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    8. I have used "jigs" in woodworking. In this case the jig does not HOLD the work piece. Rather, the jig is located relative to some key dimensions of the work piece and perhaps clamped in place. Then, one proceeds with the next cutting or drilling operation. Also, in woodworking, a fixture is a device that holds one or more work pieces for the purpose of alignment and/or additional cutting/machining or assembly.
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    14. Mechanics Corner A Journal of Applied Mechanics and Mathematics by DrD, # 37 29 April 2017 Two Balls Rolling On An Incline A Problem Where I Learned Something New Introduction In previous articles, I have mentioned another web site called Physics Forums (PF) where people post problems for which they need help. In this note, I want to present to you one such problem and it solution, along with a new insight that came from another commenter at PF, one of the advisory folk on that site. At first, I thought the adviser was wrong, but it turns out that he was correct and had something new that I had never seen before. Here is the problem. Problem Statement A thin wall spherical shell with a mass of 0.605 kg and a radius of 0.0402 m is released from rest at the top of an incline. The spherical shell rolls down the incline without slipping. The spherical shell takes 7.49 s to get to the bottom of the incline. A solid sphere with mass of 0.127 kg and a radius of 0.1123 m is released from rest at the top of the same incline. The solid sphere rolls down the incline without slipping. How much time does it take for the solid sphere to reach the bottom of the incline. Note that --- Thin spherical shell I=(2/3)MR^2 Solid sphere I=(2/5)MR^2 Discussion The original problem statement is above. Note what is given, and perhaps more importantly, what is not given. In particular, we are not given 1.The time for the solid sphere to reach the bottom -- this is the item to be determined; 2.The angle of the incline; 3.The length of the incline; 4.The local value of g, the acceleration of gravity. The last three items are things that we might expect to have given in such a problem, but here they are not. This is the major difficulty in this problem, and the solution must find a way to work around this missing information. TwoBallsRollingOnAnIncline.pdf
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    16. hello frnds, sorry in advance for my bad English, currently i'm working on 3D animated tutorial about basic transmissions types, their construction and working, i'v created 3D models in 3Dsmax2014, i'v completed animation of manual H type transmission, but now i'm stucked in sequential transmission, i watched some videos on you tube, but there is nothing about reverse gear, so plz help me in this, i want to know how reverse gear works, where is it located, and how it is controlled by selector shaft, here i post some screen caps of this transmission so you can understand easily what i'm creating and what i'm asking about, in 1st picture, all the gears which are rounded only those are connected to the corresponding shafts, and those can slide over the shaft left and right to connect with adjacent gear
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    19. Casting is a major manufacturing process which is mostly used in heavy industries. Most of the components like outer casing of turbine, lathe bed, valve casing, hydro turbine blades, Pelton wheel, Francis runner and many other parts of major machinery are made by the casting. The cast product has low strength compare to forging but any difficult parts can be cast by this technology. Types of Casting: Casting is widely used any many different shapes and material can be cast by it. There are various method of casting available which are used for different shapes and material. Casting has following types. Sand Casting: It is widely used for casting different process. Sand is easily available and has high refectory property so it is used in casting. It is done by following steps. Design is made by using software or manually. A wooden pattern is created in pattern shop. Generally patterns are made into two half and can be increased accordingly to complexity. The pattern is placed into the flask and mixture of sand and clay with water pour into it. The runner, riser, core, gating system is also fit into it. When the mould gets hard the pattern is removed from mould and molten metal pour into it. The metal is allowed to get solidify into the casting. After solidification cast is removed from casting and send to machine shop for machining. The sand casting is used for all metal and at low cost. An another advantage is that it can be used for very complex shape. It gives poor surface finish. Shell Casting: It is an another method of casting and used to cast thin section like turbine blade etc. This casting is different from sand casting. A metallic pattern is used in this type of casting. It consist following steps. First a metallic pattern is cast. The metal is used for casting is generally aluminum or cast iron The patterns is heated up to 250 degree and put into flask. The flask is filled with sand resin mixture. The resin gets solidify immediately after gating contact with heated pattern. After the sand solidify the pattern and the extra sand taken out. Now a shell of cavity is created. This shell is further heated into burner which allow proper bond. The metal is poured into the shell and allows to solidify. After solidification cast is removed from shell and send for machining. Investment Casting: In this type of process, wax pattern is used. The pattern is first created by wax dipped into refectory material. This refectory material make a shall outside the wax pattern. After it mould is heated which allow waxing out from mould. Now the molten metal poured into cavity formed by