Gears

2. Gears -Spur Gears -Worm Gears -Crown Gears By Rachel Weiner

3. Simplest type of gears • Straight cut gears • Consist of a disk with teeth projecting radially • Edge of each tooth is aligned parallel to the axis of rotation • These gears can only be meshed together correctly if they are fitted to parallel shafts

4. Worm Gears • Resemble screws • Simple and compact way to achieve high torque, low speed gear ratio • Disadvantage is the potential for considerable sliding action, which leads to low efficiency • Worm gears can be considered a species of helical gear • -helix angle is usually somewhat large (close to 90 degrees) • -its body is usually fairly long in the axial direction

5. Crown Gears • form of bevel gear whose teeth project at right angles to the plane of the wheel • -looks like a crown in this design • - reason for its name • Can only mesh accurately with another bevel gear, exceptions: • -Sometimes seen meshing with spur gears • -Sometimes meshed with an escapement such as found in mechanical clocks.

6. Rotary Motion v.s. Linear Motion • Rotary: • the act of rotating as if on an axis • A repeated rotating motion • Linear: • also called rectilinear motion • Motion along a straight line • Linear motion is the most basic of all motion • According to Newton's first law of motion, objects that experience no net force will continue to move in a straight line with a constant velocity until they are subject to a net force

7. Sites: http://en.wikipedia.org/wiki/Spur_gears#Spur http://en.wikipedia.org/wiki/Worm_gear http://en.wikipedia.org/wiki/Crown_gear http://en.wikipedia.org/wiki/Linear_motion http://en.wikipedia.org/wiki/Rotary_motion