Coin Shrinking and Can Crushing

Making Electromagnetically Shrunken Heads, Tiny Tails, & Slimmer Cans since 1998

Updated 01/31/19

Cool video clip showing a quarter shrinking in 40 millionths of a second (from our friends at Hackerbot Labs)

One page (pdf) summary - a quick and dirty explanation of how we shrink coins

How we REALLY do it - all of the gory details



Reconstructed History of Quarter Shrinking - who discovered this?



Learn more about Pulsed Power

Get a shrunken coin of your very own!

Some of our shrunken coins and Captured Lightning sculptures are also available on eBay Captured Lightning Sculptures







Side view of the Quarter Shrinker, showing the Lexan blast shield with a 40 pound transformer helping to keep it down. The large gray rectangular objects are older GE energy discharge caps. These have since been replaced with more robust Maxwell capacitors. The original trigatron switch (the small cylinder with a spark plug), bleeder resistor bank, and 10,000 volt fuse can also be seen. The trigatron has been replaced with a newer solenoid fired gap.





A sample work coil showing the magnet wire winding, a pair of dowels and coin above it. The dowels and coin fit snugly inside the coil, and the assembly is then taped together. The work coil is then bolted onto a pair of copper bus bars. The work coil explodes violently during the shrinking process, creating a potentially lethal shower of hypersonic velocity copper fragments that must be contained within a steel-lined, bullet-proof Lexan blast shield.



After bolting the work coil to the bus bars, the coil is covered by the blast shield. The energy discharge capacitors are then charged to a high voltage, storing the desired amount of potential energy. The stored energy is suddenly released into the work coil, creating an ultrastrong magnetic field inside the coil which evenly crushes the coin inward toward its center. The interior of the blast shield that's in the direct path of the copper fragments is reinforced with 1/2" thick steel armor plates. Lexan alone rapidly cracks under the repetitive bombardment of supersonic copper fragments and the explosive shock wave. Small fragments can reach velocities of 5,000 feet per second!





FIRE!

The Shrinker is triggered remotely. You really don't want to be anywhere near the system when it fires. You can also see the highly conductive arc inside the trigatron switch (the cylindrical object to the right of the blast shield) as it switches up to 100,000 amperes into the work coil. The resulting magnetic field can erase nearby credit cards. And yes, it makes a satisfyingly BIG bang...



A close-up of a Kennedy half dollar being shrunk at 6,500 joules. A neutral density filter allows us to see more detail of the ball of plasma that's created when the work coil explodes. Any residual system energy is rapidly dissipated by both the plasma discharge and via a bank of high power bleeder resistors to the left of the blast shield. Voltage metering, audio, and LED alarms warn if any dangerous charge remains on the capacitor bank. The shrunken coin is retrieved after any remaining charge in the high voltage capacitors has been safely dissipated.



The debris left after the blast, and a very hot, shrunken quarter. The quarter is greatly heated by the huge pulse of electrical current that was forced to circulate within its rim, and by frictional losses when the powerful magnetic fields plastically deformed the coin to the diameter of a dime. The actual shrinking process occurs within tens of millionths of a second! For more details, you may wish to read a more detailed description about how the "shrinking" process works.





Some of the larger coil fragments that result when a lower power pulse is applied to the work coil. The wire clearly shows the effects of tensile fracture and axial compression. A narrow band of melting can also be seen where the current was concentrated due to skin effect and proximity effect. The insulation is blown off, and the wire becomes quite work hardened.





A group of shrunken quarters showing the effects of increasing the energy level. At higher levels, a quarter becomes 0.1" SMALLER than a dime. The shrinking force on the coins is proportional to the square of the current, and is directly proportional to the energy initially stored in the capacitor bank.





A magnified of view of Washington's shrunken head. Although the pattern is basically maintained, closer observations shows that some relative shifting occurs between features. The radiating lines on the shrunken coin are called "Luder's Lines". These are sometimes created as the coin is plastically deformed. Luder's Lines are parallel to the direction of the applied shrinking force. The lines clearly show the radial forces that were applied to the coin.







The reverse side of a Delaware quarter also showing radiating Luder's lines. The better-conducting inner copper layer of a clad US coin shrinks more than the more electrically resistive outer layers. This often causes dragging and relative shifting of some surface features. On some coins, certain surface features may actually dive underneath other features. Click on the above image and note how the letter "S" has shifted so that it's partially under the horse's butt on the shrunken coin.









On some coins, such as this Kennedy half dollar, the bust may become attractively "haloed" by radiating Luder's lines. For reasons that are not completely understood, this occurs only on some Kennedy halves. The degree to which Luder's lines form is also a function of the alloys used in the coin.





