h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I need to spend some time on reading this in more detail, although ST picked up on most of the points I had done.

I agree some detail on diesels is needed, but I'm not sure how this can be best incorporated into the entry.

One minor thing; Gottlieb Daimler was also involved originally with the British Daimler - the part which has been affiliated with Jaguar since the 1960s. He then went on to work with Karl Benz and the German arm of Daimler.*

*I'm researching a Uni project on the history of most of the major British car manufacturers, and this was one thing I found. If anyone knows better, please tell me

Hi Rains, sounds like a good project, do you have a link by any chance?
I'd love to have a nose.

Six7's I'll go through this again shortly and post accordingly, this article is definitely worth doing and finishing, well done you for rescuing it, I missed it completely!

ST

The main project page is at A7440158, and all the entries are on my PS anyway - feel free to read away . RL has kind of got in the way of finishing it as quickly as I would like, though.

six7s, this will be a really good article soon, too!

Cool

So... it looks like we'll have something sorted soon-ish then

I should have some time to work on the entry on Sunday (ie Sat night UK time) so... fingers crossed

A13298330


Rains,

In anticipation of you filling the gap at <./>A13298330#Daimler</.> (and maybe more) I have added you to the Reseacher List

Thanks for the credit for the animated engine link, you didn't have to, I was glad to help. It might be worth giving Matt Keveney a quick 'hello' email just out of courtesy though. Most site owners are usually pleased to know their pages are being referenced as linking boosts their site rankings with the search engines.

Hiya Radox,

I figure if I get listed, anyone who does any research merits inclusion

Email sent to Matt K

Ok, see how you go with this then six7's. i hope it's of some use. It's, err, a bit long, sorry about that, seemed easiest way to do it in the end.

Article quote's have < > and suggestions have a * *

Not sure whether saying have fun with this is the appropriate word but have fun anyway!

ST.

ORIGINAL ENTRY DATA:
Entry ID: A633232
Edited by: Xuenyl
Date: 17 September 2001
Help wanted here
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The four-stroke internal combustion engine running on petroleum spirit (a.k.a. petrol and gasoline) forms the basis for the power plants of the majority of modern automobiles and has changed little since its invention in the late nineteenth century.

A Little History

The original four-stroke engine was patented in 1862 by a french scientist called Alphonse Beau de Rochas. Unfortunately, having perfected the theory, the Frenchman failed to build an operational engine and it was left to german engineer Nikolaus A. Otto who built a working prototype around 1867.

Engines based on Otto's principles were designed and built by another, more famous German engineer Gottlieb Daimler, who was the first to use the now widespread vertical cylinder in 1885 and then a two cylinder engine in the original 'V' arrangement in 1889.

Unlike Otto, the name Daimler is widely known today due to work in a link to Jaguar-Daimler here - see Daimler - Motoring Pioneers in A10114732(not edited yet) the eponymous brand of luxury cars (currently produced by Chrysler) and the involvement of Daimler-Chrysler with McLaren Cars, Ltd, of Formula 1 racing fame.

The Otto Cycle

Otto's eventual reward for his effort was the naming of the four-stroke cycle which gives the engine its name. The Otto cycle forms the basic principle of operation of the engine but to understand how it functions it is necessary to know a little bit of engine anatomy.

Basic Anatomy of the Four-Stroke Engine

The basic operating unit of a four stroke engine is the cylinder, so named because it normally takes the form of a cylindrical space in the engine block within which sits a flush fitting piston, also cylindrical and attached via a piston rod (which has the potential to move back and forth at its joint with the piston) through the open end of the cylinder to the crankshaft. The latter is a long metal rod which usually runs the length of the engine. There are U-shaped bends offset from the crankshaft sometimes called crankpins (similar to an old fashioned hand drill) which are normally at 90 but can also be at 180 degrees to each other.

Looking along the axis of the shaft, you would see one at each of the four points of the compass in a 4 cylinder engine. Each piston rod is attached to one of these crankpins and as the piston moves up and down in the cylinder, its 'reciprocating' motion is translated into rotation as the crankpins move around the crankshaft. The rotational motion of the crankshaft is later used to move the wheels of the vehicle via the clutch, gearbox

It's known as the final drive whether front or rear wheel drive.

