How Many Basic Types Of Gears Are There?

The type of gears depends on the kind of machine being used. For a bike, there are three kinds of gears viz. Rear derailleur, front derailleur and hub gears. Under rear derailleur, there is Mountain Bike Derailleur that has a long chain case which is normally controlled by handlebar gear shifter. Then there is Road racing rear derailleur which has a shorter chain case compared to the Mountain Bike making gear changing easier for the bike. The third one is Economy Rear Derailleur made of steel that fits into the frame rather than gear change hanger. Under front derailleur, there's Mountain Bike front derailleur with a wide chain case and Road racing front derailleur with a lighter chain case & a lesser width. The ones under hub gears, there is five or seven speed hub gears and a three speed hub gear. For other machines the gears are divided into spur gears and parallel helical gears.