mechanism

the ratio between output and input force

MA=output/input

if MA is larger than 1,output is bigger than input force

move and control things

mechanical sytem

used to change one kind of movement to another

has input,process and output

defination

specially designed and shaped pierce of material that rotates casing a lever or rod to move

common types

pear

snail

ecentric shape

converts circular movement to a kind of oscillatory motion.it cant work the another way around

gear

is a wheel with teeth around its edge

can be combined for

controlling speed

increase turning force

changing the direction of motion

spur gear

mesh and rotate in opposite direction

the smaller gear rotates faster than the bigger gear

idler gear is required for the driver gear and the driven gear to be in the same direction

bevel gear

used to transmit motion through 90degree

worm gaer

used to turn a worm wheel

reduce speed but increase turning force

one complete turn of worm gear cause the worm wheel to turn by a single tooth

used in

hand drills

bicycle

includes

set screws

used to lock collars and wheel in position on a shaft

cap screw

used to hold machine parts together,one of the parts must be threaded to act as a nut

split pins

nuts and bolts

nut

can come loose due to cibration

a second nut or split pin can be used

increase movement

change direction of movement

classes

class 1

class 2

class 3

turning point of a lever is called as the fulcrum

four bar linkage is used for converting motion

one type to another

one speed to another

one size to another

one axis to another

if the driver pulley is bigger than the driven pulley,the driven pulley turns faster than the driver.

velocity ratio of movement

show relationship between input and output force

V.R=input movement/output movement

circular

oscillating

linear

reciprocating

cranks

is an arm that has one end connected to a shaft

are often used with a slider for converting movement from circular motion,or the other way round

rack and pinion

is used in

car steering wheel

microscope

CD rom drive

bench drill

ratchet and pawl

allow movement in one direction but not the other

springs

type of springs

compression springs

tension springs

torsion spring

used to resist a turning force

flat spring

material

usually metal

return to its original shape when bent

screw

used to convert rotary motion to linear motion

cables

work well in tension

usually made of serverals strands of steel wire

direction can be changed by using bevel gears

distance can be changed by using pantograft mechanism