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Boilers: Introduction and Classification

The boiler system comprises a feed-water system, steam system, and fuel system. The feed-water system supplies treated water to the boiler and regulate it automatically to meet the steam demand. Various valves and controls are provided to access for maintenance and monitoring. The steam system heats and vaporizes the feed water and controls steam produced in the boiler. Steam is directed through a piping system to the application. Throughout the system, steam pressure is regulated using valves and monitored with steam pressure gauges. The fuel system consists of all equipment used to supply of fuel to generate the necessary heat. The equipment required in the fuel system depends on the type of fuel used in the system. Boilers Classification: There are a large number of boiler designs, but boilers can be classified according to the following criteria: 1. According to Relative Passage of water and hot gases: Water Tube Boiler: A boiler in which the water flows through some small tubes which are surrounded by hot combustion gases, e.g., Babcock and Wilcox, Stirling, Benson boilers, etc. Fire-tube Boiler: The hot combustion gases pass through the boiler tubes, which are surrounded by water, e.g., Lancashire, Cochran, locomotive boilers, etc. 2. According to Water Circulation Arrangement: Natural Circulation: Water circulates in the boiler due to density difference of hot and water, e.g., Babcock and Wilcox boilers, Lancashire boilers, Cochran, locomotive boilers, etc. Forced Circulation: A water pump forces the water along its path, therefore, the steam generation rate increases, Eg: Benson, La Mont, Velox boilers, etc. 3. According to the Use: Stationary Boiler: These boilers are used for power plants or processes steam in plants. Portable Boiler: These are small units of mobile and are used for temporary uses at the sites. Locomotive: These are specially designed boilers. They produce steam to drive railway engines. Marine Boiler: These are used on ships. 4. According to Position of the Boilers: Horizontal, inclined or vertical boilers 5. According to the Position of Furnace Internally fired: The furnace is located inside the shell, e.g., Cochran, Lancashire boilers, etc. Externally fired: The furnace is located outside the boiler shell, e.g., Babcock and Wilcox, Stirling boilers, etc. 6. According to Pressure of steam generated Low-pressure boiler: a boiler which produces steam at a pressure of 15-20 bar is called a low-pressure boiler. This steam is used for process heating. Medium-pressure boiler: It has a working pressure of steam from 20 bars to 80 bars and is used for power generation or combined use of power generation and process heating. High-pressure boiler: It produces steam at a pressure of more than 80 bars. Sub-critical boiler: If a boiler produces steam at a pressure which is less than the critical pressure, it is called as a subcritical boiler. Supercritical boiler: These boilers provide steam at a pressure greater than the critical pressure. These boilers do not have an evaporator and the water directly flashes into steam, and thus they are called once through boilers. 7. According to charge in the furnace. Pulverized fuel, Supercharged fuel and Fluidized bed combustion boilers.

Rishabh Pandey

Rishabh Pandey

 

Strength calculation

hello All,  i am working as a design engineer and i am working on sheet metal structures. i am looking at the calculations to decide on the thickness of sheet metal to carry a particular load. i calculated the sectional modulus of the design based on the cross sectional area of sheet metal and it is well within the sectional modulus of material. I would like to know werher the approach is right or are there other calculations which i should do before deciding the thickness?. request to suggest on the above please find the image below for reference

abhilashNJ

abhilashNJ

 

Pre- Crash Sensors for Pre-Crash Safety

Many research and development have been conducted  to meet society needs for safer vehicles. Particularly, occupant protection system such as air bags, developed and introduced in order to reduce occupant injuries in crashes, are currently installed in most vehicles making significant contribution to safety.   Meanwhile, many studies have been made into the development of active safety technologies that help to avoid crash accidents. Unfortunately the current situation is that the active safety technologies are not sufficient spread. Adaptive cruise control has been commercialized since 1995, but its primary use has not been convincing.Some audible warning system  are also being offered, but have not yet reached widespread use.   Toyota Motors corporation has explored the possibility of producing an active safety system employing Intelligent Transport System (ITS) technologies,through participation in the Advanced Safety Vehicle (ASV) projects started in 1991 and led by ministry of land , infrastructure and transport.   Critical basis ITS technologies for application to ASV includes a surround monitoring sensor and an obstacle determination algorithm which combines information from the surround monitoring sensor with other information to identify obstacles with which the vehicle is likely to actually crash.   The sensors and crash determination algorithm for an active safety system should be capable of reliably determining that  a crash will not occur in non-crash situation. Advanced technologies are required to make these predictions and judgments correctly while also taking into account the driver's operation and behavior and this has hampered widespread of active safety systems.   Pre-crash safety system has been developed which operates only when it is judged that a crash cannot be avoided by most drivers under normal driving conditions. Determining unavoidable crashes is restricted to a short time period immediately before the crash so as to improve the reliability of the judgement. In addition the pre-crash system is made with a mechanism and system that will not place the driver and the running vehicle in an unsafe condition even if the system is operated unnecessarily. As a result the world's first commercial system has been achieved.              

