ignition systems

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

In a car battery, diluted sulfuric acid and a water solution (electrolyte), are used together with lead plates to create a chemical reaction that produces voltage.

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

In a fourstroke petrol engine, the three main elements required for effective running are Air, Fuel and Spark.

Give an explanation of ''Dwell Angle'' in a distributor.

The dwell angle is the number of degrees of rotation of the cam/distributor during which the points are closed. During each rotation of the cam/distributor, the points must open and close once for each cylinder. The points must stay closed long enough to allow the coil primary current to reach an acceptable value, and open long enough to discharge and produce a spark.As the crankshaft rotates and pistons go through their cycles, the distributor's function is to precisely control the timing of the spark. Each cylinder's spark must occur at a precise time during the rotation of the engine. The distributor is driven off a gear on a camshaft or an idler pulley in the timing chain, such that it rotates at half the speed of the crankshaft. The drive method is dependant on engine manufacturers. The engine makes two complete revolutions in the same time that the distributor makes one 360 degree revolution.

Explain the operation of a ''Kettering Ignition System'', including all components from the battery to the spark plug.

The distributor contains a rotating cam driven by the engine's drive, a set of breaker points, a condenser, a rotor and a distributor cap. External to the distributor is the ignition coil, the spark plugs and wires linking the distributor to the spark plugs and ignition coil.

The system is powered by a lead-acid battery, which is charged by the car's electrical system using a dynamo or alternator. The engine operates contact breaker points, which interrupt the current to an  ignition coil.

The ignition coil consists of two transformer windings sharing a common magnetic core—the primary and secondary windings. An alternating current in the primary induces alternating magnetic field in the coil's core. Because the ignition coil's secondary has far more windings than the primary, the coil is a step-up transformer which induces a much higher voltage across the secondary windings.

For an ignition coil, one end of windings of both the primary and secondary are connected together. This common point is connected to the battery (usually through a current-limiting ballast resistor). The other end of the primary is connected to the points within the distributor. The other end of the secondary is connected, via the distributor cap and rotor, to the spark plugs.

The ignition firing sequence begins with the points (or contact breaker) closed. A steady charge flows from the battery, through the current-limiting resistor, through the coil primary, across the closed breaker points and finally back to the battery. This steady current produces a magnetic field within the coil's core. This magnetic field forms the energy reservoir that will be used to drive the ignition spark.As the engine turns, so does the cam inside the distributor. The points ride on the cam so that as the engine turns and reaches the top of the engine's compression cycle, a high point in the cam causes the breaker points to open. This breaks the primary winding's circuit and abruptly stops the current through the breaker points. Without the steady current through the points, the magnetic field generated in the coil immediately and rapidly collapses. This change in the magnetic field induces a high voltage in the coil's secondary windings.

At the same time, current exits the coil's primary winding and begins to charge up thecapacitor ("condenser") that lies across the now-open breaker points. This capacitorand the coil’s primary windings form an oscillating LC circuit. This LC circuit produces a damped, oscillating current which bounces energy between the capacitor’s electric field and the ignition coil’s magnetic field. The oscillating current in the coil’s primary, which produces an oscillating magnetic field in the coil, extends the high voltage pulse at the output of the secondary windings. This high voltage thus continues beyond the time of the initial field collapse pulse. The oscillation continues until the circuit’s energy is consumed.

The ignition coil's secondary windings are connected to the distributor cap. A turningrotor, located on top of the breaker cam within the distributor cap, sequentially connects the coil's secondary windings to one of the several wires leading to each cylinder's spark plug. The extremely high voltage from the coil's secondary -– often higher than 1000 volts—causes a spark to form across the gap of the spark plug. This, in turn, ignites the compressed air-fuel mixture within the engine. It is the creation of this spark which consumes the energy that was stored in the ignition coil’s magnetic field.

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

The operating temperature of a spark plug is the actual physical temperature at the tip of the spark plug within the running engine. This is important because it determines the efficiency of plug self-cleaning and is determined by a number of factors, but primarily the actual temperature within the combustion chamber. There is no direct relationship between the actual operating temperature of the spark plug and spark voltage. However, the level of torque currently being produced by the engine will strongly influence spark plug operating temperature because the maximum temperature and pressure occurs when the engine is operating near peak torque output (torque and RPM directly determine the power output). The temperature of the insulator responds to the thermal conditions it is exposed to in the combustion chamber but not vice versa. If the tip of the spark plug is too hot it can cause pre-ignition or sometimes detonation/knocking and damage may occur. If it is too cold, electrically conductive deposits may form on the insulator causing a loss of spark energy or the actual shorting-out of the spark current.

