Motor-Driven Fire Apparatus Its Construction, Operation and Care*
GENERAL FEATURE ARTICLES
A Series of Brief, Non-Technical Expositions Defining Various Types of Automobiles Employed in Fire Department Service, Explaining Principles of Design, Outlining Main Parts of the Mechanism and Their Functions, and Describing Typical Examples from Standard American and European Practice
Coincident with the rapidly augmentihg use of motor-propelled lire apparatus in even the smallest of our cities and towns comes an increasing demand for information relating to the construction, driving and care of this latest form of fire lighting machine. Much literature has been published on motoring in general, but this does not give the definite information needed, nor does it relate specifically to automobile intended for fire department use. The purpose of the. writer will be to endeavor to present this information in a concise, easily understood form, so the parts to follow will cover all phases of this subject. As these discussions are intended for intruction of the novice, the writer has assumed that anyone needing information of this nature will possess only a very general knowledge of the subject and that explanations must be made in simple, everyday language, devoid of technical nomenclature. Obviously, some matter may be presented that will seem elementary to those well versed in the art, but it should be realized that it is desired to make clear those many points that have troubled those without much mechanical knowledge in the past.
Economy, Reliability, and Durability of Automobiles
While automobiles have been used in the fire departments of our large cities for considerable time, it is only within the last few years that fire apparatus has been perfected to a point where fire engineers have faith enough in the new methods of propulsion to motorize entire departments. It is a foregone conclusion that the use of horses to draw apparatus is now in the decline, as the late exhibits displayed in connection with fire engineering conventions for several years past have been confined almost exclusively to motor-propelled types. All forms of apparatus have been motorized and much expensive horse-drawn equipment has been modernized at relatively small expense by the use of automobile tractors.
In years past about the only motor apparatus for fire department use was the combination chemical hose wagon or the squad car. and ordinary touring cars (or use of the chief or assistant engineers. It was not a difficult matter to convert the conventional pleasure car chassis to a light fire truck, as usually this involved no greater change than the removal of the touring body and installation of hose and ladder racks and chemical tanks in its place. Such apparatus was satisfactory to a degree, but some hastily developed forms failed to give the service expected because those responsible for their production made too great haste to supply apparatus for which there was a demand. In their anxiety to sell the product many overlooked the engineering aspects of the problem. The ordinary pleasure car chassis was not suited to work other than that for which it was designed, and while it worked well as a chief’s car it did not have the requisite strength to carry the weight of the heavier body and fire fighting equipment. As a result the service obtained was not always in keeping with the cost of the apparatus and expense of maintenance.
Experience soon demonstrated that practical fire apparatus must be designed with the requirements of that service in mind and that the average converted pleasure car chassis was not suited for the severe work except in some departments where the calls were few and where the automobile received but limited use. Leading makers of fire apparatus studied the problem from all angles, and this has resulted in the development of distinctive types of automobile chasses well adapted to meet the severest requirements of this exacting service. Special forms of machines, such as two, three and fourwheel tractors and four-wheel drive designs, have been developed and widely applied for this use. All of the practical prime movers have been utilized for propulsion, alone or in various combinations. At the present time automobile fire apparatus design has been developed along conservative engineering lines and forms have been evolved and designed specially for the work, instead of being adapted to it when intended primarily for something else.
*Copyright, 1913, by Victor W. Page. All rights reserved.
That automobiles are more economical than horses is now clearly recognized because they cost practically nothing to keep outside of interest charges on the investment and house maintenance (which would be needed for men and equipment in any event) when not in use. Automobiles are able to reach fires quicker and make better time through sand, mud or snow or any other conditions where traction is unfavorable. The weights of horse-drawn apparatus had to be held within certain limits because the draft of horses is sharply defined, and more than three or four animals make a hitch that is unwieldy to handle and hard to control. This prevented any material improvement during the era of horse traction, and the development of the heavier apparatus, such as aerial ladders, water towers and long ladder wagons was delayed because of the limitations of animal power. Many of these early types were of insufficient capacity to cope with fires in our large buildings. It was recognized generally that architectural development was much ahead of building protection science. With the coming of motor traction and the ability to concentrate over 110 horsepower in an engine that takes up less than half the space one horse requires, the factor of plenty of available power made it possible to materially increase the weight and dimensions of apparatus, as well as effective radius of action. This meant that extension ladders of adequate capacity and length, ample supplies of hose, powerful pumps and tall water towers could be conveyed to a fire in less time than horses could draw the lighter and less efficient apparatus. In fact, the motor provides twice or three times the speed possible with horses, even with the heaviest forms of apparatus yet devised. The only limits to the development are mainly of a structural nature, though the matter of manipulation and control are important ones. It is now certain that no matter how large and heavy such apparatus may be made in the future that it can be handled adequately by mechanical power.
