Left photo shows a small skein of steel wool (used as an abrasive cleaner) placed across the electrodes and fired at 2 kJ. The high resolution photo is nearly 2 MB but has lots of fine detail of the shower of sparks and is a nice desktop photo. The right photo shows the setup.
A series of 3 kJ shots with steel wool with me in the picture. I have a cap and earmuffs as safety gear but the sparkles are harmless and just tend to bounce off skin, just like angle grinder sparks. My son suggested the central front on shot to give a Terminator like look.
I took it out on the trailer and took a shot at 5kJ in a local industrial driveway.
Left photo shows a 4 inch strip of aluminium foil placed across the electrodes and fired at 2 kJ in a similar manner to the above. The photo is a whiteout due to the huge flash and bang. The right photo shows a mistimed shot with the burning aluminium fragments floating down after the shot. You can still see the remnants of the smoke from the shot.
The left photo above shows a hot dog across the terminals . The centre photo shows the flash at 3 kJ. The right photo shows the result. There was no charring, explosions or even any marks. Why? Well, a fatty sausage (wiener / hot dog) has a resistance which is surprisingly high at 200 k Ohm. So the cap bank charged to 3 kJ at 7 kV will deliver a peak current of only 35 mA. Certainly not like the 100 kA it could deliver.
(point to run video, 900k)
This is the very disappointing video of a hot dog across the electrodes at 3 kJ. The bang was certainly there (listen for the echo like a rifle shot) and the cap was completely discharged.
The left photo above shows a CD with ends ground down to the metal film across the terminals . The centre photo shows the flash at 1 kJ. It is very intense for the power as it is in part due to aluminium ignition and I may use this for IPL (intense pulsed light) experiments. The right photo shows the result with obliteration of most of the CD metallic film without charring. The film is actually on the label side with only a thin film over it plus the label ink. These have been blown off together.
This shows exploding wire at 2 kJ of which only about 500J is used. The wire is 30 gauge and is about 3 m long.
More exploding wire. The left photo above shows a 26 g wire exploding with 3 kJ. The red marks are the red hot copper wire fragments. The centre photo shows detail of the exploding wire. The right photo shows the result with 20 g wire.
The left photo above looks just like the game Total Annihilation with the Arm machines vs the Core machines burning each other up. It actually is an exploding wire run through an inductor. The inductor is a 3 kV winding of a 10 kW transformer. Wire is 35 G and power is 2.5 kJ at 5.5 kV. Look at the right "machine" which is just a 100 kV mobile x-ray supply which is also supporting the unrelated transformer. The flash seems to envelop the transformer. I wonder if this is due to the magnetic fields as it is not present on a shot without the inductor but arising from the same spot. The centre photo shows a different view of the same flash enveloping the transformer. The right photo shows the transformer close up with the epoxy encased secondary.
Above photo shows the 2.5 kJ shot using the same 35 G wire but without the inductor. The flash and bang is much greater.
Above photo shows an exploding iron wire with the return path being an aluminium tube. Looks good in high resolution.
Another wire exploding site from Bob LaPointe.
Each photo in the animated sequence above is taken at 5 frames per second i.e. 0.2 seconds apart.. I am covering my face with an acrylic plate and am pulling the string to trigger the big spring loaded switch. I have looped it around the fence as the string had got wet hence conductive to the 10 kV I was using. You have to be very alert re safety, particularly when circumstances like filming disrupt your routine.
The first shot above shows the moment just after power is applied and it is likely the capacitors have dissipated all their charge already. The iron wire has melted and tiny droplets of liquid iron (the orange spray) have sprayed out the ends along with a puff of grey smoke. Note that an AK47 bullet has about 2kJ of energy and the power used here is 10 kJ.
The fine iron wire is soldered on to a thin steel rod which is pushed through the watermelon then cut off. The connection looks dodgy for 100 kA doesn't it. It really just needs to be the seed for a lightning like bolt to form which will dissipate the energy within the watermelon as a sudden pressure wave.
The flash and bang is huge but most of the energy is directed outwards and the damage is surprisingly small. Interestingly much of the paint is blown off the aluminum foil. The explosion photo is taken just after sunset with a 2.5 second exposure to allow me time to pull the switch and for reasonable spark length. I had to back of the f stop to 13 to reduce total light pickup.
Note that 3500 joules is barely enough to melt 100 g of chocolate or heat
water for a cup of coffee. It is just one 2000 watt electrical kettle for 2
seconds after all. This power is underwhelming when delivered slowly. But
deliver it in 30us and the instantaneous power rises to 116 MW (megawatts). Think
of a power station output for that time. In that timeframe things happen
fast and furious. Local heating doesn't have time to escape and things
vaporize, magnetic fields due to the huge currents are intense and rapidly
changing. These fields can tear a drink can in two, shrink a metal coin or
tear a copper coil into high velocity pieces.
