internal gear hub principle

imagine pushing a beam across a roller which rotates freely on a pin the beam moves easily over the roller and a point on its surface will move as far from left to right as a point on the surface of the roller moves around its circumference now if the roller were allowed to move across the floor as the beam were pushed the point marked on the beam would travel further in a left-to-right direction than before by as much as the roller moved in the same direction as a first step in making this knowledge work for us let us give the floor the roller and the beam teeth to prevent them slipping if this simple machine is then made to operate in a circle we have the basis for a usable system of gears we must start by naming the components of this system the fixed floor has now become a fixed pinion the son pinion revolving around it the roller becomes a planet pinion it still has a pin through it which is fixed to and rotates with the planet cage finally the beam becomes the gear ring if we apply power to the planet cage and move it through 90 degrees the additional rotation of the planet pinion causes the gearing to move further in this instance an extra 30 degrees making a total of a hundred and twenty degrees conversely if the gearing is rotated 120 degrees the planet cage moves the planet pinion through 90 degrees in other words our simple system of gears gives the ratio 120 to 90 or 4 to 3 the Sturmey Archer system applies this basic principle in a bicycle hub power is introduced via a sprocket revolved of course by the chain if the sprocket could be made to turn the planet cage and the gearing were connected to the hub we would have high gear selected with the hub rotating four times for every three rotations of the sprocket if the sprocket were connected to the gearing and the planet cage turned the hub we would have low gear with the hub turning three times for every four rotations of the sprocket and if the sprocket could be made to turn the hub directly without passing the power through both planet Kage and gearing we would have normal or second gear this is the basis for the three-speed bicycle hub

Channel: Colin Zhang

Views: 42,628

Rating: 4.8137255 out of 5

Keywords:

Id: KCpQpLXy2TQ

Length: 2min 41sec (161 seconds)

Published: Wed Oct 26 2016