saurabh kumar tiwari

saurabh kumar tiwari

V2V (Vehicle to Vehicle) Communication

The objective of ambient intelligence is to create an intelligent daily space, which is immediately usable and integrated into our homes, our offices, our roads, our cars, and everywhere. This new concept must be invisible; it must blend in with our normal environment and must be present when we need it.   One of the application of this concept consists of providing our cars and roads with capabilities to make road more secure (information about the traffic, accidents, dangers, possible detours, weather, etc.) and to make our time on road more enjoyable (Internet access, network games, helping two peoples follow each other on the road, chat, etc). These applications are typical example of what we call an Intelligent Transport System (ITS) which goal is to improve security, efficiency and enjoyment in road transport through the use of new technologies for information and communication.   Traditional traffic management systems are based on centralized infrastructures where cameras and sensors implemented along the road collect information on density and traffic state and transmit this data to a central unit to process it and make appropriate decisions. This type of system is very costly in terms of deployment is characterized by a long reaction time for processing and information transfer in a context where information transmission delays is vital and is extremely important in this type of system. In addition, these devices on roads requires periodic and expensive maintenance. Consequently, for large scale deployment of this type of system, important investment is required in communication and system infrastructure. However, with the rapid development of wireless communication technologies, location and sensors, a new decentralized architecture based on vehicle to vehicle communications has created a very real interest in these last few years for car manufacturers, R&D community and telecom operators. This type of architecture relies on a distributed and autonomous system and is made up of the vehicles themselves without the support of fixed infrastructure for data routing.     The main objectives of an intelligent transportation system includes:   the improvement of trip security the improvement of global efficiency of the transportation system by reducing travel time and congestion the integration of transportation in a durable development policy particularly by reducing gas emissions for light vehicles and heavy trucks and  by optimizing maintenance of the infrastructure the improvement of user comfort by providing him with a selection of information, decision support, guidance and internet access services.                  

saurabh kumar tiwari

saurabh kumar tiwari

 

Automated Manual Transmission

MT (manual transmission) uses simple spur gears providing excellent transmission efficiency and thus typically get 10% or better fuel mileage than current ATs (automated transmissions). The object of the ATM (automated manual transmission ) is to automate starting and gear shifting while retaining this excellent fuel efficiency. A round of fierce competition was triggered among European manufacturers to see who would be the first to develop what is generally known as a conventional AMT that attempts to automate the shifting of MT. The problem with this design is that the drive torque is momentarily interrupted during shifting. This results in a very different shift feeling from an AT, and thus never saw the wide spread acceptance as a replacement for the conventional AT in mainstream vehicles. This was more recently followed by a twin clutch AMT that is receiving great deal of attention. Supporting smooth and responsive shifting much like an AT, the twin-clutch AMT has been installed by European vehicle manufacturer on some high engine capacity sport cars beginning last fall. Hitachi group has now developed an original torque-assist AMT that is fundamentally different from these other two approaches.   TORQUE-ASSIST AMT
In order to achieve widespread acceptance as a replacement for conventional transmissions, the next generation must provide the good fuel economy of an MT, the effortless shifting of an AT, and must also be compact and affordable. Unfortunately, the conventional AMT fails to achieve the seamless shifting of an AT and the twin clutch AMT is difficult to implement compactly and cost effectively.   Hitachi Group has proposed a third way that does meet all the above requirements a torque assist AMT and is now in the process of developing this system. A key advantage of this approach is that it can be implemented with relatively little modification to existing AMTs by simple adding a friction clutch called as assist clutch to the transmission. Action of the assist clutch effectively solves the torque interruption  problem of the conventional AMT while providing the smooth gear shifting of an AT.  A compact and economical torque assist AMT could thus be implemented fairly easily for application on mainstream FF (front-engine front-drive) compact vehicles with engine displacement with 2 liters.                    

