Dms Notes Ram Sir

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Module -1 Design Methodology and Morphology Design :Design is the way of defining solutions for problems not solved before, or new solutions to problems which have previously been solved in a different way. A New Product is the result of a Design activity. There is a continuous need for new, cost-effective, high-quality products. Q1. Explain the design Morphology (Structure of design) step by step.

Design Morphology:Morphology means ‘a study of form or structure'. Morphology of design refers to the time based sequencing of design operations. It is a methodology of design by which ideas about things are converted into physical objects. The logical order of different activities or phases in a design project is called the morphology of design. A design project goes through a number of time phases. Morphology of design refers to the collection of these time phases. The morphology of design as put forward by “Morris Asimow” can be elaborated as given below. It consists of seven phases. Phase 1.Feasibility Study. This stage is also called conceptual design. A design project always begins with a feasibility study. The purpose and activities during feasibility study are a) To ascertain that there really exists a need of the design. The existence of need must be supported by necessary evidences b) Search for a number of possible solutions c) Evaluate the solutions i.e. is it physically reliable? Is it economically worthwhile? Is it within our financial capacity? Phase 2 Preliminary Design. This is the stage art which the concept generated in the feasibility study is carefully developed. The important activities done at this stage are: a) Model building & testing b) Study the advantages and disadvantages of different solutions. c) Check for performance, quality strength, aesthetics etc. Phase 3: Detail Design Its purpose is to furnish the complete engineering description of the tested product. The arrangement, from, dimensions, tolerances and surface properties of all individual parts are determined. Also, the Page | 1

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materials to be used and the manufacturing process to be adopted etc. are decided. Finally, complete prototype is tested. Phase IV: Planning for manufacture This phase includes all the production planning and control activities necessary for the manufacture of the product. The main tasks at this phase are a) Preparation of process sheet, i.e. the document containing a sequential list of manufacturing processes. b) Specify the condition of row materials. c) Specify tools & machine requirements. d) Estimation of production cost. Torque Engineering Academy e) Specify the requirement in the plant. Ram Sir- 8149679293/8605455123 f) Planning QC systems. g) Planning for production control. h) Planning for information flow system etc.

Phase V: Planning for Distribution The economic success of a design depends on the skill exercised in marketing. Hence, this phase aims at planning an effective distribution system. Different activities of this phase are a) Designing the packing of the product. b) Planning effective and economic warehousing systems. c) Planning advertisement techniques d) Designing the product for effective distribution in the prevailing conditions. Page | 2

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Phase VI Planning for Consumption/use The purpose of this phase is to incorporate in the design all necessary user- oriented features. The various steps are a) Design for maintenance b) Design for reliability c) Design for convenience in use d) Design for aesthetic features e) Design for prolonged life f) Design for product improvement on the basis of service data. Phase VII: Planning for Retirement. This is the phase that takes into account when the product has reached the end of useful life. A product may retire when a) It does not function properly b) Another competitive design emerges c) Changes of taste or fashion The various steps in this phase are • Design for several levels of use • Design to reduce the rate of obsolescence. • Examine service-terminated products to obtain useful information. Q2. What are different types of design?

Types of Design:The design can be classified in many ways. On the basis of knowledge, skill and creativity required in the designing process, the designs are broadly classified into three types A] Adaptive Design B] Variant Design C] Original Design

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A] Adaptive Design In most design situations the designer's job is to make a slight modification of the existing design. These are called adaptive designs. This type of design needs no special knowledge or skill. E.g. converting mechanical watches into a new shape B] Variant Design

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This type of design demands considerable scientific training and design ability, in order to modify the existing designs into a new idea, by adopting a new material or a different method of manufacture. In this case, though the designer starts from the existing designs, the final product may be entirely different from the original product. E.g. converting mechanical watches into quartz watches, Here a new technology is adopted. C] Original Design Here the designer designs something that did not exist previously. Thus, it is also called new design or innovative design. For making original designs, a lot of research work, knowledge and creativity are essential. A company thinks of new design when there is a new technology available or when there is enough market push. Since this type of design demands maximum creativity from the part of the designer, these are also called creative designs.

Q3. What are the Key Features of Design processes?