Four Strokes, One Cycle

Each up or down movement of a piston is termed a stroke, hence the piston moves up and down twice and the crankshaft rotates twice in once cycle. Each stroke is associated with a different phase of the cycle. The four are termed Induction (or intake), compression, power (or combustion) and exhaust. An alternative terminology, much more memorable but disliked by purists is Suck, Squeeze, Bang, Blow.

Induction

In this first phase, the piston moves down, away from the top of the cylinder, increasing the space available between the two. This creates a negative pressure which, when an inlet valve in the top of the cylinder opens, draws a fuel and air mixture into the cylinder.

Compression

The inlet valve closes and the piston moves back toward the top of the cylinder, compressing the fuel and air mixture. The difference between the volume of fuel and air mixture when the piston is maximally down and maximally up is termed the compression ratio. It is normally between 8:1 and 10:1 but can be 12:1 or more if high octane fuels are used. Compression increases the potential of the fuel/air mixture to burn.

Power (Combustion)

An electrical spark generated by the spark plug in the roof of the cylinder ignites the fuel/air mixture, generating large amounts of heat and causing the mixture to expand rapidly, driving the piston downward and actively turning the crankshaft.

Exhaust

The last stroke involves the opening of the second valve (the exhaust valve) in the cylinder and the return of the piston to the upper position. The returning piston forces the remaining gasses in the cylinder out through the exhaust valve and into the engine's exhaust system.

Other Important Engine Parts

The four-stroke cycle applies to a single cylinder operating a crankshaft but many practical engines have several cylinders. There is also the problem of controlling the opening and closing of the valves. These are explained below.

Multiple Cylinders

The vast majority of internal combustion engines use more than one cylinder. This is entirely a question of efficiency. The limitation of the Otto Cycle is that it only provides power to turn the crankshaft a quarter of the time. The logical solution is to have four cylinders with pistons turning the crankshaft so at any time there is always one cylinder in the power stroke and the crankshaft is turned at a fairly even rate. An even more powerful method is to use extra cylinders at intermediate points in the cycle so that one power stroke starts before the previous one has finished.

Engines with 6, 8, 10, 12 and more cylinders have been created, either in straight rows or with the cylinders split into two banks in a V shape converging on the crankshaft. This allows for efficient transfer of power to the crankshaft without making the engine too large. Horizontally opposed engines with the banks of cylinders directly opposite each other have also been designed but these are generally limited to aircraft. Incidentally, aircraft engines usually have multiple spark plugs per cylinder as a fail safe device.

Camshafts and Valves

The inlet and exhaust valves of each cylinder need to open and close at specific times during the cycle. The most appropriate method of achieving this was found to be the mechanical linking of the valve timing to the crankshaft. Thus, when the engine turns more quickly, the valve openings speed up in proportion.



This was achieved originally by a timing chain driven via a sprocket on the crankshaft to a sprocket on the camshaft and a timing chain tensioner fitted approximately halfway between the two to take out any slack in the chain. The timing chain was used upto the introduction of overhead camshaft engines and then phased out in favour of a flexible combined rubber.canvas timing belt.

The camshaft is so named because distributed along its length . As the crankshaft rotates once every two strokes, the teardrop cams rotate at half the speed of the crankshaft. Therefore, the pushrods (which rest on the cams) are pushed upward by the tail of the teardrop once every four strokes.

*are teardrop shaped cam lobes*



raise one end of the see-saw like rockers, the other end of which presses down on the valve. The valves are shaped like mushrooms with their flattened heads inside the cylinder, held in the upward position by springs. The downward motion of the rockers pushes the head of the valve further into the cylinder and creates a space around the 'stem' of the valve, allowing the flow of gas into or out of the cylinder.

*The pushrods used on overhead valve engines*

Overhead camshafts replaced the internally fitted camshaft that required additional moving parts to operate such as cam buckets, rods, tappetts, plus the overhead valves needed regular maintenence to ensure efficient running of the engine by having the gap between the tappet and the valve constantly adjusted.

Overhead camshafts were fitted at the top of the engine directly over the valves thus doing away with the need for push rods and tappets. Early overhead cams still needed adjustment of the cam followers, the equivalen to the tappet but eventually this was done away with as hydraulic tappets were used that required no maintenence or adjustments whatsoever.




