Recumbent bicycle

[박대선]

Recumbent bicycle

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From Wikipedia, the free encyclopedia

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Recumbent bicycle" – news · newspapers · books · scholar · JSTOR (June 2021) (Learn how and when to remove this message)

Recumbent bicycleClassificationApplicationFuel sourceWheelsAxlesComponentsInventedVariationsWheelbaseSteeringSuspensionSeat

Bacchetta Corsa, a short-wheelbase high racer

Vehicle

Transportation

Human-power, Motor-power

2-4

0-2

Frame, Wheels, Tires, Saddle, Handlebar, Pedals, Drivetrain

19th century

Mountain bike, Lowracer, Highracer, Semi-recumbent, Folding, Tandem, Recumbent tricycle, Handcycle, Hand-and-foot recumbent tricycle, Recumbent quadracycle, Stationary

Long, Short, Compact long wheelbase, Convertible

Under-seat, Over-seat, Center steering

Rear wheel drive, Front wheel drive

Coil, Elastomer, Air-sprung

Mesh, Foam

A RANS V2 Formula long-wheelbase recumbent bike fitted with a front fairing

Shop for recumbents in Nijmegen, Netherlands

A recumbent bicycle is a bicycle that places the rider in a laid-back reclining position. Some recumbent riders may choose this type of design for ergonomic reasons: the rider's weight is distributed comfortably over a larger area, supported by back and buttocks. On a traditional upright bicycle, the body weight rests entirely on a small portion of the sitting bones, the feet, and the hands.

Others may choose a recumbent because some models also have an aerodynamic advantage; the reclined, legs-forward position of the rider's body presents a smaller frontal profile. Recumbents are much faster than upright bicycles,[1] but they were banned by the Union Cycliste Internationale (UCI) in 1934.[2] Recumbent races and records are now overseen by the World Human Powered Vehicle Association (WHPVA) and International Human Powered Vehicle Association (IHPVA).

Recumbents are available in a wide range of configurations, including: long to short wheelbase; large, small, or a mix of wheel sizes; overseat, underseat, or no-hands steering; and rear wheel or front wheel drive. A variant with three wheels is a recumbent tricycle.

Description[edit]

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Woman riding a Cruzbike Sofrider (PBFWD recumbent) near the end of the 500-mile (800 km) "Ride Across North Carolina" 2007

Recumbents can be categorized by their wheelbase, wheel sizes, steering system, faired or unfaired, and front-wheel or rear-wheel drive.

Wheelbase[edit]

Long-wheel-base low-rider recumbent with steering u-joint (UA)

Long-wheelbase (LWB) models have the pedals located between the front and rear wheels; short-wheelbase (SWB) models have the pedals in front of the front wheel; compact long-wheelbase (CLWB) models have the pedals either very close to the front wheel or above it. Within these categories are variations, intermediate types, and even convertible designs (LWB to CLWB) – there is no "standard" recumbent.

Wheel sizes[edit]

The rear wheel of a recumbent is usually behind the rider and may be any size, from around 16 inches (410 mm) to the 700c (or 27″ on some older models, as on upright road bikes of that time) of an upright racing cycle. The front wheel is commonly smaller than the rear, although a number of recumbents feature dual 26-inch (ISO 559), 650c (ISO 571), 700c (ISO 622), or even 29 × 4″ oversize all-terrain tires. Given the higher rolling resistance of the smaller front wheel, loss of steering and control are somewhat more likely attempting sharp or quick changes of direction while crossing over patches of loose dirt, sand or pebbles.[3] Larger diameter wheels generally have lower rolling resistance but a higher profile leading to higher air resistance. High-racer aficionados also claim that they are more stable, and although it is easier to balance a bicycle with a higher center of mass,[4] the wide variety of recumbent designs makes such generalizations unreliable. Another advantage of both wheels being the same size is that the bike requires only one size of inner tube.

One common arrangement is an ISO 559 (26-inch) rear wheel and an ISO 406 or ISO 451 (20-inch) front wheel. The small front wheel and large rear wheel combination is used to keep the pedals and front wheel clear of each other, avoiding the problem on a short wheelbase recumbent called "heel strike" (where the rider's heels catch the wheel in tight turns). A pivoting-boom front-wheel drive (PBFWD aka moving bottom bracket recumbent) configuration also overcomes heel strike since the pedals and front wheel turn together. PBFWD bikes may have dual 26-inch (660 mm) wheels or larger.

