Tandem bicycle
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The tandem bicycle or twin is a form of bicycle (occasionally, a tricycle) designed to be ridden by more than one person. The term tandem refers to the seating arrangement (fore to aft, not side-by-side) instead of the number of riders.
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[edit] History
Originally tandems were built by welding two bicycle frames together to form a two-person bicycle.[citation needed] Patents related to tandem bicycles date from the late 1800s.[1] Modern technology has improved component and frame designs, and many tandems are as well-built as modern high-end road and off-road bikes.
[edit] Performance
While a tandem has double the pedalling power with only slightly more frictional loss in the drivetrain, it has about the same wind resistance as a single bike. High performance tandems may weigh less than twice as much as a single bike, so the power to weight ratio can be similar to that of a single bike and rider. Tandems can reach relatively high speeds, especially downhill and on flat to rolling terrain. They are not necessarily slower on climbs, but are perceived as such, in part due the need for a high level of coordination between the riders, especially if the physical abilities of the two riders are very different, requiring compromises in cadence or effort level.
[edit] Terminology
On conventional tandems, the front rider steers the bicycle and is known as the captain, pilot, or steersman; the rear rider is the stoker, navigator, or rear admiral. On most tandems the two sets of cranks are mechanically linked by a timing chain and turn at the same rate.
[edit] Uses
Tandem bicycles are often used in competitions such as the Paralympics with blind and visually impaired cyclists riding as stokers with fully-sighted captains.
[edit] Variations
[edit] Independent pedaling
Some designs such as the DaVinci allow independent pedaling through the use of multiple freewheels.
[edit] Seating arrangements
- The Opus Counterpoint is an example of a tandem steered by the rear rider who sits upright while the front rider rides in a recumbent position.
- Recumbent tandem tricycles are also gaining popularity throughout the world.
[edit] Tricycles
Tandems are also available as tricycles; the conventional tandem trike has a small but devoted following in the United Kingdom, and is available in one-wheel and two-wheel drive designs.
[edit] More than two riders
Tandems can have more than 2 riders — tandem refers to the arrangement of the riders one behind the other rather than the number of riders. Bicycles for three, four, or five riders are referred to as "triples" or "triplets", "quads" or "quadruplets", and "quints" or "quintuplets" respectively. One such familiar to UK TV viewers was the "trandem" ridden by The Goodies, originally a 2-man tandem with an extra "dummy" seat attached, a full 3-man version was built for them by Raleigh. A famous ten-person bicycle or "decemtuplet", the "Oriten", was built in 1896 by the Orient Cycle Company. Perhaps the longest bicycle ever built was the Seventy four-seater built in 1984 in Queanbeyan, Australia.
[edit] Tandem specific components
Due to the additional stresses caused by multiple riders and higher weight, tandems typically require stronger components than ordinary bicycles.
[edit] Crankset
The modern tandem has a unique and specific drive train. The captain's crank typically have the chain ring on the left side while the stoker have chain rings on both cranks. The stoker's left crank will be fitted with a similarly sized chain ring as that on the left side crank of the captain thereby connecting their pedal strokes in synch. The stoker's right side traditionally appears as that of a standard single person diamond frame bicycle.
[edit] Stoker handlebars and stem
Stoker handle bars are typically connected to a stoker stem that is clamped around the captain's seatpost. The stoker handlebars are typically bull horns or very wide drop bars with "stoker pegs" instead of brake levers.
[edit] Wheels
Because of the extra weight and stresses generated by the tandem, the wheels tend to be beefier with higher spoke count and heavier rims. The rear wheels tend to run a wider hub/axle to allow the right-side hub flange to be further right of wheel center and thus reduce the total dish of the wheel. Santana tandems use a 160mm wide axle which allows a wheel that is completely "dishless". Other modern tandems use a 145mm wide axle.
Rear hubs may also be threaded on the left side to allow the use of an Arai Drum Brake
[edit] Arai drum brake
The Arai drum brake is used during long down hill decents where a typical rim brake (and many disk brakes) would overheat and fail (rim brakes melt tires, disk brake rotor warping or parts melting). The drum of the brake screws onto the left side of the tandem hub, which must be threaded for the drum. The shoe plate slips over the axle and a small toe from the shoe plate engages with the bicycle frame to prevent the plate from turning. The tension on the drum brake is typically controlled using a friction shifter like a BARCON or similar. The brake is designed to be left ON during the decent to maintain a steady speed and the standard brakes can be used to slow when approaching a momentary shaper turn.
[edit] The Eccentric
Many tandems use an eccentric that is placed in the captain's bottom bracket shell. The eccentric is used to adjust the tension of the timing chain. Cheaper tandems use a small adjustable roller which adds more weight and friction and a potential point of failure to the system.
[edit] Tandem specific riding techniques
[edit] Stoker starts clipped in while captain holds bike upright
For those who can get accustomed to the stoker always being clipped in, the distinct advantage to this technique will become obvious when trying to start at the foot of a bridge or on a hill. If the tandem team does not practice this, then they often reserve this type of start for when they are faced with a bridge or hill. This technique allows the stoker to apply continuous power as the captain steadies the bike during the initial take off. This reduces the risk of the bike toppling over due to starting on an incline. The stoker will continue to pedal as the captain attempts to get the foot used for steadying the bike clipped into the pedal.
[edit] In-phase cranks vs out-of-phase cranks
Some tandem riders arrange their cranks so that they are 90 degrees out of phase. It is said that this not only produces a smoother power stroke (the 4 banger argument) and others say that it reduces stress on the drive train because the point the power reaches a maximum is reduced to roughly half and distributed over the chain rings over that of the traditional "two banger" approach.
[edit] See also
[edit] References
- ^ Patent Pending Blog: Tandem Bike, 1891. Retrieved on 2007-03-08.
[edit] External links
- The Tandem Club — a UK-based club
- The Tandem Club of America — an originally U.S.-based, international club
- Ten person bicycle (image of) — View the picture of ten-person bicycle.