All info and images above from: http://calvinbayley.blogspot.com/

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

Capacitor discharge ignition (CDI) or thyristor ignition is a type of automotive electronic ignition-system which is widely used in outboard motors, motorcycles, lawn mowers, chainsaws, small engines, turbine-powered aircraft, and some cars. It was originally developed to overcome the long charging times associated with high inductance coils used in inductive discharge ignition (IDI) systems, making the ignition system more suitable for high engine speeds (for small engines, racing engines and rotary piston engines). The capacitive-discharge ignition uses capacitor-discharge current output to fire the spark plugs.

How it works:

A typical CDI module consists of a small transformer, a charging circuit, a triggering circuit and a main capacitor. First, the system voltage is raised up to 400-600 volts by a transformer inside the CDI module. Then, the electric current flows to the charging circuit and charges the capacitor. The rectifier inside the charging circuit prevents capacitor discharge before the moment of ignition. When the triggering circuit receives triggering signals, the triggering circuit stops the operation of the charging circuit, allowing the capacitor to discharge its output rapidly to the low inductance ignition coil, which increase the 400-600 V capacitor discharge to up to 40 kV at the secondary winding at the spark plug. When there's no triggering signal, the charging circuit is re-connected to charge back the capacitor.

Info from: http://en.wikipedia.org/wiki/Capacitor_discharge_ignition

Image from: http://www.afrayspeed.co.uk/images/af_flywheel_kit.jpg

Starting and charging systems

Give an explanation of the following starters:

Inertia: The Inertia Starter incorporates the following advantages: Minimum weight in proportion to the cranking torque capacity of the starter. High initial cranking speed thereby assuring delivery of fuel to the cylinders and permitting starting with a greater degree of spark advance. Flywheel acceleration independent of engine size, frictional torque and weather conditions, thereby assuring minimum current draw when electrically operated. Torque overload release, consisting of a multiple disc clutch under adjustable spring pressure, thereby preventing damage to the engine or starter in case of overload or engine back fire.

Pre-engage: Pre engaged starters prevent an awful lot of wear on the ring gear and Bendix gear. They were a big jump forwards in reliability. Non preengaged starters work by throwing a spinning cog at the ring gear on the flywheel to turn the engine. It will only disengage when the engine reaches sufficient speed to throw the cog out again, or the igntion key is turned back from 'start'.  A lot of wear as you can imagine.  Pre engaged have the cog already in place on the ring gear before the starter motor turns.  Once the ignition key is turned back to 'Ign' it disengages and waits until the ignition is turned off before re engaging with the ring gear.

Reduction gear: The operator closed the key-operated starting switch.A small electric current flowed through the starter relay coil, closing the contacts and sending a large current to the starter motor assembly.One of the pole shoes, hinged at the front, linked to the starter drive, and spring-loaded away from its normal operating position, swung into position. This moved a pinion gear to engage the flywheel ring gear, and simultaneously closed a pair of heavy-duty contacts supplying current to the starter motor winding.The starter motor cranked the engine until it started. An overrunning clutch in the pinion gear uncoupled the gear from the ring gear.The operator released the key-operated starting switch, cutting power to the starter motor assembly.A spring retracted the pole shoe, and with it, the pinion gear.

(info above from: http://perrinshovel.blogspot.com/)

Give an explanation of the operation of the following charging devices:

Generator: Electrical generators by definition are devices that convert mechanical energy into electric energy. The mechanical energy in turn is produced from chemical or nuclear energy in various types of fuel, or obtained from renewable sources such as wind or falling water. Steam turbines, internal-combustion engines, gas combustion turbines, electric motors, water and wind turbines are the common methods to supply the mechanical energy for such devices. Generators are made in a wide range of sizes, from very small machines with a few watts of output power to very large power plant devices providing gigawatts of power.

Info from: http://www.generatorguide.net/howgeneratorworks.html

Alternator: The alternator works with the battery to generate power for the electrical components of a vehicle, like the interior and exterior lights, and the instrument panel. An alternator gets its name from the term alternating current (AC).

Alternators are typically found near the front of the engine and are driven by the crankshaft, which converts the pistons' up-and-down movement into circular movement. Some early model vehicles used a separate drive belt from the crankshaft pulley to the alternator pulley, but most cars today have a serpentine belt, or one belt that drives all components that rely on crankshaft power. Alternators produce AC power through electromagnetism formed through the stator and rotor relationship that we'll touch on later in the article. The electricity is channelled into the battery, providing voltage to run the various electrical systems.