Version 2 was heavier with a wood block for support. Still no coin
shrinkage. I was subsequently informed that this particular coin is
magnetic and indeed it is. Possibly with nickel content and generally
higher resistance. The magnetism gives an effect opposite to the
induced current and resists the effect of coin shrinking.
Left photo shows the pieces that I could find of the first coil. The second coil, (centre photo) used heavier wire and a wooden surround and it still blew the wood apart and broke the wire in one part (right photo).
This is the oscilloscope shot which shows the current reading which is
different to the can crushing one. Current scale is 4250 A/div and timebase
20 us/div. Peak current around 13 kA. The surprising thing is that the first
current reversal is GREATER than the initial pulse. This seems most likely
due to inductance (L) reduction by a degree of interturn shorting.
Note that the magnetic forces act to compress axially (lengthways) and
expand radially (outwards).
The consequences of this are that this should NOT recur if I prevent interturn shorting or movement.
The block of ice was shattered into small pieces but the coil was still enlarged and burnt out. The "coin" was shrunk by perhaps 0.5 mm with the blue circle being the tracing before and the red after. So no real success yet. I am told that a Japanese 1 yen coin is suitable for crushing being light and aluminium.
See the discussion of my coinshrinking on the 4HV forum.
Left photo is of the fibreglass and cloth and 4 inch PVC reinforced
housing the coil with inter-turn insulation above. It is shown after firing
(centre photo) with a few ice shards that have cracked off in the shockwave.
Right photo shows the current/time trace discussed below.
shrinking results 2006
The left photo shows the ice was shattered as were all the PVC components and a panel was broken off the box. It wasn't that loud using hearing protection and much less than an exploding wire. The right photo shows the wire fragments. Interesting how one part of the coil is almost unscathed apart from doubling its diameter where the other half is fractured, compressed and in pieces.
The left photo shows the coin shrunk to 50% of the former diameter of 20 mm. It is now 10 mm x 14 mm. The coin was a little unsupported on one side so I expected a bit of a lopsided result. It is interesting trying to see the corresponding detail of the Japanese characters. The right photo shows the numeral 1 which looks like it is fracturing out.
These guys from Hackerbot labs have a 100,000 frames per sec video of a 15 kJ coinshrinking shot.
This is the result of a 4 kJ shot with a mini wrench above the aluminum, which leaves a sharp impression except in the centre where the work coil does not cover. The level of detail can be seen in the reversed "China" label.
The left photo above shows the rewound work coil 7 1/2 turns with much less dead space in the centre. Next to it is the 50 cent coin covered by a large magnetic washer to provide down force against the up force of the aluminium. The middle photo shows the setup lashed together. The right photo shows the latest coin shot at 2 kJ. An Australian 50 cent coin is neatly cut off and imprinted in reverse.
And now for some body part magneforming.
The left photo above shows the setup with a larger flat coil made of
Litz wire from a kitchen benchtop induction cooker.
middle photo shows the setup with an insulating sheet then some copper
foil then my hand. The right photo
shows the result at 1.75 kJ (4 kV). The foil at this stage is starting to
tear. It also is becoming hot enough to discolor with oxidation which can be
seen on the full size pic. To counter this I had been wetting my hand and
the areas of good contact did not heat to the point of oxidation,
nevertheless, it was hot and I had very superficial epidermal scorching on a
couple of fingers which was just visible. Nothing to see now in the cause of
science though but this is probably the limit unless there is a thermal
barrier such as a glove.
My inspiration came from watching detailed videos of a smoke ring in action
demonstrating stable movement, small size and the ability to contain
particles within the structure. I figured that this would be a good
candidate for a ball lightning carrier. It can be easily generated by a
pressure wave in a round structure so could develop in many man made areas.
The left photo shows the steel ignition chamber open. The right photo shows the top section with the aperture of perhaps half the diameter which forms the vortex. machined hole I have a discharge chamber with a hole in the top. Current from my cap bank at 4.5 kV for 2 kJ comes in from a heavily supported lead. I have in the shot below used some aluminium foil and some steel wool which will initiate the discharge.
This shows the best result to date. It shows the big tongue of plasma shooting out with the vortex moving slower but still 25 ft/sec (3 frames in 3 feet) and is just over 1 foot in diameter. The vortex is the grey ball of smoke shown by the arrow and moving upwards. It is smoke only and is not luminous. It does not appear to contain any of the iron particles.
One favoured theory is indeed vortices formed after lightning strikes into sand forming silica/silicon as the luminous substance. I have demonstrated the vortex formed from an electrical discharge. So a vortex induced by an electrical discharge is a candidate for the carrier of ball lightning. Another group in Brazil here melted a silicon wafer in an arc welder and got glowing balls that bounced around for up to 8 seconds. Bill Beaty pointed out this YouTube video that shows the balls bouncing around.
I put a gram of silicon powder and fired it with aluminum foil at 2 kJ. Just
a big flash. I was just about to discard the photo when I saw the green
This page was last updated August 20, 2010