Other Motorized bicycles ( http://en.wikipedia.org/wiki/Motorized_bicycle )
The origins of the motorized bicycle can be traced back to the latter part of the 19th century when experimenters began attaching steam engines to stock tricycles and quadracycles. This moved into attempts to fit the newly-invented internal combustion engine to the bicycle form.
Development diverged into two distinct streams: motorcycles, which are powered solely by their engines, and motorized bicycles as defined above. The closeness of the two forms in early years is demonstrated by Félix Millet's machines of 1892/93 and on. These had both pedals and an ingenious fixed crankshaft radial engine built into the back wheel. Within a few years motorized bicycles and motorcycles were recognisably divergent, with for example early motorcycles being longer, heavier and with a markedly different riding position from that of a contemporary pedal cycle. Later, development forked again with the advent of mopeds, small motorcycles fitted with pedals that can be used as a starting aid but which cannot, practically, be ridden under pedal power alone. This development appears to have been largely in order to exploit ambiguities between the regulatory framework for bicycles, powered bicycles and motorcycles - in jurisdictions where pedals were not required to meet the legal framework they were often simply omitted on otherwise identical models.
In the case of motorized bicycles, too, there were soon two parallel streams of development: motor assistance as an addition to existing machines, and purpose-built motor-assisted bicycles like the Derny and VéloSoleX, with stronger frames and sometimes with only token ability to be wholly human powered. In these cases some assert that the product is more formally a motorcycle or moped than a motorized bicycle, and some jurisdictions also take this view.
Modern motorized bicycles follow both trends, with conversions being applied by hobbyists as well as commercial manufacturers. Hub motors in particular facilitate after market conversion, being built into the wheel and not requiring modifications to the drivetrain or frame, as well as having a low centre of gravity. Converting bicycles or tricycles has proven useful for some people with physical disabilities such as arthritis. The strength of tricycles is that they will balance even while stationary, but some people find it harder to drive a tricycle and claim it lacks agility. Portability is also compromised compared to bicycles.
The modern electric bicycle is true to the concept of a pedal bicycle with assisting propulsion, being ridable without power. Batteries have finite capacity, which means that the hybrid human / electric power mix is much more likely to be emphasised than is the case with an internal combustion (IC) engine. Electric bicycles are gaining acceptance, especially in Europe and Asia, in response to increasing traffic congestion, an ageing population and concern about the environment. Electric vehicle conversion – converting conventionally-powered vehicles to electric or hybrid vehicles – is also increasingly common.
Motorized bicycles' popularity has waxed and waned largely in response to local regulatory requirements. For example, the French "vélomoteur" could be ridden by young riders without need for a license, making it very popular during the 1960s and 1970s.
Autocycle manufacturers were well established in countries such as Britain and Australia before the second world war, but the hiatus of the war appears to have set the market back, although the American bolt-on Whizzer continued until 1962. The motorized bicycle saw a resurgence of popularity in Britain during the 1950s and such bolt-on motors as the Cyclaid and the Cyclemaster motor wheel saw brief periods of immense popularity. The Cyclemaster, which was a hub motor which could be fitted to an ordinary bike, started at 25cc (painted black), but later the size went up to 32cc (painted grey). Elsewhere in Europe the motorized bicycle continued to be popular. The Italian, Vincenti Piatti had designed a 50 cc engine for driving portable lathes and this was also used to in the form of the Mini Motore to power bicycles. Piatti later licensed the design to Trojan for production in Britain as the Trojan Minimotor. Production of The French VELOSOLEX began in 1946 and continued until 1988. After French production ceased, the VELOSOLEX continued to be produced in China and Hungary. In 2003 production ceased in Hungary. Today production continues in China and has restarted in France. Velosolex America is the company that markets the VELOSOLEX worldwide.
Currently there are several companies manufacturing aftermarket Internal Combustion motorisation kits for Bicycles. These include both 4-Stroke and 2-Stroke. Notably there was also a Compression-Ignition engine kit produced using an 18 cc variable head engine - this was made by Lohmann in Germany.
Current manufacturers include Golden Eagle Bike Engines using a rack mounted belt drive, Stanton who use a rack mount with a chain drive geared transmission , and various similar kits using 49/60/70cc 2-stroke engines made to have the engine centrally frame mounted in a position echoing that of Motorbikes (again generally using chain drive, or in the case of Whizzer, a belt drive. Companies marketing the latter types include Dax & Kings. These generally have a top speed of between 25 mph (40 km/h) and 40 mph (64 km/h) (using aftermarket tuning and higher gearing ratios).