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.
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.
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.
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.
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:
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