2009 Issue

20 W E WERE SELF-CONTAINED, CARRYING ALL of our gear; camping or staying in motels some nights. Pedaling over the 11,300 foot highMonarch Pass, we realized that gravity is not always our friend. Though I tried to pack light, my 190-pound body, 30-pound bike, and 75 pounds of gear seemed like a ton as we grunted up the 6.5 per cent grade at four miles per hour. As my body rebelled against the amount of work involved, an 18-wheeler roared by at 40 miles per hour, followed by a 3,500 pound car rolling at 50 miles per hour. I was reminded of the tremendous amount of energy and fuel it takes to push our trucks, cars and bicycles over The Laws of Physics Revisited NEIL H. SPENCER, P.E., LEED AP, VAN BOERUM & FRANK AND ASSOCIATES As one rides a bicycle through the Colorado Rockies, the laws of physics come into sharp focus. I recently traded the rigors of mechanical engineering for the rigors of a six-week Physics 101 Field Trip. This summer, a friend and I bicycled from mid-Kansas to San Francisco, a trip of 1,700 miles. our highways. The hard, cold facts of the laws of physics are many times lost on us. It is so easy to push that gas pedal down an extra inch as we drive up hills. Just as Monarch Pass re taught me, $ 4 per gallon gas has taught the nation that we have been taking energy for granted too long. As we biked over several other mountain passes, I thought of ways to lighten the load. Some of that extra clothing was sent back home. As we traveled down from the Rockies and headed across the Utah deserts, we passed dozens of motor homes heading south for the winter: People driving homes-on-wheels, complete with basements, and towing a truck with an all terrain vehicle - ATV - in the back. We have become too far removed from reality. I re-learned the fundamentals of air friction and aerodynamics. As a mechanical engineer, I deal with these principles on a daily basis. I know that if we reduce the velocity through the air handlers and ductwork by 20 per cent, we can save 36 per cent of the fan energy. And, I know that transporting air in buildings is one of the major energy consumers in buildings. I also know that buildings use 40 per cent of the nation’s energy. For bicycle road racers, about 80 per cent of their energy is used up on air friction. From personal experience, riding a fully-loaded bike into a 30 miles per hour headwind seems like a 6.5 per cent grade. Experience also reinforced my understanding that small improvements in aerodynamics make a big difference: my recum- bent bike with a single-wheel trailer had less wind drag than my partner’s conventional bicycle with panniers on the sides. Bicycles are perhaps the most efficient means of human-powered transportation. Bicycling is a perfect combination of man and machine. None- theless, air friction and road friction take their toll. As we did roller-coaster sections of highways, it was always disappointing to see how short a dis- tance we coasted up the next hill compared to the height of the hill coming down. The road surface, with its associated coefficient of friction, had a substantial effect on our speed, as we discovered on those flat rides through Kansas. The lessons learned in the Physics 101 Field Trip: Lighten our loads: we usually don’t need to take our houses with us. Take a step down in the transportation food chain, walk or ride a bikewhen possible. For the engineers of the world, slow that air down and streamline the path. Mr. Spencer is a a licensed professional engineer and principal of Van Boerum & Frank Associates, with more than 35 years of experience in mechanical engineering and design.