Retro-Direct
Encyclopedia
Retro-direct is a gearing
mechanism used on some bicycles in the early 20th century, which provides a second gear ratio when pedaled backwards.
runs from the top of a chainring attached to the cranks
to the top of a sprocket attached to the rear wheel
hub with a freewheel
, as with most bicycle chain drives. The chain then, however, wraps around the rear sprocket to an idler sprocket between the rear wheel and the cranks, then runs back to a second sprocket attached to the rear wheel with a second freewheel, and finally returns to the bottom of the chain ring. Only one freewheel is engaged at a time, while the other spins backward freely. Since the chain wraps around the second sprocket in the opposite direction to the first sprocket, the cyclist needs only to pedal backwards to engage it.
Usually the second sprocket is larger, which provides the cyclist a lower gear for climbing steep inclines simply by pedaling backwards. While most historical examples of retro-direct bicycles used the reverse gear for climbing, several modern retro-direct riders prefer climbing while pedaling forward and engaging the higher, cruising gear while pedaling backwards.
Bicycle gearing
A bicycle gear or gear ratio refers to the rate at which the rider's legs turn compared to the rate at which the wheels turn. Bicycle gearing refers to how the gear ratio is set or changed. On some bicycles, there is only one gear so the ratio is fixed. Most modern bicycles have multiple gears,...
mechanism used on some bicycles in the early 20th century, which provides a second gear ratio when pedaled backwards.
History
Retro-direct was developed by French inventor Paul de Martin de Viviés (1833–1911). An early two-chain version was patented by in 1869 by Barberon and Meunier. A single-chain version was patented in 1903 Hirondelle. Some hobbyists have converted modern bicycles to use retro-direct gearing.Technical details
In the single-chain system, the chainBicycle chain
A bicycle chain is a roller chain that transfers power from the pedals to the drive-wheel of a bicycle, thus propelling it. Most bicycle chains are made from plain carbon or alloy steel, but some are nickel-plated to prevent rust, or simply for aesthetics. Nickel also confers a measure of...
runs from the top of a chainring attached to the cranks
Crankset
The crankset or chainset , is the component of a bicycle drivetrain that converts the reciprocating motion of the rider's legs into rotational motion used to drive the chain, which in turn drives the rear wheel...
to the top of a sprocket attached to the rear wheel
Bicycle wheel
A bicycle wheel is a wheel, most commonly a wire wheel, designed for bicycle. A pair is often called a wheelset, especially in the context of ready built "off the shelf" performance-oriented wheels....
hub with a freewheel
Freewheel
thumb|Freewheel mechanismIn mechanical or automotive engineering, a freewheel or overrunning clutch is a device in a transmission that disengages the driveshaft from the driven shaft when the driven shaft rotates faster than the driveshaft...
, as with most bicycle chain drives. The chain then, however, wraps around the rear sprocket to an idler sprocket between the rear wheel and the cranks, then runs back to a second sprocket attached to the rear wheel with a second freewheel, and finally returns to the bottom of the chain ring. Only one freewheel is engaged at a time, while the other spins backward freely. Since the chain wraps around the second sprocket in the opposite direction to the first sprocket, the cyclist needs only to pedal backwards to engage it.
Usually the second sprocket is larger, which provides the cyclist a lower gear for climbing steep inclines simply by pedaling backwards. While most historical examples of retro-direct bicycles used the reverse gear for climbing, several modern retro-direct riders prefer climbing while pedaling forward and engaging the higher, cruising gear while pedaling backwards.