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Safety, Convenience, and Speed
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Flywheel Energy Storage
Global warming has been caused by the use of fossil fuels, particularly in automobiles. The United States is leading in the use of automobiles as a source of global warming. An alternative for personal transportation now presents itself in the form of covered tricycles with supplemental electric motors. Electric trikes can provide safety, convenience, and power sufficient for many short personal trips. By using a trike instead of a car for many of our short trips, we can do a great deal to reduce our contribution to global warming--and air pollution. Not incidentally, we will also be taking a major step toward ensuring our own health. Recumbent trike cycling can provide aerobic and strength conditioning while sitting in a comfortable, semi-reclining position.
A small electric motor can help with hills. The major drawback to an electric motor is the weight necessary for the batteries, fuel cells, or other energy storage devices. If the electric motor is used only for short spurts to supplement pedaling, then the storage device can be small. A promising new technology, flywheel energy storage systems, promises to make energy storage more practical by storing ten times the energy of a battery. In addition to being much lighter, flywheel systems do not create pollution, last for a decade or more, are not affected by heat or cold, and can be "recharged" in a few minutes.
Light weight energy storage makes electric-assist motors more practical. Electric-assist motors make cycling a more practical option for short trips.
One of the primary weaknesses of standard upright bicycles is that they are unstable, especially at low speeds, when streets are wet, on gravel, on poorly maintained roads, and during startup. Another problem is that the rider sits high above the ground - a simple fall can result in a severe head injury. A third problem is the tendency for bikes to throw riders head-first over the handlebars in severe stops.
Recumbent (reclining) bicycles solve some of the safety problems. They are more stable at medium and high speeds because of the low center of gravity. They also bring the head much closer to the ground and they do not pull the rider over the handlebars in severe stops. Recumbent bikes allow the rider to easily and quickly put both legs on the ground for stability during stops. However, recumbent bikes are not stable during startup. Some recumbents, especially those with "under the seat" steering or short wheel bases, can be difficult to steer under difficult road conditions.
Recumbent tricycles and quadcycles solve the safety problems of both upright standard bikes and recumbents. They provide stability at startup, over wet streets, on gravel, on poorly maintained roads, and at all speeds. Recumbent tricycles and quadcycles are the safest cycling option. A new two-wheel vehicle, called the Segway, uses gyroscopic or flywheel movement to keep it upright, but it has not become commercially available yet (1-02).
A flywheel could theoretically be mounted on a hub of a bicycle. It could be powered by braking action and could make a bicycle stable at stops and going up hills, when stability is needed most. Some flywheel devices are already available that can be attached to the bike frame to increase stability, but not provide power. Other types of flywheel devices could be used to function as energy storage devices and provide extra power during startup and going up hills. Since flywheels have ten times the storage capacity of conventional batteries (by weight), they could create a practical solution for electric-assist. If magnets and copper coil are used with the flywheel, it can double as a motor and generator for the vehicle.
In cities, the addition of an electric motor and light-weight battery system can add to safety at startup and climbing hills. (If a motor is added, a cycle may have to be licensed, however.) The primary limitation of recumbent tricycles and quadcycles may be their transportability in cars, up stairs, or through doorways. The added width (compared to standard bikes) could also be a problem on some bike paths or streets.
An additional safety feature that is not yet included on trikes and quads is a roll bar to provide visibility over the rider's head and between cars. The roll bar should be equipped with front and rear lights or LEDs for even better safety. See Cycling Equipment for sources of cycles, motors, solar panels, and fairings.
If safety is the primary consideration, then consider the Rhoades 4W1P quadcycle with dual disk brakes, front and rear dual lights, seat belt, rollbar, positive traction, and a motor. Protective gear to consider, if price is not a limitation, is a professional race helmet and a HANS device.
Perhaps the two most important elements of convenience for a recumbent are transportability (up stairs, through doorways, into homes, into a car, etc.) and seat placment. Some recumbents fold, some are designed for quick disassembly for placement in a standard suitcase, and some do not disassemble easily for transport. Folding bikes and those that are designed to fit in a suitcase are marked with an (F) in the chart on the next page. If transportability is the primary consideration, then a small folding bicycle should be considered. A kit allows the Brompton to be converted to a recumbent.
Most trikes place the double wheels 30 or more inches apart to provide stability when going over 30 miles an hour down a hill or making high speed turns. However, the width makes them more difficult to carry up stairs or get through doorways. More important, the width can make them less practical on bike paths or when mingling with cars. Several designs have double wheels. Trikes that are narrow (24" wide), and therefore easier to transport, are marked with an (N) on the chart on the next page.