*the above paragraph not really required, duplicates previous one.*

Fuel Systems

The fuel and air mixture which is supplied through the inlet valve is traditionally supplied by a device called a carburettor. The most important bit of the carburettor is a narrow tube known as a venturi, through which air flows on its way to the inlet valve. Because a vacuum is created in the far end of the venturi by the intake stroke of the Otto Cycle, fuel is drawn from a jet into the venturi, vaporising as it passes through the tiny nozzle of the jet. The flow through the venturi is controlled by the engine's throttle, the higher the setting, the more air, and therefore the more fuel is drawn through the carburettor and the faster the engine can work.

Fuel Injection

Most modern cars have fuel injection systems which involve the of vapourised fuel into the inlet pipe, removing the necessity for a carburettor. The injection units are normally electronically controlled, allowing for much more accurate regulation of the amount of fuel which enters the cylinder, producing more power, more economy and fewer emissions. See the article on Fuel Injection for more details.

*or indirect injection*

Electrical Systems

As has already been alluded to, combustion in a four-stroke petrol engine has to be initiated by an electrical spark when the piston is at the top of the cylinder. This is typically timed to occur just before the end of the compression stroke, in order to allow the burn time to take hold. The spark is provided by a spark plug which is the end point of an engine's electrical system. The important bit of a spark plug is the two closely placed contacts inside the cylinder between which an electrical pulse arcs 1 creating a spark.



Note:- I would delete the paragraph above and replace with something similar to this:-

*The electrical system on a vehicle is generally referred to as a 12volt system as the static power supply is from a standard 12volt battery however when the engine is running then the alternator output increases the voltage to an average of 13.5 to 14.5 volts. This is known as systems voltage.
systems voltage fed to the ignition coil is transformed into high voltage, typically on a points ignition system, the high tension voltage is around the 70,000 volts. On newer electronic ignition systems the high voltage output from the coil can be in excess of 120,000 plus volts! This charge is carried to the distributor via the high tension coil lead, also known as the king lead.*



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HELP!!! input from an expert required here



*The points (contact breakers) are fed by systems voltage, however as the points will only operate at exactly 12volts a condensor is fitted so's to reduce the systems voltage to a stable 12volt supply.*



*Contact breakers were replaced with electronic ignition modules which were fitted either in the distributor where points used to be or on the outside body of the distributor. They did exactly the same job as points except now it was done electronically, doing away with the need for points and condensors and also being more reliable as there are no moving parts so no wear and tear and no regular maintenance or adjustments needed as in points systems.

Yet further advancement was realised by the distributorless ignition system, where the ignition is controlled by an electronic control unit (ECU).*



The alternator gives out an average of 15 to 25 amps current under normal running conditions. However as more electrical components are switched on, for example, headlights, wipers etc., then the alternator output increases to maintain charge in the battery and to run the additional electrical loads. Typically an alternator can give out as much as 70 amps at maximum output.

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Distributor

The distributor is possibly the most technical part of the electrical system. Its task is to connect the electrical energy from the coil to the spark plug supplying each cylinder in turn. Electricity is supplied via a low tension lead to the distributor that has, at its centre, a rotating arm (a.k.a. rotor)

each of which are connected (via high tension leads) to the spark plugs. For the engine to produce more power, the cylinders must fire more rapidly, which means the rotor arm must spin faster.

*the Rotor arm passes each contact in the distributor cap thus passing the spark to the plug leads, which in turn feeds the high voltage to the spark plugs creating the spark necessary to ignite the fuel/air mixture in the cylinder.*

The rotor arm speed is governed by the speed of the camshaft as the distributor is driven by the camshaft either via a gear or offset keyway. The vacuum pipe seen on early distributors actually moved the base plate in the distributor, which in turn had the effect of advancing the timing marginally, the unit shaped like a bellows on the side of the distributor was called the advance retard unit.

Starter Motor

The electrical starter motor is essentially quite a simple gadget which turns the cranshaft and allows fuel and air to be sucked into the cylinders to start the Otto cycle, which is self perpetuating once the engine is running. It is powered from the battery and can be activated once the ignition has been switched on, the latter providing power to the coil and thereby the sparkplugs.

Summary

As can hopefully be seen from this article, the petrol powered four-stroke internal combustion engine is something approaching a technological miracle. A complicated piece of equipment in which each component is intimately related to several others and dependant on them for its proper functioning. It is a testament to the original design that the essential principles have changed little in 130 years despite the improvements in materials science and electronics which have lead to significant improvements in the power, efficiency and reliability of these engines. There are few other inventions which can claim such lasting success.


