The King of Coils

Dr. Hank Electrifies Education

By Sarah Sakha, Correspondent, Black Canyon Bullet

“I got to feed the house cat,” says Henry Hurrass as he goes to fill a cat food dispenser. A stack of vinyl records next to the dispenser caught my eye; the one on top was a Karl Böhm recording of Mozart symphonies. Soon enough, a cat cautiously emerges from behind some equipment.

Three upholstered chairs, a formica-topped table and the dispenser seem out of place in the middle of this space, which is something between a large garage and a small workshop. The metal workbench has car parts and tools strewn over and music amplifiers of varying sizes are distributed here and there.

An American flag hangs on the south wall along with a POW/MIA flag. Beneath the flags stands a large, enshrouded contraption – the world’s highest voltage bipolar Tesla coil, at 500,000 volts. The coil was built right here in Black Canyon City, Arizona; and currently certified with an official Guinness World Record certificate.

Dr. Henry Hurrass, who goes by Hank, builds bipolar Tesla coils the way some folks  build model airplanes. He got into building coils after a sixth-grade field trip to the Griffith Observatory in Los Angeles, where he saw a Tesla coil for the first time. He built his first coil back in 1969 at age 12–a small, monopole coil.

Hurrass talks with great pride about that first coil. “I got an award at the Orange County Science Fair,” he reminisces. He’s been building coils ever since. He recounted how he was always “trying to one-up his friend” in an on-going rivalry, and the coils kept growing bigger and bigger, culminating in the famous “Hellcat Coil” in 2015.


(Pictured from left; Black Canyon Bullet’s Stacey Lane and Sarah Sakha standby the demonstration, and AudioTesla Hellcat, provided by Dr. Hank – center.)

“It  took me one year to build the Hellcat coil; I didn’t know whether it would even work,” comments Hurrass. But he figured it out, brought scientists out to witness the coil and verified its Guinness Book of World Records certificate.

By no means is the coil a new invention; in fact, it has been around for over a century, one of the many novel creations of inventor and electrical engineer Nikola Tesla, who also developed radio and radar waves, fluorescent lights and the AC distribution system used in our houses today.

Tesla irrevocably changed the field of electronics and our understanding of electricity. As pointed out by Hurrass, Tesla’s first big invention–the AC electric polyphase motor, or the inductor motor and generator–brought electricity into everyday use in every context. Intensified by the ardent rivalry between Nikola Tesla and George Westinghouse (not to mention Thomas Edison), the introduction of the electric power distribution systems in the late 19th century allowed electric energy to be transmitted on a scale permitting indoor lighting in every home. That historical rivalry would go down in history as the “War of the Currents.”

Understanding how a current could travel over longer distances proved to be more difficult than anticipated. Hurrass scrupulously explained how a transformer operates, using car parts to provide analogies and scribbling on the formica table, in order to understand how his bipolar Tesla coil works. Basically, it is possible to either step down (decrease) or step up (increase) the voltage of a transformer, by manipulating the input to output (or primary to secondary wire turns) ratio. Regardless of the number of turns, he said, the ratio must remain constant. Electric current goes in, to come out as heat; and what goes in, must come out, albeit transformed, as the name of the device prescribes. If electricity is to travel a greater distance, then an increase in voltage in necessary, all the while keeping the input-output ratio constant.

An ideal transformer has a one-to-one ratio, but Hurrass’ Tesla coil has a much higher ratio, with more turns on the secondary and less turns on the primary wire. Pointing to the thick black wire that encircles the outside of the coil six times, he explains, “It’s thick because there’s a lot of current going through it.”

Finally, Hurrass cranks up the machine, demonstrating with the smaller bipolar Tesla coil first and then with the Hellcat Coil. It takes a bit of time for him to “find its ‘sweet spot,’ the natural vibrating frequency.” That’s called the resonance, and everything has one; it’s just about striking it.

After tinkering with a small laptop, some wires and a few amps, the Tesla coil begins playing music in tune with a light show. It was built to reproduce high quality (read: practically deafening) audio. It’s a two-in-one audio and light show, and the Hellcat Coil’s show is much, much louder and livelier and certainly more impressive. The music choices are eclectic, switching from rock’n’roll to country to classical.

