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Coin Shrinking and Can Crushing
Electromagnetically Shrunken Heads, Tiny Tails, & Slimmer Cans  
  • One page summary about how we shrink coins
  • ALL the gory details - how we REALLY do it 
  • Go HERE for reprint of our MintErrorNews article on Shrunken Coins 
  • Go HERE for the reconstructed history of Quarter Shrinking 
  • Go HERE to learn more about Pulsed Power
  • Go HERE to purchase shrunken coins of your very own!
  • A few of our coins are always available on eBay
 
Shrinker, Side View

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 trigatron switch (the small cylinder with a spark plug), bleeder resistor bank, and 10,000 volt fuse can also be seen. 
cancrush1.jpg

A sample work coil showing the magnet wire winding, the pair of dowels and coin above it. The dowels and coin snugly fit 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 deadly shower of high velocity copper fragments that must be contained by a blast shield.
before

After bolting the work coil to the bus bars, it's covered by the blast shield. The energy discharge capacitors are then charged to the desired high voltage, storing a large amount of potential energy. The stored energy will be suddenly released into the work coil, creating an ultrastrong magnetic field inside the coil which radially crushes the coin. The interior of the blast shield is lined with steel, since Lexan alone cracks under repetitive bombardment by the copper fragments and the explosion's shockwave.
Quarter Shot, 5000J

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 over 100,000 amps into the work coil. The resulting magnetic field can erase nearby credit cards. And yes, it makes a BIG bang!
fire!
A closeup image of a Kennedy half 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. Voltage metering, audio, and LED alarms warn if any dangerous charge remains on the capacitor bank. The shrunken coin is retrieved after the high voltage capacitors have been fully discharged.
after

The debris left after the blast, and a very hot, shrunken quarter in the center. The quarter is greatly heated by a huge pulse of current that was forced to circulate within its rim, and by frictional losses as the powerful magnetic fields plastically deform the coin in millionths of a second.

A close-up of coil fragments when a lower power density 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 very work hardened.

A group of shrunken quarters showing the effects of increasing the applied 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 directly proportional to the energy initially stored in the capacitor bank.
coins5
A close-up of view of Washington's shrunken head. Although the pattern is basically maintained, there is some relative shifting between some of the features. The radiating lines on the shrunken coin are called "Luder's Lines". These are created as the coin is plastically deformed, and are parallel to the direction of the applied shrinking force. The lines clearly show the radial forces that were applied to the coin.

coins6
A close-up view of the reverse side of a Delaware quarter also showing the radiating Luder's lines. The inner layer of a clad coin shrinks a bit more than the outer layers. This adds to the shifting of surface features. Some features may actually move underneath others. Note how the letter "S" has shifted so that it's partially under the horse on the shrunken coin!

Kennedy Front

On certain coins, such as the Kennedy half dollar, the bust may become attractively "haloed" by radiating Luder 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.
coins7

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 coin was shrunk with using 5,700 joules. Notice the distortion of the horizontal lines above the collapsed center hole.
NYC Transit Token

The five-sided hole in an older style New York City transit token closes up to form a Chrysler emblem or a starfish. The metal is a nickel copper alloy and is a poorer electrical conductor. It took more energy (6,300 joules) to achieve the same effect as the previous coin. Heating discolors the token a bit.

coins9

A clad Eisenhower Dollar is reduced from about 1.5" to 1.125" using 6,500 joules. A small amount of "toroiding" (preferential thickening of the outermost portion of the coin) can be seen. It is thought that this is caused as the work coil explodes before entire coin could fully shrink. Higher voltage systems using smaller bank capacitance often show this effect to a much greater degree,  

Sacagawea - Front

Although it's not obvious, the Sacagawea "Golden Dollar" (or "Brass Buck") is actually a clad coin. The outer layers are an alloy made from copper, zinc and manganese (called manganese brass), while the inner core consists of pure copper. The Sacagawea is one of the prettiest coins to shrink, since they usually show little relative shifting and distortion of surface features and seldom develop Luder's lines. This coin was shrunk at 6,500 joules.

Sacagawea - Rear

Here's the reverse side of the same Sacagawea. During shrinking, the highly conductive copper center shrinks a bit more, making the coin's clad construction considerably more obvious. The coin's edge is hollowed in the center, creating a very marked "Oreo Cookie" effect.

SBA Front

A Susan B. Anthony (SBA) Dollar shows some interesting shifting of surface features. Compare the space between her 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. Unfortunately, even shrinking her doesn't make her any more attractive...

SBA Reverse

The reverse side  of an SBA also shows some interesting surface feature shifting. Notice that part of the e "E Pluribus Unum"  lettering has slipped underneath the eagle's wing as the outer cladding layer was actually being drug by the inner copper layer which. The copper is softer and a better electrical conductor, so it shrinks to a greater degree.

Dime

Due to its smaller size, a 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 gets Jay Leno's chin). The result is a 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 may occur.

 

UK 2 Pound Bimetal

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

A Canadian "Twonie" 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 in 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 very nicely! The combination of  the balanced surface features on the front and rear combined with the soft bronze alloy usually results in very uniform shrinkage.

Indian Head, Tail Side

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 in New Mexico, 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.

