptions and pictures of his many exploits with large quantities of electricity, notably including shrinking coins, building a Tesla coil, creating Lichtenberg figures (chaotic sculpture), and more! He has extensively outlined the equipment, procedure, and results for each of his experiments, and included many pretty pictures, too. Here are Google caches for when the site gets /.'ed: Main Page, Shrinking Coins, Tesla Coil, and Lichtenberg Figures."
I own one of these coins... very cool (Score:5, Informative)
There is a cool Popular Science article [popsci.com] for more information.
Now go buy some coins to fund Bert's efforts!
No pictures on google's cache (Score:3, Informative)
Not a Mirror, But Related (Score:3, Informative)
These guys do a lot of the same stuff.
Re:No pictures on google's cache (Score:3, Informative)
working link (Score:5, Informative)
Re:Google Cache? (Score:5, Informative)
Here, [ebay.com] Here, [ebay.com] Here, [ebay.com] And Here [ebay.com]
Tesla Coils and other cool stuff (Score:5, Informative)
Especially interesting are his high-voltage stuff [powerlabs.org].
Re:So.... why does this happen? (Score:2, Informative)
Bert's high-voltage equipment takes up most of his screened-in porch (from the looks of things, his wife drew a line at the sliding door?there's a clear border between tidy suburban house and chaotic suburban lab). Bert begins the coin-shrinking process by wrapping a quarter in copper wire and bolting the leads to copper bus bars, which are connected, by way of a triggered spark gap, to a 600-pound bank of 12,000-volt capacitors. A bulletproof blast shield encloses the coin and coil, and a high-voltage power supply charges up the capacitors. The only thing holding back the several thousand joules of energy stored in the capacitors is the tiny space between the spark gap's two brass discs.
Pressing a switch triggers the spark gap, which releases the entire charge through the coil in 25 millionths of a second. This creates a huge magnetic field, which induces a current and then a magnetic field inside the coin, which in turn pushes back against the field outside. The repulsion force between these two fields crushes the metal, instantly taking a quarter down to the size of a dime. A large amount of energy discharged in a short amount of time usually entails an explosion, and in this case the copper coil is blown apart with a brilliant flash and a satisfying bang. And, yes, the report is sharper than any drum, proving that you really can hit something as hard with magnetic force as you can with a drumstick.
yo.
Re:Is this legit? (Score:1, Informative)
Other links to shrunken coins (still up) (Score:2, Informative)
http://www.popsci.com/popsci/science/article/0,
http://home.earthlink.net/~smalldollars/dollar/
How shrinking a quarter works (Score:5, Informative)
* Results
* EM Field Theory and Wire Fragmentation?
* Isn't Defacing Money a Federal Crime?
* So Who Invented this Crazy Device?
* References
Theory of Operation:
The Quarter Shrinker uses a technique called high velocity electromagnetic metal forming, or "Magneforming". This technique was originally developed by the aerospace industry in conjunction with NASA, and has been popularized by Aerovox, Grumman, and Maxwell. It involves quickly discharging a high energy capacitor bank through a work coil to generate a very powerful and rapidly changing magnetic field which then "forms" the metal to be fabricated. While it works best with metals of relatively high electrical conductivity such as copper or aluminum alloys, it will work to a more limited extent with poorer conductors such as sheet steel.
In my current system, I charge up a large capacitor bank consisting of a number of large capacitors, each weighing about 165 pounds and about 30" high x 14" wide x 8" thick. A High Voltage relay is used to connect the caps either to a high voltage DC charging supply, or to a high power bleeder resistor chain. A 15 kV 60 mA transformer and a set of 40 kV rectifiers provide the DC charging voltage for the capacitor bank. The primary of the transformer can be overdriven to 140 volts via a variable autotransformer to speed up the charging process. The electrical energy stored in the capacitor bank is proportional to the square of the bank voltage, and the degree of "shrinking" force is directly proportional to the capacitor bank's energy.
The charged capacitor bank is quickly discharged through a single layer work coil made of heavy magnet wire. The coin is held firmly in the center of the coil by a pair of dowel rods so that it's axis of rotation is parallel to the centerline of the coil. This constrains the coin from twisting, and also helps balance the forces wanting to eject it from inside the coil. The two ends of the coil are stripped of insulation and firmly bolted to heavy copper bus bars. The high voltage "switch" that connects the capacitor bank to the work coil is actually a high power triggerable spark gap, called a "trigatron". The main gap electrodes are solid brass, 2.5" in diameter. One of the electrodes is drilled and tapped to hold the triggering electrode (actually a modified spark plug). A triggered spark gap is the only affordable device that can hold off the high voltage and then reliably and efficiently switch the high currents involved in the shrinking process (70,000 to over 100,000 amperes).
