4844 Transmission and Drivelines - Clutch, CV's and driveshaft

Constant Velocity (CV) joints are used to apply power from the final drive to the wheels. Without these we wouldn't be able to allow for the vertical and lateral movement of the wheels. Cv's are comprised of two races (inner and outer) that are connected via ball bearing held in a cage. They are quite long lasting if correctly lubricated.

Clutches transfer the power from the flywheel (Engine) to the input shaft (Gearbox) in a manual setup. The two main parts in a clutch are the pressure plate and the clutch plate. A thrust bearing applies load from the slave cylinder onto the pressure plate. When the bearing is not engaged with the pressure plate, the pressure plat eis clamping the clutch plate (Friction plate) onto the flywheel. When you push the clutch in the pressure is released from the clutch plate and allowed to spin freely from the flywheel. It is very important to align clutches properly and to machine the flywheel when installing clutches. If the flywheel isnt flat the clutch will have unbalanced wear and will wear much quicker. When you bolt up the clutch to the flywheel ensure the plate is aligned to the flywheel (spiget bearing). This ensure the gearbox will slide in much easier.

Drive Shafts transfer the drive from the rear of the gearbox to the differential in a RWD setup. The are generally made of one or two shafts that are connected by Universal Joints. They are generally pretty full proof unless you have a imbalance or worn out UJ. To rectify a imbalance take a runout test of the shaft at the front middle and rear. Add a hose clip to the shaft to counteract the imbalance of the shaft. It may take a number of attempts to get it spot on.

4844 Transmission and Drivelines - Manual Fwd Gearbox Disassemble and Re-assemble

The  FWD Gearbox transfers the torque and power of the engine to the wheels. It has a number of gears that mesh in order to provide higher and lower gear ratios. Higher gear ratios mean car can take off and drive up steep gradients. The lower ratios mean higher speeds are available at lower RPM to achieve better efficiency.

The Disassembling Was relatively easy, Although The gearboxes we used had not been apart many times so the 5th gear was relatively tight on the shaft. We didnt have the correct service tool to remove the gear but as a last measure used a puller that acted on the gear itself. This was done very carefully to ensure no damage to teeth occurred.

When inspecting the gears i looked for any pitting, chips or grooves. All the gears were in surprisingly good condition. Although as expected the reverse sliding gears had a little more wear than the rest but it would have been fine to return into service.

During the time the gearbox was apart i learned about the detent mechanisms and the interlock mechanisms. The detent balls and springs hold the gear shafts in place so the gearbox wont slip out of gear. The interlock stops the driver from selecting 2 gears at the same time. It is a very important part and is highly efficient yet is only comprised of two ball bearings.

Reassembling took longer than planned. The shafts are a bit tricky to put in correctly however with a bit of unplanned practice i soon got quicker. Due to me forgetting to turn the reverse gear idler shaft to the correct point to ensure it lines up with the casing. A Mistake i will not make again is it was very time consuming.

Once reassembled the gearbox went through all the gears properly and didnt have any issues. Great success.

Batteries

Battery is for starting the car and running accessories while the engine isn’t running. Most automotive batteries have 6 cells made of plates sitting in sulphuric acid and distilled water. This mixture is called electrolyte. Voltage is created through the chemical reaction of the lead and sulphuric acid.  A fully charged battery is 12.6V.

 When testing the battery on-car, we found water on the top of the battery casing; this could mean the alternator is overcharging. When tested the OCV (open circuit voltage) with a volt meter, it read 13V with the engine off. This indicates there is a surface charge.  This can be removed by running accessories for a few minutes. Engine running with accessories on (headlights, blower) battery was charging well and there seemed to be no descrepences.

A high rate discharge test can be performed with a carbon pile tester to find the batteries capacity and determine whether the battery is in good condition. For this test we had to find the CCA (Cold Cranking Ampere) of the battery and halve it. This is the load to use with the tester.  Connect the clamps of the tester to the terminals of the battery and turn the load dial up to half the CCA, if the voltage of the battery drops below 9.5V then a new battery is required.

Starter motors

A starter motor is used to turn the engine over. When cars first came out this would be done by hand. A ‘crank handle’ would slot into the crank and you would turn the engine over yourself. Then inertia starter motors came out. This type of starter motor uses a spiral mechanism to engage into the ring gear while pinion gear was already spinning. Problem with this is that if starter didn’t receive enough power, it wouldn’t spin the pinion gear fast enough. Resulting in gears crunching and worn ring gear over a short period. Another type of starter motor is gear reduction. These are often used in higher compression engines due to the added load on the starter. They work similar to a pre engaged starter but consist of more gears. These added gears provide a higher torque from starter.  In today’s cars the most popular type of starter motor is pre engaged. This type of starter motor engages into the ring gear before spinning. It does this with the use of a solenoid. Pull in windings activate a plunger which pushes the pinion gear into the ring gear. When the plunger is all the way in the pull in winding power down and hold in windings activate. While this is happening the plunger has connected two contacts together enabling a high flow of electricity to flow to the windings and the armature.