Illinois Tax Token

Applying a similar power level to a square aluminum Illinois Retailer's Occupation Tax token results in a strange star or jack shaped object. Because aluminum is a better electrical conductor and is softer, the uneven shrinkage is even more pronounced than with the previous token. Even though it is extremely distorted, the token's lettering can still be recognized on the shrunken token!
Twin GA Quarters at 11 kJ

If two coins are placed side-by-side and then shrunk simultaneously, high currents are induced in both coins. This causes the coins to attract each other along the rims, smashing them together while the coins are simultaneously shrinking. This causes the coins to assume an interesting cupped shape. Using a more powerful shrinker, these Georgia quarters were shrunk by Texas shrinker Bill Emery using an energy level of 11,000 joules.
Edge View of Quarter

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 to the coin's edges. Also, the better conducting 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. As a result, the coin's volume and mass remain the same, and the coin's density also remains unchanged. There's no "Honey I Shrunk the Kids!" magic involved in coin shrinking.
1 Euro
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. 
2 Euro
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.
HK 20 Cent Front
HK 20 Cent Reverse
Coins with scalloped edges work well as long as they are symmetrical. A Hong Kong 20 cent coin was reduced to about 87% of its original diameter at a power level of 5,000 joules.
10 Franc

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.

qgap

This is the high voltage switch used on the Quarter Shrinker. It's a triggered  spark gap switch (called a Trigatron), and it was built by Robert Stephens of the AREA31 Research Facility  in Ontario, Canada. The original Plexiglas plate fractured from the shockwave at 8,000 J. It has since been replaced by a more robust 1/2" Lexan plate. the Lexan plate has now survived over 2,000 shots.

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 may end before it can propagate into the center of the coin.

A 6,000 Joule "high voltage" shot by 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 the premature explosion of the work coil. This creates a "Quarter Toroid".
quarterball

Believe it or not, this "Quarter Ball" was once a Delaware quarter. Created by two friends and fellow shrinkers in Texas, Bill Emery and Phil Rembold, who used 21,000 joules to crunch it 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. 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 must be done in a steel containment vessel topped by hundreds of pounds of sandbags, and sounds like dynamite! Incredibly, 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 internal bonding defects between inner and outer cladding layers. During shrinking, these defects set up internal force imbalances which distort the shape of the coin in very unpredictable ways. Note that the actual outline of the coin is even distorted!

Here's the front side of the previous Kentucky Mutant Coin. 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..

 

Wrinkled Yen

Another form of "mutation" comes from a high voltage hobbyist in the UK, Mike Harrison. The grain pattern of the wooden dowels is impressed into an aluminum 1 Yen coin. Minor force imbalances can cause a coin to develop "waviness" during the shrinking process. The "stripes" which formed in this coin align with the grain pattern in wooden dowels that originally held the coin in the work coil.

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

$25 Gold Eagle

Even gold bullion coins can be shrunk! Here's a gold 2002 Half Eagle that a collector sent to be shrunk (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.

Sacagaweas


Identical shrinking conditions often 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. I suspect this effect may be due to differences in processing the metal strips used to make the coin blanks (planchettes) at the mint.

Pottstown Token

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 (Proof Coins) or asymmetrically positioned holes.
1 Yen Coins

Because of its excellent electrical conductivity and softness, aluminum coins shrink very well! Here's a group of Japanese 1 Yen coins from Peter Ledlie showing medium and extreme shrinkage - the bullet shaped coin on the far right is about 2.5 times as thick as its diameter!
Work Coils
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.
cancrush1.jpg
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. The fully ringing discharge is very tough on the pulse capacitors and the spark gap.
cancrush3.jpg
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.

Crushed Cans
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.
maxcap1
1700 pounds of pulse caps! These low inductance steel cased Maxwell energy discharge capacitors are rated at 70 uF at 12 kV and 100,000 amps per shot. They weigh 165 pounds apiece. Two of these capacitors have replaced the 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.
maxcap1
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 will be used with the VCR to measure peak discharge current. 
Solenoid Gap1
Instead of a trigatron, the modified Quarter Shrinker will use a solenoid triggered spark gap switch. This will provide more consistent switching for a much wider range of capacitor bank voltages (between 4 kV and 24 kV). The switch will also provide a larger volume for plasma expansion, and is designed to reliably switch over 50,000 joules.
Newgap2a

Another view of the solenoid triggered gap. The solid brass electrodes were fabricated by California shrinker Brian Basura, and were originally planned to be part of a new Trigatron. However, I decided that a solenoid gap would provide significantly more flexibility. The electrodes come close, but don't touch, thus preventing contact welding.
Positive Lightning

Some natural pulsed power at work. This massive positive lightning bolt originated at the top of a storm, and hit 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 higher peak current that also flows longer than more common (negative) lightning from the storm's cloud base. 
Sandia Discharge

Some VERY Heavy Duty Pulsed Power!
Sandia's Awesome Z-Machine is the largest pulse generator in the world! 36 Marx Generators deliver 20 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


Some Other Places to Visit:
Tesla Information Center Tesla Coil
Link to 345 kV Switch MPEG
Shrunken Coins for Sale Lichtenbergs for Sale
Tesla Info Center
Tesla Coil
More "Arcs & Sparks"
Get Shrunken Coins!
Get Lichtenberg Figures!

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This web site is maintained by Bert Hickman and his daughter, Lesley.  © 1999-2004, All rights reserved.  No portion of this page may be reproduced without consent from the authors.