Types of small engines
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Transcript of Types of small engines
TYPES OF SMALL ENGINES
• Two stoke- two cycle engine
• Four stroke- four cycle engine
• Stroke= movement of the piston within the cylinder
TWO STROKE ENGINES
• Two stroke advantages• Don’t have valves• Quick power- fire every revolution• Lighter/cheaper• All orientations- no issue with oil delivery
• Two stroke disadvantages• No lubrication system- shorter life• Expensive oil/less efficient fuel
FOUR STROKE ENGINES
• Four stroke advantages• More power• Longer lasting• More efficient with fuel/oil
• Four stroke disadvantages• Complicated• Heavy• More expensive• Limited orientation
BASIC CYCLES OF A 4 STROKE
• Intake- piston goes down, valves open • Goal: Air/fuel mixture enters cylinder
• Compression- piston heads up, valves close• Goal: Creates pressure
• Power- piston pushed down, valves closed• Goal: Spark ignites gases
• Exhaust- piston moves up, valves open• Goal: Exhausted mixture pushed out of engine
• Repeat!
IGNITION SYSTEM
PURPOSE
• Produce a spark within the spark plug • Ignites air/fuel mixture
• Timing is essential
ELECTRON THEORY
• Electrons travel in orbits around the center of an atom
• Electrons carry a negative charge• Protons carry a positive charge• Neutrons carry no charge
• Conductors allow electrons to move from one atom to another easily.
• Electrons travel when a circuit is complete & there is a difference in charge
PRODUCING ELECTRICITY
• Mechanically- generator run by water• Chemically- batteries• Statically- lightning
MEASURING ELECTRICITY
• Amperes- rate of electron flow• Volts- force that causes electrons to flow• Ohm’s- resistance to electron flow
MAGNETS & ELECTRICITY
Magnets have north & south polesOpposite attract
Magneto system- Electricity can be made through magnets
MAGNETO SYSTEM
• Armature the armature is shaped like a capital "U". The two ends of the U point toward the flywheel.• A primary coil of perhaps 200 turns of thick wire
wrapped around one leg of the U• A secondary coil of perhaps 20,000 turns of very
thin wire wrapped around the primary coil• Breaker points• A pair of strong permanent magnets embedded in
the engine's flywheel.
STEPS IN MAGNETO SYSTEM
• 1. Magnets fly past the U-shaped armature, • Creates a magnetic field• Small amount of current in coils
• A breaker point opens. This switch breaks the flow of current through the primary coil and causes a voltage spike (of perhaps 200 volts). The secondary coil, having 100 times more turns than the primary coil, amplifies this voltage to approximately 20,000 volts
• Sparks instant that breaker point opens
SPARK PLUG
• Center electrode- runs through middle• Carries high voltage current to the spark gap.• Jumps gap• Creates spark• Ignites air/fuel mixture