Mechanical Systems

1
Introduction

• Mechanical Systems
• This presentation describes some of the
  fundamental components and definitions of
  mechanical systems and mechanisms such as
• Links or bodies
• Kinematic joints (pin, sliding, pin-sliding)
• Open and closed chains
• Commonly used mechanisms

2
Pin and sliding joints
Pin and sliding joints A mechanical system
consists of links (bodies) connected by
joints. In this course all links are assumed non
deformable (rigid). We mostly use two types of
joints Revolute (pin) joint Sliding joint
link 1
?
link 2
?
link 3
link 4
3
Pin-sliding joint
link 5
Pin-sliding joint Two links of a mechanical
system may be connected by a combined pin-sliding
joint. The joint provides rotational motion as a
pin joint. It also provides sliding motion. And
it also provides both rotational and sliding
motions simultaneously.
link 6
?
?
?
4
Open and closed chains
Open and closed chains Mechanical systems can be
categorized into open chains, closed chains, or
combinations of open and closed chains.
open chain example
closed chain example
5
Closed chains (mechanisms)
Closed chain systems A system may have one or
more closed chains (loops). By definition a
mechanism contains only closed chains.
single loop mechanism
double loop mechanism
6
Commonly used mechanisms
Commonly used mechanisms Four-bar A four-bar is
a mechanism that consists of four links connected
by four pin joints. Usually only three of the
links are allowed to move. The links are numbered
clockwise with the nonmoving link being link
1. Slider crank A slider crank (or crank-slider)
is a mechanism that consists of four links
connected by three pin joints and one sliding
joint. Usually only three of the links are
allowed to move. The links are numbered clockwise
with the nonmoving link being link 1.
link 1
O2
O4
O2