FARM OIL ENGINES.

Hauraki Plains Gazette, Volume XXXIII, Issue 4384, 1 March 1922, Page 3

FARM OIL ENGINES.

CAUSES OF TROUBLES. HOW TO CORRECT THEM. (By J. T. Brown, M.1.M.E.) For the benefit pf the many farmers who have to overcome oil-engine troubles, the following notes are reprinted from the journal of the Ruakura Farm of Instruction. The notes were originally given in the form of lectures to students, by the instructor, Mr J. T. Brown, M.I.M.Ey (manager fbr the Paeroa Engineering Co., Ltd.), and have been issued with other ,lec; ture subjects in booklet form by th? School for the benefit of farmers throughout the province : The internal combustion epgine, or, as it is commonjy called, “the oil engine,” depends for its successful, operation upon the fact that a mixture of benzine (or kerosene) and air will give an explosion if sufficiently compressed.

If compressipn was carried to the limit “spontaneous combustion,” due to the heat of compression, would take place. That is to say, explosion, or, correctly speaking, expansion, will occur without assistance * from a spark plug or hot tube. , It. has been found impracticable to make use of this "high compression” in small-powered engines, such as are used for farm.--purposes, and the compression pressures used average about 60 to 701 b per square inch. This makes necessary the use of l a spark plug or other device to fire the mixture. It will be understood that the 601 b -spoken of is the pressure of the mixture in the cylinder before “explosion” takes place, and must not be confused with pressure “after” ex; plosion, which can, and does, attain 500 to 600 pounds per square inch. Now, it may be accepted that a mixture of nine parts air and one part benzine, and compression to sixty pounds per square inch, will, after /explosion, exert a mean pressure of eighty pounds on the piston during its passage from end to end of the cylinder. Oil engines work upon what is known as the "Otto" or four-cycle principle, which is as follows: On the first dowri'-stroke of the piston the mixture is .taken through th© vaporisor (or carburettor) and inlet valve into'the cylinder. On the first up- : stroke, this mixture is compressed into the top of the cylinder, where the charge is ignited, and the result; ant explosion forces the piston down on the second out stroke. On the second up-stroke of the • piston the burnt gases escape to the atmosphere • through the opening of the exhaust valve. This cycle of operations is repeated as long as the engine is running. Now this gines, whether they be of the “higfi*. tension spark plug,” low-tension make and break,” or ' “hot ’tube ignition” type. The lastnamed is the most commonIn starting up this class of engine the ignition tube is heated up by means of a "Primus” lamp. This usually takes about ten, minutes. After the engine, is running the heat of the explosion keeps the tube hot, and the lamp is not required. Ignition by means of! a “high-ten-sion magneto” is the system now generally adopted, and is the most reliable/ It dispenses with the hightension coil and battery, which were in common use before its introduction. No heating is necessary, and the engine can be started up from cold, a very helpful feature in the milkingshed, as the time saved can be usefully employed in other work. 1 The lowutension make-and-break system is now seldchtt seen, though ft has special value in the case pf engines using suction gas as the motive power. It is generally found, on the large engipes of butter factories. The system is mechanically operated (by push rods and springs, thp closing of the points causing the current necessary for ignition to flow and the separation causing an electric arc which fires the mixture. It is very reliable if the points of contact are kept bright and clean, and the fired point well insulated from the engine,.. . As failure to start the engine may be due to many causes, I propose to give sqme of the most common, with their remedies.

Lack of Compression.—This may be due to: (1) Leaky valves. (2) A broken valve spring. (3) A valve stuck in the guide. (4) Worn or broken piston rings. (5) Worn or enlarged liner in the cylinder. '(6) Defective circulation of z water in the cylinder jacket. The remedy for the . first defect is to grind the valves. This is done by smearing the seat with carborundum paste and rotating it- back and forth with an occasional lift fo..change its position on the engine seating. The operation is complete when the valve face shows a very fine unbroken line around its circumference. Never torn the valve continuously iii one direction, as this grooves the face and preh vents the making of a tight joint. If the valve face is deeply pitted and -grooved •it will be advisable to have it l turned in the lathe. If this is not possible a good job can be made by filing, if care is taken to see that the bottom of the groove is taken as a guide while doing so. The remedy for the second is obvious —replace the spring. For the third defect, remove the valve, clean the stem and the guide with kerosene. Most makers supply rings to replace breakages, and if the cylinder is not worn the fitting of new rings will prove satisfactory. To fit) the rings on the piston it is necessary to F V>ree strips d? tin about three eighths of an inch wide and three inches long. Bend bne end of each just sufficientHy to rest on top of the pis z ton and space the three at even distances around the circumference. Slip the ring over these strips until it is opposite the slott you wish it to occupy, then, dithdraw them, and the ring willj drop into position. The remedy for the fifth defect is to have the. liner rebored and a new piston and rings fitted, or re-turn the (Continued on page 4.)

IN THE MAGISTRATE’S COURT. ‘ HOLDEN AT THAMES. In the matter of “The Local Elections and Polls' Act; 1908,” and its Amendments! and in the matter of “The Local. Bodies Loans Act, 1913," and in the matter of ,a certain Poll taken in the Hauraki Plains Cotinty on the I,Bth day qf January, 1922. WHEREAS a Petition bearing date the 22nd day of February, 1922, was filed dn z the office of this Court at Thames on the 23rd day of February' 1922, praying that an Inquiry be held in terms of Sections 45 to 50, both inclusive, of the Local Elections and Polls Act, 1908 and its Amendments, with regard to a certain Poll taken on the 18th day of January, 1922, on a proposal to borrow the ' sum of thirty thousand six hundred pounds for the purchase of land, erection of County Chambers, purchase oif furnV ture, machinery, pliant, and purchase of quarries, quarry sites and machine ery and other equipment therefor, which proposal has been declared by the Returning Officer to have been carried, NOW, THEREFORE', i- John Hearsey Salmon, Stipendiary Magistrate exercising jurisdiction in the s.aid Court, do hereby appoint Tuesday, the 7th day of March, 1922, as the time 'and the Courthouse at Thames aforesaid as the place for holding such Inquiry. DATED at Thames this 27th. day of February, 1922. JOHN H. SALMON, Stipendiary Magistrate.