A Japanese 5 Yen coin demonstrates how the compressive forces squeeze the entire coin. Not only does the coin shrink, but the center hole closes up in the process. This brass alloy coin was shrunk using 5,700 joules. Notice the distortion of the horizontal lines above the collapsed center hole.



The five sided hole in an older style New York City transit token closes up to form a Chrysler emblem or a starfish. The token is made from a nickel copper alloy that is a relatively poor electrical conductor. Because of the larger losses, it took significantly more energy (6,300 joules) to achieve the same effect as the previous coin. A greater degree of ohmic heating discolors the token a bit more than other coins.

A clad Eisenhower Dollar is reduced from about 1.5" to 1.125" using 6,500 joules. A slight degree of "toroiding" (greater thickening of the outer portion of the coin) can also be seen. It is thought that this occurs when the work coil explodes before the coin can fully shrink. Higher voltage systems that use smaller bank capacitance often show toroiding to a much greater degree.

Although it's not obvious, the Sacagawea "Golden Dollar" (or "Brass Buck") is actually a clad coin. The outer layers are made from an alloy of copper, zinc and manganese (called manganese brass), while the inner core consists of pure copper. The Sacagawea is one of the prettier coins to shrink, since it usually shows little relative shifting and distortion of surface features and it seldom develops Luder's lines. This coin was shrunk at 5,100 joules. Small presidential dollars also shrink quite evenly.

Here's the reverse side of the same Sacagawea coin. During shrinking, the better conducting copper center shrinks a bit more, and the resulting "Oreo Cookie" effect makes the coin's clad construction quite obvious. Slight force imbalances (due to surface features on the other side of the coin) cause the slight dimpling effect.



A Susan B. Anthony (SBA) Dollar shows some interesting shifting of surface features after being hit with a 5,100 joule pulse. Compare the space between Susan's chin and her left shoulder and the lettering just to the right of her chin between the original and shrunken coin. Also, compare the locations of the Denver mint mark. Even shrinking her doesn't improve her appearance very much...



The reverse side of an Susan B. Anthony Dollar shows some interesting shifting of surface features. Notice that part of the "E Pluribus Unum" lettering has slipped underneath the eagle's wing as the outer cladding layer was pulled by the underlying copper layer. The internal copper layer is softer and it conducts electricity almost 13 times better than the outer copper-nickel cladding layers.

<>



Due to its smaller size, a clad Roosevelt dime takes significantly less energy to shrink. This clad dime was hit with 6,000 joules. Roosevelt's features are altered a bit (he ages 30 years, develops a long nose and grows a Jay Leno chin). The result is a very cute little M&M shaped pill of a coin that's only about 60% of its original diameter. At 6,300 joules, some melting of the coin's edges begins to occur. Because of the lower melting point of coin silver alloy, older silver dimes melt and shatter at energy levels of over 2,500 joules. They also turn an ugly greenish-brassy color as small copper crystals precipitate out of the coin silver alloy (a process called called "precipitation hardening") .

Bimetal coins often work as well! Here is an older United Kingdom bimetal 2 Pound Coin that was shrunk using 6,300 joules. The center shrank a little bit more than the outer ring, freeing it from the outer ring.

A Canadian "Toonie" has the center loosened at 6,500 joules, but the center is still held captive. At 14,000 joules, Rob Stephens, a friend and fellow coin shrinker from Ontario, Canada was able to separate the coin into two independent pieces. However, his blast shield failed during the shot, and he sustained considerable damage to his lab from shrapnel from the exploding work coil...

Older Indian Head Pennies shrink quite nicely. The combination of the balanced surface features on the front and rear and the relatively soft bronze alloy usually results in very uniform shrinkage. Once in a while, shrunken coins develop small fractures from previously hidden defects in the coin.



Reverse side of the Indian Head penny. The coin shrunk to about 75% of its original diameter at a relatively modest power level of 4,000 joules.



Shrunk by fellow coin shrinker Peter Ledlie, here's a "before" and "after" shot of a square brass coal token. The greater shrinkage in the flat section of the token was not anticipated beforehand.





Applying a similar power level to a square aluminum Illinois Retailer's Occupation Tax token results in a strange star or jack shaped object. Aluminum is an excellent electrical conductor and is softer than most other alloys, so the uneven shrinkage is even more pronounced than with the previous token. Even though it is extremely distorted, the lettering can still be recognized on the shrunken token.





If two coins are placed side by side and then shrunk simultaneously, high currents are induced in both coins. This causes the coins to magnetically attract each other along the rims, smashing them together as the coins are simultaneously shrinking. At high power levels, this results in the coins assuming an interesting hemispherical shape. Using a more powerful shrinker, these Georgia quarters were shrunk by Texas shrinker Bill Emery using much higher energy levels that we use for our coins.