The reliability of early automobiles was open. to some doubt, but with improved forms and greater experience of operators there can be no question regarding the ability to run for extended periods with but little attention. Even in the days past most of the troubles met with could be attributed to carelessness or lack of knowledge on the part of the operator. Many times the mechanism failed because of some minor loss of adjustment which could have been readjusted in but few minutes if the operator had the necessary experience. Automobile fire apparatus can receive the best of care because there is ample opportunity for this attention during the period between runs and those responsible for its maintenance have every chance to become familiar with its mechanism. Extended tests have shown that gasoline pumping engines will run for long periods with considerably less attention than demanded by even the best steam pump, and the cases are very few where motor-propelled apparatus fails to reach a fire because of defects in power plant or mechanism.
As for durability, automobile apparatus should last for an almost indefinite period. Commercial automobiles have been run for 100,000 miles without failure of any essential part and with only such replacements as could be made without rebuilding. Most of the runs made by fire apparatus are short and even when serving a large area it is doubtful if they cover more than five miles per day. This figure, of course, does not refer to small vehicles used by department heads, which receive as much use as the average car employed for business purposes and which would be subject to practically the same operating conditions. If the apparatus was run five miles every day of the year the total mileage would be less than 2,000 miles per year. On the basis of a probable life of 100,000 miles this would mean that the vehicle would last 50 years. In fact, it is very likely that it would be rendered obsolete by improved forms long before it would ever wear out in service. Of course, in some apparatus, such as motor pumping engines, where the power plant is depended on to work the pump as well as to furnish traction, the wear on the motor would be much greater in proportion than that on other parts of the apparatus. In cases of this kind the useful life of the power plant would depend to some extent upon the care it received while in service.
Requirements of Fire Apparatus
Before considering the various types of automobiles that have been fitted with fire fighting equipment it will be well to outline some of the essential requirements that designers of this type of machinery have to keep in mind. An important point is simplicity of construction, because a mechanism with few parts is not only easier to understand but is less liable to get out of order than more complex forms. If a simple machine does get out of adjustment it is not difficult to repair it. The distribution of weight is another important factor in the design of power propelled apparatus, as care must be taken to place sufficient weight on the rear wheels or other driving members to insure proper adhesion of the driving wheels and the ground. If possible, the weight should be so placed that the machine has a low center of gravity, which makes for stability when turning corners at high speed, as well as reducing the tendency to skid. The parts of the mechanism should be accessible, and any elements that are apt to need attention or adjustment should be so placed that they may be reached with minimum loss of time.
Any vehicle intended for fire department service should have exceptional strength, this applying fully as much to the power plant as to the chassis. Fire apparatus is not only heavy, but when driven at speed over the average run of city pavements the mechanism will be subjected to considerable stress if the frame holding the parts together is not sufficiently strong. The frame of a pumping engine must be considerably stronger than that of a chassis employed only for carying a load, because it must stand the vibration of pumps, especially those of the reciprocating type, when in service. The mattei of chassis strength also applies to the spring suspension, which can be stiffer than in vehicles intended for business and pleasure, and special precautions should be taken to have a large margin of safety over the actual requirement in such essentials as the steering gear, the axles, the transmission of power and the brakes. On the heavier apparatus the wheels may be shod with cushion or solid rubber tires to advantage, though on the average chief’s car, if provision is made for pneumatic tires and detachable wheels, an accident to the tires will not prove of serious moment, and the car will be more enduring and comfortable than one with solid tires.