Features of Design Process:The following features can be observed in a design process. a) Iteration:Design is completed in many phases. In each phase, repeated attempts are required to accomplish the aim. A satisfactory conclusion can be reached on, only after a number of trials.

b) Decision-making :Decision-making is essential for a designer to select one out of several. A designer often comes across several equally acceptable alternatives to meet some end. In such conflicting situations, designer has to make the best decision

c) Conversion of resources :In any design process, there is conversion of resources such as time, money, talent, materials and other natural resources. Torque Engineering Academy Ram Sir- 8149679293

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d) Satisfaction of need :All designs are aimed at satisfying some human need. Needs, whether important or unimportant is the starting point of design. Q4. Explain the design Methodology step by step.

Methodology of Design:Methodology means the actions to be followed while designing. There are six basic actions when we try to find solution of any problem. 1. Establishing or convincing that there ‘is' a problem or understanding that a solution is needed. 2. Planning of how to solve this problem 3. By analyzing the problem, deciding what is actually required from the problem-solver or we deciding the requirements. 4. Generating alternative solutions. 5. Evaluating the alternatives for feasibility and optimality. Torque Engineering Academy 6. Presenting the acceptable solution. Ram Sir- 8149679293/8605455123

Design Process using Advance Technology:i) Although Engineering is a major sector of the economy in a developing country, it has not been benefited greatly from advances in computer technology. Engineers still use computers only in peripheral tasks, such as drafting and analyzing, but not in making fundamental design decisions. ii) Current computer tools such as ‘computer-aided drafting' are restricted to the end of the design process and play no fundamental role in aiding design. It aids only in the final drafting of the specifications. iii) Computer-aided Design, (CAD) means a class of tools for creating drawing, or the physical description of the object. CAD systems have been sophisticated and 2D and 3D models are available. iv) The CAD allows the designer to conceptualize objects more easily. The design process in CAD system consists of the following stages. • Geometric modeling • Analysis and optimization • Evaluation • Documentation and drafting.

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Module -2 Design of Snatch block Assembly 1. Classify the wire ropes based on twisting of wires in a strand and state their specific use. [May11,5M] 2. Explain the concept of bends in case of the wire ropes. What is its significance? [Dec-12,5M] Torque Engineering Academy Ram Sir- 8149679293

Wire ropes Wire rope is a type of cable which consists of several strands of metal wire laid (or 'twisted') into a helix. The term cable is often used interchangeably with wire rope.Steel wires for wire ropes are normally made of non-alloy carbon steel with a carbon content of 0.4 to 0.95%. The very high strength of the rope wires enables wire ropes to support large tensile forces and to run over sheaves with relatively small diameters.

Construction of wire ropes i) Wire ropes are made from cold-drawn wires which are first wrapped into strands; the strands are then wrapped in spirals about a central element (called as Core) which is usually hemp or pulp shown in fig.

ii) Wire rope is made with either Regular lay, in which the wires and strands are twisted in opposite directions Fig. (a) and parallel or Lang lay in which the wires and strands are twisted in the same direction Fig.(b). iii) During manufacture of the rope, the hemp core is saturated with a lubricant which serves following principal purposes a) It reduces the wear from the wires rubbing on one another and on sheaves and drums b) It protects the rope from rust and corrosion. c) All wire rope should be kept clean, and lubricated from time to time for best service. iv) The construction is indicated by two numbers, the first giving the number of strands and the second being the number of wires in each strand. For example, a 6x19 wire rope has 6 strands each with 19 wires. v) The size of a wire rope is the diameter of the circle which would barely contain the rope. vi) In general, the greater the number of wires in a strand, the more flexible the rope; conversely, Page | 6

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the less the number of wires, the stiffer the rope. This leads to the conclusion that ropes made of small wires are more suitable to sharp bends.

1] Classify the wire ropes based on twisting of wires in a strand and state their specific use. [May11,5M]

Classification of wire ropes a) According to twistingof wires in strands i) Regular lay :-In Regular lay the wires and strands are twisted in opposite directions. Regular lay rope is more flexible than Lang's lay rope and easily spliced. There are two kinds of direction of lay-right hand and left hand. ii) Parallel lay or Lang lay :- In parallel or Lang lay the wires and strands are twisted in the same direction. The advantage of using Lang's lay is that such a rope as constructed offers a better wearing surface when in use, and therefore, can be reasonably expected to serve for a longer period than Regular lay rope.

b) According to number of wires in rope The construction is indicated by two numbers, the first giving the number of strands and the second being the number of wires in each strand. For example, a 6x19 wire rope has 6 strands each with 19 wires. Ropes 6X19

Properties This is a good rope to withstand abrasion or crushing on the drum.

