Rigid corridor
The term rigid gear (also called “rigid hub” or “rigid running”) comes from cycling and describes the absence of a freewheel on a bicycle. Bicycles without a free wheel are usually used in track and art cycling as well as for cycling , but especially for winter training by racing cyclists on the road.
From the turn of the millennium, racing bikes with a rigid drive came into fashion in large cities. They are also called "fixies" in modern German (from English fixed gear ). As early as the 1980s, bicycle couriers in New York began using train bikes on the streets. Due to the frequent traffic lights in the city center, the limited top speed of the rigid drive can be tolerated. The constant coupling of the legs to the drive is seen as a sporting challenge and led to the development of new movement patterns, for example when getting off the bike. By gently pushing the rear wheel while vigorously stretching one leg, you can apply the brakes fully with the rear wheel locked.
In artistic cycling, the rigid gear allows you to drive backwards and makes balancing easier with the front wheel raised. In track cycling, where racing bikes with a fixed gear are used, the racing bikes common in road racing are not permitted.
The rigid gait is also used for training methodological reasons (compulsion to high cadence , better controllability of the steady propulsion = "round step") in the preparation period during road training. On the other hand, it is not permitted in road races , as the pedals that inevitably rotate with the car can lead to accidents when cornering and driving in a tight crowd.
Even if branches, stones or other obstacles have to be overcome when driving off-road, the downward rotating pedal is a hindrance. Even when driving up a high curb there can be ground contact.
Bicycle technology
Bicycles with a rigid drive are usually used as an input gear without a gear shift. A derailleur is not possible because of the resilient chain tensioner required for this . Hub gears usually have either a coaster brake or an integrated freewheel. The SunRace or Sturmey-Archer S3X gear hub is available especially for bicycles with a rigid drive. In the 1950s, the 3-speed ASC hub gear was available without a freewheel. Alternatively, a gearbox integrated in the bottom bracket can also be used .
Bicycles with a fixed gear cannot be equipped with a coaster brake. For the Federal Republic of Germany it is disputed whether the rigid gear itself counts as a bicycle brake . According to the German Road Traffic Licensing Regulations ( Section 65 Paragraph 1 StVZO), bicycles must have two independent braking devices. For Austria, the Austrian Administrative Court decided in November 2017 that the rigid gear should not be regarded as a braking device and therefore a bicycle that only has its own front brake in addition to the rigid gear does not comply with the Austrian Bicycle Ordinance.
Since the use of a spring-loaded chain tensioner would lead to a large "play" in the drive and the frequent jumping off of the chain, the chain has to be tensioned either by turning an eccentrically mounted inner bearing (mostly only common with tandems) or by moving the rear wheel in a horizontal or horizontal position sloping dropouts can be adjusted. Sporty bicycle frames for use with derailleur gears today usually have vertical dropouts and are therefore not suitable for a rigid drive.
If the bike does not have two additional hand brakes, the careful adjustment of the chain tension is relevant to safety. Because if the chain should come off, it is no longer possible to brake the bike using the drive cranks. There are usually slight deviations from the exact concentricity of the chainring. As a result, it is often not possible to find a setting in which the chain neither slacks too much nor is tensioned elsewhere when turning the cranks. If the chainring is not firmly riveted, it is advisable to loosen the four or five fastening bolts of the chainring a little and to find out where the drive is tensioned by tensioning the chain and then turning the cranks. At this point, tapping the chain lightly with a wrench can cause the chainring to move slightly. Now you turn the cranks further until the chain is tensioned again and continue in this way until the chainring is centered.
history
The first bicycles had neither a freewheel nor a chain. The initially common high bikes have a kind of rigid gear. Their development corresponds to exactly one tire circumference (outside) per crank turn.
The safety low wheel from 1880 then introduced a chain with differently sized gears, and a short time later freewheel and in 1898 the coaster brake that it made possible were invented. The gear shift in the rear hub with freewheel was invented in 1902 and was noticeably widespread from 1924. The one-way bikes with a fixed gear were subsequently less popular for everyday bikes. In racing, however, the rigid gear was retained.
Until the 1950s, rear hubs existed that could be used on the track and on the road. They had a fixed gear on one side and a 3-way freewheel on the other side. The rear wheel hubs, which were used until the 1980s, could also be converted to a rigid gear without much effort because the freewheel was integrated into the ring gear. The ring gear together with the freewheel could easily be exchanged for a rigid pinion.
With the advent of the hub integrated freewheel this simple possibility no longer exists. Further improvements to gear shifts, such as index shift levers (1960s) and better derailleur gears (1980s), led to the extinction of the rigid gear for everyday bicycles. The use of the rigid gear on the road was then only possible using the track bike hubs that were still being produced.
Single-speed bicycles with a rigid gear were retained under bicycle couriers , which meant that they could do without wearing parts. These carried out alleycat races on the street, which became known to the public in organized events from 2000 onwards. In the second half of the 2000s, manufacturers began producing everyday technology borrowed from this subculture, commonly known as "fixie" bicycles.
A flip-flop hub can be used to switch between fixed gear and freewheeling. This has a pinion on both sides, which is rigid on one side and connected to the hub on the other side via a freewheel. To switch between fixed gear and freewheeling, the rear wheel must be removed and put back in the opposite direction. Alternatively, you can switch between freewheeling and fixed gear using a screwdriver on the special “ SRAM Torpedo-Singlespeed” hub. Switching while driving is not provided for safety reasons.
Advantages and disadvantages
advantages
- Direct power transmission, there are only a few moving components between the driver and the road, thus slightly higher efficiency (1–2%)
- Low weight transmission
- There is no need for care, maintenance or repair of gear shift components
disadvantage
- It is possible for the pedal on the inside of the curve to touch the ground, as you have to continue pedaling when driving on the curves. Likewise when driving over obstacles.
- Braking with the pedals may not be sufficient in dangerous situations.
- Adapting the cadence to inclines, slopes and other circumstances is just as impossible as resting your legs while rolling the bike freely.
- Due to the lack of gearshifts, pedaling is often done with higher torque, especially uphill and when starting off, which means that the chain, chainring and sprocket wear out a little faster.
Web links
Individual evidence
- ↑ Sheldon Brown: Fixed Gear Bicycles for the Road , Section Mounting Technique and Dismounting Technique
- ↑ Regulations of the Federation of German Cyclists on the drive of track bikes (PDF file; 823 KB)
- ^ Sheldon Brown: Articles about Fixed Gear and Singlespeed Cycling and Equipment
- ↑ On the legal assessment from the blog of a Berlin bicycle shop from August 6, 2009
- ↑ In 2009, the Bonn District Court judged the rigid gear as a brake in one case, cf. File number: AG Bonn 337 Js 1152/09. For this: Der Spiegel from August 6, 2009
- ↑ Austrian Administrative Court - “Fixie” bicycles only with “fixed gear” and front brake are not permitted according to the Bicycle Ordinance. Retrieved December 4, 2017 .
- ↑ Sheldon Brown: Fixed Gear Bicycles for the Road , Section "Centering Chainwheels"
- ↑ Michael Gressmann: Fahrradphysik und Biomechanik , Delius Klasing, 11th edition, ISBN 978-3-7688-5222-7 , p. 34f torque on the crank