Tech@Edu

Straight Bevel Gear Vs Spiral Bevel Gear Straight Bevel Gear Spiral Bevel Gear Teeth of this type of gear are straight and are cut along the axis on a cone. Here the teeth are spiral and are cut in the form of spiral curve on the pitch cone. Two teeth of the mating gears come in sudden contact. The contact is always a line of length equals to face width of teeth. Teeth of two mating gears gradually come in contact. Engagement starts with a point and gradually becomes a line. Due to sudden contact, teeth are also subjected to impact or shock loading. Here teeth are subjected to gradual loading. Sudden contact also causes noise. Its operation is quite. Shock loading induces vibration and thus its operation is not smooth. Due to gradual building up of load, it produces less vibration and thus the operation is smooth. Designing and manufacturing of straight teeth bevel gear are easier and thus these are cheaper. Complicated design and manufacturing leads to higher cost for thi

Parallel Helical Gear Vs Crossed Helical Gear Parallel Helical Gear Crossed Helical Gear Parallel helical gears can transmit motion and power between parallel shafts only. Crossed helical gears can transmit motion and power between perpendicular but not-intersecting shafts. Two mating gears must be mounted on two parallel shafts. Two mating gears are mounted on two perpendicular but non-intersecting shafts. Two mating gears should have same helix angle but opposite hand of helix. Two mating gears may have different helix angles. They may have either same or opposite hand of helix. Engagement between two teeth starts with a point contact but gradually becomes a line contact. Two meshing teeth always have point contact. Power transmission capacity of parallel helical gear is higher due to broader contact. Crossed helical gear has lower power transmission capacity due to point contact. It has wide area of application ranging from small equipment to large industrial field in

Helical Gear Vs Herringbone Gear Vs Double Helical Gear Helical Gear Herringbone Gear Teeth of the helical gear are cut in the form of a helix (either left hand or right hand helix) on the cylindrical gear blank. Identical teeth are cut in two halves of the gear blank maintaining same module, number of teeth and helix angle but opposite hand of helix. A pair of mating helical gears produces significant radial thrust force. Thrust force produces by each half of the gear is equal and opposite in direction; and thus they cancel out each other. Radial thrust force limits the helix angle to a maximum of about 25°. Absence of thrust force gives the provision to use higher helix angle (up to about 45°). Bearings that can handle both axial load and thrust load are required to use with helical gear. Since thrust force does not exist, so bearings that can handle heavy radial load can be used with herringbone gear. Power transmission capability of helical gear is comparatively small.

Spur Gear Vs Helical Gear Spur Gear Helical Gear In spur gear, the teeth are parallel to the axis of the gear. In helical gear, teeth are inclined at an angle (called helix angle) with the gear axis. Spur gear imposes only radial load on bearings. Helical gear imposes radial load and axial thrust load on bearings. Radial bearings that can handle radial load only can be employed here. Bearings that can handle both radial and axial load must be employed here. Spur gear can be used for parallel shafts only. Helical gears can be used for parallel shafts or crossed shafts. At the time of engagement, entire face of the tooth comes in contact with the mating tooth. Here engagement initiates with a point on tooth face and gradually extends across the tooth. Mating teeth are subjected to impact loading. Load on the mating teeth builds up gradually. Sudden application of load increases vibration, especially in high speed condition. Gradual loading on teeth minimizes vibration. Spur

Gear Drives “Gears are defined as toothed wheels, that transmit power and motion from one shaft to another due to the successive engagement of teeth.”  Or  “A gear or cogwheel is a rotating machine part having cut teeth or, in the case of a cogwheel, inserted teeth (called cogs), which mesh with another toothed part to transmit torque.” Advantages of Gear Drive   1. It is a positive drive and the velocity ratio remains constant.  2. The drive is compact, since the centre distance between the shafts is relatively small.  3. It can transmit more power.  4. The efficiency of gear drive is very high (99% in case of spur gears)  5. In the gearbox, shifting of gears is possible. Hence, velocity ratio can be changed over a wide range. 6. Gear drive can be used where precise timing is desired. 7. Gear drive can drive much heavier loads than others drives due to their unlimited sizes. 8. They are capable of driving loads subjected to shock speeds upto 20 m/s. 9

Sliding Contact Bearing Vs Rolling Contact Bearing Sliding Contact Bearing 1. High Starting friction due to metal to metal contact. 2. Difficult to achieve sub-micon positioning. 3. The life of sliding contact bearing is more. 4. Difficult to estimate rigidity. 5. Unsuitable for extremely low speed. 6. Good in taking shock load. 7. Required Continuous lubrication supply. 8. Suitable for high speed applications. 9. The relative motion between the contact surfaces is of sliding types. 10. Low running friction due to oil film separation the journal & bearing surfaces. 11. Suitable for high loads. 12. It take load only in one direction either radial or axial. 13. Sliding contact bearing have small radial dimension & large axial dimension for same load carrying capacity. 14. Sliding contact bearing required auxiliary equipments like pump, filter, sump, pipe lines etc.  15. In sliding contact bearing as there is no metal to metal contact, the ope

Bearing "Bearing is a mechanical element which locates two machine part relative to each other & permit a relative motion between them."  It permits a relative motion between the contact surfaces of the members, while carrying the load. A little consideration will show that due to the relative motion between the contact surfaces, a certain amount of power is wasted in overcoming frictional resistance and if the rubbing surfaces are in direct contact, there will be rapid wear. In order to reduce frictional resistance and wear and in some cases to carry away the heat generated, a layer of fluid (known as lubricant) may be provided. The lubricant used to separate the journal and bearing is usually a mineral oil refined from petroleum, but vegetable oils, silicon oils, greases etc., may be used.  Parts of Bearing The standard essential components of a  ball bearing   are defined as follows: 1. Inner Ring The Inner Ring is the smaller of the two bearing r