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Hub-center steering (HCS) is one of several different types of front-end suspension/steering mechanisms used in motorcycles and cargo bicycles. Hub-center steering is characterized by the steering pivot points being inside the hub of the wheel, rather than above the wheel in the headstock as in the traditional layout. Most hub-center arrangements employ a swingarm that extends from the bottom of the engine/frame to the center of the front wheel.
Hub steering mechanisms are complex and have a number of theoretical advantages, but in practice often provide an inconsistent driving feel due to slack arising from the complex linkages. Although conventional forks have a number of theoretical weaknesses, it is, on the other hand, a more developed and mature system.
The advantages of using a hub-center steering system instead of a more conventional motorcycle fork are that hub-center steering separates the steering, braking, and suspension functions.
With a fork the braking forces are put through the suspension, a situation that leads to the suspension being compressed, using up a large amount of suspension travel which makes dealing with bumps and other road irregularities extremely difficult. As the forks dive, the steering geometry of the bike also changes, making the bike more nervous, and inversely, acceleration becomes more lazy. Also, having the steering working through the forks causes problems with stiction, decreasing the effectiveness of the suspension.
Hub-center steering systems use an arm, or arms, on bearings to allow upward wheel deflection, meaning that there is no stiction, even under braking. Braking forces can be redirected horizontally along these arms, or tie rods, away from the vertical suspension forces, and can even be put to good use to counteract weight transfer.
The length of the typical motorcycle fork means that they act as large levers about the headstock requiring the forks, the headstock, and the frame to be very robust adding to the bike's weight.
The arms typically form some form of parallelogram which maintains steering geometry over the full range of wheel travel, allowing agility and consistency of steering that forks currently cannot get close to attaining.
The hub center steering's Achilles heel, however, has been the steering feel. Complex linkages tend to be involved in the steering process, and this can lead to slack, vague, or inconsistent handlebar movement across its range.
Evolution, rather than revolution, tends to drive advancements in new models, and dictate sales. After so many years of telescopic forks, people are used to riding a bike that handles in a specific way, and almost expect the limitations, and compensation is part of the experience. Also, there is a depth of knowledge known about fork-based chassis design that attempts each year to get around the limitations through technological advances on the current system. Thicker and thicker fork tubes are used to reduce flex, special coatings are used to mitigate stiction, and greater and greater steering angles are used to counteract dive.
The hub-center steer concept is a very old one used as early as 1910 by the British James Cycle Co, and in 1920 by Ner-a-Car, and enjoyed an aftermarket vogue in the 1970s through the work of Jack Difazio in the UK.
Mead & Tomkinson Racing pioneered the use of hub-center steering in long-distance motorcycle endurance racing. Their first version of "Nessie" was powered by a modified Laverda 3C 1000 cc triple cylinder, but they later designed a Kawasaki-engined bike that became known as Nessie II. In the 1980s, Tomkinson's efforts encouraged the Elf racing team to create a succession of endurance and GP race bikes.
In the 1990s there was a flurry of action, first was the Bimota Tesi 1D in 1991 however this was expensive and was only ever produced in small numbers. Then in 1993 Yamaha launched the GTS1000 based on James Parker's RADD design. It raced at the Isle of Man TT but was always blighted with a reputation for being a bit heavy and clumsy in use. However, Steven Linsdell changed this reputation slightly with an 8th place finish in the 1994 Formula One TT, 6th place in the 1995 Formula one TT, and 10th place in 1996 on his Flitwick Motorcycles machine, with very competitive times against factory machines from the likes of Honda and their RC45. His prototype, based on a heavily modified Yamaha GTS1000, featured a Yamaha YZF750 engine due to the Formula one regulations and achieved 178mph through the Sulby speedtrap section of the course. His average speed of over 117mph on the twisty and undulating 37.73 mile long hedge and wall-lined street course was very reputable at an international event, on a machine built in his garden workshop during his spare time away from work. Michael Tryphonos also built a prototype based on the Difazio system that did race at the Isle of Man with some success reaching 11th in the Senior TT.
Royce Creasey, the designer of feet forwards motorcycles, is an ardent advocate of hub-center steering.
