MOTOR DRIVEN FIRE APPARATUS
(Concluded.)
While troubles existing in the ignition or carburction groups are usually denoted by imperfect operation of the motor, such as lost power and misfiring, derangements of the lubrication or cooling systems are usually evident by overheating, diminution in engine capacity, or noisy operation. Overheating may be caused by poor carburction as much as by defective cooling or insufficient oiling. When the oiling group is not functioning as it should, the friction between the motor parts produces heat. If the cooling system is in proper condition, as will be evidenced by the condition of the water in the radiator, and the carburetion group appears to be in good condition, the overheating is probably caused by some defect in the oiling system
The conditions that most commonly result in poor lubrication as outlined at big. 109 are: Insufficient oil in the engine crank case or sump, broken or clogged oil pipes, filter screen filled with lint or dirt, broken oil pump, or defective oil pump drive. 1 he supply of oil may be reduced by a defective inlet or discharge check valve at the mechanical oiler, or worn pumps. A clogged oil passage or pipe leading to an important bearing point will cause trouble because the oil cannot get between the working surfaces. When simple compression pressure feed lubricators are employed, the check valves may be defective or the container may leak. Either of these conditions will prevent the accumulation or pressure on the surface of the oil, and the feed will not be positive. The sight-feed glasses may fill with oil because the pipes leading from them to the engine are full, or because the conductor is clogged with oil wax. i his gives sufficient warning, however, and the oil pipe may be easily cleared by removing it and blowing it out with air or steam under pressure. It is well to remember that much ot the trouble caused by defective oiling may be prevented by using only the best grades of lubricant, and even if all parts of the oil system are working properly, oils of poor quality will cause friction and overheating.
Cooling systems are very simple, and are not liable to give trouble as a rule, if the radiator is kept full of clean water, and the circulation is not impeded. When overheating is due to defective cooling, the most common troubles are those that impede water circulation as shown in chart, Fig. 110. It the radiator is clogged or the piping or water jackets filled with rust or sediment, the speed of water circulation will be slow, which will also be the case if the water pump or its driving means fail. Some cooling systems are so closely proportioned to the actual requirements’ that the stoppage of a cooling fan will be enough to cause the engine to overheat. Any scale or sediment in the water jackets or in the piping or radiator passages will reduce the heat conductivity of the metal exposed to the air, and the water will not be cooled as quickly as though the scale was not present. The rubber hose often used in making the flexible connection demanded between the radiator and water manifolds of the engine, may deteriorate inside and particles of rubber hang down that will reduce the area of the passage. The grease from the grease cups mounted on the pump shaft bearings to lubricate that member, often finds its way into the water system and rots the inner walls of the rubber hose, this resulting in strips of the partly decomposed rubber lining hanging down and restricting the passage. The cooling system is prone to overheat after antifreezing solutions, of which calcium chloride forms a part, have been used. This is due to the formation of crystals of salt in the radiator passages or water jackets, and these crystals can only be dissolved by suitable chemical means, or removed by scraping when the construction permits.
Overheating is often caused by some condition in the fuel system that produces too rich mixture. Excess gasoline may be supplied if any of the following conditions are present: Bore of spray nozzle or standpipe too large, auxiliary air-valve spring too tight, gasoline level too high, loose regulating valve, fuel-soaked cork float, punctured sheet metal float, dirt under float control shut-off valve, or insufficient air supply because of a clogged air screen. If pressure feed is utilized there may be too much gas pressure in the tank, or the float control mechanism operating the shut-off in either the auxiliary tank on the dash or the float bowl of the carburetor may not act quickly enough.
Considering first the member of the transmission system that will affect the efficiency of the entire assembly when deranged, it will be well to discuss the troubles common to the various types of clutches. The defective conditions that most often materialize are too sudden engagement which causes “grabbing,” failure to engage properly, slipping under load, and poor release. Clutches utilizing a leather facing will cause trouble after a time because of natural wear or some defect of the friction facing. The leather may be charred by heat caused by slipping, or it may have become packed down hard and have lost most of its resiliency. The clutch spring may be weakened or broken: this will cause the clutch to slip even if the leather facing of the cone is in good condition. The two troubles usually met with by the motorist are harsh action, as one extreme condition, and loss of power through slippage as the other.
