Gear Terminology PDF

Pitch circle - is an imaginary circle which by pure Tooth thickness - is the width of the tooth rolling action, would give the same motion as the measured along the pitch circle. actual gear Tooth space - is the width of space between the...

Pitch circle - is an imaginary circle which by pure Tooth thickness - is the width of the tooth rolling action, would give the same motion as the measured along the pitch circle. actual gear Tooth space - is the width of space between the two adjacent teeth measured along the pitch circle. Pitch circle diameter or pitch diameter. - is the. diameter of the pitch circle. The size of the gear is Backlash - is the difference between the tooth usually specified by the pitch circle diameter. space and the tooth thickness, as measured on the pitch circle. Pitch point - is a common point of contact between two pitch circles. Face of the tooth - is the surface of the tooth above the pitch surface. Pressure angle or angle of obliquity - is the angle between the common normal to two gear Top land - is the surface of the top of the tooth. teeth at the point of contact and the common tangent at the pitch point. It is usually denoted by ϕ Flank of the tooth - is the surface of the tooth below the pitch surface. Addendum - is the radial distance of a tooth from the pitch circle to the top of Face width - is the width of the gear tooth the tooth. measured parallel to its axis. Dedendum - is the radial distance of a tooth from Profile - is the curve formed by the face and flank the pitch circle to the bottom of the tooth. of the tooth. Filet radius -is the radius that connects the root Addendum circle - is the circle drawn through the circle to the profile of the top of the teeth and is tooth concentric with the pitch circle. Dedendum circle or Root circle- is the circle Path of contact - is the path traced by the point of drawn through the bottom of the contact of two teeth from the beginning to the end teeth. of engagement. Circular pitch - is the distance measured on the circumference of the pitch circle from a point of one Helix angle, α – is a constant angle made by the tooth to the corresponding point on the next tooth. helices with the axis of rotation Diametral pitch - is the ratio of number of teeth to the pitch circle diameter. Transverse Circular pitch (or simply circular. pitch), Pc - is the circular pitch in the plane of Module - is the ratio of the pitch circle diameter to rotation or the diametral plane the number of teeth Normal Circular pitch (or simply normal pitch) - is Clearance - is the radial distance which is the the distance between similar faces of adjacent difference between dedendum teeth along a helix on the pitch cylinders normal to and addendum the teeth. Whole depth or Total Depth - is the radial Belts are used to transmit power from one shaft to distance between the addendum and the another by means of pulleys which rotate at the dedendum circle of a gear. It is equal to the sum of same speed or at different speeds. the addendum and dedendum. When the frictional grip between the belts and the Working depth - is radial distance from the pulleys becomes insufficient, this may cause some addendum circle to the clearance circle forward motion of the driver without carrying the belt with it. (Belt Slip) Flat belt is limited for the transmission of moderate Sliding contact bearings (plain bearings) - the power from one pulley to another when the two sliding takes place along the surfaces of contact pulleys are not more than 8 meters apart. between the moving element and the fixed element. Rolling contact bearings - the steel balls or The rope drives are widely used where a large rollers, are interposed between the moving and amount of power is to be transmitted, from one fixed elements. pulley to another, over a considerable distance. Compressive strength. The bearing material The rope drives use the following two types of should have high compressive strength to ropes: withstand this maximum pressure so as to prevent 1. Fiber ropes extrusion or other permanent deformation of the 2. Wire ropes bearing. Pitch of chain: the distance between the hinge Fatigue strength. The bearing material should center of a link and the corresponding hinge center have sufficient fatigue strength so that it can of the adjacent link withstand repeated loads without developing surface fatigue cracks. Brake is a friction device used to regulate the motion of bodies: slowing them down, holding their Comformability - is the ability of the bearing speed constant or holding them at rest. material to accommodate shaft deflections and bearing inaccuracies by plastic deformation (or Clutch is a friction device used to connect shafts: creep) without excessive wear and heating. speeding up the driven bodies to the same angular velocity as the driving shaft. Embeddability - is the ability of bearing material to Two types of clutches: accommodate (or embed) small particles of dust, - Positive Clutches grit etc., without scoring the material of the journal. - Friction Clutches Bondability. Many high capacity bearings are Major Types of Brakes made by bonding one or more thin layers of a 1. Hydraulic brakes e.g. pumps or hydrodynamic bearing material to a high strength steel shell. brake and fluid agitator, 2. Electric brakes e.g. generators and eddy Corrosion resistance. The bearing material current brakes, should not corrode away under the action of 3. Mechanical brakes. : Radial brakes & Axial lubricating oil. brakes Thermal conductivity. The bearing material A bearing is a machine element which supports, should be of high thermal conductivity so as to guides or controls a moving machine element. It is permit the rapid removal of the heat generated by a mechanical components used to reduce friction friction. and enable smooth motion between two moving parts Thermal expansion. The bearing material should be of low coefficient of thermal expansion, so that Classifications of Bearings: when the bearing operates over a wide range of Radial bearings - the load acts perpendicular to temperature, there is no change in the clearance. the direction of motion of the moving element Thrust bearings - the load acts along the axis of rotation Oiliness. It is a joint property of the lubricant and Which is the most commonly recommended the bearing surfaces in contact. It is a measure of material for medium service for wire rope sheaves? the lubricating qualities under boundary conditions Ans. Cast Iron where base metal to metal is prevented only by absorbed film. Heating and slow cooling of a solid metal to alter physical and mechanical properties, producing Viscosity index. The term viscosity index is used particular microstructure,removing internal stresses to denote the degree of variation of viscosity with and removing gasses. Annealing temperature. The ___ is one of the rigid members / bodies joined Flash point. It is the lowest temperature at which together to form a kinematic chain. (LINK) an oil gives off sufficient vapor to support a momentary flash without actually setting fire to the A kind of braking system such that if the band oil when a flame is brought within 6 mm at the wraps partly around the brake drum, the braking surface of the oil. action is obtained by pulling the band tight into the wheel. (Band) Fire point. It is the temperature at which an oil gives off sufficient vapor to burn it continuously. What friction devices that are used to connect when ignited. shafts? (Clutches) Common Materials used for Sliding Contact Bearings - Babbit metal (Tin based & Lead Based) - Bronze (Copper 80% ; Tin 10% ; Lead 9% ; Phosphorus 1%) - Brass (88% copper and 2%zinc 10% Tin) - Cast Iron - Silver - Non-metallic bearings (plastics and rubber) Kinking: It is the term used to describe the occurrence of twist or curl in rope and chain caused by its doubling or bending upon itself. These chains are used for elevating and conveying the materials continuously at a speed up to 2 m/s. (conveyor chains) In a chain drive system, the speed of the driven shaft will decrease as the _____ increases. (sprocket ratio) Compared to a v-belt drive, a chain drive ___ is (more efficient) A chain can be described as a series of links joined by a ______ (Pin)