Currently, Bimota's Tesi 3D, the Vyrus 984C3 2V, and the 985C3 4V are the only production motorcycles using hub-center steering systems; however, Italjet also uses hub-center steering on their top-of-the-range scooters. Sidecar manufacturers occasionally employ hub-center steering in their designs, such as the GG Duetto. An aftermarket hub center steering assembly is made by ISR Brakes of Sweden. [1]
As of 2023, hub-center steering systems have only appeared on very few production motorcycles, and not with any great success.[ citation needed ]
Cargo bicycles with the cargo platform ahead of the rider have a low-set platform with a small diameter front wheel ahead of this. The conventional fork and steerer rise above this, often inconveniently for cargo loading. In 2011 Elian Cycles developed their cargo bicycle called "Cargobike" with hub-center steering to the wheel. [2]
A bicycle brake reduces the speed of a bicycle or prevents the wheels from moving. The two main types are: rim brakes and disc brakes. Drum brakes are less common on bicycles.
A utility bicycle, city bicycle, urban bicycle, European city bike (ECB), Dutch bike, classic bike or simply city-bike is a bicycle designed for frequent very short, relatively slow rides through very flat urban areas. It is a form of utility bicycle commonly seen around the world, built to facilitate everyday short-distance riding in normal clothes in cold-to-mild weather conditions. It is therefore a bicycle designed for very short-range practical transportation, as opposed to those primarily for recreation and competition, such as touring bicycles, road bicycles, and mountain bicycles. Utility bicycles are the most common form globally, and comprise the vast majority found in the developing world. City bikes may be individually owned or operated as part of a public bike sharing scheme.
A bicycle fork is the part of a bicycle that holds the front wheel.
A swingarm, or "swinging arm" (UK), originally known as a swing fork or pivoted fork, is a single or double sided mechanical device which attaches the rear wheel of a motorcycle to its body, allowing it to pivot vertically. The main component of the rear suspension of most modern motorbikes and ATVs, it holds the rear axle firmly, while pivoting to absorb bumps and suspension loads induced by the rider, acceleration, and braking.
Bimota is an Italian manufacturer of custom and production motorcycles. It was founded in 1973 in Rimini by Valerio Bianchi, Giuseppe Morri, and Massimo Tamburini. The company name is a portmanteau derived from the first two letters of each of the three founders' surnames: Bianchi, Morri, and Tamburini.
Bicycle and motorcycle dynamics is the science of the motion of bicycles and motorcycles and their components, due to the forces acting on them. Dynamics falls under a branch of physics known as classical mechanics. Bike motions of interest include balancing, steering, braking, accelerating, suspension activation, and vibration. The study of these motions began in the late 19th century and continues today.
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The Ner-A-Car was a type of feet forwards motorcycle designed by Carl Neracher in 1918. It used an unusual steel-channel chassis, much like an automobile, and hub-center steering at the front wheel, making it 'nearly a car' in design. The Ner-A-Car was the most successful hub-center steering motorcycle ever produced, with sales far eclipsing earlier or later examples of this design, such as the Yamaha GTS1000 or Bimota Tesi. About 10,000 Neracars were manufactured in the United States by the Ner-A-Car Corporation, while around 6,500 are believed to have been produced in England under licence by the Sheffield-Simplex company between 1921 and 1926 under the Ner-A-Car name.
A motorcycle's suspension serves a dual purpose: contributing to the vehicle's handling and braking, and providing safety and comfort by keeping the vehicle's passengers comfortably isolated from road noise, bumps and vibrations.
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Bicycle and motorcycle geometry is the collection of key measurements that define a particular bike configuration. Primary among these are wheelbase, steering axis angle, fork offset, and trail. These parameters have a major influence on how a bike handles.
Bicycle suspension is the system, or systems, used to suspend the rider and bicycle in order to insulate them from the roughness of the terrain. Bicycle suspension is used primarily on mountain bikes, but is also common on hybrid bicycles.
Vyrus is a small, exclusivist Italian motorcycle manufacturer based in Coriano, Italy.
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Motorcycle components and systems for a motorcycle are engineered, manufactured, and assembled in order to produce motorcycle models with the desired performance, aesthetics, and cost. The key components of modern motorcycles are presented below.
Mead & Tomkinson was a motorcycle and car dealership in Hereford Monmouth and Tewkesbury, Gloucester, England. Three of the Tomkinsons, sons Chris and Patrick, and their father, Mike, successfully built and fielded racing motorcycles. They concentrated on the Isle of Man TT and on 24-hour and 8-hour endurance races at Spa, Barcelona, Thruxton and the Le Mans Bol d'Or. One of their riders was Neil Tuxworth.
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