INTRODUCTION Flashcards
is design on the basis of
motion requirements in contrast to design on the basis of strength
requirements.
Kinematic design
rotates at a constant angular velocity,
The cam
moves
up and down.
follower
On the upward motion
the follower is driven by the cam,
on the return motion
it is driven by the action
of gravity or of a spring.
where
two cams are used per cylinder to operate the intake and exhaust valves,
automotive engine
are used in many applications to transmit motion from one shaft to another with a constant angular velocity ratio.
Gears
consists of two or more gears in series. Its application is to increase or decrease the speed or torque of the output shaft.
A Gear train
What is a good example of a gear train?
automobile transmission where
three speeds forward and one in reverse arc obtained by shifting two gears.
is a combination of rigid or resistant bodies so formed and connected that they move upon each
other with definite relative motion .
mechanism
What is an example of mechanism?
crank, connecting rod, and piston of an internal-
combustion engine
is a mechanism or collection of mechanisms which transmit force from the source of power to the
resistance to be overcome.
machine
What is an exampe of a machine?
internal-combustion engine.
When a rigid body so moves that the position of each straight
line of the body is parallel to all of its other positions,
translation.
All points of the body move in
parallel straight line paths.
Rectilinear translation.
The paths of the points arc identical
curves parallel to a fixed plane.
Curvilinear translation.
If each point of a rigid body having plane motion remains at a constant distance from a fixed axis that is perpendicular to
the plane of motion,
body has motion of rotation.
If the body rotates back and forth through a given angle, it is said to
oscillate.
When a rigid body moves so that each point of the body bas motion of
rotation about a fixed axis and at the same time has translation parallel to
the axis,
helical motion.
When a rigid body moves so that each point of the body has
motion about a fixed point while remaining at a constant
distance from it,
Spherical motion
A body moving with rotation about three nonparallel axes and
translation in three independent directions
spatial motion.
When the parts of a mechanism have passed through all the possible positions they can assume after starting from
some simultaneous set of relative positions and have returned to their original relative Positions,
cycle
The time required for a cycle of motion
period.
The simultaneous relative positions of a mechanism at a given instant during a cycle
phase.
The geometrical forms by which two members of a mechanism are joined together so that the relative motion between
these two members is consistent
pairing elements.
If the joint by which two members are connected has
surface contact such as a pin joint,
lower pair.
If the connection takes place at a point or along a
line such as in a ball bearing or between two gear teeth in contact,
higher pair.
A _______ can be either a
lower or a higher pair depending upon whether a pin and bushing or a ball bearing is used for the connection.
turning pair
A ______
will be a lower pair as between a piston and cylinder wall.
sliding pair
A _____ is a rigid body having two or more pairing elements by
means of which it may be connected to other bodies for
purposes of transmitting force or motion.
link
When a number of links is connected by means of pairs, the resulting system
kinematic chain.
If these links are
connected in such a way that no motion is possible,
locked chain (structure)
A _____ is obtained
when the links are so connected that, no matter how many motion cycles are passed through, the relative motion will
always be the same between the links.
constrained chain
It is also possible to connect links so that an _____ results, which
means that the motion pattern will vary from time to time depending on the amount of friction present in the joints.
unconstrained chain
If
one of the links of a constrained chain is made a fixed link,
mechanism.
If in a mechanism, the link which was originally fixed is allowed to move and another link becomes fixed, the
mechanism is said to be _____.
inverted
In the study of mechanisms, it is necessary to investigate the method in which motion may be transmitted from one
member to another. Motion may be transmitted in three ways:
(a) direct contact between two members such as
between a cam and follower or between two gears, (b) through an intermediate link or connecting rod, and (c) by a
flexible connector such as a belt or chain.
the _____ of a mechanism is
the number or degrees of freedom it possesses.
mobility
______ is the minimum number of independent
parameters required to specify the location of every link within a mechanism.
mobility
what is Grubler’s equation?
M = 3(n-1) - 2f1 - f2
four types of joints are commonly found in planar mechanisms.
revolute, the prismatic, and the rolling
contact joints, and the cam or gear joint
What joint has one degree of freedom?
revolute, the prismatic, and the rolling
contact joints
What joitn has a 2 degree of freedom?
the cam or gear joint
M is greater than one
the device is a mechanism with M degrees of freedom
M is equal to 0.
the device is a statically determinate structure
M is less than -1
the device is a statically indeterminate structure