This is good general purpose rope.

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This type is an extra flexible rope

It is used where flexibility is a major consideration and abrasion is not severe

Materials and Properties of Wire Ropes :i) Most of the wire ropes are made from cold-drawn steel wires of plow steel. Plow steel is a high-strength steel having a carbon content of 0.5 to 0.95 percent ii) plow steels used are in three grades. In descending order of strength, these grades are a) improved plow steel [high strength] Torque Engineering Academy b) plow steel, and [Medium strength] Ram Sir- 8149679293 c) mild plow steel [Low strength] iii) Lower strength grades, called iron and traction steel, are made as elevator rope. iv) phosphor bronze and stainless steel are also used as rope materials.

Factors affecting the Selection of wire ropes Several factors must be considered when attempting to select the most suitable type of wire rope for a job. Consideration of following factors will help attain optimum performance and extend the useful life of wire rope. 1) Resistance to breaking 2) Resistance to bending fatigue 3) Resistance to vibrational fatigue 4) Resistance to abrasion 5) Resistance to crushing

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1. Resistance to breaking Breaking strength of wire rope is very important design criteria. It is the maximum stress which the wire can carry without failure. If the breaking stress exceeds the wire fails by tensile failure. 2. Resistance to bending when a wire rope is bent around sheaves, drums, and rollers it is repeatedly bent back and forth at one point, it will eventually break this phenomenon is called as "metal fatigue" The sharper-or more acute-the bend, the quicker the fatigue factor does its work. Fatigue can be greatly reduced if sheaves and drums have, at the very least, the suggested minimum diameter. As for the rope, there is one governing rule: the greater the number of wires in each strand wires becomes more flexible and the greater the resistance of rope to bending fatigue. Page | 8

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3. Resistance to vibrational fatigue Vibration, from whatever source, sends shock waves through the rope. These waves are a form of energy that must be absorbed at some point. 4. Resistance to abrasion Abrasion is one of the most common destructive conditions affecting wire rope. It usually occurs on drums and sheaves or whenever rope rubs against itself or other material. Abrasion also occurs internally whenever wire rope is loaded or bent and it weakens the rope simply by wearing away metal from inside and outside wires. it should be noted that larger outer wires and lang lay ropes are more abrasion resistant than regular lay ropes. Torque Engineering Academy Ram Sir- 8149679293

5. Resistance to crushing Crushing is the effect of external pressure on a rope, which damages it by distorting the cross-section shape of the rope, its strands or core-or all three. Crushing resistance therefore, is the ability to withstand or resist external forces, and is a term generally used to express comparison between ropes. When a rope is damaged by crushing, the wire, strands and core are prevented from moving and adjusting normally in operation. Q2. Explain the concept of bends in case of the wire ropes. What is its significance? [Dec-12,5M] i)

A bend is defined as the change from the straight state of the rope into the bent state and back again into the straight state

ii)

A bend is defined as the change from the bent state into the straight state and back again into the bent state of the same direction.

iii)

Whenever a rope runs over a sheave the respective rope zone carries out a complete bending cycle (ie a change from the straight into the bent and back again into the straight state); we can count this as two bends.

iv)

Whenever a rope runs onto a drum it carries out half a bending cycle (ie a change from the straight into the bent state). We can count this as one bend.

Significance of Bends in Rope: i. ii.

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The life of rope decreases as the bending cycles increases. The reverse bending decreases the life of rope by great extent. Page | 9

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Module -3 Design of Belt conveyor In the process or manufacturing industry, raw materials and products need to be transported from one manufacturing stage to another. Material handling equipment are designed such that they facilitate easy, cheap, fast and safe loading and unloading with least human interference. Different methods such as fork lifting, use of bucket elevators, conveyors systems, crane, etc. has been identified for lifting or transporting bulk materials or products from one place to another in the manufacturing industries depending on the speed of handling, height of transportation, nature, quantity, size and weight of materials to be transported. Belt conveyor system can be employed for easy handling of materials beyond human capacity in terms of weight and height.

Advantages of belt Conveyor i)

A belt conveyor is easy and cheap to maintain.

ii)

It has high loading and unloading capacity and can transport dense materials economically and at very high efficiency over long distance allowing relative movement of material.

iii)

Belt conveyor can also be used for diverse materials: abrasive, wet, dry, sticky or dirty material.

iv)

Only a single drum needs to be powered by driver pulley and the idler rollers will constantly spin causing the materials to be propelled by the driving roller.

v)

Belt conveyors are designed to load and unload materials from one stage of processing to another in the fastest, smoothest, with minimum spillage without man power involvement.

vi)

A belt conveyor can be horizontal, incline or decline or combination of all.

vii)

With the aid of pneumatic cylinder, the height of the conveyor is adjustable so as to load and unload at different height.

