Chapter 22 : Combined Motion of Rotation and Translation 461
Piston, connecting rod and crank.- In a four-bar mechanism ABCD, the two points A and D are fixed while the links AB and
CD can rotate about the fixed points A and D as shown in Fig. 22.7
Find graphically, or otherwise, the velocity of B and angular velocity of the link AB, when
the link CD rotates at 240 r.p.m. in the clockwise direction. (Ans. 18.3 m/s ; 700 r.p.m.)
22.4. MOTION OF A CONNECTING ROD AND PISTON OF A
RECIPROCATING PUMP
Fig. 22.8. Motion of connecting rod and piston of a reciprocating pump.
In Fig.22.8 is shown the mechanism of a crank connecting rod and piston of a reciprocating
pump. The working of main parts of the pump mechanism is as follows ;
- The crank AB, which rotates about its axis A with a uniform angular velocity of ω radians/sec,
such that 2
rad/s
60
πN
ω=
where N = Revolutions of the crank in r.p.m.- The connecting rod BC, whose to and fro motion is governed by the crank B.
- The piston C, whose to and fro motion is governed by the connecting rod BC.
22.5.METHODS FOR THE VELOCITY OF PISTON OF A RECIPROCATING PUMP
In the last article, we have discussed the working of the main parts of a reciprocating pump. In
most of the cases, we are required to find out the velocity of piston. This may be found out by any one
of the following two methods :
- Graphical method, and 2. Analytical method.