The trigatron is fired by applying a high voltage (~40 kV) pulse to the trigger electrode, which then causes the main gap in the trigatron to ionize and fire. Once the main gap fires, current rapidly climbs in the work coil, the rate of change (di/dt) being of the order of 4-5 billion amperes/second. The natural resonant frequency of the LC circuit formed by the capacitor bank and work coil is of the order of 8-12 kHz. Through transformer action, a huge circulating current is induced in the coin, but because of skin effect, this current is confined to the outermost rim of the coin, typically penetrating to a depth of less than 0.050". In clad coins more of this circulating current flows through the better conducting copper center of the clad sandwich than in the outer layers. The coin and work coil magnetic fields oppose each other (Lenz's Law), resulting in tremendous repulsion forces between the work coil and the rim of the coin. The circulating current in the rim of the coin actually prevents the rapidly increasing magnetic field of the work coil from penetrating the interior of the coin.
The large current that's induced into the outer rim of the coin can reach a million amperes or more! The initial bank energy is typically in the range of 3,500 - 8,500 Joules (or watt-seconds) but it is being discharged in microseconds. As a result, the instantaneous power is quite large, and for a brief instant is roughly
As seen on Ebay (Score:5, Informative)
Check out the picture and prices of the some of his work on ebay [ebay.com]
Try slashdoting that!
Re:Google Cache? (Score:5, Informative)
Jonah Hex
Re:Does the metal become more dense? (Score:5, Informative)
What happens is the coin ends up _thicker_ than before. Because it is thicker, the coin in turn becomes smaller. The mass is indeed the same before and after.
There is no exotic atomic manipulation going on. Not that people have tried (aka alchemy).
Here are his ebay auctions [ebay.com]
Google Image Cache (Score:3, Informative)
Re:Not a record, but... (Score:4, Informative)
There is relatively little risk of electrocution from a properly-tuned Tesla coil, although you could easily suffer a nasty RF burn if you're not careful (those take a long time to heal, for some reason.) Skin-effect keeps the current from passing through your body, but if the unit has low-frequency harmonics superposed upon the RF waveform you can get a nasty shock. I've experimented with Tesla coils (many years ago) and could stand there holding a sharp metal rod in one hand drawing a two foot arc to the discharge sphere. Scary as hell but lots of fun.
You are at far greater risk of electrocution from an electrostatic generator. A Van de Graaf or Wimshurst of even moderate size coupled with enough capacitance can kill you in an instant.
Re:Is this legit? (Score:4, Informative)
See http://www.pennysmasher.com/ [pennysmasher.com]
Re:Is this legit? (Score:2, Informative)
Companies selling souvenir penny-pressing machines [rockyrockholt.com] often cite Section 331, which says currency may not be defaced for fraudulant purposes. However, section 333 says that it is unlawful to alter the money "with intent to render such bank bill, draft, note, or other evidence of debt unfit to be reissued." I suppose the shrunken coins would be "unfit to be reissued," but then again so would souvenir squished pennies.
Re:So.... why does this happen? (Score:1, Informative)
What he's referring to looks rather different: twoonie image [currencymuseum.ca] (1 picture == 1kw). Basically, it's like there's an annular coin and a central coin inside it. Dunno if there's any way to separate them, short of dissolving one.
The first coin of this type that I saw was the late lamented 500-lira piece [eu.int]. Apparently the 1-euro and 2-euro coins are also like this, but I haven't handled either of them yet.
I think it looks kind of neat, but I don't mind the US not having one. We are very conservative with our currency design, and I like it that way.
I think that there is enough space between the particles in the metals at the newtonian scale that there should be no significant size difference between two different metals being shrunk by this method. At the atomic or subatomic scale, there might be a measurable difference difference, but i doubt it would be enough to affect the bond between the outer ring and the center.
You misunderstand what this process does. It squeezes the coin radially inward. It does not affect the density of the metal. (It is still an amazing thing of course.)
Wayback Machine (Score:5, Informative)
Try looking here. [archive.org]
Or here. [archive.org]
The archives are kind of old [archive.org] (pre 2004) but they seem to have some of the information.
Re:Not a record, but... (Score:5, Informative)
Judging by the description above (yeah it can be wrong, but the site is down for the moment) this sounds a lot like the capacitor bank in the lab I work in. Unlike a tesla coil, this think puts out some serious current. The one we have will output around 120,000 amps at 5 kV. It won't be that much if say a human were in between the connections, but that would be enough to give 250 mA of current to anything with less than 20 kOhm resistance. This sounds very similar to the setup this guy has, so I imagine it can be very dangerous. The lab seems somewhat lax about some of it, but that is because a huge amount of the wiring is well enclosed, which tends to be the exact opposite of all of my home projects.
Even then you have to be careful around pulses of this much current, since often weird things happen with ground. The grounded vacuum chamber we fire this stuff into will often get potentials of several hundred volts across different parts of the same metal chamber. Or if you have something connected to ground in two ways, you can induce a current going from one ground to the other. So it is a matter of knowing what not to touch with your hands or certain equipment when the thing fires.
Re:Not a record, but... (Score:3, Informative)
ScrewMaster NOT REMEMBER PLANCK'S CONSTANT.
RADIATION TO "ionizing living tissue" MUST HAVE PHOTON ENERGY ENOUGH TO IONIZE. ATOMIC PHYSICS USE UNIT "Rydberg" IONIZING ENERGY FOR HYDROGEN ATOM.
