Ignition Systems

Ignition Systems

 What substances that for electrolyte in a battery?

An Electrolyte is a substance containing free ions that make the solution electrically conductive. There are two substances that form electrolyte in an Automotive/Marine battery. An acid solution, usually sulfuric acid, mixed with water forms the electrolyte that floods round the lead inserts. As electricity is pumped into the battery it is stored within this solution.

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

A four stroke and two stroke engine requires three elements to run. Air, Fuel and Spark. In the absence of any of these three components the enginne will not run. Note that a 2 stroke engine needs lubrication added to the fuel or an engine seizure will occur.

Explain the 'Kettering ignition system' and its components.

This ignition system consists of;

Battery: This is an eletricity storage device.

Ballast resistor: This is used to limit the amount of current in an electrical circut.

Ignition coil: This is a major component within the ignition system. It consist of a primary winding wraping around a more concerntrated secondary winding. This device is used to boost the current from the battery to ingnite the fuel.

Distributor: Once the high energy charge has left the coil it is transfered to the distributor, this unit the distributes the spark between the sparkplugs using the rotor within it.

Capacitor: This is a small unit designed to stop the charge from the coil jumping the gap between the points as the voltage increases.

Points breaker: The points are where the connection between the coil and the spark plugs is connected and disconnected.

High-tennsion leads: These leads are used to transfer the high voltage from the distributor to the spark plugs.

Spark plug:  This is the final comonent in the ignition system. The spark plug uses a high energy current to arch across its self igniting the fuel.

Electricity is feed through the ballast resistor to the Ignition coil. Current flows into the coil charging up the primary windings, as the distributor points are open (A capacitor within the distributor stops the coil from arching across the point gap). As the distributor rotates and the points close, the primary coil is collapsed into the secondary winding (consisting of several thousand turns of a very fine wire) boosting the voltage to 30-40 thousannd volts. The secondary winding is then channeled through the distrubutor points, rotor, high-tension leads to the spark plugs.

Explain 'Dwell angle' in a distributor.

The Dwell angle refers to the length of time the points are closed on a distributor. This is measured by degrees of rotation on the distributor shaft. Generally the manufacturer will recommend a dwell angle of 54 degrees.

Why is the heat range of a spark plug important?

The heat range is important for a number of reasons. If the tip of the spark plug gets too hot it can cause problems such as pre-ignition or detonation. If the tip of the plug is too cold then deposits can form on the insulator reducing spark current or shorting the spark plug.

What is a 'Capacitor discharge' ignition system and how does it work?

This sytem is different from the conventional kettering system. Consisting of a transformer, charging circut, rectifier, capacitor, coil and spark plug. Voltge is raised by the small transformer to betweenn 400-600volts annd then transfered to the charging circut to charge the capacitor. A rectifier in the charging circut is used to ensure the capacitor does not discharge before the moment of ignition. When sensors determine ignition timing the charging system is cut allowing the capacitor to discharge into the coil. This then raises the voltage again discharging up to 40,000volts out through the spark plug.

Referrences

Ed May Vol 1

Ed May Vol 2

http://www.wikipedia.com/

Marine Buisness Practise

Marine Buisness Practise

Warrentees- A warrentee is given to a piece of equipment such as an outboard engine. A warrantee is a legal assurance that an item will perform the task it is built for. This assurance does come with some conditions and it is important that you make sure you read the warranntee and adhere to these or the warrantee with be void. For example when you buy a new outboard engine there are certain proceedures that must be done when starting and running the engine for the first time. Such as using a type of oil or not exceedinng a certain number of revs.

Guarantees- A garrantee is an assurance of workmanship. When a part is repaired for example, you give your assurance that this part will perform its job. Should this part fail you are responsible and are expected to cover the repair cost. If this part had been replaced with a new part then it would be covered by a warrantee.

Quotations- When giving a quote it is important to remember that this is a fixed price. Taking into account all that may be needed for a job such as parts, consumables, labour. If something should not be foreseen such as extra parts or labour it is now up to the person who delivered the quotation to cover the extra cost.

Estimations- Unlike a quotation, an estimation gives you room to move. It is effectively a guess. Parts, consumables, labour are all taken into account and a price is given for the job. However this price is not fixed and should unforseen circumstances arise, this is discussed with the customer.

Charge out rates- When choosing your charge out rate it is important to take into account all your expenses. For example when working in a workshop the rate you pay, e.g $60/hr, will include three divisions. Usually along the lines of $20/hr paid the the employee, $20/hr for the owner and $20/hr to pay for overheads. Overheads such as Rent, Power, Rates, Upgrading equipment.

Courtesy services- This is the services that are offer by a buisness that are not necessary but are done out of courtesy. Such as courtesy cars, dropping off or picking up a customer, checking tyre pressures, washing a car after work is done etc

Cultural issues- Cultural issues reffer to differences between cultures such as expectations, Practises, Communication issues etc.

Marine Transmission

Marine Transmissions

Gear selection systems

Outboard gear cases - An out board gearcase uses a 'Dog clutch' system. this is a double sided engaging gear. The dog clutch is mounted to the propellor shaft with the ability to slide. The selector rod pushes the dog clutch fowards or backwards to engage the propellor shaft to the driven gears.

Stern drive - Unlike an outboard the gear selector system is in the top of a stern leg, and sits vertical instead of horizontal. In this system a selector arm pushes a tapered cone, often made of brass, up or down the driveshaft to engage the foward or reverse gear. This system works similar to a baulk ring in an automotive gearbox and uses friction to engage the gear.

Inboard gearbox - Inboard gearboxes use a hydrolic clutch type engagemet system similar to a motorbike clutch. The selector changes the flow of fluid to each clutch unit within the gearbox as pressure builds the clutch plates engage the desired gear.

What type of gears are used in Outboards & Sternlegs?

Helical cut, constant mesh, gears are used in both outboard gearcases and sternlegs. This type of gear is used because having and helical cut gear provides more contact area between gears and reduces noise. Having a constant mesh gear system also reduces moving parts reducing possible problems. These gears are then engaged to the propellor shaft via an engagement system such as a dog clutch.

Duo Propellor systems

Invented by Volvo Penta this system consists of two propellors rotating in opposite directions. The main propellor is mounted to the main shaft with a second shaft mounted through its center. A second propellor is mounted to the second shaft and spins in the oposite direction. This system in designed to reduce cavitation, vibrations and increase power and handling.

'V' drive systems
A v drive system is used instead of a standard shaft drive system when there is little space to work with. This system allows the drive line to move around tight angles or change direction as in this diagram.

 

Jet Unit or Surface drive?

Jet unit - A jet unit is like an internal propellor. Water floods through the intake as the propellor turns which inturn blows out the rear of the boat under pressure. This system is good for conditions such as shallow waterways.

Surface drive -  A surface drive unit operates with the propellors half inn half out of the water. This type of system is used because it reduces drag therfore allowing for increased speed and lower fuel comsuption.

Both systems have their own advantages however I would lean more the Jet unit as this would be suitable for both shallow and deep water. This unit also has the added safety of not having exposed moving parts, but retains power and control.