Thursday, 30 December 2010

Operation and Care of Make and Break Engines

From Marine Gas Engines, Their Construction and Management, written by Carl H. Clark, published by D. Van Nostrand Company in New York in 1914.

CHAPTER XII. Operation and Care of Engines

Starting. - Before attempting to start an engine one should acquaint himself with the operation of all parts of the engine, and the water, oiling, and ignition systems.

If the engine has been standing some time, the ignition system should be tested to make sure that it is in good order. The make-and-break system may be tested by first closing the switch in the circuit, then turning the flywheel until, by observing the action of the mechanism, the points inside the cylinder are known to be in contact, closing the circuit. The wire is then removed from the insulated terminal of the igniter and brushed across it; if the circuit is complete, a brilliant spark will result. If no spark is obtained, all connections must be examined and, if necessary, the sparking points removed from the cylinder and cleaned. After a spark has been obtained through one cylinder the other cylinders should be tested.

The jump-spark system is tested by removing the plug from the cylinder and resting it upon any of the bright metal parts of the engine with the secondary wire still in contact. With the primary circuit closed the engine is then turned until contact is made by the timer, which should be indicated by the buzz of the vibrator. The sparks should pass across the points of the plug at the same time. If no buzz of the vibrator occurs, it shows a defect in the primary circuit. If the vibrator buzzes, but no spark passes the sparking points, it shows a fault in the secondary circuit. This may often be remedied by removing any deposit of carbon or oil which may have collected on the points of the plug, or by fitting another plug. After a rain, or in damp weather, the most common sources of ignition troubles are weak batteries or a "ground." The former can be found by testing the batteries with an ammeter; the latter is caused by the current, especially the secondary, jumping across from the wire to some adjacent pipe or other part. It may be found by carefully examining the wires, or, in the case of the secondary current, the sparks may be seen to pass where the current jumps. The wiring of each cylinder should be tested in turn. At the same time that the ignition is tested, the point of ignition should be noted in reference to some point on the flywheel, and its variation with the different positions of the timer handle noted. The gear or timer should be so set that the spark occurs when the piston is at the top of its stroke.

Oil- and grease-cups should now be filled and a small amount fed from each.

The fuel supply should now be turned on, both at the tank and at the carburetor. The needle valve on the carburetor or vaporizer should be opened slightly and the carburetor primed somewhat to make sure of a good flow of fuel. The engine may now be turned over by hand in the direction in which it is to run, using the crank, lever, or flywheel rim, as the case may be. After a few trials the engine should explode a charge and turn a few turns and possibly continue to run. If it does continue to run, the fuel and air supplies should be adjusted gradually until the engine turns at its highest speed. Oil-cups should then be opened to allow the oil to feed.

If, in the case of a four-cycle engine, it does not start at once, all that is necessary is to turn it under varying conditions of fuel and air supplies, after making sure that the ignition system is operating and that fuel is flowing to the carburetor. In the case of a two-cycle engine the fuel should be shut off and the compression cock opened. It is probable that several charges of gasoline have been taken into the base and not exploded, making the mixture far too rich and "flooding" the engine, as it is turned. The flywheel is now turned several times and the mixture diluted and partially expelled. An explosion will finally take place and the engine run until the supply in the base has been used up.

Another trial can now be made, with a reduced fuel supply, and continued under varying conditions until the engine starts, always making sure that the ignition occurs properly, and taking care not to flood the base. Starting is often made easier by priming the engine, that is, by inserting a small amount of gasoline directly into the cylinder through the compression cock, or through special priming cock which on some engines is provided for that purpose. When turning the engine over by hand, care must be taken to have the sparking gear so set that the spark cannot occur until the piston has reached the top of its stroke. If this is not done and ignition takes place before the piston has reached the top of its stroke, it will be driven violently downward in the wrong direction, giving a "back kick," which is liable to cause damage.

After the engine has run a short time it will often gradually slow down and finally stop, with a muffled explosion in the base. This is a sign of a weak mixture, and the fuel supply should be slightly increased. On the other hand, if the engine labors, slows down, and finally stops, with black smoke issuing from the exhaust, it shows a too rich a mixture and the fuel supply should be cut down.

The best fuel mixture can be found only by experiment, and will even then vary somewhat, according to atmospheric conditions. The proper regulation of the air supply to the fuel supply has a marked influence upon the fuel economy.

Two cycle engines of the two-port type are easily and readily started as follows: The spark is advanced to a point somewhat below the usual running point so that the ignition will take place on the up stroke when the engine is turned in the opposite direction to which it runs. The flywheel is then turned until the piston is at the bottom of its stroke, and is then rocked backwards and forwards a few times; the piston thus acts as a pump, drawing a few small charges into the base and charging the cylinder. The flywheel is then turned quickly in the reverse direction to which it runs, bringing the piston up against the charge, which finally ignites and forces the piston down again, but in the right direction. The flywheel is then released and the engine starts. The spark is then restored to the running position.

This method cannot be used on a three-port engine, which must be started by turning it over the center.

Some engines will start with the compression cocks fully or partly open, which lessons the labor; others must be pulled over against the full compression.