Info from: http://auto.howstuffworks.com/alternator1.htm

Customer Service Thingie

Warrantees/Guarantees

warrantee: In business and legal transactions, a warranty is an assurance by one party to the other party that specific facts or conditions are true or will happen; the other party is permitted to rely on that assurance and seek some type of remedy if it is not true or followed.

(info from: http://en.wikipedia.org/wiki/Warranty)

Guarantee: The assumption of responsibility for payment of a debt or performance of some obligation if the liable party fails to perform to expectations

Quotations/Estimation

A quote is where you calculate an actual charge price for a job that you are doing for a customer, where as an estimate is just a close guess to the price that you will charge the customer before making a quote.

Charge out rates

These are the six basic steps you need to take to work out a charge-out rate for your time:
1. Decide what income you want from your business.
2. Work out how many hours you can realistically charge out per year.
3. Work out a chargeable rate to achieve your income.
4. Work out your overhead costs.
5. Work out an additional hourly rate to cover these costs as well.
6. Add a profit margin.

1. Decide what income you want

Let’s start by assuming that you want an annual income of at least $36,000 (before tax) from your business (this figure could be related to the standard of living you want, what you could earn elsewhere as a salary, or what you could earn by investing your money elsewhere, plus a risk margin for being in business).

2. How many hours can you realistically charge out?

When you’re selling your knowledge, skills and services, you’re effectively selling time. The key point here is that you have to be realistic about the amount of time you can actually charge out during any one year. For example, if you work 40 hours a week every week of the year, you theoretically have 40 x 52 = 2080 hours of working time at your disposal. However, in most cases, unless you’re prepared to work considerable overtime, you’re unlikely to work this full amount. You do need some holidays (say three weeks). If you add up all the statutory holidays (Easter, Christmas, New Year, Waitangi day, etc., you’ll find that they take away another two weeks. If you get sick,  you might lose another week. So the working year now shrinks to a more realistic 46 weeks of 40 hours, or a total of 1840 hours. This is how it’s worked out: Total year: 52 weeks x 40 = 2,080 Deduct: Holidays: 3 weeks x 40 hours = 120 Statutory Holidays: 2 weeks x 40 hours = 80 Sickness: 1 week x 40 hours = 40 Total hours to deduct = 240 Balance available = 2080 - 240 1,840 (or 46 weeks at 40 hours per week). But it would still be unrealistic to imagine that you can bill out all these hours. Think of all the other non-chargeable activities you’re involved with in running your business:
• Administrative tasks
• Banking
• Meetings
• Tendering for work
• Marketing and promotion work
• Waiting for work and travelling time
• Tea and toilet breaks, etc.
One way to find out how much time you’re spending on such tasks is to keep a diary for a week (or longer if appropriate). You might be surprised to find out how much time is taken up with such ‘non-productive’ work. Let’s assume at a conservative estimate that these non-chargeable tasks take up 25% of
your time.  So one quarter of the 1,840 available hours needs to be deducted for these tasks: 25% of 1,840 = 460 hours. Subtracting 460 from 1,840 leaves you with a total of 1,380 chargeable hours.

3. Working out your charge-out rate to cover your income requirements

Now you can work out a charge-out rate to cover the income you want from the business. You’re aiming to earn a minimum of $36,000. You’re able to charge out only 1,380 hours yearly. To get an income of $36,000 you must therefore charge your time out at $36,000 divided by 1,380 = $26.09 per hour. To this you must also add the ACC levy appropriate to your line of work. (Ask your accountant how much you should add on to cover this). Let’s say the ACC levy rate for your activity is 4%. So
$26.09 plus 4% =$27.13. So in order to earn a salary of $36,000 a year, you must at least charge your time out at $27.50 (rounded up). But this is only the labour component of your charge out rate. What about your office overheads (the cost of running a business)? You have to recover these costs as well, or you’ll be running at a loss. This takes us to step four.

