1. The document describes an experiment in a Mechanisms and Mechanical Vibrations lab course. The experiment involves demonstrating and observing the working of spur gears and helical gears. 2. Key differences between spur gears and helical gears are discussed, including that helical gears provide smoother operation due to their gradual engagement of teeth. 3. Important gear terminology is defined, such as pitch circle, pitch diameter, addendum, dedendum, and circular pitch. Classifying gears by shaft position and peripheral velocity is also mentioned.

1. MECHANISMS AND
MECHANICAL VIBRATIONS LAB

2. CLO Statement PLO Level
1
Conduct different experiments to measure different mechanical properties like
moment of inertia, natural frequencies of different systems etc. with some
confidence and proficiency
1 P4
2 Contribute effectively as an individual member of a team 9 C2
Course Title: Mechanisms and mechanical vibrations lab
Course Code: ME-411 L
Pre-requisite(s): Mechanics of Machine Theory subject
Credit Hours: 01
Contact Hours: 03
Course Learning Outcomes (CLOs)

3. Sr # Lab Experiments
1 Demonstration and working of Spur gears
2 Demonstration and working of Helical gears and rack and Pinion
3
Demonstration and working of Simple four Bar Mechanism and apply Gruebler condition and
Grashofs Condition
4
To Demonstrate the action of Simple Slider Crank Mechanism and determination of relationship
between the linear displacement of slider and angular displacement of Crank.
5 To demonstrate working of Internal gear train and find the gear ratio
6 To determine the whirling speed of shaft theoretically and compare it with experimental values
7 To determine the Theoretical speed of governor and compare it with Actual speed
8 To measure the moment produce by gyroscope and compare it to the theoretical value
9 To Determine the coefficient of friction of Journal Bearing
10 Demonstration of Corroli‟s effect
11 Bi-Filer suspension system
12 Inertia in rotation motion
13 Universal vibration apparatus
14 Torsional vibration
15 Vibration of spiral spring
16 Static & dynamic balancing

4. Safety Precautions
• OVERVIEW: This section is intended to ensure the safe operation of the heat & Mass transfer laboratory. Students are expected to conduct
experiments in a safe manner respecting the physical well-being of their fellow students and themselves. Students should read and understand all
contents of this section
• Be calm and relaxed, while working in lab.
• First check your measuring equipment.
• When working with voltages over 40 V or current over 10 A, There must be at least two people in the lab at all time.
• Keep the work area neat and clean.
• Be sure about the locations of fire extinguishers and first aid kit.
• No loose wires or metals pieces should be lying on the table or neat the circuit.
• Avoid using long wires, that may get in your way while making adjustments or changing leads.
• BE PREPARED. Read and fully comprehend the lab procedure as set forth in the lab manual before you begin any experiment. If you do not understand
the procedure, see your instructor.
• Always check your circuit connections before power it ON.
• Know emergency procedures. Make note of fire escape routes.
• Never use any faulty or damage equipment and tools.
• No food or beverage in the laboratory.
• Do not touch the equipment, the cord, the person.
• In case of emergency, disconnect the power source from the circuit breaker and pull out the plug using insulated material.
• Immediately report any spills, equipment malfunctions, injuries or other perceived safety hazards to your Instructor or staff member.
• FAILURE TO CONFORM WITH ANY OF THE ABOVE RULES MAY RESULT IN NOT BEING ALLOWED TO PARTICIPATE IN THE LABORATORY EXPERIMENTS

5. Experiment No. 1
Demonstration of Spur and helical gears
Gears
• A gear is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part
in order to transmit torque. Two or more gears working in tandem are called a transmission and
can produce a mechanical advantage through a gear ratio and thus may be considered a simple
machine. Geared devices can change the speed, magnitude, and direction of a power source. The
most common situation is for a gear to mesh with another gear; however a gear can also mesh a
non-rotating toothed part, called a rack, thereby producing translation instead of rotation.
• The gears in a transmission are analogous to the wheels in a pulley. An advantage of gears is that
the teeth of a gear prevent slipping. When two gears of unequal number of teeth are combined a
mechanical advantage is produced, with both the rotational speeds and the torques of the two
gears differing in a simple relationship

6. Advantages and Disadvantages of Gear Drives
Advantages
• 1. It transmits exact velocity ratio.
• 2. It may be used to transmit large power.
• 3. It may be used for small centre distances of shafts.
• 4. It has high efficiency.
• 5. It has reliable service.
• 6. It has compact layout.
Disadvantages
• 1. Since the manufacture of gears require special tools and equipment, therefore it is costlier than
• other drives.
• 2. The error in cutting teeth may cause vibrations and noise during operation.
• 3. It requires suitable lubricant and reliable method of applying it, for the proper operation of gear drives.

