Analysis And Usage Of Cams And Their Followers Engineering Essay

Analysis And Usage Of Cams And Their Followers Engineering Essay A cam follower, also known as a track follower,[1] is a specialized type of roller or needle bearing designed to follow cams. Cam followers come in a vast array of different configurations, however the most defining characteristic is how the cam follower mounts to its mating part; stud style cam followers use a stud while the yoke style has a hole through the middle.[2] The first cam follower was invented and patented in 1937 by Thomas L. Robinson of the McGill Manufacturing Company.[3] It replaced using just a standard bearing and bolt. The new cam followers were easier to use because the stud was already included and they could also handle higher loads.[ / CAM AND MECHANISMS A cam mechanism consists of three elements: the cam, the follower (or follower system), and the frame. The follower is in direct contact with the cam. The cam may be of various shapes. The follower system includes all of the elements to which motion is imparted by the cam. This may be connected directly to the follower, or connected through linkages and gearing. The frame of the machine supports the bearing surfaces for the cam and for the follower. A CAM changes the input motion, which is usually rotary motion (a rotating motion), to a reciprocating motion of the follower. They are found in many machines and toys WHAT IS THE CONCEPT BEHIND CAM? A CAM is a rotating machine element which gives reciprocating or oscillating motion to another element known as follower. The cam and follower has a point or line contact constitute a higher pair or you can say that it is the mechanicl component of a machine that is used to transmit the motion to the another component of the machine called the follower, through a prescribed program by direct contact.The contact between them is maintained by an external force which is generally provided by the spring or sometimes by the weight of the follower itself ,when it is sufficient. Cam is the driver member and the follower is the driven member. The follower is in direct contact with the cam. CAM MECHANISM CONSIST OF THREE MECHANISMS CAM:It may be of many shapes FOLLOWER: It includes all the elements to which motion is imparted by the cam.This may be connected directly by the cam.This may be connected directly to the follower, or connected through linkages and gearing. FRAME: The frame of the machine supports the bearing surfaces for the cam and for the follower. APPLICATIONS OF CAM AND FOLLOWERS Cam and follower are widely used for operating inlet and exhaust valve of I C engine. These are used in wall clock. These are used in feed mechanism of automatic lathe Machine. These are used in paper cutting machine. Used in weaving textile machineries. The cam mechanism is a versatile one. It can be designed to produce almost unlimited types of motioning the follower. It is used to transform a rotary motion into a translating or oscillating motion. On certain occasions, it is also used to transform one translating or oscillating motion into a different translating or oscillating motion. Cams are used in a wide variety of automatic machines and instruments. The certain usuages of cam and followers that includes textile machineries, computers, printing presses, food processing machines, internal combustion engines, and countless other automatic machines, control systems and devices. The cam mechanism is indeed a very important component in modern mechanization. CLASSIFICATION OF CAMS Based on the physical shape Disk or plate cams Working of the disc cam with reciprocating follower. Working of the disc cam with oscillating follower. Cylindrical cam Translating cam CLASSIFICATION OF FOLLOWES (i) Based on surface in contact (a) Knife edge follower (b) Roller follower (c) Flat faced follower (d) Spherical follower (ii) Based on type of motion Oscillating followe Translating follower (iii) Based on line of action Radial (in line) follower (b) Off-set follower Cams can be conveniently classified into two main groups Group a: Cams that impart motion to the follower in a plane in line with the axis of rotation of the cam (as does a cylindrical cam). Group b: Cams that impart motion to the follower in a plane at 90 degrees to the axis of rotation, as with face or edge cams.Most cams fall into this category. TYPES OF CAMS Eccentric cam: A circular cam is often called an eccentric cam because the axis of rotation of the cam is offset from the geometric center of the circular disc. Concentric disc: A concentric disc attached to a rotating shaft would have its axis of rotation coinciding with its geometric center. PROFILE SHAPES OF SOME CAMS: PEAR-SHAPED CAMS: These type cams are often used for controlling