saurabh kumar tiwari

saurabh kumar tiwari

 

DRIVERLESS CARS

For generations, the automobile industry has been a source of innovation and economic growth. The ability to drive is a symbol of mobility and independence that spans generations. Clearly, automobiles play a significant role in our lives and afford many benefits to society.   Yet for all benefits conferred on society, no other invention in the history of civilian technology has caused as much harm as the automobile. Every 30 seconds. someone dies in a traffic accident, adding up to well over 1 million deaths each year. In the US automobile accidents are the leading cause of death for people between the age of 3 and 34. Moreover,human error is the cause of over 90% of automobile accidents.   In addition the inefficiencies related with the automobile usage is staggering. Most automobiles sit unused more than 95% of their life span, and a freeway operating at maximum  efficiency has automobiles on only 5% of its surface. In congested urban areas, 40% of all gasoline used is spent when car looks for parking spaces. Furthermore, in some US cities, parking lots comprise more than third of the land, becoming the single salient landscape feature of our built environment.   Since its inception of the commercial auto industry in the late 1890s, cars have become increasingly safe and convenient. Recently, car makers have begun to introduce advanced driver-assistance systems such as adaptive cruise control (which automates accelerating and braking) and active lane assist (which automates steering). These systems have become capable enough that new luxury vehicles can drive themselves in slow moving highway traffics. Research into autonomous cars has progressed remarkably since the first demonstrations in the 1980s. In 2010, four driver less vans traveled from Italy to China. In august of 2012, google announced that its self-driving cars had completed over 300,000 miles of accident free autonomous driving. Although self-driving cars may still seems like science friction, Google, many industry analysts, auto suppliers, and car makers project that such cars will be available before 2020.                                                                      

saurabh kumar tiwari

saurabh kumar tiwari

 

CNG in India

Compressed natural gas(CNG) is a fuel that needs no introduction.  it is a cheap fuel to make and use, which is why it is so widespread in public transport. Not to mention that the second hand car market is greatly supported by CNG kits. vehicles like the Honda Civic, Accord and Toyota Corolla are favorites to be bought second hand and then have green fuel kits used to make them easy on the pocket. With diesel deregulation soon to kick in, the price of the oil will head north soon, so CNG seems like a good investment for those with regular usage. here's the brief look at advantages and disadvantages of CNG:   Advantages:   it is the green fuel. the emissions and hydrocarbons that are released as the by product of CNG usage are lesser than those created by regular fuel. Carbon monoxide emission are down by 70-85% while hydrocarbon levels are reduced by 40-60%. the price fluctuation of the natural gas is less. Look back over the past few years and you'll notice that petrol and diesel prices have been on roller coaster ride, but CNG has the relative linear movement. this is because of domestic production which has no dependency on international movements. Engine life improves.Contrary to popular beliefs, CNG is a better fuel for improving engine life as the carbon levels are greatly reduced.   Disadvantages: The performance of the car is reduced significantly. On an average CNG users experience a crash about 10% in performance.  The storage space is eaten up badly. CNG tanks a easily the size of large bag, so boot space is reduced or removes entirely as the fuel storage tank takes up all the room. Availability is not a wide spread as regular gas stations. Within the city users probably have a list of stations that falls in the route, but beyond that it is an uncertainty. This is the reason why cars aren't made to run exclusively on CNG. Blocked injectors. Cars with CNG kits should always be started on petrol and run for few kilometers before being switched to the green fuel. This warms up the engine better and gets the motor well lubricated. Petrol is expensive so drivers often chose not to use it.  Fuel range. Although CNG is a cheaper fuel, the actual range on just CNG is lesser than petrol. Not to mention, running on a close to empty tank reduces the pressure and increases the risk of valve bursting. So, even if the car uses CNG, it is always wise to keep a regular flow of petrol both in tank and in the engine usage.              

saurabh kumar tiwari

saurabh kumar tiwari

 

