Human-Powered Vehicles

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Human-powered vehicles

Finding easy modes of transportation seems to be a basic human need, but finding easy and clean modes is becoming imperative. Traffic congestion, overconsumption of fossil fuels and air pollution are all direct results of automotive lifestyles around the world. The logical alternative is human-powered vehicles (HPVs), perhaps best exemplified in the bicycle, the most basic HPV. New high-tech developments in HPVs are not yet ready for mass production, nor are they able to compete with cars. Pedal-propelled HPVs in the air, on land, or under the sea are still in the expensive, design-and-race-for-a-prize category. But the challenge of human-powered transport has inspired a lot of inventive thinking, both amateur and professional.

Bicycles and rickshaws comprise the most basic HPVs. Of these two vehicles, bicycles are clearly the most popular, and production of these HPVs has surpassed production of automobiles in recent years. The number of bicycles in use throughout the world is roughly double that of cars; China alone contains 270 million bicycles, or one third of the total bicycles worldwide. Indeed the bicycle has overtaken the automobile as the preferred mode of transportation in many nations. There are many reasons for the popularity of the bike: it fulfills both recreational and functional needs, it is an economical alternative to automobiles, and it does not contribute to the problems facing the environment .

Although the bicycle provides a healthy and scenic form of recreation , people also find it useful in basic transportation. In the Netherlands, bicycle transportation accounts for 30% of work trips and 60% of school trips. One-third of commuting to work in Denmark is by bicycle. In China, the vast majority of all trips there are made via bicycle.

A surge in bicycle production occurred in 1973, when in conjunction with rising oil costs, production doubled to 52 million per year. Soaring fuel prices in the 1970s inspired people to find inexpensive, economical alternatives to cars, and many turned to bicycles. Besides being efficient transportation, bikes are simply cheaper to purchase and to maintain than cars. There is no need to pay for parking or tolls, no expensive upkeep, and no high fuel costs.

The lack of fuel costs associated with bicycles leads to another benefit: bicycles do not harm the environment. Cars consume fossil fuels and in so doing release more than twothirds of the United States' smog-producing chemicals . They are furthermore considered responsible for many other environmental ailments: depletion of the ozone layer through release of chlorofluorocarbons from automobile air conditioning units; cause of cancer through toxic emissions; and consumption of the world's limited fuel resources. With human energy as their only requirement, bicycles have none of these liabilities.

Nevertheless, in many casessuch as long trips or travelling in inclement weathercars are the preferred form of transportation. Bicycles are not the optimal choice in many situations. Thus engineers and designers seek to improve on the bicycle and make machines suitable for transport under many different conditions. They are striving to produce new human-powered vehiclesHPVs that maximize air and sea currents, that have reasonable interior ergonomics, and that can be inexpensively produced. Several machines designed to fit this criteria exist.

As for developments in human-powered aircraft, success is judged on distance and speed, which depend on the strength of the pedaller and the lightness of the craft. The current world record holder is Greek Olympic cyclist Kanellos Kanellopoulos who flew Daedalus 88. Daedalus 88 was created by engineer John Langford and a team of MIT engineers and funded by American corporations. Kanellopoulos flew Daedalus 88 for 3 hours and 54 minutes across the Aegean Sea between Crete and Santorini, a distance of 74 mi (119 km), in April 1988. The craft averaged 18.5 mph (29 kph) and flew 15 ft (4.6 m) above the water. Upon arrival at Santorini, however, the sun began to heat up the black sands and generate erratic shore winds and Daedalus 88 plunged into the sea. It was a few yards short of its goal, and the tailboom of the 70-lb (32-kg) vehicle was snapped by the wind. But to cheering crowds on the beach, Kanellopoulos rose from the sea with a victory sign and strode to shore.

In the creation of a human-powered helicopter, students at California Polytechnic State University had been working on perfecting one since 1981. In 1989 they achieved liftoff with Greg McNeil, a member of the United States National Cycling Team, pedalling an astounding 1.0 hp. The graphite epoxy, wood, and Mylar craft, Da Vinci III, rose 7 in (17.7 cm) for 6.8 seconds. But rules for the $10,000 Sikorsky prize, sponsored by the American Helicopter Society, stipulate that the winning craft must rise nearly 10 ft, or 3 m, and stay aloft one minute.

On land, recumbent vehicles, or recumbents, are wheeled vehicles in which the driver pedals in a semi-recumbent position, contained within a windowed enclosure. The world record was set in 1989 by American Fred Markham at the Michigan International Speedway in an HPV named Goldrush. Markham pedalled more than 44 mph (72 kph).

Unfortunately, the realities of road travel cast a long shadow over recumbent HPVs. Crews discovered that they tended to be unstable in crosswinds, distracted other drivers and pedestrians, and lacked the speed to correct course safely in the face of oncoming cars and trucks.

In the sea, being able to maneuver at your own pace and be in control of your vehicleas well as being able to beat a fast retreat underseaare the problems faced by HPV submersible engineers. Human-powered subs are not a new idea. The Revolutionary War created a need for a bubble sub that was to plant an explosive in the belly of a British ship in New York Harbor. (The naval officer, breathing one-half hour's worth of air, failed in his night mission, but survived).

The special design problems of modern two-person HP-subs involve controlling buoyancy and ballast, pitch and yaw (nose up/down/sideways), reducing drag, increasing thrust, and positioning the pedaller and the propulsor in the flooded cockpit (called "wet") in ways that maximize air intake from scuba tanks and muscle power from arms and legs.

Depending on the design, the humans in HP-subs lie prone, foot to head or side by side, or sit, using their feet to pedal and their hands to control the rudder through the underwater currents. Studies by the United States Navy Experimental Dive Unit indicate that a well-trained athlete can sustain 0.5 hp for 10 minutes underwater.

On the surface of the water, fin-propelled watercraftlightweight inflatables that are powered by humans kicking with finsare ideal for fishermen whom maneuverability, not speed, is the goal. Paddling with the legs, which does not disturb fish, leaves the hands free to cast. In most designs, the fisherman sits on a platform between tubes, his feet in the water. Controllability is another matter, however: in open windy water, the craft is at the mercy of the elements in its current design state. Top speed is about 50 yd (46 m) in three minutes.

Finally, over the surface of the water, the first human-powered hydrofoil, Flying Fish, with national track sprinter Bobby Livingston, broke a world record in September 1989 when it traveled 100 m over Lake Adrian, Michigan, at 16.1 knots (18.5 mph). A vehicle that pedalled like a bicycle, resembled a model airplane with a two-blade propeller and a 6-ft (1.8-m) carbon graphite wing, Flying Fish sped across the surface of the lake on two pontoons.

[Stephanie Ocko and Andrea Gacki ]



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