Recumbent bicycle
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Tandem recumbent bicycle manufactured by BikeE |
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Two short-wheelbase recumbents in an amateur HPV race |
A
recumbent bicycle is a variety of
bicycle which places the rider in a seated or
supine position (rarely, in a
prone position). Recumbents hold the world speed record for a bicycle and were banned from international racing in 1934.
The back of the rider is supported, and the rider's legs extend forward to pedals that are at about the same height as the seat. Steering is either above- or over-seat steering (ASS or OSS) using a
handlebar in front of the rider, or under-seat steering (USS) using a handlebar under the seat. The wheels are often smaller and/or further apart than on an
upright bicycle.
Records of recumbent designs go back to the early days of cycling, however recumbent use was not widespread until the late 20th century. Recumbent riders hold world speed records for unpaced, human-powered vehicles.
Tricycles form a substantial part of the recumbent market (far more so than they do for uprights); the generic term "bike" tends to be applied to these as well.
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The Easy Racers Gold Rush, a classic American long wheelbase bike |
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The Optima Stinger short-wheelbase bike with disc brakes, rear suspension and over seat (tiller) steering; ETRTO 406 wheels front and rear - a fairly representative European recumbent bike |
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Peer Gynt long wheelbase bike with under-seat steering and mesh seat |
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A tadpole recumbent tricycle made by ICE with a transparent front fairing |
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This Barcroft Columbia is an example of how a tandem recumbent can be fitted within a compact layout for easy transport. (Photo by Will O'Neil) |
Recumbent bicycles may be classified according to their
wheelbase: 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 and intermediate types - there is no "standard" recumbent.
The rear wheel of a recumbent is usually behind the rider and may be any size, from around 20 inches to the 700c 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), ISO 571 (650c), or ISO 622 (700c) wheels. Most notable among these are "highracers" such as the Volae Team. Larger wheels generally have lower rolling resistance; the trade-off is a higher profile with its accompanying air resistance. Highracer aficionados also claim that they are more stable, and although bicycle stability increases with the height of the centre of gravity above the ground, the wide variety of recumbent designs makes such generalizations unreliable.
The most common arrangement is probably an ISO 559 rear wheel and an ISO 406 (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 called "heel strike" (where the rider's heels catch the wheel in tight turns). A front-wheel drive configuration also overcomes heel strike since the pedals and front wheel turn together. Pivoting boom front-wheel drive (PBFWD) bikes may have dual 26-inch wheels or larger.
Steering for bikes is broadly over-seat (OSS) or under-seat (USS), and most trikes are USS. USS is usually indirect the steerer acts on the front fork like a standard bicycle handlebar -- but the bars themselves may be well behind the 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.
The seats themselves are either of mesh stretched tightly over a frame (as in the Gold Rush pictured) or hard shells like the Stinger pictured, which might be moulded (as here) or assembled from sheet materials. Hard-shell seats predominate in Europe, mesh seats in the USA.
Lowracers are a type of recumbent more common in Europe among racing enthusiasts. The extreme reclined position, and the fact that the rider is not sitting atop the wheels, but is in line with them, makes this the fastest type of bicycle that can be used on roads. Foremost among new lowracer designs is the fully streamlined Velokraft NoCom.
Recumbent tricycles
Recumbent
tricycles (trikes) are closely related to recumbent bicycles, but have three wheels instead of two. Trikes come in two varieties, the
delta, with two rear wheels, and the
tadpole, with two front wheels. Most recent high-performance trikes are of the tadpole variety.
Three remarkable characteristics of recumbent trikes include: 1) the fact that the rider does not need to disengage from the pedals when stopped; 2) the trike can be geared very low to enable mountain climbing while heavily loaded and at a slow speed, without losing stability; and 3) trikes are capable of turning sharply without leaning, producing lateral "g forces" similar to sports
cars. Recumbent trikes may also be more suitable for people with balance or limb disabilities.
The Windcheetah, designed by
Mike Burrows and one of the first commercial tadpole designs, is often credited with kicking off the recumbent tricycle boom. In addition to having a long association with Giant (for whom he designed the OCR series), Burrows designs and builds two- and three-wheeled recumbent racers, as well as load bikes. The Windcheetah is still in production and is an iconic design much appreciated by cognoscenti.
