 Hello everyone, this is Shila Ratna Banshwade from Walchand Institute of Technology, Solapur. Today we are going to see the topic BIS conventions for the mechanical components like gears and springs. Learning outcomes, the students will be able to describe different types of gears. Second, the students will be able to describe tension and compression springs. The students will be able to apply BIS conventions of gear and spring in drawing. Now what is the requirement for BIS conventions? Why do we require BIS conventions? As we all know, drawing is called as the language of engineers through which they communicate different concepts, different products. Every language follows a certain grammar so the drawing language also. As we all know the engineering span is too large and is beyond the boundaries of countries and to have a better collaboration or better exchange and export of technologies there has to be certain standards that needs to be followed so that 1 cm in India is equal to 1 cm in some another country or a convention given for a spring in India should be understood and should be easily used by a person in some another country. Thus there is a need of standards for drawings as well. Standards are also available for other products and other fields of, rather than engineering. What is BIS? The International Standards Organization has formed and issued some standards where they have given few standards regarding drawing and some of the conventions that are needs to be used during drawing. Those standards have been referred and approved and modified as per the Indian requirement by the Bureau of Indian Standards which is the National Standards Body of India. It functions in 14 bodies. For BIS conventions for drawings, conventions for food, conventions for elements and so on. There are also standards for clothes, standards for food materials, standards for materials etc. It deals with the standardization and certification and quality in India. BIS is responsible or looks after the standardization of the product or service, the certification of a service or a product and quality of that particular product or service as far as India is concerned. Before moving on to the next slide, I suggest you all to pause the video at this moment and recall what a gear structure looks like and what are the different types of gears that you have studied in your previous classes. First, gears. For any power transmission system, we have either gears or we use pulleys. Gears are used when the distance between the shafts is small and you want to transfer power in a compact distance. So let us focus on the first type of gear that is, let us focus on first type of gear that is spur gear. The smaller one is called as pinion and the larger one is called as gear. The construction of a spur gear is the teeth on the wheel are parallel to the axis. These teeth can transfer high load and at high speed. Spur gear is very easy to manufacture and the manufacturing cost is low as compared to any other types of gears. Thus, spur gear finds a wide application throughout a day to day life. The most common example of spur gears are motor bicycles. The gearbox in motor bicycles or in any automobile uses spur gear. The wrist watches or the watches consist of spur gears. Now let us see how gear is represented in a convention form. So as you can see this, the bigger wheel, the bigger one that is gear and the smaller one that is pinion. This line, which is the center line, circular and this one are the pitch circles which are in contact with each other and this the darker boundary and the darker boundary represent the top surface of the teeth. So this is the conventional representation of spur gear in front view whereas the representation of gear in the side view, this image. So from this point to this line is one gear and then the other gear. The same sectional view can be seen over here. So this is where your shaft will be fixed for the pinion and this is where the shaft will be fixed for the gear. Now let us move on to the next type of gear, bevel gear. When you need to transfer power, when the shafts are at 90 degrees to each other or intersecting to each other, we go for bevel gears. This is called as straight bevel gears. The teeth are not inclined. These types of bevel gears you can see in the shutters which are at quite high of a workshop or any shop bevel gears are used. Another example is bevel gears are used in the differential gearbox of an automobile to transfer power at the rear wheels. Let us see what is the conventional representation of bevel gear. So this is the lower gear and this is the top gear. The direction of observation for this convention is from this direction. See this wheel over here and this wheel in the front view panel. Similarly the side view for this is given over here. This dotted line again represents the pitch circle diameter where the actual teeth comes in contact with each other. Let us move to the next gear that is worm and worm wheel. This type of gear is used when you want to transfer high loads at particularly a little bit less speed. Here you can see this is the worm which is similar to a screw where threads are being made over this. This is the worm gear. This might be a spiral gear or a spur gear. It is a representation in convention is you can see this as the worm and this is the worm gear. It is cross sectional view then rack and pinion. Here you can see this is a long shaft one end of which has teeth and on that rotates a gear. So this is called as the rack and this is called as the pinion. This type of arrangement is used when you want rotary motion to be converted into a linear motion or a linear motion to be converted into rotary motion. So you can see that when the pinion rotates the rack moves to and fro or in the reverse when the rack moves to and fro the pinion rotates in either clockwise or anti-clockwise direction. The conventional representation this is the rack and this is the pinion. This is the side view and this is the conventional view. So these are the some of the basic or the main types of gears that are used in most of the applications. Major applications of the gears are seen in automobiles. Now let us focus on springs. This is a leaf spring with an eye. This eye is used to clamp the spring to a machine part or a body. For example in automobiles this part will be attached to the automobile body and this part will be clubbed to the axle. The topmost leaf is called as the master leaf and the rest of the leaves are called as graduated leaves. There is rebound clipping so that the springs are intact with each other. The end of the springs are trimmed so that they do not tamper or wear the other spring in contact with it. The camber distance is provided so that the automobile or the machine which is mounted on this should not get in contact with the leaf spring body. So this is the movement that the spring gives on compression. Let us move further. This is a schematic representation of a leaf spring without an eye and its convention. This is a leaf spring with an eye and its convention. Now coming to tension and compression springs. Tension and compression springs are similar in structure but tension spring is used to keep the two bodies in contact and whereas compression spring is used to keep two bodies apart. Now here you can see an example of tension spring. This is how it is represented in drawing, its convention and diagrammatic representation. The tension spring example can be the door with a spring. When you open the door the spring is stretched and when you release the door the door closes. These are the references. Thank you.