Belt Conveyor design parameters The design of a belt conveyor system takes into account the followings parameters: i. Dimension, capacity and speed of belts ii. Roller diameter iii. Belt power and tension iv. Idler spacing Page | 10

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v. Pulley diameter vi. Motor vii. Type of drive unit viii. Location and arrangement of pulley ix. Control mode x. Intended application xi. Maximum loading capacity

Types of belt Conveyor The conveyors are basically classified into two types a) Troughed belt conveyors- Troughed conveyor is that in which the belt forms a trough on the carrying side while resting/running over idler rolls which are either in set of 5-rolls/3-rolls or 2rools. The troughing angle adopted shall be selected from the following values: 15°, 20°, 25°, 30°, 35°, 40°, 45°. b) Flat belt conveyors- Flat belt conveyor is that in which the belt runs flat on the carrying side, over an idler or a set of idlers.

Differences between troughed belt Conveyor & flat belt conveyor Troughed belt conveyor Flat belt conveyor Has high capacity of conveying materials in Has low capacity of conveying materials in tonnes/hr tonnes/hr Can be operated at high speeds Operated at low speeds Suitable for large lump size suitable for small lump size Can be used with vertical curvatures Cannot be used with vertical curvatures Can be used with or without inclinations Suitable for horizontal use, can be used maximum 6o inclinations. Can be used for declinations Not suitable for declinations

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Module -5 A) Design of Gear Pump Gear Pumps:Gear pumps are also widely used in chemical installations to pump high viscosity fluids. There are two main types of gear pumps. I] External gear pumps which use two external spur gears, and II] internal gear pumps which use an internal spur gears. Gear pumps are positive displacement (or fixed displacement), means they pump a constant amount of fluid for each revolution. Some gear pumps are designed to function as either a motor or a pump.

Theory Of Operation:As the gears rotate they separate on the intake side of the pump, creating a void and suction which is filled by fluid. The fluid is carried by the gears to the discharge side of the pump, where the meshing of the gears displaces the fluid. The mechanical clearances are small in the order of 10 μm. The tight clearances, along with the speed of rotation, effectively prevent the fluid from leaking backwards

Advantages of Gear Pump:i) Easy to operate and maintain - some can operate in two directions ii) Ideal for pumping high viscosity fluids iii) Compact and simple construction iv) Steady, controlled, pulseless flow v) Self-priming

Disadvantages of Gear Pump:-

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i) Can wear noticeably over time, ii) Cannot run dry Page | 12

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iii) Cannot properly handle suspended solids or abrasives iv) High shear placed on fluid

Applications of Gear Pump:i) Petrochemicals: Pure or filled bitumen, pitch, diesel oil, crude oil, lube oil etc. ii) Chemicals: Sodium silicate, acids, plastics, mixed chemicals, iso-cyanates etc. iii) Printing :- Paint and ink. iv) Resins and adhesives. v) Pulp and paper: acid, soap, lye, black liquor, kaolin, lime, latex, sludge etc. vi) Food: Chocolate, cacao butter, fillers, sugar, vegetable fats and oils, molasses, animal food etc.

Materials used for Gear Pump:Pumps are typically designed with a number of different materials. The base materials, which constitute the parts of the pump exposed to the pumped media and the outside environment, are the most important to consider. Fluid characteristics, pressure ratings, and operating environment factors should be considered when selecting these materials. i) Cast iron provides high tensile strength, durability, and abrasion resistance corresponding to high pressure ratings. ii) Plastics are inexpensive and provide extensive resistance to corrosion and chemical attack. iii) Steel and stainless steel alloys provide protection against chemical and rust corrosion and have higher tensile strengths than plastics, corresponding to higher pressure ratings.

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Module -5 B) Design of Centrifugal Pump Principle of Centrifugal pump An increase in the fluid pressure from the pump inlet to its outlet is created when the pump is in operation. This pressure difference drives the fluid through the system or plant. The centrifugal pump creates an increase in pressure by transferring mechanical energy from the motor to the fluid through the rotating impeller. The fluid flows from the inlet to the impeller centre and out along its blades. The centrifugal force hereby increases the fluid velocity and consequently also the kinetic energy is transformed to pressure.

