A Derny is a motorized bicycle for motor-paced cycling events such as during six-day and Keirin racing and motor-paced road races. Some riders train behind a derny on the road. The Derny is so-called as it was originally produced by the French Derny firm, but the name Derny is now applied to all small cycle-pacing vehicles, regardless of manufacturer.
The first Derny 'Entraineur' or 'Bordeaux–Paris' moped, with its petrol tank mounted ahead of the handlebars, was built by Roger Derny et Fils of the Avenue de St Mandé, Paris, France, in 1938. A fleet of Dernys was maintained for the long-established 'Bordeaux-Paris' road-race and the Derny was used for many other track and road events and for endurance training. Derny also built a touring adaptation called the 'Solo' and tandems and mopeds. 
Being a moped, the Derny had both a 98 cc (6.0 cu in) Zurcher two-stroke engine and pedals on a chainring sprocket, typically with 70 teeth on the front and 11 on the rear-wheel sprocket. The combination allows for smooth acceleration and slowing, important when the rider taking pace is only centimetres from the Derny's rear wheel. A freewheel coupling between the motor and the back wheel ensures the derny will not stop dead if the motor seizes. Top speed, with rider pedalling, is up to 50 km/h (31 mph), depending on gearing.[ citation needed ] The firm closed in 1957, after an unsuccessful venture with the 'Taon', a Roger Tallon-designed motorcycle. Another company, Service Derny, of Rue Picpus, Paris, serviced and rebuilt machines into the 1970s.
According to the Larousse dictionary, the name, derny has become a generic term for a small pacing motorcycle used in cycle races, and is now applied to all small cycle-pacing vehicles, regardless of manufacturer. There have been several attempts to copy or improve the original. One, the Burdin, was briefly used, but proved neither durable nor fast enough for repeated high-speed riding on the steep tracks used in six-day racing. Modern machines are made by a small company in Neerpelt, Belgium, and dernys are either new or have the original frames with new 90 cc (5.5 cu in) engines.
Dernys are usually bump-started. They can then pace riders up to 90 km/h (56 mph), although races rarely exceed 80 km/h (50 mph).[ citation needed ]
Another type of pacer is the Stayer. The rider sits close to the back in an upright position to provide an envelope of low wind resistance for the cyclist drafting or slipstreaming behind. Also a roller is added behind the rear of the stayer, and normally the cyclist rides on a bicycle with a slightly smaller front wheel. The photo of the Triumph motorcycle is such a stayer.
For most derny races, the cyclist sits in the slipstream for the duration of the event. In keirin races, common in Japan and familiar elsewhere, the derny brings riders up to speed then pulls off the track and the race finishes in a sprint without the pacer.
A small group of semi-professional pacers travels around Europe for the winter six-day season. Several are in their 60s and 70s and some have been pacing for more than 40 years.
In most of its later history, the 560 km (350 mi) Bordeaux–Paris classic road race was motor-paced using dernys from half-distance. Other important races on the road behind dernys have included the Critérium des As in Paris.
A bicycle, also called a pedal cycle, bike or cycle, is a human-powered or motor-powered assisted, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A bicycle rider is called a cyclist, or bicyclist.
The sprint or match sprint is a track cycling event involving between two and four riders, though it is usually run as a one-on-one match race between opponents who, unlike in the individual pursuit, start next to each other. Men's sprint has been an Olympic event at every games except 1904 and 1912. Women's sprints have been contested at every Olympics since 1988.
Keirin – literally "racing cycle" – is a form of motor-paced cycle racing in which track cyclists sprint for victory following a speed-controlled start behind a motorized or non-motorized pacer. It was developed in Japan around 1948 for gambling purposes and became an official event at the 2000 Olympics in Sydney, Australia.
A velodrome is an arena for track cycling. Modern velodromes feature steeply banked oval tracks, consisting of two 180-degree circular bends connected by two straights. The straights transition to the circular turn through a moderate easement curve.
A moped is a type of small motorcycle, generally having a less stringent licensing requirement than full motorcycles or automobiles. The term used to mean a similar vehicle except with both bicycle pedals and a motorcycle engine. Mopeds typically travel only a bit faster than bicycles on public roads. Mopeds are distinguished from motor scooters in that the latter tend to be more powerful and subject to more regulation.