7. Classification of gears
The gears or toothed wheels may be classified as follows :
Classification of gears
• The gears or toothed wheels may be classified as follows :
1. According to the position of axes of the shafts. The axes of the two shafts between which the motion is to
be transmitted, may be
• Parallel, (b) Intersecting, and (c) Non-intersecting and non-parallel.
2. According to the peripheral velocity of the gears. The gears, according to the peripheral velocity of the
gears, may be classified as :
• Low velocity, (b) Medium velocity, and (c) High velocity.
3. According to the type of gearing. The gears, according to the type of gearing, may be classified as
(a) External gearing, (b) Internal gearing, and (c) Rack and pinion.

8. Spur Gear (Parallel Shaft Axis)
• The two parallel and co-planar shafts connected by the gears is
shown in Fig-1. These gears
• are called spur gears and the arrangement is known as spur gearing.
These gears have teeth parallel to the axis of the wheel as shown in
Fig.

9. Helical Gear (parallel Shaft axis)
• A helical gear has teeth in form of helix around the gear. Two such gears may
be used to connect two parallel shafts in place of spur gears. The pitch
surfaces are cylindrical as in spur gearing, but the teeth instead of being
parallel to the axis, wind around the cylinders helically like screw threads. The
teeth of helical gears with parallel axis have line contact, as in spur gearing.
• This provides gradual engagement and continuous contact of the engaging
teeth. Hence helical gears give smooth drive with a high efficiency of
transmission.

10. The angled teeth engagegement
• The angled teeth engage more gradually than do spur gear teeth
causing them to run more smoothly and quietly. With parallel helical
gears, each pair of teeth first make contact at a single point at one
side of the gear wheel; a moving curve of contact then grows
gradually across the tooth face to a maximum then recedes until the
teeth break contact at a single point on the opposite side. In spur
gears teeth suddenly meet at a line contact across their entire width
causing stress and noise.

11. Gear Terminologies
• Pitch circle. It is an imaginary circle which by pure rolling action, would give the same motion as the actual gear
• Pitch circle diameter. It is the diameter of the pitch circle. The size of the gear is usually specified by the pitch circle
diameter. It is also called as pitch diameter.
• Pitch point. It is a common point of contact between two pitch circles.
• Pitch surface. It is the surface of the rolling discs which the meshing gears have replaced at the pitch circle.
• Addendum. It is the radial distance of a tooth from the pitch circle to the top of the tooth.
• Dedendum. It is the radial distance of a tooth from the pitch circle to the bottom of the tooth.
• Addendum circle. It is the circle drawn through the top of the teeth and is concentric with the pitch circle.
• Dedendum circle. It is the circle drawn through the bottom of the teeth. It is also called root circle.
• Circular pitch. It is the distance measured on the circumference of the pitch circle from a point of one tooth to the
corresponding point on the next tooth. It is usually denoted by
• Circular pitch, Pc = π D/T
• where
• D = Diameter of the pitch circle, and T = Number of teeth on the wheel. A little consideration will show that
the two gears will mesh together correctly, if the two wheels have the same circular pitch.
• Note : If D1 and D2 are the diameters of the two meshing gears having the teeth T1 and T2 respectively; then for them to
mesh correctly,
• Pc = π D1/T1 = Pc = π D2/T2 OR D1/D1 = T2/T2

12. Gear Terminologies
Gear Terminologies

13. Diametral pitch. It is the ratio of number of teeth to the pitch circle diameter in millimetres.
• It denoted by pd. Mathematically,
• Diametral pitch, Pd = T/D
where
• T = Number of teeth,
• D = Pitch circle diameter.
Module. It is the ratio of the pitch circle diameter in millimetres to the number of teeth. It is usually denoted by m.
Mathematically,
• Module, m = D / T
Clearance. It is the radial distance from the top of the tooth to the bottom of the tooth, in a meshing gear. A circle passing
through the top of the meshing gear is known as clearance circle.
Total depth. It is the radial distance between the addendum and the dedendum circle of a gear. It is equal to the sum of the
addendum and dedendum.
Working depth. It is radial distance from the addendum circle to the clearance circle. It is equal to the sum of the addendum
of the two meshing gears.
Tooth thickness. It is the width of the tooth measured along the pitch circle.
Tooth space. It is the width of space between the two adjacent teeth measured along the pitch circle.