Desicant Cooling System

In the last 10 years, evaporative and desiccant cooling technology for air conditioning has increased as an alternative for air conditioning systems has increased as an alternative to the conventional vapour compression systems. A typical system combines a dehumidification system that uses a rotary desiccant wheel, with direct or indirect evaporative systems, allowing a filtered and cooled air supplying temperature, humidity and speed conditions that propitiate environmental thermal comfort, even in equatorial and tropical climates. These systems causes a lot of electrical power saving, mainly in place where thermal source energy source are easily found, where the price of electrical energy is high,where the latent heat percentage is high or where the needed air dew point is low. So, evaporative cooling systems that use absorption pre-dehumidification presents a great perspective in thermal comfort. It can be used in co-generation systems, where the needed heat to regeneration can be gotten from gas turbines exhaust gases or internal combustion engines or, still, from steam in plants that use steam turbine.                                                                                                                                                                                                                                                    

saurabh kumar tiwari

saurabh kumar tiwari

 

Experimental Analysis of an Air Washer

Hello World,   Today i will like tell you all about my 4th year project which was on the topic of experimental analysis of an air washer. In the recent sanario the peoples are slowly getting conscious about the beast(pollution) intended to destroy our beautiful sphere(earth). This pollution had drastically spread in our world drastically in few years. It is sad to say but we are only responsible for it. The careless burning of fossil fuels, heavy growth in industries and inventions without considering about the earth safety pushed of us into this undesirable situation.   But now the peoples are thinking about what they are doing and what they had done including the government which taken so many steps for the control on pollution. The scientist's also get conscious about their invention which will be in the favor the reducing pollution.     In India the refrigerants like R 22 is going to be banned in upcoming few years which is one of the major reason for the depletion of the ozone layer which causes global warming and some harmful skin disease's. These things created the requirement for the replacement of old cooling systems and introduction of the new inventions which are environment friendly.   My project was on the same concern me and my friends decided to try the project which can be the one of the substitute of the recent refrigeration system. On the suggestion of our professor we modified the air washer to not only work as an evaporative cooler but also can remove the sulphure dioxide from the air which is one of the gas responsible for green house effect.   In my project my team was using spray type air washer with the very simple design since it become easier to modify.                                                                                                                                                           The spray type air washers consists of a chamber or casing containing a spray nozzle system, a sink for removing the spray water as it falls. And an eliminator section for the removal of moisture in the air. A pump recirculates water at the rate higher than the evaporation rate.   Intimate contact between the spray water and the air flow causes heat and mass transfer between the air and the water. The air washer used in the industries has the basic use to clean air and control the properties of the air as per the requirement.   The air washer can perform two kinds of cooling: 1. Direct evaporative cooling 2.Indirect evaporative cooling   The direct evaporative cooling is done by the direct contact between sprayed water and the flowing air in the chamber. Where the indirect evaporative cooling is done by providing heat exchanger at the front of air washer. The syphon present in the heat exchanger is circulated by the cold water and the hot air is passed through the fins of the heat exchanger. Which causes heat exchange between air and water.   The indirect evaporative cooling was done in my project by the use of car radiator.
AIR WASHER SPECIFICATIONS
BLOWER                suction blower with 1HP, 3PHASE, 440 V and internal diameter 4 inch   NOZZLE SECTION                     the nozzle section consist of:-   1. 4 elbow joints (0.5 inch bore) 2. 3 distributors (0.5 inch bore) 3. 10 vertical pipes (0.5 inch bore & 50 cm length) 4. 10 holes on vertical pipe each (1 mm bore) 5. 5 holes on horizontal pipe each (1 mm bore)   All the components in the nozzle section are made up of PVC material.   The body of the air washer was made up of the aluminium composite pannel.  Two layers of simple cellulose pad was use in the eliminator section to absorb the moisture in the air.                                                                                                                                                                                                                                                                                                  The picture above will give you the brief and real understanding of the project.   The analysis was done with the following aims: 1. circulating the water at normal temperature and analyzing the changes in the property of the air 2. circulating hot water through air washer and analyzing the change in the properties of air 3. circulating chilled water through air washer and analyzing the changes in properties of air   I am providing some videos of working of my project i hope you will like it.   please give reviews on my publish and don't forget to follow. your reviews are precious to me and your following will motivate to share new views thank you.                                                                                               

saurabh kumar tiwari

saurabh kumar tiwari

 

