Journal of the Department of Agriculture, Western Australia, Series 3 Volume 3 Number 2 March- April,1954 Article 3 3-1954 The farm tractor, part.1 - how the engine works Follow this and additional works at: https://researchlibrary.agric.wa.gov.au/journal_agriculture3 Recommended Citation (1954) "The farm tractor, part.1 - how the engine works," Journal of the Department of Agriculture, Western Australia, Series 3: Vol. 3 : No. 2 , Article 3. Available at: https://researchlibrary.agric.wa.gov.au/journal_agriculture3/vol3/iss2/3 This article is brought to you for free and open access by Research Library. It has been accepted for inclusion in Journal of the Department of Agriculture, Western Australia, Series 3 by an authorized administrator of Research Library. For more information, please contact [email protected]. : //;W»«!«<f»---^»i "_-—" : Part 1.-How the Engine Works TVTO driver can look after his tractor properly unless he knows something of the ll way it works. The modern tractor is a sturdy machine designed to stand con­ tinuous hard work, but it contains a certain amount of complicated mechanism. All drivers, therefore, should know enough of the working principles of a tractor to be able to undertake the "maintenance" of the one they use. If through neglect or ignorance a tractor therein may be rather too detailed and too does not get proper maintenance— technical for the new-comer to tractor 1. It will never be capable of under­ work to grasp at all readily. Moreover, taking its full duty. there is an instruction book for every single 2. Repair bills will be heavy. model, and the maintenance instructions given for one are not always a safe guide 3. It will break down, generally at busy to the maintenance of another. These times. articles have been written, not to replace 4. Its working life will be considerably the instruction book, but to give beginners shortened. in particular, and even in some cases "old hands," an insight into the construction 5. Fuel will be wasted. and use of tractors in general. Thus they In the long run the only complete guide may more easily understand the detailed to the maintenance of a tractor is the instructions given by the makers of the instruction book issued by the makers. The tractor they have to operate. instruction book is the most valuable part of the tool-kit supplied with a new tractor. THE INTERNAL COMBUSTION ENGINE The kind of engine used in a tractor is called an internal combustion engine be­ The letterpress and illustrations in this cause it converts the heat energy of fuel series of articles are from a handbook into mechanical work by burning the fuel prepared by the National Institute of inside the engine itself. Agricultural Engineering (England) A steam engine, for example, is not an and are reproduced by courtesy of the internal combustion engine because the Institute and the British Ministry for engine part of it—cylinder, piston and so Agriculture and Fisheries. on—is quite distinct and separate from the fire-box in which the fuel is actually burnt. The fuel burnt in an I.e. engine can be any one of the following:—Coal or pro­ Any owner who has no instruction book ducer gas, petrol or kerosene vapour, or for his own particular model would do well diesel oil in the form of a finely-atomised to order one. But the information given spray. 133 Journal of agriculture Vol. 3 1954 The general principle of all I.e. engines THE SINGLE CYLINDER FOUR-STROKE is the same and depends on the fact that ENGINE air combined in the right proportion with The cycle of operations is shown in Fig. 2. any one of these fuels will form an ex­ plosive mixture. The various types of 1. Induction Stroke. engine differ from one another only (a) The inlet valve opens. according to the fuel used, the exact arrangements for introducing and explod­ (b) The piston moves down the cylinder. ing it, and the number of cylinders. For (c) Fuel and air mixture is sucked into tractors the most common and important the cylinder. type is the four-stroke engine starting on (d) When the piston reaches the bottom, petrol and running on a special kind of the cylinder is full of explosive mixture and kerosene known as vapourising oil. the inlet valve closes. 