Many recumbents are designed for speed, so the seat is placed inches above the ground and/or the rider is placed at an incline of 40 degrees or flatter. Although this helps with aerodynamics, it makes entry, exit, and visibility to other drivers more difficult. A particular challenge to entry and exit of a cycle exists when the seat is low, the seat is very reclined, double wheels are in front, and the steering is under the seat. Over the seat steering (with a pivoting bar) can greatly improve ease of entry and exit when the double wheels are in front. Having double wheels in the rear can also improve entry and exit. In the chart on the next page, seats that are "high" (at least a foot above the ground) and/or with less than a 40 degree recline are marked with an (H) for "high seat." (The Raven seat can be quickly adjusted from low and reclined for speed to high and more upright for city traffic.)
Comfort is guided primarily by the seat design and placement of shocks or shock absorbing bars. Most recumbents include a shock absorbing bar on the back of the seat and on one or more wheels. Some place shock absorbing material on the bottom of the seat. A few place shock absorbers over the front or rear wheels. If a cycle has shock absorbers (more than the shock absorbing bars), the cycle is marked with an (S) on the chart on the next page.
Since most recumbent tricycles are made for speed, and therefore light weight, seats are typically made of web material. Fiberglass seats covered with foam can also be light--and much more comfortable. Also, many of the recumbent tricycles place the seat in a very low and reclining position for speed. This can be uncomfortable in entering and exiting, as well as creating a feeling of unsafe or invisible to cars.
Another issue for comfort is staying cool. A scoop can be placed in the windshield to direct air to your face if you are going to maintain over 20 miles per hour. A spray bottle with water can be another, easier option.
Power and speed are affected by a number of factors, such as gearing, aerodynamics, tire weight, overall weight, weight of the rider, size of wheels, and more. (More can be found about the relationships at Bicycle Analysis and Forces on a Bicycle Rider.
Gear inch range is a key consideration. Many recumbents have a gear inch range of around 20 to 100 gear inches. Generally, the greater the range (difference between lowest and highest number), the farther the bike will go with one pedal turn, especially as the lower number goes below 20. You can do your own analysis of how fast a bike or trike will go with different gear and wheel size combinations. For example, comparing the MR Components Swift Ultra (with Speed-Drive and 73 inch chainwheel) to the standard Kettwiesel (9 gears) can show most of the difference in speed. The Ultra with Speed-Drive has a gear inch range from 12 to 190 and the standard Kettwiesel has a gear inch range of 29 to 92. We can compare how fast the wheels would go while pedaling one turn per second on a level ground with no wind and while using the gears for most speed for each trike. The standard Kettwiesel can go up to 11 miles per hour, while the Ultra can go up to 56.5 miles per hour.
However, factors other than gears stongly affect the actual speed achieved by each cycle. It would be difficult to maintain a speed of over 20 mph without some kind of aerodynamic assistance, such as a windshield. Examples of other factors that would also influence speed include wind speed and direction, rate of incline, road surface, seat design and placement, quality of materials, tire weight, and frame flex.
Since aerodynamics of a cycle is important for speeds over 20 mph, coverings on a bike can improve speed substantially. A front fairing (windshield or nose cone) can reduce drag and improve speed by 20 percent or more by the time the rider exceeds 20 miles per hour. A rear fairing can reduce drag a great deal also, possibly another 20 percent. Coverings can also protect the rider from rain and cold.
A third important design feature that affects speed is the weight of the cycle, especially on an incline. The lower the weight, the better. Good recumbents weigh less than 35 pounds. Some recumbents have frames of titanium or carbon fiber to lower weight down to around 18 pounds--and cost accordingly.
A fourth ingredient for speed is stiffness of the frame; generally, the stiffer the frame, the more power goes to the wheels. Some recumbents build in some flexibility in the frame to make the bike ride more comfortable, however. In general, a good recumbent will have some method, such as shocks, to reduce the harshness of the ride.
Seat design affects speed. The seat needs to provide sufficient solidness to provide power, yet needs to be made of material that allows absorption of road bumps. The seat material should be porous and light. The seat should detach from the cycle easily and quickly for transport and storage. The seat should also adjust to different angles to fit the needs of different riders.
Some designs place the seat several inches above the ground and/or use a very reclining position for best aerodynamics. However, this may be too low for persons wanting to use the cycle for neighborhood errands. In the chart on the next page, cycles with a seat bottom at least a foot above the ground and with less than 40 degrees of reclining are marked with an (H) for "high seat."
Finally, and perhaps most important, a light weight electric motor and batteries could add greatly to the power of a bike or trike. A motor with light weight batteries and regenerative braking would be ideal. In order to keep the weight down to around 15 pounds, an electric motor and battery combination would be just powerful enough to supplement pedal power when going up hills or to provide a burst of speed when needed in traffic.
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