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Experiment No MOM3 : Gears & Four Bar MechanismMUHAMMAD FAZLI BIN MOHAMAD ASRIL(BK17110141)GROUP 11HK08 MECHANICAL ENGINEERINGUNIVERSITY MALAYSIA SABAHFACULTY OF ENGINEERINGTABLE OF CONTENTS 1 INTRODUCTION NO. TOPIC PAGES 2 OBJECTIVES 3 THEORY 4- 4 METHOD 5 RESULT 6- 6 DISCUSSION 7 CONCLUSIO...

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Experiment No MOM3 : Gears & Four Bar Mechanism

MUHAMMAD FAZLI BIN MOHAMAD ASRIL (BK17110141) GROUP 11 HK08 MECHANICAL ENGINEERING UNIVERSITY MALAYSIA SABAH FACULTY OF ENGINEERING

TABLE OF CONTENTS NO.

TOPIC

PAGES

1.0

INTRODUCTION

3

2.0

OBJECTIVES

3

3.0

THEORY

4-5

4.0

METHOD

6

5.0

RESULT

6-8

6.0

DISCUSSION

9

7.0

CONCLUSION

9

8.0

REFERENCES

9

1.0 INTRODUCTION A gear train is a set or system of gears arranged to transfer rotational torque from one part of a mechanical system to another, with some gear ratio performing a mechanical advantage. One of the most common uses of Gear Trains is in the gear boxes of cars. In the simplest form, the crash gear box, a collection of spur gears were arranged to give different ratios of input and output speed and in the case if the reverse gear, change the direction of the output rotation. In the range of planar mechanisms, the simplest groups of lower pair mechanisms are four bar linkages. A four bar linkage comprises four bar-shaped links and four turning pairs. The link opposite the frame is called the coupler link, and the links which are hinged to the frame are called side links. A link which is free to rotate through 360 degree with respect to a second link will be said to revolve relative to the second link (not necessarily a frame). If it is possible for all four bars to become simultaneously aligned, such a state is called a change point. In this experiment, we are required to determine gear ratio and train value of different set of gear train. Apart from that, we also need to study the power transmission system of a car engine.

2.0 OBJECTIVES 

To study the power transmission system of a car engine.



To determine gear ratio and train value of different set of gear train.

3.0 THEORY Gear trains are composed of two or more gears in mesh for the purpose of transmitting motion from one shaft to another. Gear train enables to have larger distance between the driving and driven shafts, provides control on the direction of rotation on the driven gear and facilitates increased transmission ratio.

The speed ratio of the gear train is the ratio of the speed of the driver to the speed of the driven or follower and it will be inversed of their number of teeth Speed Ratio =

𝑁1 𝑁2

=

𝑇2 𝑇1

− − − − − − − (1)

Where, N1 = Speed of gear 1 (driver) r.p.m N2 = Speed of gear 2 (driven) r.p.m T1 = Number of teeth on gear 1 (driver) and T2 = Number of teeth on gear 2 (driven) It is noted that the speed of the driven or follower to the speed of the driver is known as train value of the gear train Train Value =

𝑁2 𝑁1

=

𝑇1 𝑇2

− − − − − − − (2)

Compound Gear Trains: 

Two or more gears may rotate about a single axis.



At least one of the shafts in the train must hold two gears.



Use for large changes in speed

𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑡ℎ𝑒 1𝑠𝑡 𝑑𝑟𝑖𝑣𝑒𝑟 𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑡ℎ𝑒 𝑙𝑎𝑠𝑡 𝑑𝑟𝑖𝑣𝑒𝑛

Speed Ratio =

𝑝𝑟𝑜𝑑𝑢𝑐𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑡𝑒𝑒𝑡ℎ 𝑜𝑛 𝑡ℎ𝑒 𝑑𝑟𝑖𝑣𝑒𝑛𝑠 𝑝𝑟𝑜𝑑𝑢𝑐𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑡𝑒𝑒𝑡ℎ 𝑜𝑛 𝑡ℎ𝑒 𝑑𝑟𝑖𝑣𝑒𝑟𝑠

