Nick Field's twin coils fill the 8ft gap between toroids with slowly drifting sparks.

This system used a 100BPS synchronous rotary, and was the first twin coil to be demonstrated at a UK Teslathon.

The primary coils, capacitors and rotary spark gap were housed inside the white boxes beneath each secondary.

The two coils were joined electrically by a pair of copper pipes, and the system was operated with no RF ground !

James Barker travelled down from Edinburgh to demonstrate this Tesla coil which he built as part of his Electrical Engineering degree.

With some help from Bob Golding and Martin Fuller, this coil was running beautifully.

The picture opposite shows the coil discharging to a line of electrical bits and pieces:

A light bulb, PC motherboard, floppy disk, anti-static bag, and numerous CDs provided a path for the discharge to reach ground.

I hope that motherboard wasn't part of the bring and buy !

Colin Dancer's Tesla Coil used a 200BPS synchronous rotary spark gap. The correct setting of this was achieved using a strobe light which he modified specifically for this purpose.

The picture opposite shows an impressive spark display from two pins placed on top of the toroid.

The spark length is particularly good considering that the coil is powered from a relatively small 500VA neon sign transformer.

This coil was also topped with a spun Aluminium toroid.

Martin Fuller's Tesla Coil producing streamers into the air.

This coil was powered by a modified microwave oven transformer placed under oil. The machine also made use of an adjustable external ballast to enable the power level to be selected by the operator.

The coil is shown here running with a static gap, although Martin has also built a synchronous rotary for use with this coil.

The tank capacitor consists of several strings of Polypropylene capacitors in an MMC arrangement.

The "High Tension Effects" team.

(Left to right) Steve Bell, Mike Tucknott, Brian Le Page.

All of their control gear was built into Aluminium flight cases. This gave a very professional appearance and enabled them to get set up and running very quickly.

The control equipment was connected together with a set of interchangeable leads, and provided voltage and current metering along with a number of safety interlocks.

Steve Bell's coil was on top form as usual.

The picture opposite shows a "corona motor" fitted to the toroid.

This consists of a metal bar pivoting on a point at the centre. There are sharp points at each end of the metal bar which promote corona formation. The corona at the ends of the bar produces a force which makes the bar rotate.

After the coil had been running for several seconds the metal bar was spinning at quite a speed, and made an impressive display as sparks were thrown in all directions.

Mike Tucknott and Brian Le Page's BM3 coil. This coil was run with their new variable speed asynchronous rotary, which is capable of up to 10,000 RPM.

As the rotary was run up to speed you could feel the wooden floor vibrating, and it took several minutes to come to rest from full speed !

It was interesting to see how the spark length and appearance changed as Mike varied the speed of the rotary. The sound was incredible. Neighbours must have suspected an air raid was imminent !

Despite having a breakout bump on the left side of the toroid, the coil still insisted on breaking out from both sides. Well, if you will use an 11kV pole pig…

Mike's big coil mercilessly attacks a grounded target that was positioned well within striking range.

The metal pole was roughly 6 ft from the toroid, and there was an almost constant power arc between the two.

The arc would strike near the middle of the pole, and then rise gradually. When it got near to the top it would break and then strike again lower down.

The ferocity of this sustained arc had to be seen to be believed.

Duncan Cadd standing behind two miniature Tesla Coils.

The system on the left is a small magnifier powered from an induction coil. Generous use of wood, tufnol and brass gave this a very authentic "vintage" look.

(However, Duncan did tell me that there are a couple of those yellow polypropylene capacitors hidden inside one of the tufnol boxes !)

The system on the right is a vacuum tube Tesla coil.

Both of these were beautifully built, but unfortunately I didn't get a close-up picture of the magnifier.

This picture shows Duncan's vacuum tube Tesla coil.

The system produced a silent plasma flame at the top of the resonator. A refreshingly quiet change from the other less peaceful coils.

The resonator consisted of a helix of thick enamelled wire and was self supporting. There were not many turns on this secondary so the resonant frequency must have been very high.

This coil was operating throughout most of the day, which shows that the design is very stable and robust.

Alan Sharp operating the controls of his new Solid State Tesla Coil.

Sophisticated power electronics were used to generate the high frequency electricity needed to make the Tesla Coil work. There was not a HV transformer or spark gap in sight.

This coil was a particular favourite of mine.

Alan demonstrated the capabilities of the electronic interrupter which controls the firing rate of the coil. The change in tone was similar to that of a variable speed rotary. However, Alan showed how the pitch could be quickly swept from 50Hz up to something that only dogs can hear ! A very popular demonstration.

Another Solid State Tesla Coil.

This unit was built by Bernie Wright, and used a Class C amplifier to produce the RF power and drive the Tesla Coil via a primary winding.

Sparks were 3 to 4 inches in length, and distinctly sword-like in appearance.

Alan Sharp and Martin Fuller stand next to Alan's coil with the new "Mega-toroid" fitted up top.

This monster toroid is roughly 4ft in diameter, and 18 inches thick !

It was fabricated in 4 quarters from plywood and hardboard. The 4 pieces were then bolted together and the whole thing was covered with Aluminium foil tape.

The toroid was carefully lifted into place and balanced on top of the secondary winding.

Alan's coil generating long branched streamers into the surrounding air.

This coil used a 395 BPS asynchronous rotary, 94nF of tank capacitors and was powered by my Mike's pole transformer.

Power level was approximately 6kW during this test run.

The energy stored on the monster toroid is evident in the picture opposite.

This picture was taken during set-up on Friday night and shows an 8ft arc to a grounded metal pole.

The arc was brilliant white in colour, thick and _very_ loud.

Mike Harrison brought this miniature Marx Generator. It was built from 14 ceramic capacitors soldered together and used bent wire for all the spark gaps.

The animation opposite shows the generator blasting metal off a CD. (Mike must have had a bad experience with AOL !)

Tim Davey's Van Der Graaf generator.

Tim demonstrated how it was possible to draw a series of sparks from the discharge terminal to a grounded metal rod.

Sparks of 2 ft in length were common, and at one point the discharge terminal actually arced to the base of the VDG, which must have been more than 3 feet.

Tim then removed the ground connection from the metal rod and took the current to his body ! As he moved the metal rod further from the discharge terminal, his arm twitched more at each spark.

(He is an expert. Don't try this at home !)

Several brave volunteers were also charged up from the VDG in classic "hair raising" fashion…

A Wimshurst machine, made by Jonathan Leech.

I had not seen one of these working before, but I was surprised at how quickly the machine charged up. It was possible to get regular sparks between the two balls with only a gentle winding of the handle.