bike - Single-speed bicycle
Photograph by Velo Steveon Flickr.
Belts have failed to over take chains in popularity for bicycles because they have historically been less efficient. In the United States market, bicycle companies Bianchi, Cannondale, KHS, Kona, Raleigh, Giant, Specialized, Felt, and Trek all have recently produced and marketed single speed bicycles. Single speed mountain bikes are either constructed without suspension (fully rigid) or with front suspension forks.
These allow the rear wheel to be moved fore or aft as necessary. Full-suspension single speeds offer increased weight and complexity in contrast to the light and simple qualities of un-suspended single speeds.
While these belts cannot be shifted between gears like a chain, they offer singlespeed or hub geared drivetrains with improved increased wear resistance, quieter operation, and lubrication-free cleanliness. A straight chainline, lack of chain drag from rear derailleur jockey pulleys, and lack of chainrings, ramps and pins all improve efficiency. As a single rear cog takes less space than the typical seven to ten cogs present on most multi-geared rear cassettes, rear wheels can be built with little or no dish, which is inherently stronger by virtue of the wider base in the triangle formed by the hub, spokes and rim. As the single-speed bicycle lacks alternative gearing ratios, it is less versatile, as it cannot be pedaled efficiently outside of its single gearing range. Without lower gearing options, the single speed bicycle is generally more difficult to pedal up extremely steep terrain. Conversely, its dedicated gear ratio also limits top speed, and is slower than a multi-geared bicycle on flat or descending terrain once bicycle speed exceeds the rider s ability to maintain continuing increases in cadence (pedaling revolutions per minute), typically 85-110 rpm. While Track bicycles are always single speed, mountain bicycles, road bicycles, cyclo-cross bicycles, and hybrid bicycles can be made as or changed into a single speed.
Ideally, the freewheel sprocket would be one or two teeth larger than the fixed sprocket. . Mountain bike single speeds designed for trail riding often have a relatively low, or easy and slow, gear ratio.
Usually one side has a track-type threading, (with lock ring) and the other side is threaded for a single-speed standard freewheel. It is possible to find them with track threading on both sides, but not easily. The usual way to use a flip-flop hub is to have a fixed gear on one side, and a single speed freewheel on the other.
However, increased popularity of the single speed has resulted in the design, marketing, and production of many models. Another method uses an eccentric mechanism either in the bottom bracket , can be used to take up chain slack.
Also replacement of the one-piece belt requires traditional diamond bicycle frames to have a special split chainstay. Single-speed bicycle builders have converted many former multi-geared cycles into single or fixed speed through the removal of the gear cassette and associated hardware. The most common method is horizontal rear dropouts or track ends.
This keeps the pitch of the belt s teeth constant and dramatically decreases wear on gear teeth. This typically requires the rider to be more fit or skilled than the average rider in order to traverse the same terrain.
Because one of the goals of a single speed mountain bike is simplicity, it is extremely uncommon to run across a full-suspension single speed bicycle. Single-speed bicycle builders have devised a variety of methods for producing and maintaining the proper chain tension. Single speed bicycles designed for road riding typically have higher, or harder and faster, gear ratios. Single speed bicycles and fixed gear bicycles are popular with bicycle messengers for their reliability and durability.
As well, finetuning the combination of chainring, cog, and chain length may suffice until the chain develops significant wear. Throughout the years bicycle designers have produced belt-driven bicycle. The difference is that a fixed-gear bike does not have freewheel mechanism to allow coasting. A single-speed bicycle is generally cheaper, lighter, and mechanically simpler than its multi-geared equivalent. Without derailleurs or other gearing systems, there are fewer parts on the bicycle that require maintenance making this type of cycle ideal for city commuting in all weather. The drivetrain efficiency of a single-speed can be greater than today s typical multi-geared bicycles.
Belts also do not change length during their lifespan in the same way that chains stretch or increase in pitch as their link pivots wear. This allows them to climb hills and deal with obstacles and gradients better.
Depending on the situation, a messenger may prefer a mountain bike based single-speed, which can roll over many obstacles, or a fast and light road bike-based single-speed. Statements by cycling industry representatives and journalists that major bicycle manufacturers discouraged modern single speed bicycles. A single-speed bicycle is a type of bicycle with a single gear ratio.
These bicycles are without derailleur gears, hub gearing or other methods for varying the gear ratio of the bicycle. Many individuals looking to improve the efficiency, speed and comfort for bicycle riders developed freewheel systems and gearing systems for bicycles.