Handlebar setup for under-seat steering (USS)

Steering[edit]

A Flevobike showing pivot steering (and FWD)

Steering for recumbent bikes can be generally categorized as

• over-seat (OSS) or above seat steering (ASS);
• under-seat (USS); or
• center steering or pivot steering.

OSS/ASS is generally direct—the steerer acts on the front fork like a standard bicycle handlebar—but the bars themselves may extend well behind the front wheel (more like a tiller); alternatively the bars might have long rearward extensions (sometimes known as Superman or Kingcycle bars). Chopper-style bars are sometimes seen on LWB bikes.

USS is usually indirect—the bars link to the headset through a system of rods or cables and possibly a bell crank.[5] Most tadpole trikes are USS.

Center steered or pivot steered recumbents, such as Flevobikes and Pythons, may have no handlebars at all.[6][7]

In addition, some trikes such as the Sidewinder have used rear-wheel steer, instead of the more common front-wheel steer. They can provide good maneuverability at low speeds, but have been reported to be potentially unstable at speeds above 25 mph (40 km/h).[8]

Drive[edit]

Most recumbents have the cranks attached to a boom fixed to the frame, with a long drive chain for rear wheel drive. However, due to the proximity of the crank to the front wheel, front wheel drive (FWD) can be an option, and it allows for a much shorter chain. One style requires the chain to twist slightly to allow for steering.[9]

Cruzbike Silvio (2009) A moving (pivoting) bottom bracket, front wheel-drive, 700C road bike (with rear rack).

Another style, pivoting-boom FWD (PBFWD), has the crankset connected to and moving with the front fork.[10] In addition to the much shorter chain, the advantages to PBFWD are use of a larger front wheel for lower rolling resistance without heel strike (you can pedal while turning) and use of the upper body when sprinting or climbing. The main disadvantage to all FWD designs is "wheelspin" when climbing steep hills covered with loose gravel, wet grass, etc. This mainly affects off-road riders, and can be ameliorated by shifting the weight forward, applying steady pressure to the pedals, and using tires with more aggressive tread. Another disadvantage of PBFWD for some riders is a slightly longer "learning curve" due to adaptation to the pedal-steer effect (forces applied to the pedal can actually steer the bike). Beginner riders tend to swerve along a serpentine path until they adapt a balanced pedal motion. After adaptation, a PBFWD recumbent can be ridden in as straight a line as any other bike, and can even be steered accurately with the feet only. Cruzbike is the only PBFWD recumbent currently in production, and features a traditional steering axis similar to most standard and recumbent bikes. Flevobike formerly produced a center-steered FWD bike similar to the Python Lowracer.

Yet another drive-train variation is on rowing cycles where the rider rows using arms and legs.

Fully suspended bikes[edit]

Modern recumbent bikes are increasingly being fitted with front and rear suspension systems for increased comfort and traction on rough surfaces. Coil, elastomer, and air-sprung suspension systems have all been used on recumbent bikes, with oil or air-damping in the forks and rear shock absorbers. The maturation of fully suspended conventional mountain bikes has aided the development of these designs, which often use many of the same parts, suitably modified for recumbent use.

Leitra Velomobiles

Fairings[edit]

Main article: Bicycle fairing

Some riders fit their bikes with aerodynamic devices called fairings. These can reduce aerodynamic drag[11] and help keep the rider warmer and drier in cold and wet weather. Fairings are also available for upright bikes, but are much less common. Fully enclosed bikes and trikes are considered velomobiles.

Seats[edit]

The seats themselves are either of mesh stretched tightly over a frame or foam cushions over hard shells like the Stinger pictured, which might be moulded or assembled from sheet materials. Hard-shell seats predominate in Europe, mesh seats in the USA.

Variations[edit]

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Challenge Hurricane: a mid-racer.

Mountain bike recumbents[edit]

With the right equipment and design, recumbent bikes can be used for riding unpaved roads and offroad, just as with conventional mountain bikes. Because of their longer wheelbase and the manner in which the rider is confined to the seat, recumbents are not as easy to use on tight, curving unpaved singletrack. Large-diameter wheels, mountain gearing and off-road specific design have been used since 1999. Crank-forward designs that facilitate climbing out of the saddle, such as the RANS Dynamik, also can be used off-road.[12]

Lowracers[edit]

Lowracers are a type of recumbent more common in Europe among racing enthusiasts. These typically have two 20″ wheels or a 26″ wheel at the rear and 20″ wheel at the front. The seat is positioned between the wheels rather than above them. The extreme reclined position, and the fact that the rider is sitting in line with the wheels rather than atop them, makes this type the most aerodynamic of unfaired recumbents.

