mechanism
movement
distance can be changed by using pantograft mechanism
direction can be changed by using bevel gears
cranks,racket,springs
cables
usually made of serverals strands of steel wire
work well in tension
screw
used to convert rotary motion to linear motion
springs
type of springs
flat spring
return to its original shape when bent
material
usually metal
torsion spring
used to resist a turning force
tension springs
compression springs
ratchet and pawl
allow movement in one direction but not the other
rack and pinion
is used in
bench drill
CD rom drive
microscope
car steering wheel
cranks
are often used with a slider for converting movement from circular motion,or the other way round
is an arm that has one end connected to a shaft
basic type of motion
reciprocating
linear
oscillating
circular
levers
velocity ratio of movement
V.R=input movement/output movement
show relationship between input and output force
if the driver pulley is bigger than the driven pulley,the driven pulley turns faster than the driver.
four bar linkage is used for converting motion
one axis to another
one size to another
one speed to another
one type to another
turning point of a lever is called as the fulcrum
classes
class 3
class 2
class 1
change direction of movement
increase movement
fasterner
includes
nuts and bolts
a second nut or split pin can be used
nut
can come loose due to cibration
split pins
cap screw
used to hold machine parts together,one of the parts must be threaded to act as a nut
set screws
used to lock collars and wheel in position on a shaft
cam and gears
gear
used in
bicycle
hand drills
worm gaer
one complete turn of worm gear cause the worm wheel to turn by a single tooth
reduce speed but increase turning force
used to turn a worm wheel
bevel gear
used to transmit motion through 90degree
idler gear is required for the driver gear and the driven gear to be in the same direction
the smaller gear rotates faster than the bigger gear
spur gear
mesh and rotate in opposite direction
can be combined for
changing the direction of motion
increase turning force
controlling speed
is a wheel with teeth around its edge
converts circular movement to a kind of oscillatory motion.it cant work the another way around
common types
ecentric shape
snail
pear
specially designed and shaped pierce of material that rotates casing a lever or rod to move
defination
mechanical sytem
has input,process and output
used to change one kind of movement to another
move and control things
mechanical advantage
if MA is larger than 1,output is bigger than input force
MA=output/input
the ratio between output and input force
