Gear Box of a Car
 

In a number of machinery such as machine tools, cars, etc., we would like to obtain several speeds from a constant speed input. The gears are engaged or disengaged by shifting or there are clutches or slide-keys to engage or disengage gears to a shaft. A car transmission box is a typical example.

Walking Toy
 

Mechanisms have been applied into toys in great many ingenious ways. One such application is a toy walking mechanism (you can make the head and the tail of the animal shaped toy oscillate while it is walking, if you like). Link 2 is coupled to a small electric motor or a spring wound drive. The rear legs will oscillate about Bo while the front legs will have more complicated motion (the path of point D will closely be an ellipse). The resulting motion of the toy will be such that it will look as if it is walking. There is a very interesting application of mechanisms for wooden toys(? or for wooden moving sculptures) made in a very artistic and interesting way. This site may also show you that "science is art and art is science".

Level Luffing Crane
 

The crane shown in is also known as Demag jib-crane. It is very often used at ports. After the load is lifted up we would like point D to move horizontally so that minimum energy is used while moving the load from one position to an-other. A four-bar arrangement approximately satisfies this requirement while its load carrying capacity is acceptable.