Post on 06-Feb-2016
description
VELOCITY & ACCELERATION DIAGRAM
NAZIHAH BINTI MOHD NOOR
O
VELOCITY DIAGRAM
Crank, Connecting Rod and Piston
A
Bω
crank
Connecting Rod
Piston
O
A
Bω VAO
VBA
O
A
BωVAO
VBA
O
A
BωVAO
VBA
O
A
B
ω
O
A
B
EXERCISE 1
The mechanism shown has a crank 50 mm radius which rotates at 2000 rev/min. Determine the velocity of the piston for the position shown. Also determine the angular velocity of link AB about A.
From Calculation :
1ST STEP
Skeleton Diagram
Scalelukisan : asal1cm : 0.01m
2ND STEP
Velocity direction at every mechanism ( )
CrankConnecting
Rod
Piston
O
A
B
VAO
VBA
VB
3RD STEP
Scale1cm : 1m
CrankConnecting
Rod
Piston
O
A
B
VAO
VBA
VB
o
A
B
Velocity Diagram
VBA
VB
4TH STEP
From Velocity Diagram
Measure VBA
Ukuran dari Velocity Diagram
Tukar mengikut scale1cm : 1m/s
9.2cm : 9.2m/s
So;
2. Find the velocity of the piston for each case below and the angular velocity of AB about point A.
i. The crank OA rotates anti-clockwise at 3000 rev/min
SKELETON DIAGRAM
Scale1cm : 0.02m
O
A
B
Velocity direction at every mechanism ( )
3000rev/min
O
A
B
VAO
VBA
VB
Velocity DiagramScale1cm : 5m/s
4 BAR CHAIN
VBA
VCB
AD
C
B
VCD
ACCELERATION DIAGRAMS Acceleration produce inertia process
Must consider 2 forms of accelerationi. Centripetal Accelerationii. Tangential Acceleration
ACCELERATION DIAGRAMS
A = ω2 r or A = v2/r
EXAMPLE
A piston, connecting rod and crank mechanism is shown in the diagram. The crank rotates at a constant velocity of 300 rad/s. Find the acceleration of the piston and the angular acceleration of the link BC. The diagram is not drawn to scale.
SKELETON DIAGRAM
Scale1cm : 0.02m
2.5cm8.5cm
A
B
C
Velocity Direction
A
B
C
VBA
VCB
VC
Velocity Diagram
Scale1cm : 2m/s
A
B
C
VBA
VCB
VC
A
B
7.5cm
C
VBA
VC
VCB
A
B
7.5cm
C
VBA
VC
VCB
From Velocity Diagram
ACCELERATION DIAGRAM
From skeleton diagram, draw acceleration direction
A
B
C
A
B
C
ACCELERATION DIAGRAM
Scale1cm : 300m/s2
A
B
C
A
B
15cm
1.19cm
From Acceleration Diagram