The Circuit Rider

Published 14/10, 2008

It is hard to imagine that aircraft can have anything to do with concrete cutting. But that is the truth and Ed Dempsey knows why. PDi can tell the story. PDi’s US Editor Jim Parsons reports.

If life was a DVD player, Ed Dempsey’s finger would always be on the “fast-forward” button. This is a man who has raced dragsters, stock cars, and motorboats, and experimented with various types of conventional and alternative vehicles to find the best combination of speed, performance, and endurance. In 1999, Dempsey’s “White Lightning” set the current world land speed record for electric vehicles weighing more than 1,000 kilograms, clocking a blistering 245.524 mph on the famed Bonneville Salt Flats in Utah.

First with high cycle in concrete cutting
Veterans of the construction industry know Dempsey for different kind of speed; his pioneering work and the application of high-cycle, or high-frequency, electrical power for concrete cutting machines in the early 1960s. Taking advantage of high-revving 400 Hz motors’ smaller size and greater power, Dempsey developed a complete high-cycle concrete cutting system for his nationwide Concrete Coring Company chain, which he owned until 1986.
Over the years, hydraulic systems overshadowed high-cycle equipment due to the latter’s cost and limited parts availability. But Dempsey’s faith in the technology never did not waver, nor did his instinct for tinkering.
Thanks in part to technological advancements that make 400 Hz equipment more compatible with more conventional electric sources, high-cycle sawing and drilling equipment is enjoying a revival among the world’s machine manufacturers. Not surprisingly, Dempsey is on the cutting edge of high-cycle research and development through his Santa Ana, California based venture, 400 Hertz Engineering.
Dempsey says that 400 Hz concrete cutting systems are ideal for an industry that, like him, craves speed, performance, and reliability.
Along with providing more power to cut faster and deeper with less wear on diamond blades and motors, “high-cycle systems are smaller, lighter and versatile than hydraulics,” says Dempsey. “You can work cleanly and efficiently with a highly mobile power system that also powers other equipment. Compare that with the heavy, oily hoses of hydraulic systems that have to be used close to their power source, and can run only one machine at a time.”

Innovative iterations
Dempsey’s interest in perfecting the concrete cutting process dates back to 1958, when he left college temporarily to sell diamond tools and other equipment for his then-room mate’s father. Three years later, he launched Concrete Coring Company and began working for contractors across Southern California.
As demand for his services increased, Dempsey and his classmate and partner at the time, Ken Barnes of Concrete Wall Sawing in San Leandro, California, looked for ways to improve the efficiency of his conventional 120-volt electric handsaws while also reducing the wear. He pieced together a rack and transport system that would allow the saw to be bolted to the wall, helping ease the strain on the operator. All that was needed was a more efficient power source.
Dempsey’s first attempt was compressed air that provided the needed power, but proved too noisy and messy, not to mention unexpectedly expensive because of the large air compressor required, and clean up of oil on the work surface. “We got a lot of big bills from owners who had to paint walls marred by oil from the air motor exhaust,” says Dempsey. “We also had to have union operators on hand to start and stop the compressor.”
Experiments with direct-current motors and hydraulics fell short of Dempsey’s expectations as well. Then, while visiting a local military surplus store, he found a 7.5 hp 400 Hz motor that had been used to turn a radar dish.
Dempsey was already familiar with the potency of 400 Hz motors, and their ability to run approximately seven times faster than the more commonplace 60 Hz motor, allowing them to be smaller and lighter. “The military and commercial aircraft industry had been using high-cycle power for many years, and it’s still their standard today,” says Dempsey. “I adapted the motor to a wall saw and hooked it up to a Crosley-powered 400HZ generator, and it worked well with small and large blades up to 30 inches in diameter.”
Through further experiments with the high-cycle system, Dempsey’s cutting business was able to provide customers with faster, deeper cuts hundreds of feet from the power source. Tests with larger high-cycle generators and motors led to improvements in the saws and gearboxes; distribution boxes to run multiple units; and, ultimately, his patented high-cycle cutting system with a near-infinite range of uses.
The rest, as the old saying goes, would have been history had a fire not destroyed Dempsey’s high-cycle testing and production lab in 1991. The loss of development momentum compounded a longstanding limitation with 400 Hz motors and generators—cost. Because of their use in military and aerospace applications, the U.S. government requires component producers to meet stringent specification and validation requirements.
As a result, cutting equipment manufacturers turned to more affordable sources such as hydraulics and conventional electricity. But Dempsey was hardly deterred, remaining watchful for an opportunity to make high-cycle cutting both practical and cost competitive.
The answer came through the evolution of inverter technology that can convert standard 50 and 60 Hz DC power into virtually any other form of electric power. As components shrank in both size and cost, Dempsey was eventually able to craft relatively small, 13kg, 60 Hz to 400 Hz inverter boxes, as well as motors capable of providing 10 times the power of a 60 Hz motor of the same size and weight.
Little by little, high-cycle technology regained its promise as a practical and, perhaps more importantly, affordable option for concrete cutting manufacturers.

Picking up the pace
Now, assisted by 10 employees and numerous subcontractors, Dempsey is sharing his experience and application knowledge with manufacturing partners interested in taking high-cycle equipment to the next level. “We’re a prototype and engineering company,” says Dempsey of 400 Hertz Engineering. “We design, build, and test different types of tools in different applications and conditions.”
Along with selling 400 Hz equipment via 400 Hertz Engineering’s website (, Dempsey is working with Diamond B on a line of handsaws, core drills, self-propelled flat saws, and high-cycle components. Other manufacturers in the US and overseas are also incorporating 400 Hz equipment into their sawing and drilling product lines. Floor grinding and polishing equipment looms as another potential new frontier for 400 Hz power.
Still, Dempsey recognizes that cutting into hydraulic power’s dominance will take time. He must both introduce high-cycle to those unfamiliar with the technology, and overcome old misperceptions. “There’s some resistance among mechanics who have maintained only hydraulic equipment,” says Dempsey. “They’re so not used to 400 Hz, so they’re cautious about having to work with something new.”
To help fund his high-cycle research, Dempsey has returned to his diamond tool roots by operating Value Diamond Tool Company, which supplies blades to professional masonry and concrete cutting contractors in the US. He marvels at the strides industrial diamonds have made during his half-century in the business. “They cost about $10 to $12 per carat when I started using them in 1958,” he says. “Now, they cost about 25 cents per carat, but provide much better quality due to the ability to precisely size and shape them.”
Value Diamond also continues another Dempsey tradition of rigorous performance testing to ensure consistent speed and durability. While the Asian-manufactured blades are priced lower than those of US based producers, Dempsey understands the reasoning behind the Diamond Sawblade Manufacturers Coalition’s anti-dumping suit. “Anti-dumping tariffs will result in higher prices for imported blades,” he says. “But it remains to be seen how much effect they have on the overall market.”
Regardless of where the diamond tools come from, Dempsey is confident that more of them will be used with high-cycle drills and saws in the coming years. “As labour becomes more and more expensive the use of 400HZ power will increase because of the speed and flexibility of a lightweight high-cycle system and the ability of operators to setup and break down equipment quickly,” says Dempsey.

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