Highracers[edit]

Highracers are distinguished by using two large wheels (usually ISO 559, 650c or 700c). This necessitates a higher bottom bracket than on a lowracer so that the rider's legs are above the front wheel, and this in turn requires a higher seat. The seating position may be otherwise identical to that on a lowracer allowing similar aerodynamics. "Racer" in the name implies that this will often be the case, since these bikes strive for speed.

Highracers are generally more maneuverable than lowracers since their higher center of mass make them easier to balance at lower speeds.[4] Given the same seating position they may be faster than lowracers, since it is widely believed that rolling resistance is inversely proportional to wheel diameter.[13] However, lowracer proponents reply that their design is faster due to aerodynamics. The reasoning is that the riders body is in line with the wheels, reducing drag.

Hip and elbow injuries are more common on highracers than on lowracers due to the greater height from which the rider can fall. However, the injuries are very rare and seldom serious.

Semi-recumbent and crank forward bicycles[edit]

Bicycles that use positions intermediate between a conventional upright and a recumbent are called semi-recumbent or crank forward designs. These generally are intended for casual use and have comfort and ease of use as primary objectives, with aerodynamics sacrificed for this purpose.

Tandem recumbents[edit]

This Barcroft Columbia is an example of how a tandem recumbent can be fitted within a compact layout for easy transport.

Just as with upright bicycles, recumbents are built and marketed with more than one seat, thus combining the advantages of recumbents with those of tandem bicycles. In order to keep the wheelbase from being any longer than absolutely necessary, tandem recumbents often place the stoker's crankset under the captain's seat. A common configuration for two riders in the recumbent position is the sociable tandem, wherein the two riders ride side by side. There are also hybrid recumbent designs such as the Hase Pino Allround[14] that utilize a recumbent stoker in the front, and an upright pilot in the rear.

Recumbent tricycles[edit]

A tadpole recumbent tricycle made by Inspired Cycle Engineering with a transparent front fairing

Hand and foot recumbent tricycle

A modern touring 4-wheel recumbent quadracycle – a 2011 model Quattrocycle four seater with canopy[15]

Recumbent tricycles (trikes) are closely related to recumbent bicycles, but have three wheels instead of two. The three wheels can be arranged in two ways: delta trikes have one front wheel and two rear wheels, while tadpole trikes have two front wheels and one rear wheel. [16]

Handcycles[edit]

Main article: Handcycle

In order to accommodate paraplegics and other individuals with little or no use of their legs, many manufacturers have designed and released hand-powered recumbent trikes, or handcycles. Handcycles are a regular sight at human powered vehicle (HPV) meetings and are beginning to be seen on the streets. They usually follow a delta design with front wheels driven by standard dérailleur gearing powered by hand cranks. Brake levers are usually mounted on the hand holds, which are usually set with no offset rather than the 180° of pedal cranks. The entire crank assembly and the front wheel turn together, allowing the rider to steer and crank simultaneously.

Although arms are weaker than legs, many hand cyclists are able to make use of the power of the whole upper body. A good hand cyclist can still achieve a respectable pace in competitions. Handcycles have also been used for touring, though few designers incorporate mudguards or luggage racks. Also, the gear ratios of standard handcycles tend to be less useful for long steep climbs.

Hand-and-foot recumbent tricycles[edit]

Recumbent cycles offer the possibility of combined hand and foot power inputs, and thus the potential for a full-body workout, and the option for persons with a weak or missing leg(s) to power a cycle. In one recumbent tricycle design the user makes the two front wheels change direction by shifting his center of weight, and moves forward by rotating the rear wheel.[17] There are also hybrids between a handcycle, a recumbent bike and a tricycle; these bikes enable cycling by use of legs, despite a spinal cord injury[18]

Recumbent quadracycles[edit]

Main article: Quadracycle

Recumbent four-wheel cycles have the same general advantages of tricycles.[19] For quadracycles with only one seat the stability improvements of the fourth wheel offer only a marginal advantage over a tadpole recumbent tricycle. More wheels introduce more weight and more complexity. The fourth wheel is only of the most benefit to the single-seat rider when going off-road.[20] When two and sometimes four riders want to ride together in a sociable configuration the four-wheel recumbent cycle is a viable option.[21]