4. Working out your overheads

You should know what your overhead costs are likely to be, either from your Business Plan or from your Cashflow Forecasts. (You can also check your previous Profit and Loss Statement and isolate all of the overheads on it). Let’s assume, for this exercise that they are something of this order:
. Accounting fee $1,000
. Advertising $2,000
. Cleaning $500
. Depreciation $1,000
. General expenses $500
. Heat, light, power $1,000
. Insurance $600
. Legal fees $600
. Motor vehicle $3,000
. Printing $800
. Rent $6,500
. Repairs and maintenance $900
. Telephone $1,200
. Other $200
TOTAL $19,800

Let’s round this off to $20,000. (Very few businesses can realistically operate with overheads of less than $20,000 a year). So $20,000 divided by the 1,380 hours means you need to add another $14.49 to your hourly charge-out rate of $27.13. Adding a profit margin So far the charge-out rate will enable you to achieve your required income, plus an extra amount per hour to cover your business expenses and overheads. There’s one extra factor to add: a profit margin. In addition to making your target salary of $36,000, you do also need to make a profit margin. After all, you will need to replace equipment that wears out and make repairs.

You don’t want to be taking this money out of your salary, or else you won’t really be earning that $36,000 a year. So the final calculation is: Charge-out rate to cover your income requirements  $27.13 Charge-out rate to cover your overheads (business expenses) $14.49 Subtotal $41.62
Profit margin (say 15%) $6.24 Final charge-out rate $47.86 This means that your charge-out rate should be realistically be at least $48 an hour minimum, (or $54 per hour if you’re quoting on a GST inclusive basis, since you’d have to add GST of 12.5% per hour, = $5.98, to this figure). Is the rate competitive?
At this stage you might be worried that the charge-out rate is uncompetitive compared to what others in your industry are charging. In some cases you might have to remain within an industry scale of fees.

In any event  you do have to be aware of the average in your industry as you might struggle to get work if you are a long way out. Here are some options: Lower than average. If your calculated charge-out rate is lower than the industry average, then you don’t have a problem - instead you have an opportunity to earn a better income and you can set your sights higher. For example, if you determine that your charge-out rate should be $48 per hour and you know the industry average is $60 per hour, you can raise your rate to this level or close to it.

Lack of confidence Many businesses undercharge at the start - mainly through lack of confidence or because they have not worked out how much it actually costs to run a business and make a reasonable profit! Might this be the problem here? Charging too little for your skills and services can be as bad for business as charging too much because it can undermine people’s confidence in you. They might wonder why you are so much cheaper
than others. Higher than average If your charge-out rate is higher than the industry average, then:

• It may be that other new start-ups are charging at unrealistic levels. This is a common problem in service trades (such as building, plumbing. electrical
work, etc.) where many begin a business not realising the true costs involved (such as overheads and taxes). They gain business at the expense of more
established businesses but may face difficulties after a year or so when the true costs finally impact on them. There is little you can do to counter this problem. Your one consolation is that these people are not likely to be in business for long, but in the meantime they have spoilt the market for others.

• Go over all the figures carefully again. Is anything unrealistic? After a year or so of operation, you’ll be in a better position to gauge more accurately the number of billable hours you can actually achieve in a year. For example, you might learn that 1,200 billable hours is a more realistic maximum per year. In the meantime, it pays to be conservative. One way to lower your charge-out rate is increase the number of hours you can charge out. For example, if you can bill out at $48 per hour, and there is plenty of work around, does it make sense for you to do administrative tasks that someone else could do at, say, $15 per
hour? (The Solution Guide: ‘Taking on your first employee’ will help you here). Increasing your billable hours will allow you to decrease your charge-out rate per hour and perhaps make your rate more industry competitive.

• If your rate is still well above average, then you might look at emphasising the value-added components that justify the difference, such as guarantees, superior quality and service (such as a premium for 24-hour call outs), backup and training, etc

(info from: http://www.nationalbank.co.nz/business/banking/information/guides/SG074Calculatingachargeoutrate.pdf)

Cultural issues:

In business there are different people from different cultures who speak English in different accents compared to others, so it can be hard when talking to someone who has a “thick accent” so to speak, and also, their cultural background may reflect in how they dress/appear in public. So the courteous approach would be is to have good communication skills  and try to pick out what a person with an odd accent is saying to you and try to understand them, because if they are a paying customer and you keep asking them to repeat what they have just said to you, then they may or will get annoyed or offended and say to others that you are not a very good place/business to go to.

cooling and corrosion

Explain the terms ( Kinetic energy) Conduction, convection and radiation.
Indirect cooling?
Direct cooling?
What are the the problems you get with indirect and direct cooling?
What is the purpose of a thermostat?
Pressure cap?
Why is engines fitted with a core plug, and what is the purpose of a core plug
What is the purpose of a heat exchanger?
How does the heat exchanger work?
How does the centrifugal circulating water pump work?
Why is it important to lubricate the impellor when fitting from new?
When fitting a impellor what should you check before refitting the housing and why?
What is the process of a intercooler/after cooler how does it work?
Why do we have Inhibitors & antifreeze?
How do you test Antifreeze?
What is galvanic corrosion?
Describe the terms
Stray corrosion?
Stress corrosion?
Corrosion Fatigue?
Crevice corrosion?
What is Electrolysis?
How do you prevent corrosion?
What are sacrificial anode made off?

