MECHANISMS
Mechanisms are devices that transmit and convert forces and motion from a driving force or input element to an output element. They allow us to carry out certain tasks more easly and more efficiently.
LEVERS equation: F . d = R . r It's called the law of the lever
CLASS 2
CLASS 3
CLASS 1
PULLEY
Movable pulley: A movable pulley is balanced when it satisfies this equation: F= R/2
Compund pulley: This is a system of fixed and movable pulley, often called block and tackle. It have two equations: F= R/2.N and F= R/2n
Fixed pulley: A fixed pulley is balanced when the effort F is equal to the resistance of the load, R: F=R
ROTARY MOTION MECHANISMS
click to edit
Friction drives
The ratio between the rotation velocity of the wheels or pulleys depends on the relative size of the wheels. It is expressed by the following equation: N1 . D1 . = N2 . D2 - D1/D2=N2/N1
Pulleys with belt: they consist of two pulleys or wheels that are a certain distance apart. Uses: industrial machines, vehicle engines, washing machines and drills
Gear mechanisms and cogwheels: Cogwheels are sets of wheels that have teeth called cogs. The ratio between the rotation velocities of the wheels depends on the number of teeth on each wheels. It's expresses by this equation: N1xZ1=N2xZ2 -- Z1/Z2= N2/N1
Worm gear This is a screw that moves a helical cogwheel that is set perpendicular to the screw. A worm screw fulfils this equation: Nwheel= Nscrew x Zgrooves/ Zwhee
Gear mechanisms with a chain These are two cogwheels with parallel axles that are a certain distance apart, they rotate simultaneously by mean of a metal chain or a toothed belt stretched over both wheels. The relation between the rotation velocities of the wheels depends on the number of teeth on each gear: N1xZ1= N2xZ2 -- Z1/Z2=N2/N1
Gear train This is a system of more that two gears, connected together as shown in the diagram. The gear ratio between the drive wheel and the driven wheel depends on the number of geared teeth in the system: N4/N1= Z1xZ3/ Z2xZ4
Pulley trains with belts The gear ratio between the drive pulley and the driven pulley depends on the relative size of the pulleys in the system, It's expressed as a function of their diameters: N4/N1 = D1xD3/ D2 x D4