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A few comments on OHC versus OHV

put simply overhead cam engines are more fuel efficient, use less horse power to be driven hence increased power to the engine and ultimately final drive, hence a faster car in mph terms.
There are less moving parts so weight of engine and wear and tear also vastly reduced. There is no regular adjustments to make on OHC engines, cambelts need to be changed but the intervals for change are quite long in terms of time or mileage, typically 100,00 miles or 3 years, some cars today it's even higher.
Valve timing is more accurate with OHC as the tolerances can be a lot closer in terms of the gap between cam lobe and valve head.hydraulic tappets means any wear is automatically taken up without need for manual adjustment hence running costs are lower as less servicing required.

OHV
usually run via a timing chain that wears and rattles over a period of time, too many moving parts used to make what is a simple operation work. Apart from chain and tensioner, there are cam buckets that sit on the cam lobes, push rods then sit in these up to the top end where they sit under the tappet. the tappet has a nut and screw in one end that is used to set the gap between the tappet and the valve, this requires regular adjustment to prevent rattles and ensure the best possible operating efficiency in opening and closing the valves the right length of time for each cycle.

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the term 'petrolheads' is one which qualified motor engineers/mechanics and technicians refer to as enthusiatic amateurs who 'play' around with engines and motors without any formal qualifications or mechanical training. The Top Gear presenters are a classic example in my view of petrolheads.</>


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1 Jumps

Ooops a daisy, meant to cut some off, have copied instead, sorry about that. Did'nt intend copying the lot like this!

I'm back... having been distracted by RL and a dose of the 'flu

I have (I hope) incorporated what Straighttalker supplied above

I have added a footnote to ROTOR

I think it would be a good idea to have something about ROTARY engines - any tips/ideas/etc?

The bit about direct/indirect is still messy

There are still a few loose ends:

<./>A13298330#Daimler</.>
Need to find a link to Daimler. (A10114732 is NOT edited... yet)



<./>A13298330#interp</.>
This is where I need Straighttalker to have a close look and see if/where I have got anything wrong - which is highly likely, as I had some input from an engineer friend... and the convo was rather tangential at times



<./>A13298330#help</.>
Things are still quite messy here.
Any input welcome



<./>A13298330#toDo</.>
There is still quite a bit to do at what is (currently) the bottom of the page.

I would really like to better incorporate the bit about 'petrolheads' (with the link to Top Gear'




-----------------

Although there's still quite a bit to do, I think this entry should stay in PR for now as, going by the last flurry of activity, a lot can happen quickly... as long as RL doesn't get in the way

Hi six7's Ok, in order to make this a bit easier I'll do this in sections so's to avoid another boo boo when i post. Apologies again for earlier, it looks a mess!!

starting with this part:-



1/ **For effective combustion, a spark plug is supplied 70kV, which is acheived simply acheived by converting the ??amp, 12V supply to ??A, 70kV in the ignition coil, which is connected, via HT leads, to the rotor within the distributor.**

As 70kV would burn the points, a condensor is used in order to reduce the systems voltage to a stable 12-volt supply at the points.

2/**in excess of 120,000 volts, modern systems the old points and condensor distributors have been superceded by electronic ignition modules and also being more reliable as there are no moving parts so no wear and tear and no regular maintenance or adjustments needed as in points systems.

Yet further advancement was realised by the distributorless ignition system, where the ignition is controlled by an (ECU).

-----------------------------------------------------------------------

1/ ** In order for combustion to occur a spark is deliverd to the cylinder via the spark plug which ignites the fuel/air mixture within the cylinder. The spark is provided by the distributor via High Tension Leads, known as HT leads or simply as spark plug leads. Number of cylinders per engine dictate how many plugs and plug leads there are.The spark is distributed to each plug lead by the rotor arm within the distributor which passes a contact in the distributor cap where the plug leads are fitted.
The original source of the spark is generated by the ignition coil which feeds the distributor via a single high tension lead known as the king lead. The coil can generate up to 70kv in standard points ignition systems. This is a high tension feed and does not feed the points in any way.There are 2 circuits to an ignition system, Primary and seconday. Primary is the standard 12v feeds and the secondary is the high tension/voltage feed.

2/** in modern systems the old points and condensor distributors have been superceded by electronic ignition modules and are more reliable as there are no moving parts so no wear and tear and no regular maintenance or adjustments needed as in points systems. The modules do the same as the points in making and breaking a circuit only modules do it electronically rather than mechanically. Yet further advancement was realised by the distributorless ignition system, where the ignition is controlled soley by an with various electronic sensors placed on the engine.(ECU).