valves. For example, they are used on motor car camshafts to operate the engine valves. A follower controlled by a pear-shaped cam remains motionless for about half a revolution of the cam. During the time that the follower is stationary, the cam is in a dwell period. During the other half revolution of the cam, the follower rises and then falls. As the pearshaped cam is symmetrical, the rise motion is the same as the fall motion. Edge cams It must be appreciated that this type of cam, where the follower is in contact with the edge of the cam disc, is only capable of imparting positive motion to its follower in one direction, that is, during the rise portion of the cam movement. During the fall portion of the cam movement the follower must be maintained in contact with the cam either by the mass of the follower and its mechanism or, more usually, by a spring. Both methods have their advantages. Box cams A groove can be milled in the face of cam discs. As the cam rotates, a follower located in the groove has its motion guided by the groove. This type of cam is called a box cam. Cylindrical cams: Cylindrical cams are used when motion has to be transmitted parallel to the axis of rotation of the cam. The cylindrical or barrel cam consists of a rotating cylinder with a helical (screw shaped) groove in its curvedsurface. A follower with a tapered roller end is located in the groove. As the cylinder turns, the follower moves in a straight line parallel to the axis of the rotation barrel cam. This type of cam is often used to guide thread on sewing machines, looms and fabric making machines. CIRCULAR CAMS: These cams are sometimes called eccentric cams. The cam profile is a circle. The center of rotation of the cam is often from the geometric center of the circle. The circular cam produces a smooth form of motion called a simple harmonic motion. These cams are often used to produce motion in pumps. Circular cams are often used to operate steam engine valves. As the cam is symmetrical, the rise and fall motions are the same. HEART SHAPED CAMS: This cam causes the follower to move with a uniform velocity. Heart-shaped cams are essential when the follower motion needs to be uniform or steady as, for example, in the mechanism that winds thread evenly on the bobbin of a sewing machine. A heart-shaped cam can be used for winding wire evenly on the former of a solenoid. UNIFORM ACCELERATION AND RETARDATION CAMS: A cam shaped as shown controls the motion of the follower so that it moves with uniform acceleration and retardation. The follower gains and looses velocity at a constant rate. Uniform acceleration and retardation cams are used to controls the motion of linkages in complex machinery. Types of Cam Followers There are three types of cam followers, and since the type of follower influences the profile of the cam it is worthwhile considering the advantages and disadvantages of each type. The three types are the knife-edge, the roller follower and the flatfoot or mushroom follower. The Knife Edge Follower: This is the simplest type, is not often used due to the rapid rate of wear. When it is adopted, it is usually for reciprocating motion, running in slides and there is considerable side thrust, this being a component of the thrust from the cam. The Roller Follower: This eliminates the problem of rapid wear since the sliding effect is largely replaced by a roller action. Some sliding will still take place due to the varying peripheral speed of the cam profile, due to the changing radius of the point of contact. Note also that the radial position of the contact between the cam and the roller, relative to the follower center, will change according to whether a rise or fall motion is taken place: this fact has to be considered when constructing the cam profile. Again,with the roller follower, considerable side thrusts are present, a disadvantage when dealing with reciprocating motions. This side thrust will be increased when using small rollers. The Flat Foot or Mushroom Follower: This has the advantage that the only side thrust present is that due to the friction between the follower and the cam. The problem of wear is not so great as with the knife-edge follower, since the point of contact between the cam and follower will move across the face of the follower according to the change of shape of the cam. A trick to lessen further the effect of wear is to design the follower to be capable of axial rotation and arrange the axis of the follower to lie to one side of the cam. Thus the contact with the cam will tend to cause rotation of the follower. The cam profile, to work with a flatfoot follower, must be convex at all parts, in order to prevent the corners of the follower digging into the cam profile. The minimum cam radius should be as small as possible to minimize sliding velocity and friction. All three types of cam followers can be mounted in the following ways: 1) In-line with the cam center line, 2) Offset from the cam center line, or 3) Mounted on a swinging radial arm. CAM-VALVE CAM TERMINOLOGY Trace point: A theoretical point on the follower, corresponding to the point of a fictitious knife-edge follower. It is used to generate the pitch curve. In the case of a roller follower, the trace point is at the center of the roller. 