In starting the engine with a crank or lever it should be held loosely in the hand, so as to be quickly released in the event of a back kick. Frequent accidents happen from the discard of this precaution.

Oiling. — When the engine is well started the fuel and air supplies should be regulated until the engine is running on the least possible amount of fuel. The oil supply should be refuted to a point just below that at which smoke would issue from the muffler. Blue smoke coming from the muffler usually shows that too much oil is being fed, which instead of being of use in the engine is burned or carried away by the exhaust, and wasted.

The cylinder oil-cups should be adjusted to feed from three to six drops per minute, according to the size of the engine. Where splash lubrication is used, oil must be fed into crank case or base at intervals. Exterior parts, such as thrust bearing, igniter gear, and pump journals, are, of course, oiled from an oil can when necessary. In running a new engine, oil should be used rather freely at first while the bearings are wearing down into place. The cylinder surface may be greatly improved by feeding in some powdered graphite mixed in oil, which fills up the pores and helps to form a sort of scale on the bore of the cylinder. While too much oil should not be fed, as it is not only wasted, but makes the engine dirty, a sufficient lubrication should be made certain at all times, as much damage may be done in a short time if bearings are allowed to go dry.

Under some circumstances good results can be obtained by mixing the lubricating oil with the gasoline in the tank and feeding both together. No difficulty is experienced with the vaporization and the lubrication is simplified. Although the relative amounts will vary considerably, a fair proportion seems to be about one pint of oil for every five gallons of gasoline.

Spark Advance. — While running the engine it will soon be noted that the time of ignition has a great effect on the speed. It will be found that the engine runs best when the ignition takes place just before the piston reaches the top of its stroke. This is due to the fact that the burning of the charge is not instantaneous, but requires an appreciable time. If the charge is fired at the moment when the piston is at the top of the stroke the time taken by the charge to thoroughly ignite allows the piston to descend through a part of the down stroke, so that some of the effect of the impulse is lost. If the spark is so timed in advance that the charge is completely ignited at the time when the piston is just ready to descend, the full effect of the impulse is received and absorbed.

This advance of the spark is called the "spark advance" or "lead." It will of course vary somewhat according to the speed. The speed of the engine can be varied by shifting the point of ignition, and this is advocated by many. Starting with the spark occurring as the piston is at the top, it will be found that up to a certain point the speed will increase as the spark is advanced. Beyond this point the engine will pound and act irregularly. If the spark is retarded until after the piston has begun to descend, the speed will decrease. The speed of the engine may thus be regulated by changing the spark advance, but this practice is not to be recommended, as nearly the same amount of fuel is passed through the engine per stroke at all speeds. At low speeds the charge ignites so slowly that all the heat generated cannot be absorbed, but is passed along into the exhaust pipe and muffler, heating them beyond their usual temperature. The speed of the engine should be regulated by the throttle which is usually provided for that purpose; in this way the amount of the mixture is cut down in proportion with the speed. The speed should be regulated by the throttle and then the spark advanced to the best point by trial. In this way the greatest economy in the use of fuel may be obtained. Extremely slow speed must, however, be obtained by retarding the spark, in connection with the throttle.

Care of the Engine. — The degree of care which the engine receives, not only when running, but when laid up as well, has a great effect upon its life and also its satisfactory operation. Many engines which are well taken care of while in operation are allowed to suffer from exposure during the time when they are not in use. If the engine is in a cabin boat it is very easily kept in good shape, but if in an open boat, constant care is required to prevent it from being damaged by rust. A cover should be made from waterproof canvas, which will fit snugly over the engine and shed all rain. A water-tight pan under the flywheel will prevent the bilge water from rising around it and causing it to rust. Before leaving the engine for a few days all bright parts of iron or steel should be smeared lightly with grease, which may be readily removed with cotton waste. This precaution will save a large amount of scouring and polishing later.

One should become thoroughly familiar with the construction of his engine as soon as possible. It is not meant by this that the engine should be pulled down just to see how it is constructed, but quite the contrary. As long as the engine is running, particular pains should be taken not to disturb it. The construction should, however, be studied so that in case of necessity it could be taken down. Much expense can often be saved by this knowledge, as there are many small repairs which can easily be made by the amateur owner.

Before starting on a run all nuts and bolts should be examined, and any which may be loose should be tightened.

Engine Troubles. — The presence of trouble in the engine is usually indicated by a peculiar hammering noise, known as a "knock." It may be caused by excessive friction on some part and the oiling system should be at once examined and perhaps an additional amount fed for a few moments. A similar knock may be caused by the failure of the water-circulating pump, which may be told by the unusual amount of heat radiated from the cylinders. The lack of cooling water causes the cylinders to become much too hot for use, increasing the friction and eventually causing damage to cylinders and pistons. If the knock cannot be found in this way, the engine should at once be stopped, as damage may be caused. The knock is probably caused by some part which has become loosened, and all parts should be thoroughly examined. A loose flywheel is a common cause of knocking. Where the flywheel is fastened with a key, the keyway may become worn so as to leave a small space between it and the sides of the key, allowing the flywheel to “play” slightly around the shaft. If this is the case the key should be withdrawn and a slightly wider one fitted, or a thin “shim" of steel may be carefully fitted into the keyway and the key driven in alongside of it.