At present, the trike market is led by companies such as
Inspired Cycle Engineering (ICE) and Greenspeed, with touring being a strong market but sporting use also being common. ICE has produced a sub-20lb trike - all the more remarkable for being steel framed and fitted with a hard-shell seat, full mudguards, and luggage rack. As the market expands, costs continue to drop. Stein has launched a range of budget recumbent trikes made in Eastern Europe, the KMX Kart stunt trike, and others.
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A competition handcycle |
Handcycles
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 HPV meets and are beginning to be seen on the streets. These usually follow a delta design with front wheels driven by standard derailleur 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 less strong 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. Georgiev's
Varna bikes have been well represented over the years (see also Records below) and in 1995 Jacob Heilveil achieved 52.47 km/h (32.60 mph) in the flying 200 m.
Handcycles have also been used for touring, though few designers incorporate mudguards or luggage racks. Additionally, the gear ratios of standard handcycles tend to be less useful for long steep climbs.
Fairings
Some riders fit their trikes with
aerodynamic devices called
fairings to reduce wind drag (fairings are also available for upright bikes, but are much less common). Fairings are available for the front and rear of the vehicle. Some riders also use a "sock," a fabric covering which connects the front fairing and the rear fairing, enclosing the rider for even less drag. Front and rear fairings have been shown to be beneficial for long wheelbase bikes, but front fairings are less beneficial for short wheelbase bikes.
Empirical results indicate that a faired tailbox can increase speed on a low short wheelbase bike by around 5-10%, but this has not been validated formally. The design of the fairing is important: a long, sealed fairing gives best compensation for the added weight; for road riding a tailbox may well not repay the weight penalty. The most exotic machines have lightweight full-body fairings, tested in wind tunnels, but these are not practical for street use. Indeed the pilots of many of these bikes must be taped in, and the bike launched by handlers on the outside.
For the ultimate in all-weather riding, a
velomobile has a fully-enclosed body, is usually a three-wheeled design, and keeps the rider warm and dry in all weathers.
The striking difference in appearance between recumbents and upright bikes begs comparison.
Advantages
Recumbents have several advantages over traditional upright bicycles.
Variety. A specific recumbent can be purchased that best meets the physical needs and aesthetic preferences of the rider. Models can range from semi-upright to a full reclined position, short wheelbase to long wheelbase, and many others. (This could be considered a disadvantage; see below).
Safety. The recumbent bicycle's low center-of-gravity and low distance from the ground significantly reduce the danger of falling off (when compared with an upright bicycle), and the reclined position of the rider removes the risk of being flung over the handlebars during emergency braking.
Comfort. The recumbent riding position reduces strain on the body, making it particularly suitable for long rides and touring. It is very easy on the neck, wrists, hands, arms, shoulders, lower back, and
ischial tuberosities ("sit bones"). Riders who suffer back pain or genito-urinary trouble often find that recumbents allow them to make significant rides without pain.
Health. The inherent stability of three wheels allows very low gearing to be used, so that hills can be climbed without strain on joints. Also, on some recumbents, the riders legs are nearly at the same height as the heart. This reduces the rider's
hydrostatic pressure, thus allowing
venous blood to more easily return to the
heart. This physiological effect of improved
circulation suggests an increase in rider endurance and/or increased power output on long rides.
Speed. On the flat, recumbent bicycles are generally faster than upright bicycles for the same level of effort because the
aerodynamic profile of the rider reduces
wind resistance. It is this feature which led to the Union Cycliste International (UCI) banning them in the 1930s (see
History).
Disadvantages
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Balance. Balance is easier to effect with a higher
centre of gravity, because of the "pendulum effect" (it is easier to minutely change the angle at which
ordinary bicycles lean).
*
* International Human Powered Vehicle Association
* Recumbent Cyclist News enthusiast magazine
* alt.rec.bicycles.recumbent Usenet newsgroup
* British Human Power Club
* 'BentRider - Forum, Buyer's Guide and more
* Cycling Forums - Recumbent bicycles
* WISIL (WISconsin and ILlinois) HPV - shared ideas, photos, plans and more
* Winning Forbidden: The Real History of the Recumbent Bicycle
* Recumbent Types (in German)
* Cycle America Recumbent Sources and Info
* Recumbent Bicycle Source