Cycle sport is competitive physical activity using bicycles. There are several categories of bicycle racing including road bicycle racing, cyclo-cross, mountain bike racing, track cycling, BMX, and cycle speedway. Non-racing cycling sports include artistic cycling, cycle polo, freestyle BMX and mountain bike trials. The Union Cycliste Internationale (UCI) is the world governing body for cycling and international competitive cycling events. The International Human Powered Vehicle Association is the governing body for human-powered vehicles that imposes far fewer restrictions on their design than does the UCI. The UltraMarathon Cycling Association is the governing body for many ultra-distance cycling races.
A track bicycle or track bike is a bicycle optimized for racing at a velodrome or outdoor track. Unlike road bicycles, the track bike is a fixed-gear bicycle; thus, it has only a single gear ratio and has neither a freewheel nor brakes. Tires are narrow and inflated to high pressure to reduce rolling resistance.
A fixed-gear bicycle is a bicycle that has a drivetrain with no freewheel mechanism. The freewheel was developed early in the history of bicycle design but the fixed-gear bicycle remained the standard track racing design. More recently the "fixie" has become a popular alternative among mainly urban cyclists, offering the advantage of simplicity compared with the standard multi-geared bicycle.
Motobécane was a French manufacturer of bicycles, mopeds, motorcycles, and other small vehicles, established in 1923. "Motobécane" is a compound of "moto", short for motorcycle; "bécane" is slang for "bike."
The Bordeaux–Paris professional cycle race was one of Europe's classic cycle races, and one of the longest in the professional calendar, covering approximately 560 km (350 mi) – more than twice most single-day races. It started in northern Bordeaux in southwest France at 2am and finished in the capital Paris 14 hours later. The professional event was held from 1891 until 1988. It was held as an amateur event in 2014.
This is a glossary of terms and jargon used in cycling, mountain biking, and cycle sport.
The six main types of motorcycles are generally recognized as standard, cruiser, touring, sports, off-road, and dual-purpose. Sport touring is sometimes recognized as a seventh category or integrated with the touring category.
A motorized bicycle is a bicycle with an attached motor or engine and transmission used either to power the vehicle unassisted, or to assist with pedalling. Since it sometimes retains both pedals and a discrete connected drive for rider-powered propulsion, the motorized bicycle is in technical terms a true bicycle, albeit a power-assisted one. Typically they are incapable of speeds above 52 km/h (32 mph).
An electric bicycle is a motorized bicycle with an integrated electric motor used to assist propulsion. Many kinds of e-bikes are available worldwide, but they generally fall into two broad categories: bikes that assist the rider's pedal-power and bikes that add a throttle, integrating moped-style functionality. Both retain the ability to be pedaled by the rider and are therefore not electric motorcycles. E-bikes use rechargeable batteries and typically are motor-powered up to 25 to 32 km/h. High-powered varieties can often travel more than 45 km/h (28 mph).
Many countries have enacted electric vehicle laws to regulate the use of electric bicycles. Countries such as the United States and Canada have federal regulations governing the safety requirements and standards of manufacture. Other countries like the signatories of the European Union have agreed to wider-ranging legislation covering use and safety.
A pedelec or EPAC, is a type of low-powered electric bicycle where the rider's pedalling is assisted by a small electric motor. However, unlike some other types of e-bikes, pedelecs are classified as conventional bicycles in many countries by road authorities rather than as a type of electric moped. Pedelecs include an electronic controller which cuts power to the motor when the rider is not pedalling or when a certain speed – usually 25 km/h (16 mph) or 32 km/h (20 mph) – is reached. Pedelecs are useful for people who ride in hilly areas or in strong headwinds. While a pedelec can be any type of bicycle, a pedelec city bike is very common. A conventional bicycle can be converted to a pedelec with the addition of the necessary parts, e.g., motor, battery, etc.
The British National Derny Championships are annual bicycle races held in the UK.
A scooter is a motorcycle with an underbone or step-through frame, a seat, and a platform for the rider's feet, emphasizing comfort and fuel economy. Elements of scooter design were present in some of the earliest motorcycles, and motor scooters have been made since at least 1914.
Motor-paced racing and motor-paced cycling refer to cycling behind a pacer in a car or more usually on a motorcycle. The cyclist follows as close as they can to benefit from the slipstream of their pacer. The first paced races were behind other cyclists, sometimes as many as five riders on the same tandem. Bordeaux-Paris and record attempts have been ridden behind cars. More usually races or training are behind motorcycles.