Care should be taken in gearing the motor to the driving members so that the apparatus should not be too fast. With mechanical power designers are apt to err in this regard and provide vehicles which are actually dangerous when operated through the streets of the average city or town. Heavy apparatus capable of more than a moderate speed is not only harder to control than the slower forms, but the damage is much greater in event of accidents. It is better to have an apparatus that may be a few minutes slow in getting to a fire than one which is apt to pile itself up against a curbstone or post half-way to the point where it is needed so badly.
In considering the power plant, especially in those forms where the gasoline engine is depended on, outside of having a strong and simple engine it is imperative to safeguard all liabilities of stops due to failure of any of the auxiliaries to the power plant. For example, in connection with the fuel supply it is not only sufficient that a tank of large capacity be provided, but this also must be exceptionally strong so that there will be no possibility of a leak, In fact, it would be profitable to make the tank a double member having two sets of walls separated by an air space. In event of failure of the inner tank there will be no danger of losing the fuel, which will be held by the outer container. Two sets of pipes of larger bore than ordinarily fitted on the average commercial vehicle should be led to the carburetor, and each of these should be controlled by a separate stopcock so arranged that in event of failure of one gasoline line .the other could be used in its place. All joints in the piping should be brazed instead of soldered, because vibration is more apt to break soldered joints than those held together by the more secure method. Double ignition systems should be provided which will derive current from two independent sources. In addition to the usual high tension magneto which supplies one set of spark plugs there should be a battery and coil system entirely independent of the mechanical generator to supply another set of spark plugs. In event of failure of one ignition system the other can be brought into action. Another thing ,to be carefully considered is adequate protection of the power plant from the elements. The carburetor should take air from some well covered point where there would be no possibility of failure to aspirate only warm, dry air. The parts of the ignition system, notably the high tension magneto, all wiring, and the spark plugs should be encased so that water cannot short-circuit the current. This feature is especially valuable on pumping engines that are liable to be called upon to work for several hours at a time under extremes of weather conumons.
The matter of cooling the engine is also important, and all water connections should not only be amply large and securely fastened, but the pump arive should be so large that there would be no possibility of its _____ The radiator should not only be carefully suspended by springs independent of the chassis supporting members so the joints win not be loosened up by vibration, out it should be well protected by a suitable buffer member so it will not be damaged in event of ordinary collisions wild other vehicles. Another safeguarud that can be adopted to advantage is the use of a Heavy wire screen in front of the radiator to prevent that member from damage due to stones or other missiles, The average lubrication system as provided on pleasure cars should be supplemented by an auxiliary handoperated plunger pump which can draw oil directly from the container and force it to the crank case of the engine should any part of the regular system fail to function properly. The engine should be placed in an accessible location and yet snould be well protected by substantial frame members.
in considering the change speed gearing and clutch of gasoline cars the first essential is that these be simple in design, The cone type of clutch is well adapted for this service. The change speed gears snould be considerably heavier than those used in the average commercial vehicle and should not only have a wide face, but should have teeth of large size as well, The four-speed gear box with selective control is the best form. An interlock should be provided between the gearshitt lever and the clutch so the gears cannot be shitted without hrst releasing the clutch, and it the clutch is a cone or three-plate type it will be well to provide a clutch brake to stop its rotation as soon as released, in the final drive etnciency can be sacrificed to other considerations, because in apparatus that is not receiving constant use the difference of ten or fifteen per cent, in efficiency between the varying methods of power transmission is not of sufficint moment to warrant any sacrifice of strength or convenience to obtain the more efficient drive. While enclosed shaft driving a live rear axle through single bevel or worm gearing is suitable on the lighter apparatus such as combination chemical and hose wagons, the heavier apparatus will depend on double reduction systems of various types, and, in fact, there will be forms that can be better propelled by the combination of gasoline and electricity than by either system alone. It is well to state that while some of the precautions recommended may seem a trifle overdrawn, careful consideration will show that a delay due to the ‘breaking or derangement of some minor part that would be a matter of little consequence to the average motorist may mean the opportunity for a fire to spread because of the delay and do damage that would have paid for taking the proper precautions when the apparatus was built many hundred times.