ONE RYDBERG BE 13.6 electron volts. NOT ALL IONS REQUIRE SO MUCH, BUT CLEARLY ORDER OF VOLTS. THINK OF BATTERY; CHEMICAL BATTERIES PRODUCE VOLTS.
Planck's constant [google.com] be equivalent to [nist.gov] 3.28 10^15 Hz. Even 1 eV be 2.41 10^14 Hz, or ABOUT TEN THOUSAND TIMES HIGHER than 2.4 10^9 Hz = 2.4 GHz.
HANDY CAVEMAN RULE OF THUMB: GET CANCER FROM UV SUNLIGHT, NOT INFRARED FIRE. FIRE THERMAL BURN ONLY, NOT IONIZING.
Since people are interested... (Score:5, Informative)
http://www.eskimo.com/~billb/ [eskimo.com]
Wrong Fun (Score:3, Informative)
Submitter got it wrong: Physics is F=uN!
(You know, force equals mu times N, friction and stuff? Never mind.)
Re:Is this legit? (Score:3, Informative)
The idea behind the "fit to reissue" concept is that paper money (when the U.S. was on the gold standard) represented gold in some bank vault, and the bank printed only as many bills as it had gold. If you brought the bill back to the issuing bank, you could get the gold, if you wanted, or the bank could destroy the old bill and print a fresh one. Always preserving the link between paper money and the gold backing it.
If you alter the bill so that the bank can't tell anymore that it is valid, or can't tell how much the bill is worth, then you've broken the link. The risk is that the bank might be fooled into printing more paper money than it has gold to back it (OH MY GOD! THE GOLD STANDARD HAS COLLAPSED! RUN FOR YOUR LIVES!), or they will fail to replace a bill, meaning that there will not be as much paper money as gold. That is not a crime against the gold standard, but still causes a problem: if you run out of paper money, you have to use coins or barter, which are inconvenient, or wait for more gold to be dug out of the ground and end up in a bank vault somewhere.
Of course, none of this gold standard nonsense applies anymore, but it is still good to have laws to protect paper money.
Re:Not a record, but... (Score:4, Informative)
Uh oh. Be careful with such statements. I charged a PC power supply filtering cap (electrolytic, 100uF) to 600V and (accidentally) touched it with both hands. I flew across the room with a loud "ieek". I'm happy I survived that. Really. That was more than 250mA.
I have some other 10kV/1uF-Caps here, discharging them from 3kV (did not try more yet => destroyed my PC with them once because of EMI!) is enough fire, smoke and thunder to satisfy my pyromanic HV ego. I have never touched them, handle them with a 2m pole (literally!) and I'm also not going to go close to them (if charged) in any way.
Someone stated that caps charged with energies less than 10 Joule are safe (i.e. unlikely to be lethal - no warranty!), but take capacitors serious. In the setups described, the caps contains KILOjoules of energy and will SURELY kill you if you even get close to them (because of that nasty gap-jumping property of HV).
Re:So.... why does this happen? (Score:4, Informative)
Re:Not a record, but... (Score:5, Informative)
It is true that you won't get a lethal shock directly from the high voltage side of a Tesla coil.
One thing you have to watch is the shielding on the 'low' voltage side of homemade equipment. You're going to have components running off 120 V or 240 V line current. If the high voltage side arcs to a low voltage component, suddenly you've got a conducting path through the air (technically, a plasma) attached to potentially several amps of line current. It is possible to deliver a a deadly current this way.
Aside--an arc back to the line can wreak all manner of havoc on other electrical equipment on the same circuit. Your computer won't like it, that's for sure. Please, have properly grounded metal shielding around all line conductors in your experimental area!
Re:Not a record, but... (Score:5, Informative)
Regarding the resistance of the human body (to calculate lethal voltages), I remember being told in several HV-safety courses in physics classes that the human cross-body resistance (index finger to index finger) is generally 100 kohms to 1 mohm, depending mostly on the level of sweat on the body, and thus on environmental conditions like heat and humidity. That doesn't mean that 5 kV isn't dangerous, though: remember the 1/10/100 rule: you can feel 1 mA, can't let go at 10 mA due to involuntary local muscle contraction, and at 100 mA you are presenting a serious danger to your heart. Thus, with your 5 kV supply, you'll probably find yourself unable to let go of the power supply's terminals should you touch them. Even the voltages in your house are dangerous, in the right situation (the bathtub scenario: drop a 110v appliance into your bathtub, with you providing a path to ground, and it might not take too much to cause unconciousness and drown you). It's all a matter of knowing what you can do safely.
Internet Archive (Score:2, Informative)
I noticed on some pages (the Quarter Shrinking Theory page) the text is 'invisible' using Firebird, but you can read it by selecting the entire page (ex. ctrl-a) which highlights everything.
I've done this in the past with slashdotted sites and it seems to work most of the time.
Re:Google Cache no -- use the Wayback Machine (Score:3, Informative)
Re:Does the metal become more dense? (Score:4, Informative)
All of the above is completely wrong.