2.Pitch curve: The path generated by the trace point at the follower is rotated about a stationary cam. 3. Working curve: The working surface of a cam in contact with the follower. For the knife-edge follower of the plate cam, the pitch curve and the working curves coincide. In a close or grooved cam there is an inner profile and an outer working curve. 4. Pitch circle: A circle from the cam center through the pitch point. The pitch circle radius is used to calculate a cam of minimum size for a given pressure angle. 5. Prime circle (reference circle): The smallest circle from the cam center through the pitch curve. 6. Base circle: The smallest circle from the cam center through the cam profile curve. 7. Stroke or throw: The greatest distance or angle through which the follower moves or rotates. 8. Follower displacement: The position of the follower from a specific zero or rest position (usually its the position when the follower contacts with the base circle of the cam) in relation to time or the rotary angle of the cam. 9. Pressure angle: The angle at any point between the normal to the pitch curve and the instantaneous direction of the follower motion. This angle is important in cam design because it represents the steepness of the cam profile. Some question arises regarding cam and followers: When is a flat faced follower preferred as compared to roller followers and why? Flat faced followers are preferred to roller followers where space is limited for eg: cams with flat followers are used to operate valves of an automobile engine but in case of stationary and oil engines, roller followers are preferred because more space is available. What data is plotted on displacement diagram of cam and follower motion? Ans:Plot of linear displacement i.e. lift or stroke (s) of follower (on Y axis direction) versus angular displacement (ÃŽÂ ¸) of the cam for one rotation (on X axis direction)

Paraphrasing the Poem entitled “My Last Dutchess” Essay

Look into the wall so that you may see the last of my beloved woman with glee Wondering why upon looking at it comes alive for it is made intensively out of love. Everyday the painter worked expansively as he watched my woman to a pause. Asking for the painter to take a look at my girl and create a painting of her. On the painter’s face, I can see that he is mesmerized by her. I believe in the capacity of the painter – a well known artist. In my eyes I picture you so differently and other would say, If it is her true beauty and I reply, it is. So other now always looks unto her face. Not only had I told the painter that made the woman blushed. I remember after she was painted, she made a wonderful look and say â€Å"Thank you.† It is her smile – the smile that nurtures my being since then until now. But the vestige is her daughter – my daughter. I need to start all over again for it was the destiny of life. Recollecting the surroundings as what the painter created in my woman’s background, Her beauty cast me away, like an â€Å"Innsbruck in bronze† – for me. Reference Browning, R. (1842). My Last Dutchess. Retrieved 26 March 2008. http://wps.prenhall.com/wps/media/objects/680/696357/student_library/pdf/browning.pdf

Consensus Decision Making Essay Essay

A decision is a determination of a question or doubt by making a judgment. Decisions are a part of everyday life for normal human beings and can be as insignificant as to where to eat lunch, or as important as whether to pop the marriage question to a longtime girlfriend. Decisions can be made in a variety of ways, but most of the time they are either made individually or in a group setting. Both individual decision making and group decision making have their pros and cons, and can even determine the type of individual a person is. Decision making is not always an easy process, but is a part of life. There are major differences between group decision making and individual decision making. When individuals are in a group, decision making could not only involve one person’s opinion, but everyone’s opinion which could become vital to the final outcome. This could sometimes make it easier for a final decision to be reached, or maybe make it even harder to reach a final decision. Arguments and disagreements can occur in group decision