Dr. Hurrass runs his “shop” in Black Canyon City, where he has been living for the past 22 years. “Let’s put it this way: I was living here before any other houses existed on this hill!” he reports with a laugh–a hearty laugh. He’s retired now, having worked at the power company building substations. He pointed out how the lines coming in through Black Canyon City run to power plants located all the way from Page at one end to Holbrook at the other.

The Hellcat Coil has attracted the interest of people from all over the world. Dr. Hurrass mentions three doctors from Romania, a man from Denmark and a kid from Bulgaria as recent visitors. Drop-ins increase during the Western Winter Teslathon, held in Black Canyon City.

Hurrass now dedicates a lot of his time to teaching kids about electricity, showing elementary and junior high students his Tesla coils.  He reckons that a sixth-grade trip is integral to this stage of his life in which he hopes to electrify the trajectory of the kids’ intellectual lives as well.

Dr. Hank Hurrass’s license plate perhaps best sums up the experience of touring his lab: absolutely, inexplicably, wonderfully “INSANE.”

For more information visit; www.audiotesla.org or contact Dr. Hank via e-mail at [email protected]

Additional notes from Dr. Hank –

Nikola Tesla was a brilliant and prolific inventor who, in the late 1800’s, invented such things as the Polyphase (AC) Electric Induction Motor, far superior to Edison’s DC electric motor, the modern electric distribution system that we use today, Radar, Transmission of Wireless Power and Fluorescent Lights just to name a few. There probably isn’t a single appliance in our homes that can’t be traced back to one or more of Nikola Tesla’s patents. However, over the years, his name has fallen shadow to others and he basically has not receive recognition for his many inventions until recently.

One of my goals is to educate our young to Nikola Tesla’s achievements. Our kids are the future of America. I can’t stress enough how important it is to learn about history, science and physics at a young age. This knowledge and the skills brought by this can very well lead to a successful and gratifying career and life.

Audiotesla’s HELLCAT Bi-Polar Tesla Coil and the Guinness Word’s Record™ Award


My personal motto is “If You Dare Dream It, Build It!”…… And if you’re going to build it, build it right. 

So about five years ago, we (Audiotesla) built one of the first audio modulated bi-polar Tesla coils in the world. We were very pleased with the results. Although a bit tougher to initially design and build, the ease of operation couldn’t be disputed. This relatively small coil (about a one-tenth scale version of the current HELLCAT coil) was found to be very reliable and became the basis for the design and construction of the much larger HELLCAT Tesla Coil.

Inspired by lifelong friend Jim O’Malley’ one evening, we decided that if building something big was good, then building something really big was even better. (That’s why we love Jim) So why not build the largest Bi-Polar Musical Tesla Coil in the world? The requirements were that not only should this Tesla Coil be larger than the current Guinness World’s Record™ holder, but it should blow the old record clean out of the ballpark, so to speak. And that’s exactly what we did. We were aware that this new Tesla Coil would also be substantially louder than the one-tenth scale coil model. So if the smaller coil would run our shop cat “Squirt” off into the wild, we figured the new coil would likely aggravate the mountain lions in the area! During this time we were also admiring Jim’s new Dodge Hellcat Challenger when we said:”Hey, why don’t we name the new coil “Audiotesla’s HELLCAT; the biggest, baddest most powerful musical Bi-polar Tesla Coil in the world, Period!”

Well, it took about a year of work, but our efforts eventually did pay off. On October 27 th , 2015 we initiated the first lightning bolts from the HELLCAT Bi-Polar Tesla Coil. On November 21 st , 2015 we held the official “unveiling” in Black Canyon City, Arizona. The event was attended and witnessed by Electrical Engineers, Scientists and Friends.

After that we filled out the required paperwork for challenging the then present Guinness World’s Record™ holder. (The Guinness folks do require lots of proof, evidence, pictures, videos, etc.)

On March 29 th , 2016 we received the prestigious Guinness World’s Records™ approval. That was a real exciting day and one of the best days anyone could have. 

In conclusion I wanted the say thank you to my friends for their support and encouragement including Jim O’Malley, Bruce Combe and my wife Sharron.