it and allows solidifying. The cast is taken out after proper solidification of cast and send for machining. The main advantage of this process is that a very high accuracy and surface finish can obtain by it. It is used for complex shape and batch production. Plaster Mould Casting: These method uses plaster mould for casting. First plaster mould is created using patterns. After removal of pattern, the plaster mould allows to dry into an oven. After dried, molten metal is poured into it and allow solidifying. After complete solidification cast is sand to the machine shop. Mostly zinc and aluminum is used as molten metal. This casting is used to create prototype. Ceramic Mold Casting Ceramic mold casting is same as investment casting but it does not use wax pattern. The slurry of ceramic and liquid binder is pour on pattern which is easily solidify. There is no wax pattern is used so there is no limitation of size of casting. This type of casting is mainly used to cast heavy component like valve bodies, military equipment etc. Pressure Dies Casting: This casting is mostly used to cast aluminum, lead etc. In this casting a liquid metal is pumped at high pressure into a metallic die and allow to solidify. The metal is allowed to solidify there and take out after solidification .The die is again used for next cast. It is well suitable for batch production of casting low melting point metal. It is not suitable for high melting temperature metals. The tooling cost is also high. Centrifugal Casting: It is one of the most suitable casting processes of casting symmetrical cylindrical component. In this process a liquid metal is poured at the center of a rotating die. The die rotate and a centrifugal force act on the molten metal which forces it to towards circumference. It is used to create hollow shape. The light impurities crowed near center which is removed by machine. This process eliminates the use for core and gating system. This type of casting is used to make pipes etc. Continuous Casting: It is a different casting process which is used to create continuous cast. In this process we do not use mould or cope and drag. It is different in principle. In this process the molten metal poured into a trash which is connected to a copper pipe. The copper pipe is surrounded by water cooling. The metal is directly or immediately cooled after when running through pipe. The casting product takes out from other side. This process continuously run and molten metal continuously pour into it. It is used to create square or other shape simple block which further used for rolling or other process. These all are main types of casting.
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    21. Pattern is replica or model of object which to be created. It is used to make hollow cavity in sand mold in which molten metal is poured and allow solidifying to create object. The size and shape of cast object is highly depends of shape and size of pattern. Mostly pattern are made by aluminum, wood, wax etc. Metal pattern are used for mass production. The pattern making is most critical work in casting because the object is highly depended on it. A good pattern should follow following requirements. Low cost and easy to cast. Easy to repair. It should light in weight which make it easy to handle. It should able to withstand ramming forces without deformation. It should does not change its dimensions in presence of moisture. It should be easily removable from mould. It should have long life without change in its dimensions. Types of pattern: As we discussed, casting objects are highly depend on pattern. According to the shape and size of casting and method of making cavity, pattern can be classified as follow. Single Piece Pattern: It is simplest type of pattern which is made in single piece. It is used for simple objects. It is either placed into cope or in drag according to the simplicity of operation. It is used to cast stuffing box of steam engines. Split Pattern or Multi Piece Pattern: These patterns are made into two or more pieces. The first half of pattern placed into cope and other half into drag. It is used for complex objects where removal of single piece pattern from mould is impossible. When pattern is made in more than three parts cheeks are also used for easy removal. Cope and Drag Pattern: These are two piece split pattern as discussed above. It is used for large objects Match Plate Pattern: Match plate pattern is a split pattern in which cope and drag section mounted on opposite sides of a plate. The plate is known as match plate. These will make easy to cast any shape with high production rate. Mostly runner, gates etc. are also mounted on same plate which will easy to mould making work. These patterns are used for mass production. Loose Piece Pattern: When removal of pattern is impossible due to an extended surface at either upper half or lower half, the extended part made as loose piece so this extended part can be removed first before removal of whole pattern. This will make easy removal of pattern without effect on the cavity. These patterns are known as loose piece pattern. Gated Pattern: These are simply more than one looses piece which are attached with a common gating system. These are used for mass production. It is used to produce small size cavities into one mould. Sweep Pattern: These pattern are used for large rotational symmetrical casting. A sweep is a section of large symmetrical object which is rotated along a edge into sand which make a large symmetrical mould. These patterns makes easy pattern making work of large objects. Skeleton Pattern: These patterns used for large simple castings. In these patterns, skeleton like structure made by using simple pattern sections. These will save both time and material. Follow Board Pattern: Follow board is a wooden board which is used to support pattern during moulding. It acts as sit for pattern.
