Module 3   :  Dynamics of Reciprocating Machines with Single Slider;Unbalance in Single
                       Cylinder Engine Mechanisms

Lecture 1 :   Dynamics of Reciprocating Machines with Single Slider;Unbalance in Single
                       Cylinder Engine Mechanisms
 

PISTON

From the geometrical construction shown in Fig 3.1, we have:
 

(3.1)
 
(3.2)
 
(3.3)
  It is to be observed that if r > L, the crank wont rotate fully. Even if r = 0.5 L, the transmission angle will still be poor. Therefore, in practical crank-slider mechanisms used in IC Engines, crank radius ”r” is less than one-fourth of the length of the connecting rod. Thus
 

                 
(3.4)
  We can therefore approximately write:
                                                               
 
 
(3.5)
 

Note: For r/L = 0.25, the error involved in the above approximation is just 0.05% and thus is negligible for all practical purposes. However, for multi-cylinder engines(high possible because of better balance), the higher harmonics ( etc.) become significant and are typically included in the dynamic analysis.

1