ME6401-Kinematics of Machinery
UNIT 1 – BASICS OF MECHANISM
Differentiate between Machine and Mechanism.
Machine is a mechanism or collection of Combination of rigid or resistant bodies
mechanism which transmits force from the connected that they move upon each other
source of power to the resistance (load) to with definite relative motion,
overcome and thus performs useful
Eg. Lather, Shaping Machine etc.
Eg. Single slider mechanism in IC engine
All machines are mechanism
All mechanism are not machine
2. Write down Kutzbach criterion to find the mobility of a planar mechanism.
The Kutzbach criteria which calculates the mobility. F = 3(n – 1) – 2j – h ; Where, F- Degrees of
freedom, n – number of links, J – number of joints, h – no of higher pairs
3. Define transmission angle and its significance.
The acute angle between the coupler and the driven link. In
Figure, if AB is the input link, the force applied to the output
link, CD, is transmitted through the coupler link BC. (That is,
pushing on the link CD imposes a force on the link AB, which is
transmitted through the link BC.) For sufficiently slow motions
(negligible inertia forces), the force in the coupler link is pure
tension or compression (negligible bending action) and is
directed along BC. For a given force in the coupler link, the
torque transmitted to the output bar (about point D) is maximum
when the angle between coupler bar BC and output bar CD is
Therefore, angle BCD is called transmission angle.
When the transmission angle deviates significantly from /2, the torque on the output bar decreases
and may not be sufficient to overcome the friction in the system. For this reason, the deviation angle
=| /2- | should not be too great. In practice, there is no definite upper limit for , because the
existence of the inertia forces may eliminate the undesirable force relationships that is present under
4. Enumerate the difference between a Machine and a Structure. [Anna University, June 2014]
Machine is a mechanism or collection of
mechanism which transmits force from the
source of power to the resistance (load) to
overcome and thus performs useful
Structure is the assemblage of resistant
bodies without any relative motion
between the links.
Eg. I C Engine
Eg. Bridges & Dams
5. List out the inversions of a double slider crank chain.
Inversions of Double Slider Mechanism - First Inversion – Scotch Yoke mechanism, Second
Inversion – Oldhams Coupling , Third Inversion – Elliptical trammel, Fourth Inversion – Hand Pump
6. State Grashof’s law for a four bar linkage.[Anna University, December 2012]
It states that for a planar four bar linkage, sum of the shortest and longest link – lengths must be less
than or equal to the sum of the remaining two link-lengths, is there is to be a continuous relative
motion between two members - S + L ≤ P + Q ; Where, S – Length of shortest link, L – length of
longest link, P and Q – remaining two link lengths.
i) If L + S < P + Q, then we call this a Grashof Mechanism
G.1 = crank-rocker if S is the crank and either of the adjacent link is the
fixed link G.2 = double-crank if S is the fixed link
G.3 = double-rocker if the link opposite S is the fixed link
ii) If L + S > P + Q, then we call it non-Grashof’s mechanism only double-rocker: no link is
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