 

Conduction:

Heat spontaneously flows from a region of higher temperature to a region of lower temperature, temperature differences over time, approaching thermal equilibrium.

Info from: http://en.wikipedia.org/wiki/Conduction_%28heat%29

Radiation

Thermal radiation is electromagnetic radiation generated by the thermal motion of charged particles in matter. All matter with a temperature greater than absolute zero emits thermal radiation.

Examples of thermal radiation include visible light emitted by an incandescent light bulb, infrared radiation emitted by animals and detectable with an infrared camera, and the cosmic microwave background radiation.

Info from: http://en.wikipedia.org/wiki/Thermal_radiation

Convection:

Convective heat transfer, often referred to as convection, is the transfer of heat from one place to another by the movement of fluids. The presence of bulk motion of the fluid enhances the heat transfer between the solid surface and the fluid. Convection is usually the dominant form of heat transfer in liquids and gases.

Info from: http://en.wikipedia.org/wiki/Convective_heat_transfer

An image showing the different types of heat transfer:

Image from: http://www.beodom.com/en/education/entries/principles-of-thermal-insulation-heat-transfer-via-conduction-convection-and-radiation

And a song from YouTube about this stuff

Direct cooling:

The difference between direct cooling systems and indirect cooling systems, also known as secondary refrigeration, lays in the physical separation between  the primary circuit, where the cold is generated, and the secondary system, where cooling takes place.

Info from: http://www.zitrec.com/Applications_indirect_cooling_systems.htm

Image from: http://www.betterbricks.com/building-operations/cooling-towers

Indirect cooling:

Indirect cooling in supermarkets

The combination of these benefits is why typically in public buildings, such as supermarkets, indirect systems are promoted.  In supermarkets, the cold needs to be transported to a variety of fresh and frozen displays in an effective, safe and economical way.  All the cooling effect required is produced in the machine room, far from the display cases, resulting in high flexibility and a lower risk of leakage. A heat recovery system, also situated in the machine room, can provide heating for the supermarket when required. In this way  the use of unwanted refrigerant such as ammonia in a public place is avoided, although it can still be used in the primary system, kept in a safe sealed room, away from the public.  

  (info from: http://www.zitrec.com/Applications_indirect_cooling_systems.htm)

 

The purpose of a Thermostat:

The thermostat acts as a valve that stays closed during engine warm-up. When the thermostat is closed, it prevents coolant from leaving the engine and circulating through the radiator. When the engine gets warm, the thermostat’s spring valve opens, allowing coolant to circulate through the radiator to be cooled.

(Info from: http://www.matthewsvolvosite.com/replace-thermostat-volvo-850-s70-v70-c70-or-xc70.html)

(Image from: http://www.matthewsvolvosite.com/replace-thermostat-volvo-850-s70-v70-c70-or-xc70.html)

Pressure cap:

(image from: http://www.motorera.com/dictionary/pr.htm)

The radiator cap actually increases the boiling point of your coolant by about 45 F (25 C). How does this simple cap do this? The same way a pressure cooker increases the boiling temperature of water. The cap is actually a pressure release valve, and on cars it is usually set to 15 psi. The boiling point of water increases when the water is placed under pressure.

When the fluid in the cooling system heats up, it expands, causing the pressure to build up. The cap is the only place where this pressure can escape, so the setting of the spring on the cap determines the maximum pressure in the cooling system. When the pressure reaches 15 psi, the pressure pushes the valve open, allowing coolant to escape from the cooling system. This coolant flows through the overflow tube into the bottom of the overflow tank. This arrangement keeps air out of the system. When the radiator cools back down, a vacuum is created in the cooling system that pulls open another spring loaded valve, sucking water back in from the bottom of the overflow tank to replace the water that was expelled

(info from: http://auto.howstuffworks.com/cooling-system7.htm)

Core plugs and their purpose:

Core plugs, sometimes wrongly called freeze plugs or frost plugs, are plugs that fill the core holes found on water cooled internal combustion engines. The sand casting cores are used to form the internal cavities in the engine block or cylinder head(s), usually forming the coolant passages. The traditional plug is a thin, domed, disc of ferrous metal which is pressed into a machined hole in the casting. Alternatively a non-ferrous metal such as brass offers improved corrosion prevention.

