we use the wheel and axle in gears. Gears have teeth around the outer rim. When the teeth of two gears fit together and one gear turns, it will cause the other gear to turn, but in the opposite direction. When the gears are the same size and they have the same number of teeth, they both turn at the same speed. if one gear is larger than the other, however, the smaller gear will turn faster. We use gears to regulate speed and direction of motion in complex machines and to increase/decrease the force applied.
machines that use gears include clocks, bicycles, cars, egg beaters and other small household appliances.
The Single Gear
A gear is a modification of the wheel and axle. it just has teeth around it. Like all simple machines, gears my distance over which a force is applied.
The Gear Train
Gears work in teams. Two gears working together is called a gear train. The gear on the train to which the force is first applied is called the driver and the driven gears are called the idlers.
Notice the arrows on top of the gears. They are showing that the gears move in different directions.
Meshed Gears
the diagram below shows five meshed gears. The first Gear that the force is applied is called the driver gear. Notice that the arrows show how the gears are turning. Every other gear is turning clockwise. The very last gear is the driven gear. All of the gears in between are called idlers.
Spur Gear
When two spur gears of different sizes mesh together , the larger gear is called a wheel, and the smaller gear is called a pinion. In a simple gear train of two spur gears, the input motion and force are applied to the driver gear. The output motion and force are transmitted by the driven gear. The driver gear rotates driven gear without slipping.
Bevel Gears
Bevel gears have teeth cut on a cone instead of a cylinder blank. They are used in pairs to transmit rotary motion and torque where the bevel gear shafts are at right angles (90 degrees) to each other.
Why Do Clocks Have Brass Gear?
Brass gears are often used in clocks where they work well without any lubricant. Oil causes dust to adhere to the gears and this causes gear-tooth wear. An advantage of brass gears is that constant meshing work hardens their teeth. Because of this, the brass gears in well used old clocks show little sign of wear.
Worm and Worm wheel
A gear which has one tooth is called a worm. The tooth is in the form of a screw thread. A worm wheel meshes with the worm. The worm wheel is a helical gear with teeth inclined so that they can engage with the thread-Like worm. The worm wheel Transmits torque and rotary motion through a right angle. The worm always drives the worm wheel and never the other way round. Worm mechanisms are very quiet running.
Rack and Pinion
A rack and pinion mechanism is sued to trams form rotary motion in to linear motion and vice versa. A round spur gear, the pinion, meshes with a spur gear which has teeth set in a straight line, the rack.
Internal Gear
Internal Gear have better load-carrying capacity than external spur gears. They are safer in use because the teeth are guarded.