=

− − − (3)

𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑡ℎ𝑒 𝑙𝑎𝑠𝑡 𝑑𝑟𝑖𝑣𝑒𝑛 𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑡ℎ𝑒 1𝑠𝑡 𝑑𝑟𝑖𝑣𝑒𝑟

Train Value = =

𝑝𝑟𝑜𝑑𝑢𝑐𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑡𝑒𝑒𝑡ℎ 𝑜𝑛 𝑡ℎ𝑒 𝑑𝑟𝑖𝑣𝑒𝑟𝑠 𝑝𝑟𝑜𝑑𝑢𝑐𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑡𝑒𝑒𝑡ℎ 𝑜𝑛 𝑡ℎ𝑒 𝑑𝑟𝑖𝑣𝑒𝑛𝑠

− − − (4)

Reverted Gear Trains: A reverted gear train is very similar to a compound gear train. They are both used when there is only a small space between the input and output shafts and large changes in speed or power are needed. There are two major differences between compound and reverted gear trains. First, the input and output shafts of a reverted train must be on the same axis (in a straight line with one another). Second, the distance between the centers of the two gears in each pair must be the same.

𝑇1 + 𝑇2 = 𝑇3 + 𝑇4 − − − − − − − − − − − −(5) Speed Ratio =

product of number of teeth in drivens product of number of teeth in drivers

− − − − − − − (6)

4.0 METHOD 

The 1st gear of engagement is drawn.



The power flow path for 1st gear engagement is shown.



The gear ratio and train value for 1st gear engagement is determined.



Step 1 and 3 for the 2nd,3rd, 4th, 5th and Reverse Gear is repeated.

4.1 APPARATUS The apparatus and materials were then setup as shown in figure 1:

5.0 RESULT Type of gear

Number of teeth Output gear, N1

Input gear, N2

Speed ratio

Train value

N1/N2

N2/N1

1

37

13

2.846

0.351

2

29

18

1.611

0.621

3

31

29

1.069

0.935

4

26

33

0.788

1.269

5

24

35

0.686

1.458

Reverse

46

17

2.706

0.370

Gear Ratio

Neutral

Second Gear

Third Gear

Fourth Gear

Fifth Gear

Reverse Gear

5.0 DISCUSSION Based on the experiment conducted, the speed ratio for type of gear 1,2,3,4,5 and reverse are 2.846, 1.611, 1.069, 0.788, 0.686 and 2.706 respectively. The train value for type of gear 1,2,3,4,5 and reverse are 0.351, 0.621, 0.935, 1.269, 1.458 and 0.370 respectively. A “gear train” is the combination of gear wheels which is used to transmit motion and power from one shaft to another. Apart from that, the gear train are used to either speed up or steeped down the speed of the driven shaft or the follower. There are various types of torques in gear train which are manual gear box consist of engine, clutch, gear box, proper shaft, final drive ratio and differential unit & tyres. There are also Automatic Manual Transmission consist of normal clutch and gear box assembly with two additional motors for automatic clutch operation and gear shifting. Next, automatic transmission, a hydromechanical unit with torque converter & planetary gear box and last but not least, is Continuously Variable Transmission. The advantages of gear train are its efficiency, its compactness, its large transmission ratio and its large power-to-weight ratio.

Definition of Four Bar Mechanism A four-bar linkage, also called a four-bar, is the simplest movable closed chain linkage. It consists of four bodies, called bars or links, connected in a loop by four joints. Generally, the joints are configured so the links move in parallel planes, and the assembly is called a planar four-bar linkage. Spherical and spatial four-bar linkages also exist and are used in practice.

6.0 CONCLUSION In conclusion, the power transmission system of a car engine has been studied and the gear ratio and train value of different set of gear train is determined. The objective of the experiment has been achieved.

7.0 REFERENCES 

Experiment No.: MOM3 Gears & Four Bar Mechanism retrieved from lab sheet.



Khurmi, R. et al.; Theory of Machines, 14th ed.; S. Chand & Co. Ltd., New Dehli 2005...