(Info from: http://en.wikipedia.org/wiki/Core_plug)

(Image from: http://www.pauls-place.com/products-chevy-block-accessories.asp)

The purpose of a heat exchanger:

The classic example of a heat exchanger is found in an internal combustion engine in which a circulating fluid known as engine coolant flows through radiator coils and air flows past the coils, which cools the coolant and heats the incoming air.

(info from: http://en.wikipedia.org/wiki/Heat_exchanger)

(Image from: http://en.wikipedia.org/wiki/File:Straight-tube_heat_exchanger_1-pass.PNG)

How the heat exchanger works:

There are two primary classifications of heat exchangers according to their flow arrangement. In parallel-flow heat exchangers, the two fluids enter the exchanger at the same end, and travel in parallel to one another to the other side. In counter-flow heat exchangers the fluids enter the exchanger from opposite ends. The counter current design is most efficient, in that it can transfer the most heat from the heat (transfer) medium. In a cross-flow heat exchanger, the fluids travel roughly perpendicular to one another through the exchanger.

(Info from: http://en.wikipedia.org/wiki/Heat_exchanger#Flow_arrangement)

Parallel flow heat exchanger:

(image from: http://en.wikipedia.org/wiki/File:Heat_exc_1-1.svg)

Cross flow heat exchanger:

(image from: http://en.wikipedia.org/wiki/File:Heat_exc_2-1.png)

How does the centrifugal circulating water pump work?

The centrifugal pump is powered by an electric motor in a waterproof housing. That motor drives a device called an impeller. The impeller is a wheel with angled blades. When water gets caught in it, it is driven by centrifugal force to the outside of the spinning wheel. The shape of the blades then compresses the water and shoots it out in a jet

(info from: http://www.ehow.com/how-does_4963320_circulator-pump-work.html)

(Image from: http://media.web.britannica.com/eb-media/58/3658-004-061948E8.gif)

Why is it important to lubricate the impellor when fitting from new?

When the impellor is fitted from new, it will be dry, and all impellors rely on being wet as a way of lubrication, so a little silicone is to be used so that the impellor can turn/slip easily in the housing before it is surrounded by water.

When fitting a impellor what should you check before refitting the housing and why?

When refitting a new impellor, check to see if there isn’t any shredding or cracks, because when the impellor turns, the force of the water will have a possibility of stressing the weakened area and cause it to get bigger until a blade is torn off and jams the pump.

What is the process of a intercooler/after cooler how does it work?

An intercooler (sometimes referred to as an aftercooler) is designed to remove heat from the compressed air coming from the supecharger (or turbo) before it enters the engine's induction system. An intercooler works just lie a radiator - air is cooled by fins, bars, louvres, and plates inside the intercooler that are cooler than the compressed air coming from the supercharger. The reduction in air temperature increases the density of the air (more air molecules per cupic foot), which consequently increases your engine's ability to make more horsepower and torque. The decreased air temperature allows you to run more boost on a given octane of fuel before detonation occurs..

(Info from: http://www.angelfire.com/hiphop3/ppddaiddddyy/Intercoolers.html)

(image from: http://heatexchanger-design.com/wp-content/uploads/2011/02/intercooler.jpg)

Why do we have Inhibitors & antifreeze?

Antifreeze (engine coolant) performs several functions in addition to providing freeze protection. Antifreeze contains chemicals that inhibit corrosion and scale formation in the engine and radiator. Antifreeze (engine coolant) provides protection against boiling in the summer. At one atmosphere pressure pure water boils at 212 °F (100 °C) but a 50/50 blend of water/ethylene glycol boils at 223 °F (106 °C).

(info from: http://www.eetcorp.com/antifreeze/antifreeze-faq.htm#q2)

(image from: http://mypetshappiness.com/wp-content/uploads/2009/07/iStock_000001212761XSmall.jpg)

How do you test Antifreeze?

What is galvanic corrosion?

Galvanic corrosion is an electrochemical process in which one metal corrodes preferentially to another when both metals are in electrical contact and immersed in an electrolyte. The same galvanic reaction is exploited in primary batteries to generate a voltage.

