This document defines key terms related to mechanisms and describes the beam engine mechanism. It consists of four links with one end of lever CDE connected to a piston rod. The crank rotates about a fixed center A, causing the lever to oscillate about a fixed center D. This converts the rotary motion of the crank into the reciprocating motion of the piston. Beam engines were widely used in steam engines historically to pump water from mines or into canals.

2. 2
Link
A component forming a part of a chain; generally rigid with
provision at each end for connection to two other links
Mechanism
A combination of rigid bodies (links) connected by
kinematic pairs.
Kinematic pair
A joint which is formed by the contact between two bodies
and allows relative motion between them.
Machine
A collection of mechanisms which transmit force from the
source of power to the resistance to be overcome.
TERMINOLOGY

3. MECHANISM
When a kinematic chain with one of its link is fixed,
is called a mechanism.
A mechanism is a skeleton diagram of a machine to
transmit the definite motions between various
links.
Example: type writer, clock work, etc.

4. Four Bar Chain or Quadric Cycle Chain
•It consists of four links
• Each of them forms a turning pair at A, B,
C and D
•. The four links may be of
different lengths.
Grashof ’s law
The sum of the shortest and longest link
lengths should not be
greater than the sum of the remaining two
link lengths if there is to be
continuous relative motion between the two
links.

5. What is inversion?
 Inversion is the
method of obtaining
different mechanisms
by fixing different
links in a kinematic
chain, is known as
inversion of the
mechanism.

6. INVERSIONS of FOUR BAR
CHAIN
BEAM ENGINE (CRANK
OR LEVER MECHANISM)
COUPLING ROD OF A
LOCOMOTIVE(DOUBLE
CRANK MECHANISM)
WATTS INDICATOR
(DOUBLE LEVER
MECAHNISM)

7. Inversions of four bar kinematic
chain
 The four bar chain mechanism consists of four turning
pairs.
 The four different mechanisms are obtained by fixing
one link at a time.
 Kinematically, all four inversions of kinematic chain
are identical.
 However there mobility can be varied by suitably
changing the proportions of lengths of various links.

8. BEAM ENGINE A part of the mechanism of a beam engine (also known as
crank and lever mechanism).
 Beam engine introduced in Wanlockhead in 1745
 Consists of 4 links.
 The purpose of this mechanism to convert rotary motion
into reciprocating machine..

9. The crank rotates about the fixed center A, the
lever oscillates about a fixed Centre D. The end E of
the lever CDE is connected to a piston rod which
reciprocates due to the rotation of the crank.

11. Beam engine mechanism

12. Applications
 It is used to draw out water from mines, as well as to
pump water into canals.
 This mechanism is widely used in steam engines but
nowadays it is used in water pumps, oil rings, specially
sewing machine.
 It is type of steam engine where a pivoted overhead beam
is used to apply the force from a vertical piston to a
vertical connecting rod
 It is basically 6 link mechanism that converts rotary
motion of crank into reciprocating motion of piston.

13. Degree of freedom(DOF)
 DOF of a mechanical system is the no of
independent parameters that defines its
configuration.
 n = 3 (l – 1) – 2 j – h
 It has two degree of freedom i.e rotation of link
about axis perpendicular to the plan and vertical
motion.

14. Stuart Beam Engine
This is a design perfected by James Watt in 1794.
Example of beam engine

15. A watt engine : showing entry of steam
and water