Starting and Charging systems

Give an explanation of the operation of the following starters:

A starter motor is a high torque electric motor that is tasked with cranking over the engine to start up the process of combustion and running of the engine. Prior to starter motors engines were hand cranked to start which was an arduous process. They are feed power from the battery and different types have emerged over the years.

Inertia:

An inertia starter motor refers to the way that the drive pinion is engaged. The drive pinion slides freely up and down on a worm gear on the spline, when the motor is engaged the rotation of the armature drives the pinion up the spline and engages the pinion into the teeth on the ring of the flywheel, which in turn cranks the engine. when the key is released the momentum of the flywheel drives the pinion the opposite direction and the pinion goes back down the spline into the neutral position. Advantages are the inertia drives simplicity and ease of function, the disadvantages are that the drive pinion can wear and possibly damage the ring gear on the flywheel as the pinion is driven into the flywheel at high speed, it is also noisy.

 

 Pre engaged starter motor:

A pre engaged starter motor is an improvement on the inertia starer motor. A solenoid attached by a lever to the drive pinion acts as the engagement mechanism. When the key is turned the solenoid forces the drive pinion to mesh with the gear on the flywheel, when it is meshed the motors starts cranking the engine over. When the engine has started the solenoid retracts the drive pinion. This starter removes the problem of damage by pre engaging the pinion, with slighly more complexity added by the solenoid.

 

Reduction gear starter:

A reduction gear starter was developed to counter the increasing size and weight of starter motors, larger engines needed larger and heavier starters so to counter this a normal sized high torque starter with a pre engaged mechanism (or inertia gear on some types) was housed with a set of gears this meant that a small motor could still start a large engine by multiplying torque through a gearbox. This is more complex than other types but makes up for it in weight savings.

A type of reduction gear starter

This one has a planetary gear system with a inertia drive

Alternators

An alternator is the charging mechanism on a engine. Drive is transmitted by a belt to create power in the alternator. This is done in the opposite way as a starter motor the central rotor of magnets is driven inside a stationary iron core with magnets called a stator and power is created by  cutting the magnetic field lines on the magnets. the alternator charges the battery to run all the cars electrical devices and it creates the power for the spark of the spark plugs. An automotive alternator uses rotor winding this means the voltage delivered can be controlled and voltage peaks are evened out to stop damage to electrical components.

Generator

A generator or dynamo is an an older type of charging system for engines. it operates on much the same principle as an alternator, except it has a stationary magnet setup with a rotating commutator. The commutator rotates and intersects the field lines of the magnets. this creates less power than a alternator. This system was used widely on early cars and outboard motors for much longer. In an outboard setup there are rotating magnets on the inside of the flywheel which rotate around a stator of windings.

A diagram of a magneto system on a Johnson outboard motor

A simple diagram of a generators operation

Marine business practice

Warranties and guarantees:

A warranty is an agreement between buyer and seller that  that specific details and conditions of their transaction are true and that the word of the party can be trusted. A guarantee is a formal agreement usually a document that ensure the quality of a product or service. In the case of a marine business specifically a marine repair business a warranty could be a guarantee to the service being provided to the boat, or a guarantee to the quality of parts being installed into a boat.

Quotations and estimates

A Quotation is an agreement between two party's on the price of a item or service. A quotation can be taken as a formal agreement and if one party does not honour the quote they could be liable to legal charges. An estimation is a rough estimate of the price required for a item or service. Unexpected difficulty's can mean the original estimate is too low and a new estimate will be needed. In a Marine repair business a quotation or estimate could be changed severely because of unforeseen problems or malfunctions.

Charge out rates

A charge out rate is the amount of money required when charging for a service for example an automotive or marine workshop. A business owner will calculate a charge out rate for their business before it starts. When a charge out rate is being calculated all costs of the business are taken into account including overheads like rent and machinery costs. Other costs involved are labour costs and profit margins. Charge out rates should not be too low as to make the business unprofitable, and not too high as to make it unattractive to customers.

