1888a123_Beginner_Dirt_Bike___GICL_Wiki_Dirt_Bike_Parts_List_Function
[Part and Quantity] Gear Shift (1) [Part Number] DR70-125 [Materials] Mostly metal, probably aluminum because of its light weight [Forces] The only force would be those applied when the rider shifts gears. Thus the force would only be the a percentage of the rider strength [Manufacturing Process] Several parts created, the welded together. This can be seen because of welding marks near joints. The two end pieces are just metal tubing, while the middle is bent metal. [Shape] The shape is dictated by two things. The first is to allow enough torque to change gears, with little force needed from the rider. Also the shape is designed for comfort of the rider, with there being no sharp edges. [Part Complexity] 2 [Function] 
Functional: Allows rider to shift gears while riding bike
Group 11 - Beginner Dirt Bike - GICL Wiki