>> Mechanical Engineering
As per the requirement of the assignment we have to make a survey from the market about the competitive designs of small engine and about the current standards of designing of small engine and also the cost for making it. After completing the survey we have to design a small engine for a lawn mower.
This design mainly will be focused on the following key factors like-
• The design will be for a 4-stroke engine.
• Type of joint forces acting on the engine.
• Type of shaking / vibration forces acting on the engine components.
• All the details about the bore, crank length, stroke, and the connecting rod.
Some description about the engine: -
- Internal combustion engine (IC engine) is a mechanical device that use controlled explosion of air fuel (petrol, diesel, gasoline etc.) mixtures in order to produce power for the movement of the components and hence the movement of wheels.
- In a reciprocating engine (to and fro type engine) air fuel mixture explodes and forces the connecting piston to move up and down in a cylinder.
- The motion of piston inside the cylinder is transmitted to the crankshaft which ultimately transmits the same to the wheels via connecting rod.
- Firing order of a engine is the sequence of the strokes in function.
2. Calculation of joint forces with the variation of crank angle
1. Calculation of the joint forces at the joint of connecting rod and the crank shaft: -
Fc = force on the connecting rod
As by equating the horizontal components of the forces:
Fc x cos β = F
As per the question, in intake process. Lie between = 0-180degree
By this we have the value of Fc is (F to -F)
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The requirement of the assignment is to design a small engine for a lawn mower and the engine may of any type therefore I am choosing a 4-stroke internal combustion engine.
This assignment needs to be focused on the design of a small engine for a lawn mower after surveying from the market as this engine will be a reciprocating engine (to and fro type engine). This engine will be consisting of basically its working strokes and power system of the engine which will needed to be considered during its design.
In a suction stroke the piston inside the cylinder moves from the top dead centre to bottom dead centre and creates the suction inside the cylinder, due to the suction it sucks the air from the environment and taken in the cylinder. The air inside the cylinder is at very low pressure.