A bearing which has become overheated and ground out will cause a knock; this is a more difficult cause to remedy, and is likely to require the services of a machinist to reset the bearing.

Sometimes the engine will run with apparently no trouble, and yet will show less than the usual power. This may be due to loss of compression, or in other words, a leakage from the compression space. This may be due to a loose plug or screw at some point, or in the case where the cylinder head is fastened on with studs, it may mean that the gasket under the head has become broken at some point and may be remedied by fitting a new gasket. If the cylinder has been flooded too freely with oil, the excess may carbonize and collect around the piston rings, cementing them to the piston and allowing the gas to escape by the piston. This may often be remedied by flushing the cylinder with kerosene oil. It may often be necessary to remove the cylinder and separate the rings from the piston. In removing the rings from the piston great care is necessary as they are of cast iron and very brittle. Before attempting to remove them they should be well washed with kerosene, to loosen them as far as possible. In removing a ring, one comer should first be raised with a screw-driver or other tool, and a narrow strip of tin placed across the groove under it to keep it from springing back; this is followed up all around the ring, tapping it lightly and adding more strips until the ring is entirely supported clear of the groove. It may then be slid from the piston. Rings and grooves should be thoroughly cleaned with the help of kerosene. In replacing the rings the reverse operation is followed.

In the four-cycle engine it is necessary to "grind in" the valves at intervals when the seats and surfaces become pitted or worn. When the valves are arranged, the inlet valve may be removed to allow access to the exhaust valve. The springs are removed from the stems, the valve is raised and the bevelled edge smeared with a paste of oil and emery. The grinding is done by rotating the valve in its seat by means of a screw-driver or brace; the process is continued until the surfaces are left smooth and polished with no sign of corrosion. This paste is then removed and the finish put on with a mixture of water and pumice. During the grinding the entrance to the cylinder should be carefully stopped with a wad of waste to exclude the emery from the cylinder, where it would do great damage. If the inlet valve is removable it may be ground while held in the hand.

In replacing the valves it may often be found difficult to compress the springs sufficiently lo allow them to be replaced. If no other means is at hand the spring may be compressed in a vise and bound with a few turns of strong cord. It may then be slipped on the stem and the key and washer put on. The string may then be cut and the spring let out.

Care of Spark Coil and Ignition Outfit. — The entire ignition outfit is somewhat delicate and requires its share of attention. It should be examined at intervals to make sure that all binding screws are tight and all contacts good. The insulation should be examined and any places where it becomes worn should be taped. Two parallel wires should never be fastened by a single staple, as the insulation is likely to chafe through, causing a short circuit. Each wire should have its separate staples.

The most common place for a wire to break is at some place where it is bent back and forth, as where the wires are connected to the timer; a short coil at such points will greatly increase the life of the wire.

The entire system, including the plugs and sparking points, should be kept clean and free from oil. Oil on the outside of the plug will cause a short circuit, as does the collection of soot around the points.

The spark coil should be looked over and if necessary readjusted slightly. Many operators set the vibrator adjusting spring too tight, with the idea that the very rapid motion gives a stronger spark. This may seem true when tested in the atmosphere, but on a quick running engine it may give trouble by skipping. A more reliable spark is given with a moderately rapid vibration of the buzzer, with considerably less battery consumption. A satisfactory adjustment of the vibrator may be obtained as follows: The vibrator adjusting screw is drawn back until it is clear of the spring; the spring is then set so that the iron button is from 1/16 to 1/8 inch from the end of the core. The adjusting screw is then screwed in until it touches the spring lightly. The engine is then started and the screw turned in slightly until the engine runs steadily; the spring should be left as weak as possible and still have the engine run steadily. The spring must bear against the screw when the engine is not running, as otherwise no current will pass and the engine will not start. In testing the spark in the secondary circuit, the spark should not be drawn out to the limit, as this strains the coil and is almost sure to cause trouble if there is any weakness in the coil.

Batteries. — The batteries also should be examined occasionally. Weak batteries may be located by testing with an ammeter. When new, dry batteries of the usual size should test from 18 to 25 amperes, and as a rule they should not be used after they have fallen below about 8 amperes. A single weak battery will spoil the action of an entire set; even if no new ones are at hand the action will be improved by cutting out the weak one. In testing a battery, the ammeter should be held across the terminals only long enough to get the reading, as if held there even for a short time the battery s quickly run down.

Batteries which have been run out may be temporarily revived by punching a hole in the top and pouring in the water.

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As an armed forces brat, we lived in Rockcliff (Ottawa), Namao (Edmonton), Southport (Portage La Prairie), Manitoba, and Dad retired to St. Margaret's Bay, NS.
Working with the Federal Govenment for 25 years, Canadian Hydrographic Service, mostly. Now married to Gail Kelly, with two grown children, Luke and Denyse. Retired to my woodlot at Stillwater Lake, NS, on the rainy days I study the life and work of A. Hyatt Verrill 1871-1954.