The document is a lecture on gears, their types, and applications in mechanical engineering, specifically focused on refrigeration and air conditioning systems. It covers the classification of gears based on tooth profiles and relative positions, along with gear terminology and calculations involving torque and gear ratio. Practical examples demonstrate the functionality of different gear arrangements in power transmission.

1. Prof.Dr. Tahseen Fadil / Al-Farahidi University
MECHANICAL DRAWING
Technical College of Engineering
Department of Refrigeration and AC
Engineering Techniques
Prof. Dr. Tahseen Fadhil
2nd
Year Refrigeration and AC Engineering
2024-2025
LECTURE 7
(26 Slides)

2. Prof.Dr. Tahseen Fadil / Al-Farahidi University
Gears are machine elements, which are
used for power transmission between
shafts, separated by small distance.
Irrespective of the type, each gear is
provided with projections called teeth
and intermediate depressions called
tooth spaces. While two gears are
meshing, the teeth of one gear enter
the spaces of the other.
Gears

3. Prof.Dr. Tahseen Fadil / Al-Farahidi University
Types of Gears
Gears are classified on the
basis of the shape of the
tooth profile and the
relative position of the
shafts between which,
power transmission takes
place. The pictorial views of
some of the most
commonly used gear trains,
are shown in Fig.

4. Prof.Dr. Tahseen Fadil / Al-Farahidi University
Gear Terminology

5. Prof.Dr. Tahseen Fadil / Al-Farahidi University
Spur Gear

6. Prof.Dr. Tahseen Fadil / Al-Farahidi University
Assembly of Spur Gears

7. Prof.Dr. Tahseen Fadil / Al-Farahidi University
Assembly of Helical Gears

8. Prof.Dr. Tahseen Fadil / Al-Farahidi University
Assembly of Bevel Gears

9. Prof.Dr. Tahseen Fadil / Al-Farahidi University
Assembly of Worm & Worm Wheel

10. Prof.Dr. Tahseen Fadil / Al-Farahidi University
1. Tooth length, h
2. Tip diameter, da
3. Root diameter, df
4. Pitch circle diameter, d

11. Prof.Dr. Tahseen Fadil / Al-Farahidi University
H.W

12. Prof.Dr. Tahseen Fadil / Al-Farahidi University
Gears are used to do the following for rotating shafts:
A) increase speed
B) decrease speed
C) change direction of rotation
D) all of the above

13. Prof.Dr. Tahseen Fadil / Al-Farahidi University

14. Prof.Dr. Tahseen Fadil / Al-Farahidi University

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20. Prof.Dr. Tahseen Fadil / Al-Farahidi University
Two mating spur gears have 40 and 120 teeth respectively. the pinion rotates at 1200
rpm and transmit a torque of 20 N-m. The torque transmitted by the gear is?
a) 6.6 Nm b) 40 Nm c) 20 Nm d) 60 Nm
The torque transmitted by gears is inversely proportional to the gear ratio.
A smaller gear will have a higher torque if the speed is lower.
Step 1: Find the gear ratio between the two gears The gear ratio is the ratio of the number of
teeth on the larger gear to the number of teeth on the smaller gear. Given:
Gear ratio = ​
Step 2: Calculate the torque transmitted by the gear

21. Prof.Dr. Tahseen Fadil / Al-Farahidi University
Large speed reductions (greater than 20) in one stage of a gear train are
possible through:
a)spur gearing b)worm gearing c)bevel gearing d)helical gearing
Gear ratio is around 20:1to 50:1.‘X’rotation of worm will cause 1 rotation in
Worm wheel.

22. Prof.Dr. Tahseen Fadil / Al-Farahidi University
A motor is running at 1440rev/min. It is to be connected to a stirrer running at
36 rev/min. The gearing arrangement suitable for this application is:
(a) Bevel gear
(b) Helical gear
(c) Spur gear
(d) Worm gear

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https://www.youtube.com/watch?v=edZnqd638-w