A side view of a quarter that's been shrunk to the diameter of a dime. Minor force imbalances often create a bit of rippling or waviness of the coin's edge. Also, the better conducting internal copper layer of clad coins causes it to shrink more, resulting in an "Oreo Cookie" effect. The thickness proportionally increases as its diameter is reduced. A shrunken coin's volume and mass remain the same, so its density remains unchanged. There's no "Honey, I Shrunk the Kids!" magic involved in coin shrinking.





Here's the reverse side of a German 1 Euro coin before and after blasting it with 6,300 joules. The outer ring shrinks to about 90% of its original diameter. However, the center portion shrinks even more, freeing it from the outer ring.



The reverse side of a German 2 Euro coin before and after being hit with 6,300 joules. The poorly conducting outer ring only shrank about 0.010". However, the center shrinks more, easily freeing it from the outer ring.





Coins with scalloped edges work well as long as they are symmetrical. Here a Hong Kong 20 cent coin was reduced to about 87% of its original diameter at a modest power level of 5,000 joules. This older French 10 Franc bimetal coin also ended up with a center that's smaller than the outer ring, and after shrinking, the two halves came apart. This coin was blasted with about 6,300 joules. This was the Trigatron (high voltage switch) that was previously used on the Quarter Shrinker. It's a triggered spark gap switch (called a Trigatron), and it was originally built by Tesla coiler Robert Stephens in Ontario, Canada. The original Plexiglas plate fractured from the shock wave at 8,000 J. The plate was replaced by a more robust 1/2" Lexan plate which survived over 5,000 shots before the trigitron itself was replaced by a more reliable solenoid-triggered switch.



Texas shrinker Phil Rembold's 1 Ton Quarter Shrinker! 60 kV Pulse Caps Blast Quarters into toroids! At 45 kV, compression is concentrated only at the OUTER rim - the force apparently ends before it can propagate all the way into the center of the coin.



A 6,000 Joule "high voltage" shot by Texas shrinker Bill Emery. It is thought that the compressive shock wave ended before it had a chance to completely propagate to the center of the coin due to premature explosion of the work coil. The result is a "Quarter Toroid".

Believe it or not, this "Quarter Ball" was once a Delaware quarter. It was created by Texas shrinkers Bill Emery and Phil Rembold. They used over 21,000 joules to crunch it down to this size. The coin's diameter is now actually SMALLER than its thickness! The incredible forces also caused a bonding failure between cladding layers in the center of the coin. Even so, the horse's feet, head and some lettering can still be recognized!



Another "Quarter Toroid". Bill Emery and Phil Rembold used a 45,000 volt blast to reshape this quarter into a toroid 0.44" in diameter and 0.22" thick! The resulting blast was done inside a large steel containment vessel topped by four hundred pounds of weights and sandbags. The force of the electrical blast still lifts the top of the containment chamber, and it sounds like dynamite exploding. The coin's lettering is still clearly visible.



Once in a great while, a coin will shrink very unevenly due to the presence of hidden bonding defects between the inner and outer cladding layers. During shrinking, these defects cause internal force imbalances which distort the shape of the coin in unpredictable ways. Notice that the actual outline of the coin is even distorted...

Here's the front side of the previous Kentucky Mutant Quarter. It looks like poor ole' George has sprouted a real "honker" and aged another 30 years. But he's also been working out - just look at those huge neck muscles. He's also appears to have developed a mammary gland in the back of his head... must be from the steroids. These "Mutant Coins" could be considered the "error coins" of quarter shrinking..

Another form of "mutation" comes from a high voltage hobbyist in the UK, Mike Harrison. The grain pattern of the wooden dowels was actually impressed into an aluminum One Yen Japanese coin. Minor force imbalances can cause a coin to develop "waviness" during the shrinking process. The "stripes" which formed in this coin precisely align with the grain pattern in the wooden dowels that originally held the coin in place within the work coil!



Larger coins, such as Morgans, Peace Dollars, or Silver Eagles will also work. Here's an example showing "before" and "after" size comparison on a 1.5" diameter Morgan Silver Dollar that was shrunk using a 6,300 joule shot. And no, the coin's dates don't change during the shrinking process...

Even gold bullion coins can be shrunk! Here's a 2002 1/2 ounce American Gold Eagle coin that a collector sent to be shrunk (and yes, he wanted it back!). The gold, copper, and silver alloy turned out to be surprisingly tough. This coin was lovingly blasted with 5,000 joules. After the dust cleared, it was reduced to about 91% of its original diameter. A softer pure gold coin, such as a Canadian Maple Leaf, would likely shrink to a greater degree, perhaps similar to pure aluminum coins.