making based on other people’s opinions. Sometimes people try to persuade other individuals to change their decision to the one they want, by giving them their own opinions and making them seem like facts. Group decision making can also be positive because there is more brain power involved which can ultimately lead to a quick and more efficient type of decision making. The other type of decision making is individual decision making. This type of decision is basically based solely on one opinion and one opinion only, which ultimately gets the individual what they want. The individual decision making also comes from one point of view and only from the knowledge from the individual. This could lead to a misunderstanding on how to decide because the individual was presented the information to process and had a hard time understanding on which way to decide. The individual’s knowledge on the topic they are deciding on may be little to none, and could lead to a poor decision. Either way, individual decision making and group decision making both have their major differences, positives, and negatives. All of the activities in class and the film â€Å"12 Angry Men,† give us individuals some perspective into decision making and also show us the explicit pros and cons. One very interesting and fun assignment we had to  do was the NASA assignment were as individuals we were given 15 choices of important items and had to rank them based on what we thought was important. Then we were put into groups and had to decide which ones were most important barring our opinions. Many people had conflicting views on what was important and what was not, and some had not realized how important an item was until they were in a group. It was extremely interesting to see how all of the group members came to decisions on this although conflict had occurred. Another group activity that we did in class was the time capsule activity. This was another strongly opinion based activity but because there were other people in the group there were many items being tossed around. There wasn’t a set list of items to choose from like the NASA activity, so there were unlimited amount of choices and some choices were surprising. Some important items were many of the times overlooked by the people in the group because their opinion came into play, which was just like the NASA activity. There were many disagreements while working in a group setting because some people may have different priorities. The movie â€Å"12 Angry Men† showed us more positives and negatives of individual and group decision making. In the beginning of the movie all but one juror votes individually decide that the man was guilty without any deliberation of the evidence. After discussing each piece of evidence the jury slows takes a turn towards not guilty. Although some were stubborn, the fact that all of the jurors talked out their opinions and had a reasonable doubt had some of the change their decision to not guilty. After much deliberation and conflict, the jury was unanimously deciding that the accused was not guilty after all. This was after almost all of the jurors had decided guilty, which meant that the group decision making was much more successful than the individual decision making. The right decision was made in the end because of the talking and opinions that were thrown around which ultimately had the jurors changing their initial decisions. This movie again showed us the positives and negatives when it comes to decision making. Many believe that group decision making is a much more efficient way of deciding outcomes which is why it is so often used in the United States Government. Examples like the House of Representatives and Congress show how many people deliberate about new decisions. Many new laws are discussed  by these groups of people and then eventually passed to the president. This just exemplifies how people opinions and votes do matter to the government. Of course the judicial branch is the branch the uses group decision making a lot. Jury’s make decisions on crimes by deliberating and talking about evidence and whether there is a reasonable doubt. They reach a verdict together and all have to agree on the same thing. The executive branch also uses group decision making. The president just doesn’t make decisions based on his opinions, he usually consults many people about new changes that he wants to make. The president is only one brain, and if he gets more opinions from other brains he can ultimately decide on whether or not this is going to benefit society as a whole. Individual decision making and group decision making have major differences. Both of them have their positives and negatives which are a part of everyday life, and are prevalent in the government.