When the cone clutch, such as shown at the top of Fig. Ill, engages too suddenly it is generally caused by the surface of the leather lining becoming hard and not having sufficient resiliency to yield to some extent when first brought into frictional contact. To insure gradual clutch application, the facing should be soft and elastic. If the leather is not burned or worn unduly it may often be softened by rubbing it with neatsfoot oil. Kerosene oil is often enough to keep the clutch leather pliable and it possesses so little lubricating value that the clutch members are not liable to slip because of a reduced coefficient of friction such as is often caused by the application of more viscous lubricants. Kerosene has other advantages, among which may be mentioned quick penetration of the leather and not collecting grit or gumming.
When a cone clutch slips it is usually due to a coating of oil on the frictional material that decreases the value of the coefficient of friction to such a point that the pressure of the clutch spring is not enough to maintain sufficient frictional contact between the male and female members to insure driving. The remedy for this condition is to absorb the surplus oil by rubbing a small quantity of Fuller’s earth into the leather surface. When the clutch cone is in place it is not easy to reach the surface of the leather, so the first step would be to disengage or release the clutch and to place enough of the Fuller’s earth on a piece of paper or card so it can be sprinkled into the space left between the male and female members when the former is properly released. Borax is sometimes recommended for the same purpose, and when the earth or borax are not available the carbide dust or lime residue from an acetylenegas generator may be used to advantage. If slipping is caused by weakening of the clutch spring it may be prevented by substituting springs of proper strength or by increasing the degree of compression of the weak springs by some means of adjustment if provided for the purpose, such as the nuts on the spring studs of the clutch at the top of Fig. 111.
Another annoying condition that sometimes obtains when a cone clutch is used is spinning or continued rotation of the male member when clutch spring pressure is released. This may be the result of natural causes, but it is sometimes caused by a defect in the clutch mechanism. If the bearing on which the cone revolves when disengaged seizes because of lack of lubricant, the male member of the clutch will continue to rotate even when spring pressure is released. The ball-thrust bearing employed to resist spring tension may become wedged by a broken ball and this will cause the rotation of the crankshaft to be imparted to the cone member, through the spring, which must turn with the crankshaft instead of remaining stationary, as would be the case if the ball-thrust bearing was functioning properly.
On those cars fitted with multiple-disk clutches, as shown at Fig. 112, the same troubles may be experienced as with other types. If a multiple-disk clutch does not release properly it is because the surface of the plates have become rough and tend to drag. The plates of an all metal multiple-disk clutch should be free from roughness, and the surfaces should always be smooth and clean. Harsh engagement also results by the absence of oil in those types where the disks are designed to run into an oil bath. Spinning or continued rotation of a multiple-disk clutch often results from seizing due to gummed oil, the presence of carbon or burned oil between the plates, and sometimes by a lack of oil between the members. When a multipledisk clutch slips it is generally caused by lack of strength of the clutch springs or distortation of the plates. To secure the best results from a multiple-disk clutch it is imperative that only certain grades of oil be used. If one uses a cheap or inferior lubricant it will gum and carbonize because of the heat present when the plates slip, or it will have such viscosity that it will gum up between the plates. Most authorities recommend a good grade of light or medium cylinder oil in multiple-disk clutches where lubricant is required. In some cases faulty multiple-disk clutch action is due to “brooming,” which is the condition that exists when the sides of the keyways or the edges of the disk become burred over and prevent full contact of the plates.
Faulty clutch action has often been traced to points separate from the clutch mechanism. Some cases of failure of clutch to release have been found due to imperfect relation of interlocking levers and rods or wear in some mechanical parts. If a clutch-shifting collar is worn unduly or the small pins in the rod connecting the clutch pedal with the release mechanism have worn to any extent the pedal may be fully depressed and yet the pressure of the spring depended upon to keep the parts in contact will not be reduced to any extent. Sometimes the emergency brake lever may have an interlocking leverage to release the clutch when it is applied, and when the brake rods are shortened to compensate for wear of the brakes the change in length of the operating rods may throw out the clutch mechanism slightly and cause slipping of the clutch because the spring pressure may be partially relieved.
