Tech@Edu

Design of Piston A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms.  It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod. In a pump, the function is reversed and force is transferred from the crankshaft to the piston for the purpose of compressing or ejecting the fluid in the cylinder. In some engines, the piston also acts as a valve by covering and uncovering ports in the cylinder. Function of Piston- The Piston Performs The Following Functions-  1. Receive the thrust produced by the combustion of the gas in the cylinder and transmit it to the connecting rod.  2. Piston reciprocates in the cylinder as a gas-tight plug generating suction, compression, expansion and exhaust strokes. 

Lewis Equation For Spur Gear The beam strength of gear teeth is determined from an equation (known as Lewis equation).   In 1892, Wilfred Lewis investigated the strength of gear teeth. He derived an equation which is now extensively used by industry in determining the size and proportions of the gear. In the Lewis equation certain assumptions were made- 1. Gear was considered as a cantilever beam will load applied at the lip and is uniformly distributed over the entire face width. 2. Radial force effects are neglected. 3. Tooth sliding friction, and stress concentration due to abrupt changes in area were also neglected. 4.  Tooth shape is considered a parabolic curve. 5. Stress concentration in the tooth fillet is negligible. Consider each tooth as a cantilever beam loaded by a normal load (W N ) as shown in Fig. It is resolved into two components i.e. tangential component (W T ) and radial component (W R ) acting perpendicular and parallel to the centre

Involute Tooth Vs Cycloid Tooth Gears Involute Tooth Profile  1. Being the angle made by the common tangent of base circles with a common tangent to pitch circles at pitch point, the pressure angle remains constant throughout the engagement. This ensures smooth running of the gears.  2.  Involute tooth profile consists of a single (involute) curve and the track cutter used for regenerating the profile has straight teeth. The rack cutter is cheaper and the method of manufacture is simpler. This leads to reduction in the cost of manufacture of involute teeth.  3.  Perhaps the most desirable feature of involute teeth is that a small variation in Centre distance does not change the velocity ratio. Thus distance between shafts need not necessarily be maintained exact as per design specifications. This gives great flexibility during assembly and larger tolerances may be permitted.  4.  Since involute curve doesn’t exist within base circle, interference is always possib

Hydrodynamic Journal Bearing The Hydrodynamic lubricant bearing is also called Thick film lubricant Bearing. The thick film bearings are those in which the working surfaces are completely separated from each other by the lubricant.  History of lubrication theory O. Reynolds published famous equation of thin fluid film flow in the narrow gap between two solids ( Reynolds 1886 ). This equation carries his name and forms a foundation of the lubrication theory.  Hydrodynamic Journal Bearing- A little consideration will show that when the bearing is supplied with sufficient lubricant, a pressure is build up in the clearance space when the journal is rotating about an axis that is eccentric with the bearing axis. The load can be supported by this fluid pressure without any actual contact between the journal and bearing. The load carrying ability of a hydrodynamic bearing arises simply because a viscous fluid resists being pushed around. Under the proper conditions, this res

Bevel Gear Vs Worm Gear Bevel Gear Worm Gear Bevel Gear having rolling friction. Worm Gears having Sliding friction. The efficiency of bevel gear is high. The efficiency of worm gears is low. Efficiency of bevel gears are constant irrespective of ratio and input speed. Efficiency of worm depends on ratio and input speed There is no self-locking in bevel. Worm becomes self-lock when efficiency reduces below 50%. It’s easy to rotate input shaft in bevel gear with rotating output shaft. It’s not easy to rotate input shaft in worm gears with rotating output shaft because depend on ratio. In bevel gear Input and output shafts are perpendicular and interesting. In worm gears Input and output shafts are perpendicular and non-intersecting. Bevel gear ratio not depended on a terminology of number of starts in bevel shafts. Worm gears ratio depended on a ter