(info from: http://en.wikipedia.org/wiki/Galvanic_corrosion)

Describe the terms
Stray corrosion: Stray current corrosion refers to corrosion damage resulting from current flow other than in the intended circuit(s).
Stress corrosion: Failure by cracking under the conjoint action of a constant tensile stress, which is applied to residual, in certain chemical environments specific to the metal.
Corrosion Fatigue: Damage to or failure of a metal due to corrosion combined with fluctuating fatigue stresses.
Crevice corrosion: Corrosive degradation of metal parts at the crevices left at rolled joints or from other forming procedures; common in stainless steel heat exchangers in contact with chloride-containing fluids or other dissolved corrosives. Also known as contact corrosion.

(Info from: http://calvinbayley.blogspot.com/search?updated-max=2011-06-27T13%3A16%3A00-07%3A00&max-results=7)

What is Electrolysis?

In chemistry and manufacturing, electrolysis is a method of using a direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction.

(Info from: http://en.wikipedia.org/wiki/Electrolysis)

How do you prevent corrosion?

10 ways to prevent corrosion:

Choose products that are made of non-corrosive metals like stainless steel and aluminum.

Metal Corrosion can be best controlled by maintaining a dry environment using suitable moisture barriers and drying agents.

Make sure that your electrical connections are clean.

To prevent metal corrosion on a car or truck, apply a thin coating of petroleum jelly after you clean the terminal.

Always clean and dry the blades of garden tools after every use as this eliminates moisture. Also wash away soil from shovels, hoes and rakes before storing them in a cool and dry place. In addition, wash your garden tools with soap and water, dry them and rub motor oil on the metal parts before you put them away for winter season.

Coat metals with oil, paint, grease or varnish because it can prevent corrosion.

Utilize cleaning agents like soaps, solvents, emulsion compounds and chemicals to efficiently get rid of oil, grease, dirt and other unwanted foreign deposits and follow the correct procedures in applying them.

Metal Corrosion that has already formed on car batteries can be removed by using a mix of cola and baking soda to create a paste. The paste will eat at the corrosion.

To prevent soil corrosion, install correctly copper or copper alloy plumbing underground. The main reasons that lead to corrosion of copper pipelines are poor drainage and moisture. A loose layer of backfill such as limestone or pea level must be put down in the trench before laying copper pipes.

Galvanizing also provides metal corrosion protection. This is the process of giving a thin coating of zinc or steel material by immersing the object in a bath primarily composed of molten zinc. Galvanizing is an efficient way to protect steel because even if the surface is scratched, the zinc still protects the underlying layer. This process is widely used by the automotive industry.

(info from: http://www.smithandarrow.com.au/blog/rust-corrossion/10-ways-prevent-corrosion-metals/)

What are sacrificial anode made off?

Sacrificial anodes are made off zinc, and are very common in the marine industry, to help protect components in the salty environment.

(info from: http://calvinbayley.blogspot.com/search?updated-max=2011-06-27T13%3A16%3A00-07%3A00&max-results=7)

Marine transmissions

1. Explain the different type of gear selection systems (in outboard gearcases and stern drivers and Inboard marine gearboxes)

For outboard… a dog clutch is used which consists of a gear which is on the output shaft that slides in either direction to lock the forward or reverse gear to the shaft. the gears are in what’s called a gear case which is in the bottom of the outboard system, different to the set up of a sternleg or an outboard where the gearcase is in the top of the leg. The stern leg uses a similar dog clutch system, except it uses coned syncro hubs similar to that as the syncro cones on a manual gearbox. this is so there is smooth sync as the gears are selected instead of the rough clacking made by the teeth from dog clutch as on an outboard. The gear is engaged once the cone/selector is pushed more into the gear and becomes tight enough for the two components to engage.

A dog clutch system on an outboard

2. What type of gears are used in outboards and stern legs? (Give an explanation of why manufacturers choose this type of gear)

Helical type gears are used for gears in the outboards and sternlegs. The gears are angled at 45 degrees so that they can mesh properly as there is one shaft, meshing with another shaft at an angle of 90 degrees.

3. Explain what a duo propeller system is and how it works/operates

 

(Image from: http://www.volvopenta.com/SiteCollectionImages/VPC/Drives/758x228/ML_DPS_Duoprop_758x228.jpg)

Duo prop design:

• One of the main benefits of the IPS and DuoProp is highly increased propulsion efficiency. This means that less engine power and fuel consumption. In water, propellers function better when they are designed to pull, instead of push. Because of the placement of engines at the rear of most boats, however, this propeller orientation is rare. The DuoProp overcomes this limitation by using two propellers instead of one.