The starter motors principal is to turn electrical energy into mechanical energy. It does this with the use of electro-magnetism.  Because the iron core is surrounded by windings, when the electromagnetic fields cut across each other an electric current is created and absorbed into the windings. The brushes on that push onto the commutator allow electricity to pass through armature. Because the commutator is split into sections it turns windings on and off.  It is this action of turning them on and off that cause the armature to spin.

Alternators

To diagnose any problems with the charging system on a vehicle, you must first take the OCV of the battery and perform a CCA test on the battery. You do this because  if the battery isn't holding enough charge then the fault may not be the chargeing system. If under load the battery cannot hold a voltage reading of 9.5 then it is a fail. It must be charged to continue the test.


 If battery is fine, perform a visual check of wiring and connections. If any loose connections tighten them. Then you perform a voltage drop test across the wiring. A high result means that there is added resistance in the wire, which is drawing voltage away from the battery.

I learnt how to check the charging system for faults and how to diagnose certain problems.

4842 Automotive Engines questions 3

1.What is the firing order of a four stroke engine?
2.What is the difference between a S.I and C.I engine?
3.Is there any difference between a S.I and C.I piston if so what?
4.What year was the diesel engine invented and by whom?
5.What is the purpose of the oil jet on the connectng rod, and where does it spray?
6.On the connecting rod where is the big end and little end?
7.What is the purpose of the thrush washers on the crankshaft?
8.On a diesel engine whats the difference between direct injection and a indirect injection type?
9.Explan the term valve timming?
10.Why do we have valve clearance?




1. Basically 1342 but, each engine has a different firing order. But on the twin cam mazda engines we are working on when the 1st cylinder is at TDC the 2nd and 3rd are at BDC and the 4th is at TDC. So when the 1st cylinder is travelling upward toward TDC it is on the compression stroke while the 4th cylinder that is travelling toward tdc is exhausting. Mean while the 2nd cylinder is on a power stroke the 3rd cylinder is on intake.

2. Spark ignition engines use spark plugs to ignite the fuel where as a compression ignition engine relies on the high compression to ignite the fuel.


3. The pistons in a C.I engine are shaped alot differently to the S.I engine. Their piston crowns are are shaped differently due to the fact that these engines rely on compression. Also the compression engine pistons are made stronger due to being under higher stresses. 

4. The diesel engine, well the C.I. engine was invented by Herbert Ackroyd-Stuart in 1890.

5. The oil jet on the con rod sprays oil into the cylinder while the piston is travelling toward TDC. It does this because there is alot of friction created in the cylinder. So the oil is used as a lubricant to keep friction to a minimum.

6. On the conrod the big end is connected to the crankshaft and the little end is connected to the piston via the gudgeon pin.

7. The thrust bearing stops the end play in the crankshaft. Because the engine is turning clockwise it automatically forced the crankshaft forward. so the 'spacers' stop the play.

8.

TTEC 4843 automotive engines (2)

What is taper and ovality in the bore, how is it caused how do you check it?
What is side clearance on a piston and how is it checked? 
How can you tell the difference between a inlet and exhaust vavle and why?
What sort of tempatures do the inlet and exhaust valves get upto?
What temperatures and speeds must the piston be able to cope with?
Why do we have piston ring end gap clearance ?
What could the result be if the piston ring end gap is too small?
Why do aluminum cylinder heads usually have a steel shim (washer) between the valve spring and the cylinder head surface ?
What is meant by the terms S.I and C.I in a four stroke engine?
7/4/11 What is the purpose of the margin on the valve


The taper and ovality of the bore is the curvature of the bore and how worn the cylinder is from wear and tear. To check these you take dimensions of the bore. To do this you take dimensions across 'A' and 'B' of the bore. you repeat this 3 times at the top, middle and bottom of the bore. To check ovality subtract 'A' measurement form 'B'. To work out the taper of the bore subtract the measurements you took from the top of the bore from the ones you took from the bottom. 

The side clearance on a piston is gap between the piston ring and the ring groove on the piston. To check this gap you need feeler gauge. Use the feeler gauge on a smaller dimension and slip it in between the groove and ring. Continue to try this with bigger gauges until you cant fit one in and record the size you fit last.

