2008年11月10日 星期一

Tall bike

A tall bike is an unusually tall bicycle, typically built for the purpose of fun and recreation, though with occasional practical use.

Modern tall bikes are most commonly constructed by individuals from spare parts. Two conventional bicycle frames are connected, by welding, brazing, or other means, one atop the other. The drive train is reconfigured to connect to the upper set of pedals, and the controls are moved to the upper handlebar area.

Alternatively, a bicycle can be built by inverting the frame, and inserting the forks from the 'wrong side', flipping the rear wheel, and adding a long gooseneck and tall handlebars, then welding a long seatpost tube to the 'bottom' (now the top) of the frame. This type of tall bike is made with only one bike frame, and is often called an upside-down bike rather than a tall bike, though the seat can be quite high, depending on the frame shape used. This type can be somewhat safer, as there is less tubing between the rider's legs and dismounting in a hurry can be easily accomplished.

Tall bikes are a popular mode of transportation for modern 'bicycle clubs' (SCUL, Rat Patrol, Zoobomb, Black Label Bike Club, The Winking Circle, Dead Baby Bikes, C.h.u.n.k. 666, Cyclecide, etc.) and activist groups. They are also a mainstay among builders of Clown bikes, art bikes, Clown alleys and parade groups. Bicycle modification is considered a fun and cheap hobby, and never fails to attract a lot of attention. Most modern cities contain large quantities of unused or abandoned bicycles that provide the raw materials for tall bikes and other mutant cycles.
Practical uses

Tall bikes can be used for general transportation and recreation, just like other bicycles. Regular tall-bike commuters note that both their increased visibility and the simple 'wow factor' give them a safety advantage in automobile traffic over 'short bikes.'

A Giraffe Lamplighter Bicycle, manufactured in 1898.

Historically, one of the first practical uses of the tall bike was as a late 1800s lamp lighting system, by which a worker would mount a specialized tall bicycle while equipped with a torch for lighting gas lamps. As the worker rode to each lamp, they would lean against the lamp post, light the lamp, and then ride to the next. Upon completing the circuit of lamps, an assistant would help the rider dismount.

In Bugbrooke, Northamptonshire, England The Clark Brothers in the 1950s built tall bikes to get to work when it flooded. These bikes they called 'Flood Bikes'. They have been on BBC TV and even did a Welsh language programme on them. They are currently in a museum somewhere.

Sporting

Tall bike jousting is a popular sport among bicycle hackers, and is commonly considered to have been introduced by Jake Houle and Lil' Bob of the Hard Times/Black Label Bike Club. Combatants arm themselves with lances, and attempt to score points by dislodging the other rider. Rules vary by area, and with the mood of the combatants. Like all jousting games, participants consider it a sport where honor plays a role and dishonorable wins are frowned upon.

Jousters create lances that vary from simple PVC pipe and foam devices that are flexible, soft, and relatively safe, up to wooden or metal lances that may be quite dangerous. Regional rules vary, some specifying flaming lances for effect, or glass containers attached to the end, the goal being to break the glass container in order to score points.

Design considerations

Tall bikes present some interesting design considerations, and different localities tend to have different methods of dealing with them.

One consistent issue is that the seat tends to end up in line with, or behind, the rear axle, which creates a powerful tendency to lift the front wheel of the bicycle on acceleration. Some bicycle builders simply accept this tendency, but others solve the problem by moving the seat post forward, lowering the handlebars, or by using a smaller wheel in front, typically a 24" instead of a 26".

Stability can also be negatively affected, and enhancements such as extended wheelbase by welding extensions on the front and rear dropouts can benefit stability. Contest holders often place restrictions on such modification to prevent unfair advantages.

See the bicycle and motorcycle geometry and bicycle and motorcycle dynamics articles for more on these issues.


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