EXPERIMENT NO.3
OBJECTIVES:
To measure the forces in jib and tie of a Crane Apparatus.
APPARATUS:
Spring balance, Tie Hook, Length Adjuster, Base Frame, weights, ruler.
THEORY:
A Jib crane set up consist of a compression member (Jib) and
a tension member (Tie) which is connected to a rod as shown in Figure 3.1.
External force is supported by Jib and tie.
Figure 3.2: Schematic Line Diagram of Jib Crane Apparatus
Force Balance Diagram of Joint B:
The Force Balance Diagram of joint B (Figure 3.2) shows
that there are three forces acting at
point B.
Figure 3.3: Free Body Diagram at Point B
Weight W acting
downwards, Tensile force (T)
develops in tie and Compressive force (C)
develops in jib.
Coplanar Concurrent Force System:
In Force Balance Diagram of joint B (Figure:3.3) since all the three forces lie in the same plane and meet at the common point B. The system is Coplanar Concurrent force system.
According to Lami’s Theorem
PROCEDURE:
1. The
Jib is erected by attaching the Tie at joints B and C such that the
height of C was greater than that of B.
The weight hanger is attached at point B.
2. Some
load say 1.5 kg is placed in pan so that the tie is at least stout. This may be
treated as zero weight (including weight of hanger).
3. Initial
readings of forces in jib and tie are recorded in kg.
4. Now
some load W (say 1kg) is added to
the hanger.
5. The
lengths AB, BC and AC are measured with the help of
measuring scale and recorded.
6. Take
readings on five different loads.
OBSERVATIONS:
•
Verify the experimental results by finding the
forces in jib and tie of a crane analytically.
• Plot
the graph between weight on x-axis and forces in jib and tie of a crane on
y-axis using Microsoft Excel.
CONCLUSION:
Discuss the impact of load on the forces in jib and tie of a crane.
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