Last Post -- Time to Hang It Up

Mechanics Corner
    A Journal of Applied Mechanics and Mathematics by DrD
    © Machinery Dynamics Research, 2017
Last Post
Time to Hang It Up    
This will be the final post of Mechanics Corner here on Mechanical Engineering Forums. It has run almost exactly two years, and there have been ups and downs along the way. In this final post, I want to reflect a bit on my original goals for the blog, and also on what has actually happened. When our host first proposed to me that I might write a blog for ME Forums, I was excited about it. About half of my career had been spent in engineering education, and I always loved working with students. It seemed like a way to get back to something that I had long enjoyed, and so I accepted his suggestion. A long time ago, back when I was about 14 or 15 years old, in Junior High School, my shop teacher mentioned, in an off-hand way in class, that various curves could be described mathematically. I’d never heard that before, but I thought immediately, “This has interesting possibilities.” Moving ahead a few years, I discovered that I wanted to study and build my career around was the area known as Applied Mechanics, although it was a time before I first heard that term. In my freshman physics class, I discovered the laws of motion, and thought to myself, “This is great stuff! I can use math to describe how things move!” All of that happened back in the 1950s, and I’m still doing the same thing today (some might say I am in a rut!). As a teacher, I taught mostly undergraduate engineering courses, although I taught my share of graduate courses as well. It was the undergraduate courses that I liked most, because I firmly believe that the economy of a nation is strongly dependent on the quality of the baccalaureate level engineers produced in that nation. Engineers with graduate degrees are valuable as well, but the vast majority of the national engineering workload falls to BS level engineers.    Thus, I envisioned Mechanics Corner as a sort of continuation of the several undergraduate courses I most enjoyed teaching — kinematics, dynamics of machines, vibrations, and mechanics of materials. For the most part, I have stuck to the plan, so that most of the technical posts I have made have dealt with problems that I considered suitable for undergraduate engineering students, say perhaps, junior level. I have posted a few topics from my industrial experience, but those have been situations that baccalaureate level engineers would be expected to handle. Now I knew it would not be exactly like continuing to teach my classes. In particular, you would not have any homework or tests, and I would not have any grading to do – a win-win, or so I thought. I did hope, that even with no assigned homework, readers would take an interest in the problems discussed, even to the point of working through the details for themselves (I was terribly naive, apparently!). I knew from my own experience that the only way I ever really learned a new idea was to get in and work with it, work some problems, make some numbers, plot some curves, until I really understood what it was all about. I’ll venture to say that nobody ever learned any technical material simply by reading only. In actual fact, in the early days, I had one or two folks say that they would in fact work through the problems, so I was encouraged. What I was not prepared for, however, was the fact that the vast majority never seemed to even read very carefully, much less work through the problems! The questions that have come, and there have been a few, have largely been about matters totally unrelated to the posts. The most common question has been, “Suggest a topic for my final project,” which relates to not a single post. Needless to say, that aspect of my vision was totally unfulfilled. But there is another side. I ventured to write a few “philosophical” articles, items dealing with academic integrity and cheating, with how to ask for help, with how to write a report or a paper, and various other matters. I really thought all of this would be considered obvious and trivial, so I was completely unprepared for the excitement that some of these articles generated. There were, in some cases, many, many comments, and people seemed to really be interested. I’m left to wonder: why? Are these ideas foreign to the culture of India and SE Asia? Are these things not all taught at home and in the public schools? I don’t know, but there was a lot of interest in these matters. But Mechanics Corner was intended to be primarily a technical blog, and there, it just did not excite the interest of the readership. As time passed, there was less and less interest. First, the comments dropped off to just about zero, and later, there were fewer and fewer who even bothered to “like” the articles. Finally, the number of reads has dropped to almost nothing (there may be no one left to read this final note). Well, there could hardly be any more clear indication that it is time to stop. I asked for opinions about this from some of the administrators, and was told that the blog was just over the heads of the readership. That makes me sad; that was never the intent. If it is true, I do not see how engineering has a very bright future among this readership. Even so, I wish all of you the best for your careers. I hope that you are able to find rewarding and beneficial work in which you will be happy and make a real contribution to your societies. To use an old cowboy metaphor perhaps familiar to many of you from Bollywood, “It is time to hang up the bridle and saddle, and say, ‘Adios’ (Adios is literally, “to God”).  

DrD

DrD

 

A Problem in Statics & Dynamics, #34

Mechanics Corner
    A Journal of Applied Mechanics and Mathematics by DrD, # 34
    © Machinery Dynamics Research, 2015
A Problem in Statics & Dynamics     
    
Introduction         A problem was recently posted on this Forum, requesting help, that has led me to consider a somewhat more general problem for this post. The scope of this post will include the original problem, although not by the method required there, but will also go beyond to a more general geometry. We begin here by stating the present problem; interested readers are invited to search back for the original problem posted 19 December, 2016, by iivii.
    