Components of Centrifugal pump

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Net Positive Suction Head (NPSH) NPSH is a term describing conditions related to cavitation, which is undesired and harmful. Cavitation is the creation of vapour bubbles in areas where the pressure locally drops to the fluid vapour pressure. The extent of cavitation depends on how low the pressure is in the pump. Cavitation generally lowers the head and causes noise and vibration. Cavitation first occurs at the point in the pump where the pressure is lowest, which is most often at the blade edge at the impeller inlet, see figure 2.10. The NPSH value is absolute and always positive. NPSH is stated in meter [m] like the head, see figure 2.11. Hence, it is not necessary to take the density of different fluids into account because NPSH is stated in meters [m]. Distinction is made between two different NPSH values: NPSHR and NPSHA. NPSHA stands for NPSH Available and is an expression of how close the fluid in the suction pipe is to vaporization. NPSHA is defined as:

where

NPSHR stands for NPSH Required and is an expression of the lowest NPSH value required for acceptable operating conditions. The absolute pressure can be calculated from a given value of NPSHR and the fluid vapour pressure by inserting NPSHR in the formula (2.16) instead of NPSHA. To determine if a pump can safely be installed in the system, NPSHA and NPSHR should be found for the largest flow and temperature within the operating range. A minimum safety margin of 0.5 m is recommended. Depending on the application, a higher safety level may be required. For example, noise sensitive applications or in high energy pumps like boiler feed pumps, European Association of Pump Manufacturers indicate a safety factor SA of 1.2-2.0 times the NPSH3%. Q What is cavitations in centrifugal pump and how to reduce it? Cavitation is the creation of vapour bubbles in areas where the pressure locally drops to the fluid vapour pressure. The extent of cavitation depends on how low the pressure is in the pump. Cavitation generally lowers the head and causes noise and vibration. Cavitation first occurs at the point in the pump where the pressure is lowest, which is most often at the blade edge at the impeller inlet.

Cavitations in Centrifugal pump The risk of cavitations in systems can be reduced or prevented by: i) Lowering the pump compared to the water level - open systems. ii) Increasing the system pressure - closed systems. Page | 15

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iii) Shortening the suction line to reduce the friction loss. iv) Increasing the suction line’s cross-section area to reduce the fluid velocity and thereby reduce friction. v) Avoiding pressure drops coming from bends and other obstacles in the suction line. vi) Lowering fluid temperature to reduce vapour pressure.

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Module -6 Design of Gear Box for machine tools Gear Box Gearbox often referred as transmission is a unit that uses gears and gear trains to provide speed and torque conversions from a rotating power source to another device. Gearboxes are employed to convert input from a high speed power sources to low speed (Eg. Lift, Cranes and Crushing Machine) or into a many of speeds (Lathe, Milling Machine and Automobiles). Single stage gearbox:- A gearbox that converts a high speed input into a single output it is called a single stage gearbox. It usually has two gears (one pair) and two shafts. Multi-speed gear box :- A gearbox that converts a high speed input into a number of different speed output it is called a multi-speed gear box. Multi speed gear box has more than two gears and shafts. A multi speed gearbox reduces the speed in different stages.

Types of Gear Box 1. Sliding mesh gearbox 2. Constant mesh gearbox 3. Synchromesh gearbox

Gear Box for machine tool i) Machine tools are characterized by their large number of spindle speeds and feeds to cope with the requirements of machining parts of different materials and dimensions using different types of cutting tool materials and geometries. ii) The cutting speed is determined on the bases of the cutting ability of the tool used, surface finish required, and economical considerations. iii) A wide variety of gearboxes utilize sliding gears or friction or jaw coupling. iv) The selection of a particular mechanism depends on the purpose of the machine tool, the frequency of speed change, and the duration of the working movement. v) The advantage of a sliding gear transmission is that it is capable of transmitting higher torque and is small in radial dimensions.

Kinematic Layout of Gear Box Page | 17

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A kinematic layout is a pictorial representation of a gearbox, describing the arrangement of gears. It provides information like number of stages, number of shafts used, and number of gears on each shaft and number of gear pairs and its arrangement. The following diagram is the kinematic arrangement of a 3 stage 12 speed gear box.

