Coin
Shrinking and Can Crushing
Electromagnetically Shrunken Heads, Tiny Tails, & Slimmer Cans
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- 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
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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. |
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.
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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.
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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!
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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.
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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.
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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.
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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.
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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.
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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!
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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. |
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.
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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.
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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,
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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. |
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.
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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...
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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.
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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.
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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.
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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. |
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.
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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.
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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!
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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.
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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.
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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.
A Hong Kong 20 cent coin was reduced to about 87% of its original
diameter at a 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 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. |
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". |
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.
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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!
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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..
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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.
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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...
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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. |
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.
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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.
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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!
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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.
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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.
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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.
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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.
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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.
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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. |
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. |
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.
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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.
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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 |