View Factor Orientation (or View factor or shape factor) plays an important role in radiation heat transfer. View factor is defined as, "fraction of radiation leaving surface 'i' and strike 'j' ". Summation Rule (View Factor) If there is are similar surfaces 'i' and 'j' , then: Blackbody Radiation Exchange Radiation Exchange between Opaque, Diffuse, Gray surfaces in an Enclosure 1. Opaque 2. Surfaces 3. Two surface enclosure Radiation Shield It is used to protect surfaces from radiation act like a reflective surface. References: Material from Class Lectures + Book named Fundamentals of Heat and Mass Transfer by Theodore L. Bergman + My knowledge. Photoshoped pics are developed. Some pics and GIF from Google. Videos from YouTube ( Engineering Sights ).
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Clutch
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Clutch
It is defined as, "a machine element component used to connect driver shaft to a driven shaft".
It will stop driven shaft without altering driven shaft using lever.
Driver ↔ anything which produces power is called Primover or Driver.
Driven Machinery ↔ anything which consume this power is called Load or Driven Machinery.
Design Considerations
Design consideration factors are described ahead:
Coefficient of Friction ↔ should be high enough to hold load and minimum amount of axial force.
Moment of Inertia ↔ clutch moving components should have less weight to minimize inertia load at high speed.
Heat Generated at Contact Surfaces ↔ heat should dissipate rapidly.
Wearing of surfaces ↔ provision for taking up the wear of contact.
Cover Projecting Parts ↔ guard projecting parts for the provision of easy repair.
Material Requirement
The actual friction surface is friction lining which gets in severe rubbing operation. Qualities of material of friction surfaces are:
It should have high coefficient of friction.
It should have high resistance (prowear).
It should withstand a high compression load.
It should be chemically inert which means oil or air has no effect on them.
It should have high heat conductivity.
Have excellent compatibility with cast iron facing.
Types of Clutches
There are two types of Clutches which are discussed below
1. Positive Type Clutch
It is used when there is no slip between driver and driven shaft (means both have same speed under any condition).
Power is transmitted using interlock of jaws (or teeth).
Used where synchronous power transmission required.
Engagement is not possible at high speed (limited to 600 rpm).
There are two types of Positive Type Clutch:
Square Jaw Clutch ↔ It transmitted power in both direction (CW or CCW).
Spiral Jaw Clutch ↔ Transmit power in one direction (left or right handed).
2. Friction Type Clutch
Power is transmitted due to friction between surfaces (clutch disk and plane surfaces).
The driver shaft get contact with other shaft by means of compression springs.
It consist of inner curve which is attached to the driven shaft and follow cone.
Male cone is movable and can axially move over the driven member.
Inner side of female cone (fixed) fits outer side of male cone.
Slope of cone is small which gives high normal force (angle 8-15 degrees).
Fork lever is used to dis-engage clutch.
b. Centrifugal Clutch
It is used to disengage driven shaft at a particular speed.
It is used engine which has trouble in starting under load.
It has number of shoes or friction pads arranged radically in symmetric position inside a rim.
Working of Centrifugal Clutch
Spring produce inward force to kept in original position.
As speed increase ↔ centrifugal force increases.
If centrifugal force = spring force ↔ shoes start floating.
If spring force < centrifugal force ↔ shoes moves outward and touch the surface of drum ↔ torque is transmitted.
As load increases, speed decreases ↔ shoes come to original position.
c. Plate or Disc Clutch
It consist of two flanges. One of them is lined with high friction material and rigidly keyed with driven shaft while the other is free to move along driven shaft due to splined connection.
Compression springs used to push these flanges against each other.
Torque is transmitted by friction.
Parts of Plate or Disc Clutch
Clutch Plate ↔ Main component. Single thin metallic disc having both sides frictional surfaces (friction lining) . It is assembled between flywheel and flange.
Pressure Plate ↔ to maintain proper contact between flywheel and clutch plate by means of spring.
Springs ↔ used to move clutch plate towards the flywheel to ensure proper contact between flywheel and clutch plate.
Flywheel ↔ connected to engine output shaft and used to transmit power.
Working of Disc Clutch
Single plate is mounted on spline clutch shafts. Flywheel is mounted on engine crankshaft. When paddle is pressed clutch shaft moves in, spring loosen shaft disengaged.
Projection: The term Projection is defined as: Presentation of an image or an object on a surface. The principles used to graphically represent 3-D objects and structures on 2-D media and it based on two variables: Line of Sight. Plane of Projection. Line of Sight & Plane of Projection: Line of sight is divided into 2 types: Parallel Projection Converging Projection & A plane of projection is an imaginary flat plane upon which the image created by the lines of sight is projected. Orthographic Projection: When the projectors are parallel to each other and perpendicular to the plane of projection. The lines pf sight of the observer create a view on the screen. The screen is referred to as the Plane of Projection (POP). The lines of sight are called Projection lines or projectors. Rules of Orthographic Projection: Edges that are parallel to a plane of projection appear as lines. Edges that are incl...
Welded Joints A permanent joint which is obtained by the friction of edges of two parts to be joined, with or without the application of pressure and a filler material. Used in fabrication as an alternative method for casting and forging . Used as a repair medium . If filler material is used ↠ Strength of Joint > Base metal strength . If filler not used ↠ Joint strength < Base metal strength . Grinding Finish ↠ Welding at top and bottom off the plate. Machining Finish ↠ Welding at bottom surface after welding machining operation. Want to learn more about welded joint, click here . Designing of Butt Joint Design of Lap Joint or Fillet Joint Lap or Fillet joint is " formed by the overlapping of plates and then welding the edges of plates " . There are two types of fillet joints: Single and Double Transverse Fillet Joints ↣ are designed for tensile loading. Parallel Fillet Joints ↣ are designe...
Gear Forming by Machining Formation of gear through machining consists of following methods: Form Milling by Disc Cutter Form Milling by End Mill Cutter Shaper, Planner and Slotter Broaching 1. Form Milling by Disc Cutter It is defined as, " Tooth is cut one by one by plunging the rotating cutter into the blank " . Each gear needs a separate cutter. 8 - 10 standard cutters are available for producing 12 - 120 teeth gears. Used for big spur gears of large pitch. 2. Form Milling by End Mill Cutter It includes the cutting of tooth at a time and then indexed for the next tooth space for cutting. For a small volume production of low precision gears. Set of 10 cutters ↠ 12 - 120 teeth gears . Used for teeth of large gears/module. To reduce cost, same cutter is often used for multiple sized gears resulting in profile errors . Characteristics: Use of Hardened stainless steels (HSS) form milling cutters. Use of Ordinary milling machines. Low production rate (need of indexing...
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