MECHANICAL DESIGN
Four Bar Mechanism
A four bar mechanism is used to rotate the swing bar. The need for using this mechanism is to acquire high speed for the swing bar rotation. The speed at which the swing bar swings is critical, because for slow speeds the number it displays cannot be read/perceived by the users' eyes. The concept behind the ability to to read the number is persistence of vision.
For the design of four bar mechanism such that one of the link rotates by 360 degrees, the condition to be satisfied is
(length of shortest link + length of longest link) < (sum of lengths of other two links)
For the design of four bar mechanism such that one of the link rotates by 360 degrees, the condition to be satisfied is
(length of shortest link + length of longest link) < (sum of lengths of other two links)