Assembly Drawing, with Dimensions   StatDynProb.pdf

DrD

DrD

 

What are hydraulic cylinders,working principles !!

Hydraulic cylinders haven’t really changed a lot over the years. The manufacturing processes are much more streamlined and the tolerances are much tighter, but for the most part cylinders are still the hard working push/pull tools they have always been. These things have literally shaped the world around us. Anything that gets lifted, pushed, hauled, dumped, dug, crushed, drilled or graded has gotten that way by some truck, crane, dozer or tractor using a hydraulic cylinder. But how do hydraulic cylinders work?
The amazing amount of force a cylinder exerts is due to the simple mechanical principle of pressure exerted on the surface area of the
piston . Simply put, the larger the diameter of the cylinder, the more it will lift. 

SK sharma

SK sharma

 

If There Is a Fastener There Will Be a Tool That Requires Access.

I get great satisfaction when working with my hands. When I do so I always ask why the item I am working on is as it is. One source of frustration I believe many have experienced it the lack of tool access. Sometimes n-1 fasteners are a breeze to access and the nth takes more time to remove than all the other combined. I don’t recall from my machine design class ever addressing this real world situation. I learned how to size bolts, bearings, and cross-sections but I don’t recall any mention of tool access. I learned there existed standards for tool access when I entered industry. In the auto industry one thing you tried to avoid was the need for special tool kits. These were not cheap and every automobile dealer and repair shop needs to purchase the special kits if they intend to make the particular repair. As much as this was avoided 30 years ago (and I assume still today) these special kits existed. While working in a different industry we were cleaning up a lab area. I came across an Allen Wrench (hex key) that did not make the usual 90 degree bend. It brought to mind the special kits I mentioned above. It had been modified to have a second bend nearly 90 degrees. I taped it to the wall in the design department with the following note. Do Not Design Anything That Needs a Tool Like This! There are reasons a lack of tool access happens. Parts designed for one application may have been created with adequate access. The same item is later used on a different application and the surrounding space is already accounted for. But there are cases where there simply is not enough thought applied or too many bean counters controlling the design function. As the Wyoming winter approaches there are things that need attention. Today two of those frustrations had to be addressed. I have a generator for times when power goes out and an ATV (all terrain vehicles) for snow removal. Both have batteries for starting. Battery removal is more difficult than it should be for both.The generator can be manually started but if needed when it is -20F (-29C) that can be quite an effort. For the ATV the battery is held in place with two screws and a padded flat metal bar across the width of the battery. This is an (n-1) example. One of the two screws has plenty of access and the other is under a plastic housing. What would make it more user friendly (for those who buy the products) would be to make the end of the retaining bar that is under the plastic housing, slip into a slot of some kind. The other end which is very accessible would use the one screw. This would eliminate one fastener, eliminate the captured nut or tapped hole (can’t see what is there) and make battery removal so much easier for little or no cost. My solution which could easily be incorporated at the factory was to cut a slot on the end of the bar with poor tool access. Doing so eliminated the need to remove the hidden fastener. Just loosen enough to slip the retaining bar out then back in. You can rotate the retainer but it must pass over the positive terminal and the bar is grounded to the frame. Better to remove it.  For the generator I speculate this is the multi application issue. The same design is sold with and without battery start. These options don’t come cheap and if as in the auto industry, have a handsome margin. So why punish the big spenders? The panel with all the outlets is welded to the frame. The panel extends quite a distance down to provide a billboard for the power rating. Behind the immovable plate lies the battery. Accessing the battery retainers and cables would be simple if the lower portion of the plate was either detachable or eliminated. Since I don’t transport the generator I leave the retainers off. Access to the cables is still more difficult than it need be. So for those who have not yet entered industry let these two examples provide food for thought when you are designing equipment. Many small improvements can be incorporated for little or no cost prior to production release of the design. Those about to enter industry seek out the senior engineers and ask for the standards books. Spend some time, even your own time, skimming through the manuals. They contain thousands of man-years of experience. Also spend time in the manufacturing and service facilities if possible. These efforts will provide an insight to what is not taught in class. Photo 1 Is a top down view of the battery retainer.  Photo 2 You can see the hidden fastener and the modification to the retainer. Photo 3 Is the generator. The bottom half of the battery can be seen. Photo 4 Is the side view of the battery. Photo 5 Shows the bottom half of the battery more clearly than photo 3.  

