Last week in
Alternative Cars Part 3 we looked at the possibilities of turbine-powered cars. This time we look at
vehicles powered by humans.
A human-powered vehicle sounds like an oxymoron.
How can just legs power a vehicle? However that reaction is more an
indictment of the limited variety of available vehicles than any intrinsic
impossibility. If the vehicle weighs – say – 30kg, can carry a person and their
goods, can keep them dry and protected from the weather, and can achieve
reasonable speed and range for urban use, then by most broad definitions it’s a
vehicle.
For many people and in many environments, it’s
also quite a viable option.
Function
Human-powered vehicles that fit the above
description already exist. They’re called velomobiles and are most popular in
Europe.
The most frequently used configuration is a
tricycle wheel arrangement, with two front steering wheels and a rear powered
wheel. This format gives stability without the driveline requiring driveshafts
with universal joints or a differential.
The rider lies back in a semi-recumbent seating
position, so lowering the height of the vehicle and also providing greater
comfort because of the large area of body support. The pedals are positioned
forward of the rider and at, or a little above, the height of the seat base. The
pedals, chain drive, gears and wheels all follow well-proven bicycle practice.
For example, derailleur gears, internal hub gears, spoked wheels and so on are
used.
Steering geometry of the front wheels is chosen to
provide zero or negative scrub radius and Ackerman steering is usually
implemented. Steering control is via fore-aft levers positioned either side of
the seat or by a joy-stick-type of control between the rider’s legs. Suspension
is often fitted.
A key ingredient is a fully enveloping body work,
either completely covering the rider or alternatively, allowing their head to
remain exposed. These ultra lightweight bodies, that include an undertray, are
shaped to give very low aerodynamic drag, vastly reducing the amount of required
power needed at speeds over about 15 km/h. Compared with a conventional bicycle
that on flat ground at 36 km/h requires a rider power of 345 watts to overcome
wind resistance, a fully faired recumbent velomobile requires just 30 or 40
watts!
Some velomobiles are electrically-assisted and
feature head- and tail-lights, windscreen wipers and indicators.
Advantages
The advantages of a human-powered velomobile are
many. If the cost of food is ignored, running costs are very low – effectively
free in fact. The exercise has major health benefits and emissions are zero.
Human powered vehicles are quiet and in car terms,
cheap. They take up little space on the road and because their maximum speed is
relatively low, traffic density can be high. When used on dedicated cycle
trails, commuting times can be quicker than conventional cars travelling on
heavily congested roads.
If appropriately maintained, their life can be
expected to be long, in turn reducing the cost per kilometre even further.
A human-powered vehicle with well designed
suspension and steering can be both comfortable and fun.
Disadvantages
However, disadvantages are also many!
For people of average fitness, range and speed are
severely limited. In hot environments the rider will need to shower and change
their clothes after finishing their ride, which limits work commuting to
relatively short distances to workplaces that provide appropriate shower
facilities. In very cold environments the lack of heating is problematic.
Human powered vehicles are limited in carrying
capacity, normally to just one person and minimal luggage. While the work effort
of propelling the vehicle can be quite low, entering and exiting these vehicles
requires agility and flexibility.
Use of human-powered vehicles (which are wider
than bicycles) can be dangerous on roads that don’t provide appropriate lane
space. Hills – even small hills – greatly increase the required pedalling
effort.
In part because of their very small production
numbers, velomobiles are about 5-10 times as expensive as a good bicycle.
Solution
The technology of human powered vehicles is well
known. In terms of steering, suspension, power transmission, aerodynamics and
seating, there is excellent existing knowledge. However, for human powered
vehicles to take off, the following needs to occur:
-
Development and production of a velomobile by a
major company. Current velomobiles (and human powered vehicles in general) are
produced by boutique manufacturers - often small family companies - with very
limited capital. Because the market is currently tiny, major bicycle
manufacturers have not entered it. (And it can be argued that bicycle
manufacturers are not particularly well placed to develop, manufacture and
market velomobiles anyway.) The major development cost is in the body, which
because of its extreme lightweight requirement, is best moulded from composites
like carbon fibre.
-
Implementation of dedicated cycle paths that
separate motorised vehicles and human powered vehicles on all but local feeder
roads. Cycle path construction is certainly booming, but here in Australia at
least, they often end abruptly (forcing riders onto main roads), are poorly
maintained and are often placed where it’s easy to put them rather than
satisfying traffic requirements.
Conclusion
Velomobiles clearly don’t suit all uses to which
we put current cars - in fact, they couldn’t replace the majority of car trips.
However, where the topography is flat, cycle ways are provided and single person
trips are frequently short, human powered vehicles have the potential to become
widely used.
Next week: steam powered vehicles
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