20-03-2014, 01:02 PM
Whirling of shafts apparatus
[attachment=60312]
OBJECTIVE and APPARATUS
The fundamental objectives of this laboratory are
1) Observe the whirling phenomenon
2) Measure the natural frequency of steel shaft
3) Compare the measured natural frequency to that obtained theoretically
4) Discuss the sources of error.
Apparatus :
1) Whirling of shafts apparatus : (see figure1)
Features1
Compact experimental analysis of whirling of shafts
Fitted with transparent safety guard
Shaft configuration clearly observed during whirling
Observation of phase changes possible
Sliding bushed end freely accommodates lateral shaft movement during test
Kinematic coupling prevents any restraint on the shaft
Stroboscope available as optional ancillary
Electronic tachometer
Finally,the important point is that our apparatus’ left end is fixed and right end is free.
perimental Procedure
Before appliying the experiment, necessery information about the aparatus and the experiment
is given by the teaching assistant. It is told that the aim of this experiment is to observe how length and
width affect the natural frequency of shafts. To observe that the natural frequencies of shafts that are
made of same materials, namely steel, with different length and width are compared.
Firstly, the shafts are divided into three groups, namely short-thin one ,long-thin one, long-thick one
for convenience. As the first specimen, short-thin one is mounted on the whirling machine by
tightening the left blue-painted chuck, as a fixed end, with a setscrew and tightening also the right
chuck, as a free end. In this part of the experiment, tightening the right chucks and tightening them
appropriately are crucial to prevent causing any failure of shafts and damaging the whirling machine.
After mounting the shaft to the machine, shaft is exposed to a bit of a tension by pulling the adjustable
support in order to make the shaft tenser and more resistant to any possiblity of excessive bows, which
may occur as a result of technical or mechanical problems.
Conclusion:
The mechanical properties and the whirling behavior of shafts are observed during this
experiment. Three different steel shafts are used. First shaft has 3,157 mm diameter and
0,6096 m length, second one has 3,157 mm diameter and 0,9144m length and the third one
has 7,143 mm diameter and 0,9144 m length. By using these values we can directly calculate
the moment of inertia of these shafts and weight/length ratios. Also, from mechanical
properties of steel we know the modulus of elasticity of the shafts. Using these datas, we
calculate the theoretical critical speeds of each configuration. For shaft A and C the first
natural frequencies, for shaft B both the first and second natural frequencies are collected. We
take their average angular velocities and compare them with the measured natural frequencies
of the shafts. Finally, we calculate the percentage of error between the theoretical and
measured natural frequencies.
[attachment=60312]
OBJECTIVE and APPARATUS
The fundamental objectives of this laboratory are
1) Observe the whirling phenomenon
2) Measure the natural frequency of steel shaft
3) Compare the measured natural frequency to that obtained theoretically
4) Discuss the sources of error.
Apparatus :
1) Whirling of shafts apparatus : (see figure1)
Features1
Compact experimental analysis of whirling of shafts
Fitted with transparent safety guard
Shaft configuration clearly observed during whirling
Observation of phase changes possible
Sliding bushed end freely accommodates lateral shaft movement during test
Kinematic coupling prevents any restraint on the shaft
Stroboscope available as optional ancillary
Electronic tachometer
Finally,the important point is that our apparatus’ left end is fixed and right end is free.
perimental Procedure
Before appliying the experiment, necessery information about the aparatus and the experiment
is given by the teaching assistant. It is told that the aim of this experiment is to observe how length and
width affect the natural frequency of shafts. To observe that the natural frequencies of shafts that are
made of same materials, namely steel, with different length and width are compared.
Firstly, the shafts are divided into three groups, namely short-thin one ,long-thin one, long-thick one
for convenience. As the first specimen, short-thin one is mounted on the whirling machine by
tightening the left blue-painted chuck, as a fixed end, with a setscrew and tightening also the right
chuck, as a free end. In this part of the experiment, tightening the right chucks and tightening them
appropriately are crucial to prevent causing any failure of shafts and damaging the whirling machine.
After mounting the shaft to the machine, shaft is exposed to a bit of a tension by pulling the adjustable
support in order to make the shaft tenser and more resistant to any possiblity of excessive bows, which
may occur as a result of technical or mechanical problems.
Conclusion:
The mechanical properties and the whirling behavior of shafts are observed during this
experiment. Three different steel shafts are used. First shaft has 3,157 mm diameter and
0,6096 m length, second one has 3,157 mm diameter and 0,9144m length and the third one
has 7,143 mm diameter and 0,9144 m length. By using these values we can directly calculate
the moment of inertia of these shafts and weight/length ratios. Also, from mechanical
properties of steel we know the modulus of elasticity of the shafts. Using these datas, we
calculate the theoretical critical speeds of each configuration. For shaft A and C the first
natural frequencies, for shaft B both the first and second natural frequencies are collected. We
take their average angular velocities and compare them with the measured natural frequencies
of the shafts. Finally, we calculate the percentage of error between the theoretical and
measured natural frequencies.