Machines of all kinds are essentially an assembly of several moving parts. Motion of one part is often transmitted to another part which sets it into motion. This is what makes machines highly useful and efficient. In this exhibit you can see the different mechanisms that transfer rotation. Observe the effect of direction and speed of rotation that you impart on one rotating mechanism on the other.
Transmission of motion often involves the usage of the gears to provide speed and torque conversions from a rotating source to another device. These gears are usually seen in bicycles, motor vehicles, machines etc.
Gears have teeth that mesh up with another toothed part to transmit torque. A Gear train has atleast two gears. One that is attached to the rotating source is the drive gear called input gear or pinion and the other is driven gear or simply a gear. The mechanical advantage of the gear train is the ratio of the number of teeth in the output gear to the number of teeth in the input gear. If the output gear has more teeth than the input gear , the gear train amplifies the input torque. And, if the output gear has fewer teeth than the input gear, then the gear train reduces the input torque.
There are various types of gears.Spur gears are the simplest types of Gears where the edge of each tooth is straight and aligned parallel to the axis of rotation. These gears mesh together correctly only if fitted to parallel shafts
In this exhibit, we have a gear train consisting four Spur gears. Rotating the smaller one drives the larger one. This larger one has a smaller one fixed on it which also gets driven and thereby drives the other larger one.
Sometimes the teeth of the gears are not meshed up as such but still one drives the other through a chain or belt. We see here a gear and chain system as well as a gear and belt system. In both the cases the larger one drives the smaller one. Hence we can see the smaller one rotating faster than the larger one.
We have a Bevel gear in which we see the transmission of torque between two intersecting shafts.
In the worm gear we can see the transmission between a screw like structure and a gear. The shafts of the two intersect at right angles.