Identical shrinking conditions may deliver different results. These Sacagawea dollars were all shrunk with the same energy under the same conditions. However, the surface roughness between coins is considerably different. This may be due to subtle differences in the processing of the metal strips used to make the coin blanks (planchettes) at the mint. Consistent differences have been even been noticed between coins minted at the Denver Mint versus the Philadelphia Mint.





Another token from Peter Ledlie. Although the shrinking forces were uniform, the holes in the coin caused uneven shrinkage as the holes collapsed. Similar behavior can occur with certain coins that have high surface features, such as proof coins, or tokens with asymmetrically positioned holes.





Because it has excellent electrical conductivity and is mechanically softer, an aluminum coin shrinks very well! Here's a group of Japanese One Yen coins from Peter Ledlie showing medium and extreme shrinkage. The bullet shaped coin on the far right is actually 2.5 times as thick as its diameter...





Magnetic forces reshape the work coil just before it explodes. If a much smaller pulse of energy is applied to the work coil, the effects of radial expansion and axial compression forces on the work coil can be seen. By carefully centering the coin within the coil, most of the forces on the coin can be balanced and we can evenly shrink the coin.





The same system can also crush a can. In this case, the work coil consists of 3 turns of #4 AWG solid copper wire insulated with vinyl tubing. Since the coil remains intact, most of the energy is dissipated in the spark gap switch. However, the ringing (oscillatory) discharge is very tough on the pulse capacitors and the spark gap.



Slim 'n' trim aluminum cans. The center can was hit with 3,000 joules. Higher energy levels rip the can apart due to heating and softening of the aluminum walls and the sudden compression of the interior air. Compression occurs so quickly that trapped air can't escape, and the weakened can is blown apart. In 2005, Peter Terren electromagnetically crushed a FULL Red Bull can. You can see the amusing results in the "Can Crushing" section of his his web site...



More examples of crushed pop cans at various power levels. Because of its much better electrical conductivity, aluminum cans crush much better than steel cans. Large diameter copper tubing can also be necked down by the same process, such as these examples from California coin shrinker Ross Overstreet.





These low inductance steel cased Maxwell energy discharge capacitors are rated at 70 uF at 12 kV and 100,000 amperes per shot. They weigh 165 pounds apiece, ~1700 pounds total. Two of these capacitors have replaced previously failing GE caps in the Quarter Shrinker. When fully modified, the new design will use a bipolar charging supply of +/- 12 kV and four or six of these capacitors.





Four Maxwell caps connected in series/parallel can deliver up to 24 kJ of shrinking power. The cylindrical object in the center is a special low inductance Current Viewing Resistor (CVR) designed to accurately measure peak currents of up to 300,000 amperes. A battery powered floating sample-and-hold amplifier or inexpensive battery-powered scope will be used with the VCR to measure peak discharge current.



Instead of a trigatron, the Quarter Shrinker has been modified to use a solenoid triggered spark gap switch. This provides more consistent switching over a much wider range of capacitor bank voltages (ultimately between 3 kV and 24 kV). The switch also provides a larger volume for plasma expansion, and is designed to reliably switch over 50,000 joules/shot. The "hairpin" current loop also creates magnetic forces which sweep the plasma across the electrodes for more even electrode wear.





Another view of the solenoid-triggered gap. The solid brass electrodes were originally fabricated by California coin shrinker Brian Basura, and were initially planned to be part of a new Trigatron. However, I later decided that a solenoid-driven spark gap switch would provide a much wider voltage switching range. During "firing" the electrodes come close (~0.030"), but don't quite touch. This prevents contact welding when used at lower power levels. Over time, the interior of the switch becomes coated with a white powder of zinc oxide as zinc is evaporated and oxidized from the brass electrodes. As zinc is evaporated, the surfaces of the brass electrodes begin to resemble a dry, cracked river bed with discrete islands of copper.





An example of natural pulsed power at work. This powerful positive lightning bolt originated at the top of a storm, hitting the ground ~5 miles away! This "Bolt from the Blue" probably surprised nearby folks who could look up and see clear blue sky above! Positive lightning is "hot" with peak currents that are often 10X those of negative lightning from a cloud base, and the current also flows considerably longer. Here's a MUCH closer image of one of these massive bolts striking the ground...



Some VERY Heavy Duty Pulsed Power! Sandia's awesome Z-Machine is the largest pulse generator in the world. 36 Marx Generators deliver 18 Million Amperes for 10 billionths of a second for X-ray and fusion experiments. This above picture is the "left over" energy safely dissipating in water long after the main power pulse has come and gone! The peak power in this discharge vastly exceeds that of natural lightning.

Please visit some other areas of our web site:





Tesla Info Center

Tesla Coil

More "Arcs & Sparks"

Get Small Change

Lichtenberg Figures!

Go to Stoneridge Engineering Home



