GEAR TYPES

SPUR GEAR: A gear wheel having radial teeth parallel to the axle.

BEVEL GEAR: A gear wheel meshed with another so that their shafts are at an angle less than 180 degrees ( LEGO® size 90 degree with 14 teeth )

CROWN GEAR: A gear wheel with teeth set in the rim perpendicular to its plane. ( LEGO® size 24 teeth ).

WORM GEAR: A short rotating screw that meshes with the teeth of another gear. As a worm gear is an inclined plane, it will be the driving gear in most cases ( THE LAW OF THE WORM! ).

DIFFERENTIAL GEAR: A certain arrangement of gears connecting two axles in the same line and dividing the driving force between them, but allowing one axle to turn faster than the other. It is used in the rear axles of automobiles to permit a difference in axle speeds while turning. ( 2 LEGO® sizes 28 teeth either crown or spur, or 24 teeth spur ).

RACK GEAR: A toothed bar into which a "pinion," ( worm gear spur etc ) meshes. ( LEGO® size 1 x 4 with 10 teeth )

PINION: A small cogwheel, the teeth of which fit into those of a larger gearwheel or those of a rack.

COGWHEEL: A wheel with a rim notched into teeth, which meshes with those of another wheel or a rack to transmit or recieve motion.

IDLER GEAR: A gear wheel placed between two other gears to transmit motion from one to the other. It does not alter the speed of the output, but it does alter the direction it turns. ( ODD number =reverse rotation, EVEN number = same rotation )

RATCHET: A toothed wheel or bar that catches and holds a PAWL, which thus prevents backward movement.

PAWL: A mechanical device allowing rotation in only one direction.

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