Saturday, August 17, 2013
Mechanical engg
WOODRUF KEYS are semicircular shaped, such
that, when installed, leave a protruding tab. The keyway in the shaft is
a semi-circular pocket, the mating part, a longitudinal slot. They are
used to improve the concentricity of the shaft and the
mating part, which is critical for high speed operation. The main
advantage of the Woodruff key is that it eliminates milling a keyway
near shaft shoulders, which already have stress concentrations.
High-Efficiency Belt Drives
Belt drives are frequently used in motor systems and offer advantages such as providing flexibility with positioning of the motor, allowing speed adjustments with the use of pulleys with differing diamaters, low maintenance requirements, decreased noise levels, and high efficiency. However, the efficiency of belt drives differ based on their type and condition.
V-type belts are most commonly used and offer efficiencies between 93 to 98%. However, their efficiency drops by about 4% by age and by an additional 5–10% with poor maintenance.
Wedge or cogged belts can maintain efficiencies that are around 2% higher than ordinary V-belts
Synchronous/flat/ribbed belts offer efficiencies between 96 to 99%, and require less maintenance. Advancements with these kinds of belts have widened their application possibilities, and it is worth exploring the potential to switch over to these.
Belt drives are frequently used in motor systems and offer advantages such as providing flexibility with positioning of the motor, allowing speed adjustments with the use of pulleys with differing diamaters, low maintenance requirements, decreased noise levels, and high efficiency. However, the efficiency of belt drives differ based on their type and condition.
V-type belts are most commonly used and offer efficiencies between 93 to 98%. However, their efficiency drops by about 4% by age and by an additional 5–10% with poor maintenance.
Wedge or cogged belts can maintain efficiencies that are around 2% higher than ordinary V-belts
Synchronous/flat/ribbed belts offer efficiencies between 96 to 99%, and require less maintenance. Advancements with these kinds of belts have widened their application possibilities, and it is worth exploring the potential to switch over to these.
The articulate or jointed arm robot (or
sometime called Anthropomorphic arms) closely resembles the human arm.
The mechanical structure has at least three rotary joints which forms a
polar coordinate system. The Figure shown an articulate robot
with 6 degree of freedom. The basic three rotary joints able Arm swap,
shoulder swivel and elbow rotations. Additional 3 revolute joints (Roll,
Yaw, Pitch) and one prismatic joint allow the robot to point in many
directions, and then reach out some radial distance.
Application area:
Arc welding
Spot welding
Assembly
cleaning/spraying
Cutting
Deburring
Die casting
Gluing/sealing
Grinding/polishing
Injection moulding
Machine tending
Material handling
Packing
Palletizing
Picking
Pre-machining
Press brake tending
Application area:
Arc welding
Spot welding
Assembly
cleaning/spraying
Cutting
Deburring
Die casting
Gluing/sealing
Grinding/polishing
Injection moulding
Machine tending
Material handling
Packing
Palletizing
Picking
Pre-machining
Press brake tending
Wednesday, August 7, 2013
Mechanical Vibration Assignmnet No 1
Assignments No –
I
Date of Issue: 8th August,
2013 Date of Submission: 14th August,
2013
1.
Represent
the periodic motion given in figure 1 by harmonic motion
Figure 1
2.
Find the
sum of harmonic motion of equal amplitude but of slightly different
frequencies. Discuss the beat phenomenon that results from this sum.
3.
Split up
the harmonic motion 8 sin (ωt + π/4) into two harmonic motions one of which has
amplitude of 10 and phase difference zero.
4.
A steel
shaft 6 cm diameter and 50 cm long fixed at one end carries a flywheel of
weight of 1000 kgf and radius of gyration 30cm at its free end. Find the frequency
of free longitudinal transverse and torsional vibration E= 2 x 106
kgf/ cm2, C = 3.8 x 106 kgf/ cm2.
5.
A shock
absorber is to be designed so that its overshoot is 10% of the initial
displacement when released. Determine the damping factor. If the damping factor
is reduced to one half this values, what will be the overshoot?
6.
A simple
U tube manometer filled with liquid is ahown in figure 2. Calculate the
frequency of resulting motion if the minimum length of a manometer tube is
0.15m.
Figure2
7.
A gun
barrel having mass 560kg is designed with the following data: Initial recoil
velocity 36 m/sec, recoil distance on firing 1.5 m
Calculate:
(a)
Spring
constant
(b)
Damping
coefficient
(c)
Time
required for the barrel to return to a position 0.12 m from its initial
position
8.
A
vibratory system is defined by the following parameters:
m
= 3kg, k = 100 N/m, C = 3 N- sec/m. Determine
a. The
damping factor
b. The
natural frequency of the damped vibration
c. The
logarithmic decrement
d. The
ratio of two consecutive amplitudes
The number of cycles after which the original
amplitude is reduced to 20 percent.
Note: On the last date of submission of your assignment, a
minor test of 20 marks will be conducted
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