Poverty and Underdevelopment Analysis - Free Essay Example

Sample details Pages: 3 Words: 965 Downloads: 9 Date added: 2019/04/15 Category Society Essay Level High school Topics: Poverty Essay Did you like this example? The World of Poverty by Isbister voices the struggles of 5 different people throughout the world that live in Third World countries. Isbister describes these countries as unimaginable to live in. The Third World carried a sense of opposition tension and struggle (Isbister 1998). Don’t waste time! Our writers will create an original "Poverty and Underdevelopment Analysis" essay for you Create order He also states that these countries bring promise by hoping the ones struggling now hopefully wont be in the future. A myth that many believe is that these countries are not changing. Isbister states that these stories are told through interviews about the peoples firsthand experiences with poverty. These people all share many unimaginable experiences of living in third world countries, and living in poverty. I chose Domitila Barrios de Chungara to analyze with Karl Marxs Marxist Theory. In chapter two of Isbisters A World of Poverty, we were introduced to Domitila was a mother of seven, and a wife to a miner. They lived in the underdeveloped Siglo XX, a mining camp in the central highlands of Bolivia (Isbister 1998). Bolivia is a very underdeveloped and poor country. Most of its people live in unimaginable poverty. When the laborers of the mine went on strike, shootings took place, people were deported, and many arrests were made. The women went on a hunger strike to protest the arrests, which lead to the formation of the Housewives Committee of Siglo XX. Domitila lead the committee, which eventually lead to her arrest during one of the strikes. Domitila was tortured and beaten multiple times during the time of her arrest (Isbister 1998). Domitila bit one of the abusers hands, who happened to be the son of the Commanding Colonial. The abuser took over the beatings from then on, and thre atened to get revenge on her son. During the birth of the child, Domitila passed out, and awoke to the abuser throwing her dead baby at her. Domitila survived with medical care, but still refused to leave the Housewives Committee of Siglo XX (Isbister 1998). I believe Domitilas life demonstrates relative poverty. Relative poverty is defined as one thinking of oneself as poor only if others are rich, and ones poverty is measured against that richness (Isbister 1998). Absolute poverty is defined as standard of living so pressing that brings with it life threatening malnutrition and disease (Isbister 1998). Domitila was barely making ends meet, but she still had the funds to sustain life at Siglo XX, unlike those living in absolute poverty. I believe if Domitila couldnt provide food or shelter over her familys heads, then Domitilas life could be considered absolute poverty. Domitilas life at Siglo XX fits into many of the characters of poverty we know. Domitila and her family were living in poor living conditions, an underdeveloped community where there was wage labor but not enough employees. Domitilas husband was working eight-hour shifts and she was selling salmas on the side just to make ends meet (Isbister 1998). Domitilas lived a life full of insecurity because of the worry her husband would lose his job. If her husband lost his job they would lose the house and have to leave the camp. Isbister states that bad luck can strike anytime and I think that was a fear that Domitila had. Domitilas family were deprived of security, especially for her husbands job and the roof of their heads. Next, I will be comparing Domitilas situation to Karl Marxs Marxist Theory. I believe this theory is a perfect example of the Marxist Theory. The Marxist Theory is a political theory on class structure and conflict, and mode of production. The theory was written by Karl Marx. One of the main points of the theory talks about workers needing to see themselves in the objects they prepare. I feel like this applies well to Domitilas scenario since her husband had to work and live at the mine. His identity was developed around the mine, which meant his familys was too. The theory also talks about workers getting paid little while capitalist get rich. I think this really applies to Domitilas case since her husband was doing very difficult work, but not getting paid well at all. The owners of the mine were somewhere else, not doing the manual labor, and earning money from the miners work, such as Domitilas husband. I think the mining camp also reflects Marx point of capitalism is unstable. L ike previously mentioned, Domitilas husband potentially losing his job at any given time was a huge threat to their security (Isbister 1998). Karl Marx had proposed an economic system that would benefit the poor, such as Domitila. Karl Marx believed there should be no classes. The government would control all resources and means of production to maintain equality with everyone. Karl Marx stated that means of production would not be owned by the wealthy, but by the laborers themselves. I believe an economic system like this would benefit Domitila for a variety of reasons. Firstly, Domitila would not have to live at the mining camp, and her family could have a home and space of their own. Domitilas husband would receive the money he rightly earned for his hard work, instead of only receiving small payments for his work. In essence, the people living in the third countries are living lives unimaginable to others who arent. The roof over her and her families head wasnt promised and their basic needs were barely being met. Not having guaranteed access to basic things caused Domitila to be consumed with deprivation, insecurity, domination, and power. Domitilas situation supported the Marxist Theory by the mining company making money while the workers suffer and are in terrible conditions. The more powerful benefited while the workers suffered heavily. Since the United States is such a developed country I feel like we should put more effort to educate and do more to help the underdeveloped countries.