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    23. Ideal fluid: A fluid, which is incompressible and having no viscosity, is known as an ideal fluid. Ideal fluid is only an imaginary fluid as all the fluids, which exist, have some viscosity. Real fluid: A fluid, which possesses viscosity, is known as real fluid. All the fluids, in actual practice, are real fluids. Example : Water, Air etc. Newtonian fluid: A real fluid, in which shear stress in directly proportional to the rate of shear strain or velocity gradient, is known as a Newtonian fluid. Example : Water, Benzine etc. Non Newtonian fluid: A real fluid, in which shear stress in not directly proportional to the rate of shear strain or velocity gradient, is known as a Non Newtonian fluid. Example : Plaster, Slurries, Pastes etc. Ideal plastic fluid: A fluid, in which shear stress is more than the yield value and shear stress is proportional to the rate of shear strain or velocity gradient, is known as ideal plastic fluid. Incompressible fluid: A fluid, in which the density of fluid does not change which change in external force or pressure, is known as incompressible fluid. All liquid are considered in this category. Compressible fluid: A fluid, in which the density of fluid changes while change in external force or pressure, is known as compressible fluid. All gases are considered in this category. Graphical representation of different fluids: Tabular representation of fluid types: Types of fluid Density Viscosity Ideal fluid Constant Zero Real fluid Variable Non zero Newtonian fluid Constant/ Variable T = u(du/dy) Non Newtonian fluid Constant/ Variable T ≠ u(du/dy) Incompressible fluid Constant Non zero/zero Compressible fluid Variable Non zero/zero CLASSIFICATION OF FLOWS ON THE BASIS OF MACH NUMBER. Incompressible flow-M less than 0.3 Compressible subsonic flow-M between 0.3 and 1 Transonic flow-M ranging between values less than 1 and more than 1 Supersonic flow-M greater than 1 but less than 5 Hypersonic flow - M greater than 5
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      ME208( theory of manufacturing processes) Presentation of my professor as taught in spring 2017 Subtopics: 1. Forging and its types 2.TTT diagram for steel 3.Hot working Cold working 4.Sheet metal working
    25. I have uploaded few powerpoint presentations on Manufacturing processes. if you get time do review them so, I can rectify the mistakes and add some more info if left. thanks in advance.

      1. saurabhjain

        saurabhjain

        thank you very much

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    29. what is the difference between refrigeration and air conditioning? A major difference between refrigeration and air conditioning is the point of supply for the gases. Refrigeration systems have gas installed in a series of tubes. In old refrigerators, this gas was chloro-flouro-carbon, or CFC, but this has harmful effects on people, so refrigerators not contain HFC-134a. HFC-134a is the sole gas used as a coolant in refrigeration systems. Air conditioning systems use built-in chemicals, but also air from the room or rooms being heated. Gases built into air conditioning units cool air that circulates through the unit; the unit then redistributes the cooled air through the room. Air conditioners have circulation systems designed to project cool air away from the units while refrigeration units have circulation systems designed to retain coolant in a confined space. Refrigeration systems circulate cool liquids and gases through a series of tubes and vents. Cool air from within a refrigerator is sucked into a compressor that recycles the gas through the tubes. Air conditioners, while also employing tubes in the coolant system, have fans for the dispersal of air. Unlike refrigeration systems, which keep gases contained to a pre-determined space, air conditioning systems disperse cool air throughout areas of unknown volume. Refrigeration refers to processes that take thermal energy away from a place and gives off that energy to a place with a higher temperature. Naturally, thermal energy flows from a place with a higher temperature to a place with a lower temperature. Therefore, refrigeration runs against the natural heat flow and so it requires work to be done.Refrigerator is a name that we use for devices that are used to keep food at low temperatures. A refrigerator consists of a fluid called refrigerantwhich gets expanded and compressed in a cycle:
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