Gears, Chains, and Sprockets - VEX Robotics

SprocketsSprockets, although similar in appearance to gears from a distance, are distinctly different in designand use. Gears are designed to mesh directly with each other, while sprockets are incapable of directlymeshing. They are specifically designed for meshing with a chain to transfer power.Other Types of ChainsIn light duty applications, plastic chains are finding their place. Although not as durable as metalchains, they do not need constant lubrication. Another advantage is they are easy to resize and do nothave as many parts in their construction. The VEX Robotics System uses a plastic chain and matchingsprockets. It is similar to a metal chain pintle design. Pintle chains are used in unprotected, dirty, ordusty environments where lubrication is not effective or desired.Chain Drive Gear RatiosThe real nature of gear ratios is a little more complex than just counting teeth on gears. Gear ratio isactually defined as the number of rotations that the driving axle needs to make in order to turn thedriven axle around once. When dealing with toothed gears, you can find the number of turns neededby counting teeth, as you have seen previously. All the gear ratios you have looked at so far have usedspur gears.In sprocket and chain reductions, you can still “count the teeth” to find a gear ratio, because as withspur gears, the teeth count is proportional to the sprocket diameter.18■Unit 6: Gears, Chains, and Sprockets