14-08-2012, 03:46 PM
Gear transmission system
10ME021(GEAR TRANSMISSION SYSTEM).docx (Size: 4.06 MB / Downloads: 50)
ACKNOWLEDGEMENT
At this stage of my seminar, I take this opportunity to express my heartiest gratitude and thanks to my guide Mr. Anand Patel for her valuable guidance and encouragement during each stage of my work. I would especially thank his, as they have helped me lot to present my seminar related work in a much better way. He always listens to problems patiently and suggests the best possible solution and especially thanks for her extensive comments on thesis write up.
Starting off, I am indebted to our Head of Department Prof. Piyush Gohil who also helped me to present my seminar related work in a much better way, and also as a Head of Department who gave me an opportunity to elect an appropriate subject for my seminar. I would especially thank him, as he helps me while facing problems and suggests the best possible solutions. He is very supportive and heartily acknowledged for providing laboratory support.
Last but not the least; I would like to thank my seniors, friends, and especially my parents for their support and acknowledgement.
INDEX
Serial no. Contents Page no.
1 Introduction to gears… 7
2 Terminologies used in gears 8
3 Types of gears 9
4 Helical gear 12
5 Worm and Worm gear 14
6 Worm and worm gear efficiency 16
7 Bevel gear 17
8 Advantages and disadvantages of gears 18
9 Gear train 19
10 Conclusion 21
LIST OF FIGURES
Figure no. Figure name Page no.
1 Gear Drive 8
2 Terminologies used in gear 8
3 Spur gear 10
4 Spur gear 11
5 Spur gear with pitch circle 12
6 Helical gear 13
7 Helical gear 13
8 Worm and worm wheel 15
9 Worm and worm wheel 16
10 Bevel gears 17
11 Molder and bolster bevel gear 18
ABSTRACT
• Power transmission is the movement of energy from its place of generation to a location where it is applied to performing useful work. To adopt the transmission of power from one shaft to another shaft, we would use belts, chains, ropes or gears. But the main agenda of using gears in the system is to transmit more power when the distance between two shafts is small.
• According to the purpose of the design, we could use different types of gears as discussed below. We can also utilize the combination of two or more gears.
• A gear is a component within a transmission device that transmits rotational force to another gear or device
• So, to comprehend the operation of gears, we will study the different functions and usages of them in manifold areas predominated over the mechanical purposes.
• Thus gears aid us to implement different operations efficiently. And that’s why it is most used in automobile field and several prominent areas in which we could use gear transmission system by gaining ease in running condition.
INTRODUCTION TO GEARS……
Why the gears are invented?
There are so many mechanical devices which are used to transmit the motion. Before a days belt and belt drives were used to transmit the power from one to another shaft. The slipping of belt is common phenomenon in the transmission of power between two shafts. In order to reduce the slipping effects and velocity ratio of a system gears were invented which is also known as positive drive. We can also use the gear drives when there is a small distance between the driver and driven shafts.
It is possible to transmit the power between two shafts which are parallel, intersecting or neither parallel nor intersecting. Commonly types of gears are spur gear, helical, gear, bevel gear, worm gear etc.
Gear drives are a very important drive in mechanical power transmission. Gear drives are preferred when large or moderate power is to be transmitted at constant velocity ratio.
A gear is a rotating part of machine tools having cut teeth. The gears are used for transmitting the power between two shafts. An advantages of a gear is that it prevents the slipping.
Circular pitch: – from any point on a gear tooth to the corresponding point on the next tooth. It is also equal to the circumference of the pitch circle divided by the number of teeth. (See Figure)
The formula for determining circular pitch (p) follows:
• p = πd (where d (or D) = the pitch diameter) ÷ n
(Where n (or N) = the number of teeth)
Pitch diameter: The pitch diameter is the diameter of the pitch circle. On both miter and bevel gears, the pitch diameter is measured on the pitch circle – at the large end of the teeth. The formula for determining the pitch diameter follows: (See Figure)
• Pitch Diameter (P.D) = Number of Teeth ÷ Pitch (D.P)
• Addendum – the distance the tooth projects above, or outside of, the pitch line or circle.
• Dedendum – the depth of a tooth space below, or inside of, the pitch line or circle. (Note: In order to provide clearance, the dedendum is usually greater than the
Addendum of the mating gear tooth.)
• Clearance – the amount of space by which the dedendum of a gear tooth exceeds the addendum of a mating gear tooth.
• Whole Depth – the total height of a tooth, including the total depth of the tooth space.
• Working Depth – the depth of the teeth of two mating gears at the point at which the teeth mesh. Working depth is also equal to the sum of the teeth’s addenda.
• Ratio: Ratio may be determined when any of the following factors is known:
• Numbers of Teeth (T)
• Pitch Diameters (PD)
• Revolutions per Minute (RPM)
• Ratio = Number of Teeth in Large Gear ÷ Number of Teeth in Small Gear
Velocity: Velocity (V) is distance traveled in a given time, usually noted in feet per minute (FPM). Velocity is determined by dividing the distance (feet) traveled by the time (minutes) required to travel that distance.
• Velocity (in ft. per min.) = Distance (in feet) ÷ Time (in minutes)
TYPES OF GEARS[3]
There are many different types of gears are used in various engineering applications. Some of them most commonly used are as shown below:
1. Spur gears
2. Helical gears
3. Spiral gears
4. Bevel gears
5. Worm and worm gears
6. Rack and pinion
SPUR GEAR:
It is a cylindrical in shape, with teeth on the outer circumference that are straight and parallel to the axis (hole). There are a number of variations of the basic spur gear, including pinion wire, stem pinions, rack and internal gears.
The spur gear is the most basic mechanical power transmission product. In fact, there are applications for these gears almost “every place a shaft turns”.
Working:
As in our introduction, a gear is essentially a toothed wheel or cylinder that works in tandem with another gear (or gears)to transmit motion, or to change speed or direction. In a spur gear, the teeth, which are on the outer surface of the cylinder, are straight and parallel to the hole (or axis) so when two come together – mesh – they do so in the same plane. As a result of how they meet, spur gears can increase or decrease the speed or torque of whatever they are “moving”.