The difference between the exhaust and inlet valves are the size. The inlet valves are generally bigger. This is because when the inlet and exhaust valves are open together bad things could happen. The fresh mixture and air may enter through the inlet valve and simply exit through the exhaust valve. The cylinder will be unfilled and produces a gas called Carbon-monoxide (Co1). This is a very harmful gas and may be fatal to your health if dose is high enough. The piston crown is generally at normal operating temp of 300 Degrees but is brought down with use of coolant. An interesting note is that forced induction engines have a operating temp of 600 Degrees at the piston crown.

The ring end gap is very important for the operation of the piston. As with all metals the ring expands when it gets hot. So the gap left at the end of the ring is to allow for the expansion of the ring. If this gap wasn't left as the ring expands it would have no where to go and distort and buckle and may cause seizure of the piston. 

We use a steel shim between the valve spring and aluminium head as aluminium is a soft metal. When under heat and higher tension the spring may cause galling on the head. The steel shim prevents this added wear on the head as it is a harder metal and the bigger surface area on the head spreads the pressure.

On a slightly different note we check the alignment of conrods today. I think the one below may be a little bend. But you would have to check to be sure. I think not.

4842 Automotive Engines

How does a four stroke engine work? Name the cycles ,I want to know what the piston is doing and the valves on each stroke. 
Who and what year was the  four stroke engine invented.
What is the purpose of the crankshaft,camshaft,vavles collects(keepers),vavle sterm seals,head gasket,pistons,piston rings name them all, cambelt,flywheel?
What is the bore and stroke.
What i am looking for is a good explaination about each component, use you-tube for videos,


The four stroke engine needs for four strokes to make power. The four cycles to make power are as follows:


Induction- The piston starts at top dead center. The piston then travels down the cylinder and as this happens a mixture of fuel and air is inducted into the cylinder. (induction valve open)


Compression- The piston now at bottom dead center is pushed up. As this happens the mixture of air and fuel is compressed. (both valves closed)


Power- The compressed mixture of fuel and air is ignited by the spark plug and the explosion causes the piston to travel downward. (Both valves closed)


Exhaust- The piston travels upward and the gas produced from the explosion is pushed out the combustion chamber. (Exhaust valve open)

Nikolavs August Otto from Germany invented the the 4 stroke principle in 1876. 

The crank shaft transfers the pistons vertical motion into a torque motion. The camshaft controls when the valves open and close. The valve stem seals prevents oil entering the fuel and air mixture. The head gasket seals the head on the block. The piston is the component being forced down because of an explosion. That is what makes the power. The Piston rings have 3 purposes. The first ring is to keep compression in the cylinder, the 2nd ring is to remove excess oil from the cylinder on the downstroke. The oil ring stores a layer of oil for lubrication. The cambelt keeps the cams in time with the crank. The flywheel bolts to the back of the crank and holds to momentum of the engine. It also provides a place for the clutch to engage to the engine and transfer power to gearbox.                

Head Lamp Requirements

As shown of VIRM.

All auxiliary lights must turn off when dip beam is on. This can be achieved by running the lighting trough a relay so when dip beam is activated. The relay turns the high beam off. Also lights must not focus to the right. Headlights that focus to the right are mostly found on American and European vehicles. Lighting that focuses toward the right fail because they are blinding oncoming drivers. Where as left focusing lights focus toward the footpath.

Circuits: Series/Parallel

 During the Level 4 Electricity circuits we made series, parallel and compound circuits. We started with simple series circuits. These involve hooking up components in one loop. So one of my examples is, a wire from the positive terminal of power supply to a fuse. Then from the other side of the fuse to a switch, then to a bulb and back to earth again. If another bulb is added to the circuit mentioned before the bulbs will be half as bright. This is because the original 12V that the one bulb received has been split between the two bulbs. But the current in both circuits would be the same as the Amperage throughout a series circuit will be the same as it only has a single path to follow.

 Parallel circuits are different because they have more than one path the flow of electrons may follow. An example i did was to hook up two bulbs in a parallel circuit. In this circuit the two bulbs remained bright as they are both receiving 12V. However I found that the amperage is now not the same throughout the entire circuit. This is because the current now has two pathways to travel. So if the current is checked on each pathway you will find that it is half the current if checked just after the Power source.

 Parallel circuits can be found in the lighting systems of cars. All the dash lights and head lights at wired in a parallel manner. They wire it in this way so that if/when one bulb fails the others do not also go out. If they were wired in a series manner when one bulb blew the circuit would be completely broken and all bulbs on that circuit would fail.

Safety and Safety Equpment

 Safety is a very important issue for the course. For all the practical sessions we must have the minimum of safety boots and overalls. This is because there are many hazard's in the environment we learn in. Also we are required to attend a first aid course so we are prepared in the event of an emergency.

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