See what you think of this six7's.

I'll plod on with the other shortly.
ST.

Ref. petrol heads:- not sure whether it should be in the article as such, it was more an observation on what we in the trade referred to them as. Boy racers also comes to mind for same reason, they know very little if anything about a vehicle yet, so say, tune engines to max and race them resulting invariably in blown engines or worse.
The term boy racers today means something completely different, as in youngsters driving like idiots.



1/**Overhead camshafts were fitted at the top of the engine directly over the valves thus doing away with the need for push rods and tappets. Although early overhead cams still needed adjustment of the cam followers (the equivalent of tappets), by 19XX these had been superceded THE INVENTOR'S NAME's hydraulic tappets, which require no routine maintenence whatsoever.

1/**To be honest not sure of the year OHC's first started appearing. As is usually the case we were some 15 to 20 years behind the Americans on this as we were with catalytic converters. Nor do I know who actually invented the now commonly used hydraulic tappetts, again the americans were using this system long before we started to.

ST.

Thanks!

Is the following right?

Yet further advancement was realised by the distributorless ignition system, where the ignition is controlled solely by an electronic control unit(ECU) with various electronic sensors placed on the engine.

(The words "electronic control unit" were missing in what you wrote above - and I guessed )

did I mention in my ps I sometimes make 2 short planks look intelligent?

You are correct sir! My mistake.

Simpost city!

Thanks again

I like the 'petrolheads' bit - but, as you say, it ain't crucial

I can (will?) do some research myself on the history of OHCs... cos I think it would add a bit, esp for the 'lay' reader

I shall dig out the remains of my college study books in the meantime, I'm sure there must be something there as well. Be a trip down memory lane if nuffink else!

I don't think they're in hiroglyphics [sp] still



*mutters, darn sure thats not how it's spelt*

I have been a-Googling for info on the history of overhead valves/cams and found some amazing stuff

Weird thing is... cos I'm not the expert, I need/want you peers to tell me which bits are important

There's guff (with links) on:
A replica of The Otto-Langen Atmospheric Engine,
The Springfield Type A (the first overhead cam engine with fuel injection)
A 1913 overhead cam Isotta-Fraschini (80+mph!)
and
David Dunbar Buick - who produced the revolutionary "Valve-in-Head" overhead valve engine



Rather than clogging up this thread, I have pasted them to the bottom of the page - where they can be deleted

<./>A13298330#pasted</.>

Also... suggestions please as to where the link to 'keveney.com: Animated Four Stroke Engine' should go

hi six7's, I think we need to decide just how deep/technical this article is going, it could end up quite large at the rate we're currently going. we have'nt even touched on diesel engines yet or the rotary.

Food for thought as they say.

six7s, RL has been a bit hectic .

The Jaguar/Daimler entry isn't edited yet - the uni project it's part of (and the entry itself) isn't 100% complete. The house rules state that you can't link to unedited entries so you probably won't be able to link to it.

Daimler-Chrysler don't make Daimlers - the luxury brands are Mercedes-Benz and Maybach. Jaguar make Daimlers - though these are retrimmed and re-badged Jaguar XJs. Despite the name, there is now no connection whatsoever between Daimler-Chrysler and Daimler (Jaguar).

Gottlieb Daimler worked closely with Dr Otto on the internal combustion engine - he also hired Wilhelm Maybach to help with this research, whom Daimler set up his own workshop with in 1892.

Incidentally, Karl Benz and Gottlieb Daimler never met, despite the fact that they both worked in Stuttgart and Mannheim on internal combustion engines, and today's company uses both their names.

<< we need to decide just how deep/technical this article is going >>

I have been wondering about that too

I have a hunch that it would be an intersting read if:
-----
a paragraph or two (max?) was added about Otto, Daimler and maybe one or two other 'names' - anecdotal stuff (like what Rains has written above) that make the names 'real'
-----
the 1st few paragraphs (down as far as/including the bits about Suck, Squeeze, Band and Blow) were left (pretty much?) as they are now
-----
everything after that was deleted and replaced by a paragaph that includes the terms

# Multiple Cylinders
# Camshafts and Valves
# Fuel Systems
# Electrical Systems

as links to other webpages... My thinking being that thanks to the curators, as and when guide entries on those topics are written, the links could be quickly changed to suit
-----

Waddaya reckon?