Human Powered Vehicles

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BOB KEIM
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."

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!