The tandem bicycle is a form of bicycle designed to be ridden by more than one person. The term tandem refers to the seating arrangement that is fore to aft, not side-by-side. Compared to a conventional bicycle, a tandem has double the pedaling power with only slightly more frictional loss in the drivetrain. Tandem bicycles have about the same wind resistance as a conventional bicycle. High-performance tandems may weigh less than twice as much as a single bike, so the power-to-weight ratio may be slightly better than that of a single bike and rider. On flat terrain and downhill, most of the power produced by cyclists is used to overcome wind resistance, so tandems can reach higher speeds than the same riders on single bicycles. However, tandem bicycles may be slower on climbs, in part due to the need for a high level of coordination between the riders, especially if the physical abilities of the two riders are very different, requiring a compromise on cadence.
In conventional tandems, the front rider steers as well as pedals the bicycle and is also known as the captain, pilot, or steersman; the rear rider only pedals and is also known as the stoker, navigator, or rear admiral. On most tandems two sets of cranks are mechanically linked by a timing chain and turn at the same rate. The transfer of power from all pedals to the rear wheel requires a drive train. Typically, the front most crankset turns the timing chain, which in turn connects to the rear crankset, which transfers this power to the drive chain that connects to the rear wheel. This configuration is called crossover rear drive, and requires both of the rear riders crank arms to have chainrings mounted. Tandem riders may choose to synchronize their pedaling through in-phase (IP) or out-of-phase (OOP) pedaling. In in-phase pedaling, each rider's cranks are in the same or opposite clock positions at any point in time. In out-of-phase pedaling, both riders have their cranks in differing non-opposite positions.
Bicycles, including tandem versions, are built on a frame to which wheels and other components are fitted. The frame is typically constructed from a series of tubes arranged as triangles. A diamond frame 10 typically is formed of two triangles, as shown in prior art FIG. 1, a main triangle 12 and a paired rear triangle 14. The main triangle 12 has a head tube 16, top tube member 18, down tube 20, and seat tube 22. The rear triangle 14 includes the seat tube 22, and paired chain stays 24 and seat stays 26. The head tube member 16 contains the headset, the steering bearings for the fork 28 via the steerer tube, and interfaces with the steering handlebars 30. The fork 28 secures the steerable front wheel 32, while the junction of the chain stays 24 and seat stays 26 acts as an attachment point for the rear wheel 34. The top tube member 18, or cross-bar, connects the top of the head tube member 16 to the top of the seat tube 22. The seat tube 22 accommodates the post 36 from the seat 38 or saddle.
Traditional tandem bicycles have certain drawbacks that include a long wheelbase of that reduces the portability and maneuverability of the bicycle, as well as storage and transport of the bicycle. The rear rider of a tandem bicycle has no control over the steering of the bicycle, and in general the forward field of vision of the rear rider is impaired by the front rider. Furthermore, besides reducing the rear rider's view, the seating arrangement of a tandem bicycle also separates the riders from each other so that they cannot interact or communicate easily. The separation of the riders on a tandem bicycle is a serious detriment for social or leisure riding. In fact, riders on a tandem bicycle may feel more isolated from one another than if they were riding side-by-side on separate standard bicycles. The lack of the rear rider's control, sense of participation, and separation from their fellow rider is potentially detrimental to their experience of riding a tandem bicycle.
An example of a short tandem that can be ridden by a single rear rider is known for example as the “Buddy Bike” with the first distance between the head tube and front seat post is typical or near Union Cycliste Internationale (UCI) standard teachings, rather the short length of said tandem types is derived by shortening the second distance between the front seat tube and rear seat tube compared to standard length tandems. The short tandem Buddy Bike has a front distance that is 17 percent greater than the rear distance. While a standard UCI racing tandem has a first distance of 75-90 percent of the second distance. The UCI tandem's first distance is typical of all bicycle prior art. The UCI tandem are not like short tandems, and the second distance is greater in length due to added space for the rear rider to get into a long aerodynamic body shape, thus the first position would be less. As a result the first distance reduction can be construed to be unrelated to frame shortening technology.
Thus, there exists a need for a more compact and easily transportable tandem bicycle that increases the involvement and participation of the rear rider.