The chief trouble with a planetary transmission, as used in Ford cars, and shown in Fig. 113, is caused by slipping clutch bands. These are provided with adjustments that can be tightened in case of wear, and should grip positively. If either the slow speed or reverse bands are adjusted too tight they will bind on the drums and produce friction, which in turn will decrease the efficiency of the drive. Noisy action of planetary gearing is usually caused by lack of lubrication or excessive wear in the gearing. If the oiling is properly taken care of, this condition will be practically eliminated. Sometimes the high-speed clutch may slip, but most planetary gears are provided with adjustable clutches so any wear may be readily taken up.
When slide-gear transmissions are used, the most common defect is difficulty in shifting gears, and noisy operation. The difficulty met with in gear shifting is usually caused by the edges of the teeth of the shifting members having burred over so that they do not pass readily into spaces between the teeth of the gears they engage with. Another cause of poor shifting is deterioration of the bearings, which may change the center distances of the shafts to a certain degree, and the relation of the gears may be changed relative to each other so they will not slide into mesh as freely as they should. Noisy operation is usually due to a defective condition of lubrication, and if the gears are not worn too much it may be minimized to a large extent by filling the gear case with oil of sufficient consistency to cushion the gear teeth and yet not be so viscous that it will not flow readily to all bearing points. A difficulty in shifting is sometimes due to binding in the control levers or selective rods, and these should always work freely if prompt gear shifting is required. If considerable difficulty is experienced in meshing the gears and the trouble is not found in the gearset, it will be well to examine the clutch to make sure that the driven member attached to the gearset main shaft is fully released when clutch pedal is depressed. Typical sliding gearsets are shown in Fig. 114.
While power transmission by chains is not as common at the present time in fire department car practice as it has been in the past, side chain-drive is often employed on the heavier apparatus. Trouble and rapid chain wear can be traced to faulty shaped sprocket teeth, which may not be of the best form adapted for the chain designed to run over them. As most chains are exposed and run without a covering of any kind, the action of the road dust and gravel is to combine with the grease often rubbed on the outside on the pretext of oiling the chain, and forms an abrasive that will produce rapid wear between chain and sprocket and the various links of which the chain is composed.
To obtain the best results from chain drive the chains must be maintained in correct adjustment by the radius rods provided for the purpose. If a chain is allowed to run too loose it will “whip” and is liable to climb the teeth of the sprocket. If the chain is adjusted too tight there will be strain on all parts, and it is apt to “snap” when it leaves the sprocket, especially if the teeth are worn hook shape.
A safe rule to remember when adjusting chains is to have it tight enough so that it is not possible to raise it from the first tooth with which it meshes on cither sprocket, even with the aid of a lever such as a large screw driver or tire iron.
Chains must be kept clean and properly oiled. The best method of removing the dirt is to take the chain off the sprockets and let it soak long enough in a large pan containing kerosene so all the dirt and gummed oil is removed thoroughly from all the interior bearing surfaces. It should be gone over thoroughly with a stiff bristle brush until each link wprks freely. The chain is then immersed in a pan of gasoline to remove any small particles of grit that the kerosene may have failed to dissolve. After the gasoline bath it is wiped with a clean cloth until it is dry and clean The proper method of chain lubrication is not generally understood and in many instances it is accomplished by coating the” outside of the chain with a graphitegrease combination that serves no useful purpose, and acts merely as a collecting agent for dust and grit. The correct method of chain oiling is by immersing the cleaned chain in a molten mixture of tallow or mineral grease and graphite. The entire chain is immersed in this mixture, which is kept hot so it will penetrate all the minute interstices of the chain links and produce a thin coating of lubricant at all the working surfaces. The chain is removed from the bath of lubricant and while still hot all surplus oil is wiped off until the outside of the chain is dry and clean. This method insures proper lubrication of the many small joints usually neglected. and should be done every thousand miles.
But little trouble is experienced with shaftdriving systems because the driving gearing and universal joints are so well enclosed on modern axles The bevel-driving gears are packed in lubricant as a rule, and but little wear is noted, even after several seasons of use. An important point to observe with all forms of axles is to make sure that the antifriction hearings are kept properly cleaned and oiled. The oil should contain no acid and should be of the best quality. Care should be taken in washing the car so that water will be prevented from entering the bearing points. If the bevel gears of the real axle grind it ts due to improper adjustment or excessive wear between the teeth. Grinding sounds usually result from meshing the gears too deeply, while loose adjustment is manifested by rattling.
