Friday, July 21, 2006
Unique lightning rod goes up — and up and up — on West Street
Jic Davis of West Street, concerned that his area of Carlisle has a reputation for excess lightning hits, recently erected a self-designed lightning protection system. He designed the system with the help of his friend Stan Harrison, a M.I.T. graduate who "is brilliant," and understands high voltage, said Davis. "He was brutal in the technical specifications," he said. Harrison shot down his first design and helped educate him on the fundamentals of lightning systems. "Picture one million volts," he explained. "You can't predict how big it is or how long it will stay in the lightning system."
Americans' use of lightning rods began after Benjamin Franklin performed his famous electrical current experiments in 1750. Noting how voltage would follow a sharp-point rod through a conductor to a grounded end, Franklin recommended his "Franklin Rods," as they soon were called, to prevent or minimize damage from lightning. Though it was soon proven that the rods could not prevent lightning Is Carlisle at high risk for lightning strikes?
strikes, the Lightning Protection System (LPS), as it is known today, is basically the same system Franklin recommended to minimize lightning damage. The system usually consists of a long rod, either sharp- or flat-pointed, attached to a low-resistance wire, cable or metal rod, which ends into a grounding unit (usually the ground) where the voltage can be discharged safely. Davis said it is important to have moisture in the ground around the dissipation point, and to sink it away from electrical wires and the water pump.
The rod, made of three-fourths inch copper pipe, extends above the tower on his three-story house and ends in a sharp point. "Flat points say 'hit here'," he explained, by offering a larger surface. Davis' copper tubing flows up the side of his house, curving gently over the eaves, and ending in a tall spire festooned with two hand-blown glass balls. "I spent two exhausting days installing it," he explained. Using his friend's hydraulic lift, which was necessary to reach to the top of his tower, he turned and pointed to the woods beyond his house. "There is water coming out of the high points" in the hill beyond, he explained, which makes his sloping land very moist. He said he has a small spring emerging on the other side of his house.
Path of least resistance
The rod is held ten inches away from the house by fiberglass rods, he pointed out. The "gentle bends" in the rod are necessary. "High voltage does not turn corners," and would "jump" from the rod if curves weren't used. Once lightning strikes, it will follow the path of least resistance. It is important to ground the rod, he stressed, so the voltage can be discharged into the earth. "If the rod isn't grounded, the lightning leaves the system when it wants to." He sank the rod eight feet into a hole about two feet from his house. He says he would like to put a coil with a fuse at the base. This would allow him to test whether the rod was hit during a storm (the fuse would be blown).
According to the National Severe Storm Laboratory, which is a research branch of the National Oceanic and Atmospheric Association, lightning "is the most dangerous and frequently encountered weather hazard that most people experience each year. It is the second most frequent weather-related killer in the United States with nearly 100 deaths and 500 injuries each year. (Floods and flash floods are the number one cause of weather-related deaths in the US.)" Massachusetts ranks about 25th for damage, injury and death reports in the country.
But is it possible that Carlisle, with woodlands and wetlands, is at a higher risk than most Massachusetts towns? Trees make good conductors — they are tall and they contain moisture. Some lightning strikes literally blow the tree open, causing vertical stripes or spirals around the trunks. Trees can also be damaged or killed by "silent" strikes in which a current runs through the ground to their roots.
Lightning strikes were recorded in the violent thunderstorms that hit Carlisle on the afternoon of July 11. At 3:23 p.m. the fire alarm at a Hartwell Road house was activated by smoke inside the house which might have been caused when lightning struck a tree near the house. An hour later, at 4:44 p.m., lightning struck a barn on Peter Hans Road. There was no fire, but electrical wiring might have been damaged. A Concord Street house was also hit by lightning at 5:07 p.m., activating the fire alarm and causing damage, but no fire.
(The Mosquito is working on weather- and nature-related disasters and risks in Carlisle for future publication.)
Beauty and function
Having the Lightning Protection System gives Davis a sense of safety as well as pride in completing the project. The copper-brown of the pipe blends in with the side of the house making it seem part of the house design. The glass balls near the top of the rod catch the sunlight and add a touch of history. Glass balls were added in the 1800s for beauty and function, often used to indicate whether a strike had occurred (they would shatter). As the hydraulic lift descended, Davis pointed to a dragonfly poised on the sharp peak of the rod. Though Davis has created a well-planned lightning protection system, the dragonfly, with its airy perch, is not protected. We can hope it moves before the next storm.
© 2006 The