JAG Engineering LLC

JAG Engineering LLC

 

MACHINE DESIGN :- 40 POSSIBLE QUESTIONS

1. What are the differences between true stress, engineering stress, proof stress.
2. What do you men by factor of safety and what is its significance
3. What do you mean by Young’s modulus, modulus of rigidity and bulk modulus.
4. What do you mean by resilience.
5. What is pure torsion and what do you mean by flexural igidity.
6. What is the difference between endurance limit stree and endurance strength.
7. What do you understand by efficiency of riveted joint.
8. What is caulking and fullering in riveted joint.
9. What do you mean by stress conc. Factor and what are the methods to reduce stress conc.
10. Why stress conc. Is more serious in brittle materials. 11. What do you mean by fatigue .
12. Springs are subjected to which type of streses.
13. What are the difference between through bolt, tap bolt and stud.
14. What is check nut and what is the function of washer.
15. Cotter and knuckle joints take which type of load and where they are used.
16. What are the difference types of couplings and what is their function.
17. What is the function of key and which type of stress they are subjected to?
18. Generally shafts are subjected to which type of stress.
19. What are the difference types of mechanical drives and which is the best for different situations.
20. What is the function of a bush why it is phosphor bronze.
21. What are difference types of threads and which threads are used for power transmission and why.
22. Why the pulley arms are elliptical in cross section and it is made up of cast iron.
23. Why it is required to change the all V belt if one of them is broken.
24. Why V belts transmit more power than flat belts.
25. What is the meaning of 6*37 or 6*7 in a rope drive.
26. What do you mean by pinion sprocket and wheel sprocket and which one is used for driving shaft.
27. What is the function of flywheel and why its material is cast iron.
28. Why the leaf springs are laminated as reducing length.
29. What is the function of clutch and is the difference between uniform wear and uniform pressure.
30. Now a days which type of clutches are used in automobiles. 31. Why disc brake is more efficient than mechanical brake.
32. What is the function of bearings and what are the different types.
33. What is bearing characteristics number and bearing modulus.
34. What is the significance of the digits of a rolling contact bearing number 6304?
35. Which type of gear drive is used for perpendicular transmission of power?
36. Why helical gears transmit more power than spur gears.
37. What do you mean by different terms like back lash, pressure angle, circular pitch in a gear drive.
38. Why involute tooth profile is better than cycloid tooth profile?
39. What is interference in gear drive and how to avoid it?
40. What do you mean by law of gearing

saurabhjain

saurabhjain

 

Over Engineered or Over Designed?

I recall many years ago first hearing the term Over Engineered. It rang a sour note but I had not given it much thought. I still hear this said today about older equipment. For instance the DC Generators at Pratt Institute in Brooklyn NY have been in operation for over 100 years. http://inspectapedia.com/heat/Steam_Systems_Pratt_Milster.php I had the opportunity a few years ago to visit my alma mater. To my surprise and delight the Chief Engineer who provided the tour of the facility to my class in about 1977 was still on the job as was the equipment. But I digress. Over Engineered is often brought up when speaking about 1950’s vintage American automobiles. “They don’t build them like that anymore”. They don’t build them like that anymore because they don’t design like they use to. When I worked in the auto industry in the late 70’s and early 80’s engineering was in good part “seat of the pants” designing. A lot less analysis than one would expect. Two-D CAD was just getting introduced. There was extensive testing before production. What a lack of analysis left unknown, testing –often brutal testing- would reveal. If a component broke it was made stronger by adding more material or eliminating tight radii or other stress concentration features. Whether the rest of the system was just good enough or 10 times stronger than needed was an unknown. Over time components that never failed were targets for cost reduction. This also was not as analytical as it is likely today. Getting back to the subject of this blog, I would offer that the "weaker" a device is, the more it was engineered. Weaker, because it is designed closer to the expected loads. This of course is aside from shoddy design work.  For greater strength the addition of material will usually achieve this. For an item like the generators at Pratt added weight can also help with vibration. The penalties are the onetime cost of added material and greater shipment weight. Adding more material globally to a system such as a rocket, aircraft and to today’s automobile is forbidden. This requires much move engineering. I hope I have provided a better understanding of the term Over Engineered and realize it is really a misleading expression. Equipment back then was Over Designed because the factors of ignorance were much greater just a few decades ago.

JAG Engineering LLC

JAG Engineering LLC

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