Courtesy service

A courtesy service is a service provided by a business which enhances the experience for the customer and entices them to come to that business again, this can include small things like a cup of coffee on entry or getting something for free with a purchase to more expensive things like providing a courtesy car to a customer who's car is being worked at the mechanics. These all help to create a customer base and customer loyalty (customers that come back to your business)

Cultural issues

The world we are in is far more culturally diverse than it used to be with many different cultures and ethnicity's living and working together. Cultural issues have to catered for in the modern working place. Different cultures have different customs in business and religion and so on, for a business to be seen a diverse and therefore welcoming to all types of people then cultural protocols must be in place. If cultures are respected then employees and staff will integrate better into the company.

Ignition systems

The ignition system is one of the most important systems on the internal combustion engine. The purpose of the system is to ignite the fuel-air mixture in the combustion chamber. There are several components in the system which are used to create spark and regulate timing. Diesel systems do not have an electronic ignition system as pressure is used to ignite the fuel, however glow plugs are used to preheat the combustion chamber. Virtually all petrol engines have spark ignition.

What two substances are mixed together to form electrolyte a battery?

An automotive battery has lead plates and an electrolyte solution which is made up of Sulfuric acid and distilled water. This cause a chemical reaction and releases electrons and produce electricity.

What three elements are required to make a petrol engine run effectively?

For a petrol engine to run effectively and efficiently it requires: Spark, Air, and Fuel. This include the quality and delivery of these elements. The spark needs to be powerful to overcome the compression in the cylinder and ignite the fuel. it also has to be delivered at precisely the right moment. The flow of air into the engine has to be consistent and the amount of air has to sufficient otherwise the engine will not run. Fuel must also be delivered consistently and in the right amounts. to little and the engine will not run or will run poorly, too much fuel and the engine will flood.

Explain the operation of a 'kettering ignition system', including all components from the battery to the spark plug

The Kettering ignition system is a mechanical ignition timing system used on outboard motors and early cars. Electricity from the battery travels to the coil and charges it up there are capacitors on the line which stop voltage spikes , the release of spark is controlled by a cam on the crankshaft which opens a contact breaker and creates a spark. the spark is distributed to the spark plugs by a distributor or on multi coil engines through a C coil on cylinder head. disadvantages of the Kettering system is the potential for wear on the contact breakers and cam lobe, which in turn affects sparking.

Give an explanation of dwell angle in a distributor

Dwell angle is a measurement of the amount of time that a coil has to charge before it releases another spark. An average dwell angle on a 4 cylinder engine is 52 degrees. Which means that the coil has 52degrees to recharge and fire a spark on the distributor. if the dwell angle is too small the spark may not be fully charged and if it is too large the engine may misfire. Dwell angle can be adjusted on a distributor engine with a mechanical adjustment ( a screw, or movement). Dwell angle is adjusted on electronic ignition systems through a computer.

 

Explain why the 'Heat range' of a spark plug is so important.

A spark plug operates in a specific heat range to maximise efficiency some plugs have more thermal efficiency than others. If a spark plug is not hot enough when it is idling then the spark plug can be fouled up quite easily. If a spark plug is not 'cold' enough when the engine is at high RPM then the tip of the spark plug make cause detonation or knocking  because of high temperature. The spark plug needs to operate in the heat range that is required by the engine.

What is a capacitor discharge system and how does it operate? 

Capacitor discharge is a type of electronic ignition. It is used widely in outboard motors. It operates on similar principles to other electronic ignition systems. The voltage in the system is increased to about 400-600 V by a transformer in the capacitor module. This system has a large capacitor which stores a high amount of voltage and then fires this voltage to a coil when it is triggered. When the release is triggered a rectifier allows current to flow to the coil and voltage is increased further from the 400-600V of the capacitor discharge to about 40kV at the spark plug. This system is quite simple and reliable with no parts that can wear and affect the ignition. it also has a very fast recharge time for the capacitor reducing the dwell angle. however the limited spark duration can be too short to provide reliable ignition in some engines.

The capacitor module contains the transformer and capacitor.