2. Compression Stroke. Fig. 1 shows a diagram of a four-stroke I.C. engine cut across the middle, and (a) Both valves are closed. viewed from the end. All the most import­ (b) The piston rises. ant parts are labelled, and will be referred (c) The mixture in the cylinder is com­ to throughout this book by these names. pressed into a much smaller space. Sparking Plug CYLINDER HEAD VALVE Valve Guide Compression Rings INLET or EXHAUST PORT CONNECTING ROD CRANKCASE Big End " ' XCrankshafr Timing Gear CRANKSHAFT SUMP FIG. I THE 4-STROKE ENGINE 134 Journal of agriculture Vol. 3 1954 ^THm£tse th,s § d Ve, arduo Ver 3SMl *«*«» 'heca?rV" n7h y «s ande\,Z'" *«)> 'ough roads J',"«»? «**b over tone ,i;",C cond'''t "s > C kea U • • • '^te^^^^m^'^e . JZ 'S '^ greasing and oil ft" epairs *«"<? beenZiT^0"^"'0^ ? Mr. Ferguson adds. „ ""• Australia^ ol°ufc^vear,nr p d r from owner, wh SET' ? ^o m r <^SB5SR*- i *°£&%°£^.*rf*ned and built, A Australia's Own Utility Australia's Own Pane! Van Australia's Own Cai HOLDEN #• Registered Trade Mark. •Jr There are two Air Chief Car Radios specially designed for Holden. *• Convenient hire ourohase terms are available through G.M.A.C.—General Motors' own finance companv Metropolitan & Statt Distributors: Metropolitan Distributors: SYDNEY ATKINSON MOTORS LTD. CITY MOTORS PTY. LTD. 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MS542M (Inc. in Gt. Britain) Please mention the 'Journal of Agriculture, W.A.," when writing to advertisers Journal of agriculture Vol. 3 1954 MIXTURE INDUCTION STROKE COMPRESSION STROKE EXHAUST • FIRING STROKE FIG. 2 EXHAUST STROKE 3. Firing Stroke. 4. Exhaust Stroke. (a) At the end of the compression stroke (a) The exhaust valve opens as the both valves are still closed. piston reaches the bottom of the firing (b) As the piston reaches the top of this stroke. stroke a spark at the sparking plug ignites (b) The piston moves up the cylinder the compressed mixture. again. (c) The force of the explosion of that (c) The burnt gases are driven out past mixture drives the piston down the the exhaust valve. cylinder. (d) The exhaust valve closes. \ 137 Journal of agriculture Vol. 3 1954 Then once more the inlet valve opens— or 1-2-4-3 depending on the make of the fresh mixture is drawn into the cylinder tractor. The more common is 1-2-4-3: but and the whole cycle starts over again. the firing order will usually be found An engine of this kind is called a four- marked somewhere on the engine. A four- stroke engine because, as indicated above cylinder engine runs smoothly and gives there are four strokes of the piston for a fairly uniform output of power because, each explosion. The explosion stroke is whatever the position of the crankshaft, the only working stroke, i.e., the only one one or other of the pistons is actually on in which the piston drives the crankshaft. the firing or "working" stroke. During the remaining three strokes of the cycle the crankshaft continues to turn PETROL STARTING FOR TRACTORS round because of the momentum of the RUNNING ON VAPOURISING OIL flywheel. Most tractors in this country use vapour- ising oil (kerosene) as fuel because it is THE FOUR-CYLINDER ENGINE relatively cheap. But a tractor cannot be Smoother running and a more uniform started from cold on vapourising oil be­ output of power will obviously result from cause this fuel will not turn into vapour using several cylinders with the corres­ until it has been warmed up. For this ponding pistons all coupled to the same reason all vapourising oil tractors are crankshaft as indicated in Fig. 3. started on petrol and should be run on petrol until their engines are hot enough The vast majority of tractor engines have four cylinders working on the above prin­ to vapourise the normal fuel properly. ciple, i.e., they have what are called four- cylinder four-stroke engines. In such an OTHER KINDS OF TRACTOR ENGINE engine one cylinder fires for each stroke: In America petrol is cheaper than it is that is, two cylinders fire during each com­ here so it is more often used as a tractor plete revolution of the crankshaft and fly­ fuel.