  Like traditional shaft-driven boat systems, the system features propellers that are fully submerged. This, however, is where most similarity ends. Instead of standard propellers, IPS employs two propellers per unit. These duo props are counter-rotating. One propeller spins clockwise, while the other rotates counterclockwise. This reduces wasted energy and results in better efficiency through the water.

(Info from: http://www.ehow.com/how-does_5336911_volvo-outdrive-duoprop-works.html)

Volvo IPS system:

(Image from: http://www.tomjenkinsyachtsales.com/img/news/13_Volvo%20Penta%20IPS.jpg)

4. Why would a V drive be used instead of a standard shaft drive system 

V-drive is a propulsion system for boats that consists of two drive shafts, a gearbox, and a propeller. In a "V-drive" boat the engine is mounted in the rear of the boat and the front of the engine faces aft. Connected to the rear of the engine is the transmission. The first drive shaft connects the rear of the transmission to a gearbox mounted in the centre of the boat. The second drive shaft extends from the gearbox to the rear and out the bottom of the boat to where a propeller is mounted.

(Info from: http://en.wikipedia.org/wiki/V-drive)

V drive diagram

 

(Image from: http://www.gknservice.com/typo3temp/fl_realurl_image/for-remote-v-drives-3c-17-91.jpg)

With the standard shaft drive setup, the engine is further forward in the hull with a shaft driven straight to the propeller.

(Image from: http://www.michiganmotorz.com/images/article/Inboard.jpg)

5. Compare a jet unit with a surface drive unit and give reasons why you would choose one system over the other

Jet unit:

In a boat hull the jet unit is mounted inboard in the aft section. Water enters the jet unit intake on the bottom of the boat, at boat speed, and is accelerated through the jet unit and discharged through the transom at a high velocity. The picture below shows where water enters the jet unit via the Intake (A). The pumping unit, which includes the Impeller (B) and Stator (C), increases the pressure, or "head", of the flow. This high pressure flow is discharged at the nozzle (D) as a high velocity jet stream. The driveshaft attaches at the coupling (F) to turn the impeller.

Reverse is achieved by lowering an astern deflector (E) into the jetstream after it leaves the nozzle. This reverses the direction of the force generated by the jet stream, forward and down, to keep the boat stationary or propel it in the astern direction.

(Info and image from: http://www.hamjet.co.nz/hamiltonjet_waterjet/how_a_waterjet_works)

Surface drive:

(Image from: http://www.francehelices.fr/surface-drive-system-uk.htm)

What are surface drives, and how do surface drives work? Put quite simply, surface piercing propellers operate half in and half out of the water in the planing wake region of a boat just behind the boats transom. Having the propeller at the surface level reduces drag and reduces the vessels draft, making the surface drive suitable for many applications where the owner is looking to reduce fuel costs, increase speed and create a more efficient vessel.
There are advantages and disadvantages for all propulsion systems for water craft. But for planing and semi-planing vessels, surface propulsion has several distinct advantages over its competitors in the propulsion marketplace.

(info from: http://www.seafury.com/a/About-Surface-Drives)

Over all, I would choose to have a Jet unit rather than a surface driver as the propeller is inside the mechanism and wont be disturbed by any external obstructions, and because the water is being sucked from under the hull,  so it doesn’t matter how shallow the water can be, it will still be able to drive without a propeller hitting the sea floor.

Marine transmissions

1. Explain the different type of gear selection systems

A)  in outboard gearcases and stern drivers.

B) Inboard marine gearboxes

2. What type of gears are used in outboards and stern legs?

A) Give an explanation of why manufacturers choose this type of gear

3. Explain what a duo propeller system is and how it works/operates

4. Why would a V drive be used instead of a standard shaft drive system

5. Compare a jet unit with a surface drive unit and give reasons why you would choose one system over the other

Engine reflection 2

I worked on an inboard motor before working on a gear case for an outboard motor, what I had to do was to make sure the engine drive sprocket was square with the drive shaft sprocket with out any restriction when you turn the driven shaft. I measured the diameter of the drive sprocket and use a DTI gauge to check the amount of runout it had which was 0.03mm. By using spacers, which were little plates of metal, i inserted them in where the engine mounts were to get the engine lined up with the propeller shaft properly.

I also used a feeler gauge/flare gauge and placing it between the drive and driven sprockets to check if there is any deflection between the two, if the flare gauge gets stuck in one place, but is fine as the rest of the shaft spins, that means that the engine isn’t inline and will have to be adjusted, either spun left or right slightly, tilted up or down. or moved to a side then twisted round slightly to match perfectly.