Selection of Gear ratio The Gear ratio is the ratio with which the speed varies from one gear pair to another. In a multi stage gearbox the product of the gear ratios of each stage gives the final gear ratio. Mechanical gearbox has a highest, a lowest and intermediate gear ratios. The highest is determined from the condition for maximum tractive effort, i.e. maximum load and grade-ability specified or lowest speed required. On the other hand, the lowest ratio is determined knowing the maximum required vehicle speed. The intermediate ratios are classically chosen according to different types of mathematical progressions The following mathematical progressions are commonly used for determining the intermediate gear ratios of the automobile transmission: 1. Arithmetic Progression 2. Harmonic Progression 3. Geometric progressions,

Q. What is geometric progression ratio and what is its significance in gearbox design?

Geometric Progression ratio ( i) Geometric progression, also known as a geometric sequence, is a sequence of numbers where each term after the first is found by multiplying the previous one by a fixed number called as progression ratio or step ratio in gear box design. ii) Geometric progression is given by

(

)

where,

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iii) In gearbox design a set of preferred step ratio or preferred numbers is used to obtain the series of output speed of gearbox. iv) The preferred step ratio is mentioned as basic series named as R5, R10, R20, R40 and R80. v) Each basic series has a specific step ratio. The R in basic series is added to honour the Engineer Charles Renard, who introduced the usage of preferred numbers.

Significance of Geometric Progression ratio ( i) In order to get a series of output speeds from a gearbox, geometric progression is used. ii) By using geometric progression the speed is reduced uniformly in different stages. iii) Maximum speed reduction in any stage can be expressed in terms of geometric progression ()

Procedure of Gearbox Design 1. Determine the maximum and minimum speeds of the output shaft. Calculate the number of steps or speed reduction stages for this range. This depends on the application as well as space optimization. Higher reduction stages require more space because of more number of gears and shafts requirements. 2. Select the type of speed reducer or gear box based on the power transmission requirements, gear ratio, positions of axis, space available for speed reducer. Also make sure that for low gear ratio requires single speed reduction. Select worm gears for silent operation and bevel gears for intersecting axis. 3. Determine the progression ratio which is ratio maximum speed and minimum speed of output shaft of Gear Box. The nearest progression ratio should be a standard one and is taken either from R 20 or R 40 series. 4. Draw the structural diagram and kinematic arrangement indicating various arrangement possibilities during speed reduction or increment. 5. Select materials for gears so that gear should sustain the operating conditions and operating load. Normally cast iron is chosen for housing and cast steel or other alloy can be selected as per the load requirements. 6. Determine the centre distance between the driven and driver shaft based on the surface compressive stress. Page | 19

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Q what are structure diagrams and what are conditions of optimum structure diagram

Structural Diagrams i) Let us assume 'z' speed has to be obtained from a single input, it is not possible to mesh 'z' pair of gears in two shafts to get the required speed. ii) The maximum number of speed that can be obtained from two shafts is three. Hence its necessary to use intermediate shafts between the input shaft and output shaft. iii) The structural formula helps to arrive the number of stages and required gears to obtain the desired speeds. iv) The structural diagrams are drawn from the structural formulae which is a graphical tool used to find the range ratio of transmission groups. v) The structural diagram gives information about the number of shafts and the number of gears on each shaft, the order of changing transmissions in individual groups to get the desired spindle speed and the transmission range and characteristics of each group. vi) The following fig shows the structure diagram of a formula 2(1)3(4)2(2) of 3 stage 12 speed gear box.

Optimum Structural Diagrams For best structure diagram following guidelines are important. 1)The number of gears on the last shaft (spindle) should be minimum possible. 2)The transmission ratio between spindle and the shaft preceding it should be the maximum possible i.e. speed reduction should be the maximum possible.

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3)The structure diagram should be narrow towards the starting point (on input shaft) i.e. parabolic in nature. 4) The structure diagram must follow the condition of maximum transmission ratio i.e. 5) The structure diagram must follow the condition of minimum shaft size i.e.

Ray Diagrams i) The structural diagram only gives the range ratio whereas with the help of ray diagram the transmission ratio of all transmissions and the rpm values of gear box shafts can be determined. ii) It is necessary to plot the speed chart to determine the transmission ratio. iii) The line joining points of adjacent shafts in a speed chart gives the transmission ratios. iv) Following conclusions can be drawn from ray diagram. a) If the line is horizontal, it means the transmission ratio i=1, i.e. no speed change. b) If the line is inclined upward, it means the transmission ratio i>1, i.e., speed increase. c) If the line is inclined downward, it means the transmission ratio i