Human Powered Vehicles

An annual road racing contest in California is the place to see the latest innovations in human-powered vehicles.

| September/October 1981

  • 071 human powered vehicles - cal poly phoenix
    The radical Cal-Poly/ A.S.M.E. Phoenix features an aerodynamically favorable composite body (with a tubular substructure), minimal ground clearance, and a top speed near the "double nickel."
  • 071 human powered vehicles 2 greg johnson
    Greg Johnson's 50-MPH machine relies on a lightweight, fish-shaped fairing and "prone power" to cut down on aerodynamic drag.
  • 071 human powered vehicles 3 upright bike w shield
    Some entrants merely adapted wind-cutting fairings to modified bicycle frames. This tandem is capable of traveling at over 43 miles per hour.
  • 071 human powered vehicles 4 hpv frame
    Human powered vehicles typically use ultralight frames just strong enough to serve their purpose. Notice the speed-inducing "stiff" gearing ratio shown here.

  • 071 human powered vehicles - cal poly phoenix
  • 071 human powered vehicles 2 greg johnson
  • 071 human powered vehicles 3 upright bike w shield
  • 071 human powered vehicles 4 hpv frame
As we've noted in this magazine before, a bicycle is about the most efficient transportation device yet developed. With its light weight and its highly effective roller chain-and-sprocket drive system, the two-wheeled conveyance is about five times more energy-thrifty—when distance and weight are taken into account—than is either an unaided human or an automobile.

It should come as no surprise, then, that a lot of folks would like to put this potential fuel-saver into proper perspective in our energy-scarce world. Of course, in many countries, the bicycle already plays as important (or more so!) a transportation role as does the motorized vehicle, but in North America it's generally been relegated to sporting or pleasure status. The International Human Powered Vehicle Association, however, hopes to change all that. This Claremont, California-based group—founded  in 1974 by bike-racing enthusiasts who were interested in expanding the design frontiers of human powered vehicles—has sponsored annual speed championships since its inception. As a result of the competitions, a new sort of machine has emerged which just might be the forerunner of a swift, practical human-powered commuter vehicle!

This year's IHPVA competition included several events in two categories—single-and multiple-rider vehicles—and contestants challenged each other for a total of $5,000 in cash prizes. In the first event, the 200-meter time trials, entrants competed to achieve the greatest possible velocity over a flat 656-foot stretch (the machines used an acceleration runway to build up speed before their run was recorded). The second contest was an 18-mile road race designed to test the maneuverability and road-handling capability of the pedal-powered vehicles. And the speeds recorded in both events were impressive, about 32 miles per hour for the distance race and peaking at close to 60 MPH in the sprints.

In order to achieve such speeds, HPV builders must concentrate primarily upon aerodynamic design, though rider position does come into play, too. For example, at 30 miles per hour, 90% of the energy expended by the rider of a conventional bicycle is wasted trying to overcome wind resistance. Even more may be lost because the standard seating position doesn't allow for maximum pedal pressure. To decrease such inefficiency, the more radical human-powered vehicles use tubular frames surrounded by airfoil-shaped Hexcel fiberglass shells (or, alternatively, load bearing—and "slippery"—composite-construction bodies with small tubular subframes at stress points), and place the rider in a supine (reclining on the back) or prone (on the stomach) posture for maximum comfort and pedaling power. Of course, some of the HPV designers practice "middle ground" technology by placing lightweight fairings over slightly modified ten-speed bike frames.

At any rate, it's clear that a number of changes are in store for the bicycle over the next few years, though today's racing HPV's certainly aren't ready to hit the streets commercially as yet. Nevertheless, any vehicle that uses only 1/4 horsepower to move rapidly down the highway deserves a lot of attention. We hope these little energy-savers get plenty of it as time goes on!

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