Methods of Propulsion
As steam power had been widely applied for operating water pumps long before the successful gasoline engines were evolved, it is but natural that the efforts should have been made to apply the steam engine to propulsion as well as using it for pumping water. The various methods of propulsion and their application to automobile chassis are clearly outlined in simple diagram forms at Fig. 1. At A a plan view of the earliest form of self-propelling apparatus is depicted. This is the regulation type steam pumping engine with the crankshaft of the engine extended on each side of the frame sufficiently so driving sheaves carried by it could transmit their motion to larger members attached to and driving the rear wheels. A self-propelling steam engine with all important parts clearly outlined that may be considered representative of former practise, is shown at Fig. 4 and will be described in proper sequence.
The chassis at B is the next form that was applied to fire service. This is the straight electric drive in which current from a storage battery actuated an electric motor which in turn operated the rear wheels through a countershaft carrying sprockets which were connected to similar members on the rear wheels by chains. The diagram at C illustrates a straight gasoline drive and is suitable for light apparatus and chiefs’ cars. The power plant, which is a four-cylinder gasoline engine, is mounted at the front end of the vehicle in most constructions and drives through a change speed gear box to a live rear axle by means of a drive-shaft extending from the gear box to suitable driving and speed-reducing members in the rear axle. The heavy type of gasoline chassis is outlined at D. The arrangement of the power plant is similar to that previously described, except that a double reduction system of power transmission is employed. Instead of the drive being direct from the gearset to gearing in the rear axle, as in the form outlined at C, the driveshaft of the change speed gearing turns speedreducing members in a countershaft assembly. This countershaft carries sprockets and drives the rear wheels, which revolve on a fixed rear axle, through the medium of driving chains. It will be noted that in the steam engine shown at A the entire front axle swings on a turntable or fifth wheel to permit the conveyance to round corners. In the later forms of automobiles, such as depicted at B, C and D, the steering is accomplished by moving the wheels, which arc carried by movable spindles at the end of a fixed front axle.
While the steam engines that were evolved proved to be practical and capable of satisfactory service, there were several objections to their use that prevented their general adoption. On the early forms two men were necessary to handle the machines, the driver sitting on the front seat and steering, while the engineer on the back platform regulated the vehicle speed. As each of those responsible for the control of such apparatus were called upon to exercise, their judgment independently, there was often misunderstandings which resulted in serious accidents. The public objected to the self-propelled steam fire-engine on account of the sparks flying out of the stack and also because it frightened horses. When not in use self-propelled steamers had to he kept under pressure by connecting the boiler with some auxiliary source of steam and sufficient pressure had to be maintained in the boiler at all times to insure that power would be available as soon as the alarm was rung in to furnish traction. While the engine was on its way to the fire the boiler was supposed to generate steam enough to keep it going, but often a fire was reached with the steam pressure down to such a low point that the pumps could not be operated efficiently. This objection did not obtain with horsedrawn fire engines because the steam generated en route was available for operating the pumps as soon as connection had been made with a hydrant and the lines of hose run to the fire.
The disadvantage which militated against the adoption of the straight electric system was mainly lack of capacity and weight of the storage battery depended on for power. The electric chassis was not as well suited for general application as the forms operated by gasoline engines, but as they were easy to control and as the mechanism is relatively simple many of the advantages incidental to the use of electric power have been retained by the application of combination gasoline-electric drives.
The advantages of the gasoline power plant and those which make it the most suited of all for application to self-propelled vehicles are first, that it is a self-contained power plant and does not need stored energy, as the steam engine or the electric motor does. Second, it is always ready to start when kept in proper adjustment by the simple movement of a crank or by merely pressing a button of an electric or compressed air motor starter. Third, that it requires no naked flame with its element of fire risk as does the steam engine, and that it is just as easily controlled and requires much less attention than the steam boiler. Fourth, it has a larger radius of action than either the steam or electric propelled types. Fifth, it involves no maintenance expense when not in use as does the steam propelled form which must always be kept under steam pressure or the straight electrically propelled form where the storage battery must be charged and discharged periodically, whether used or not, to keep it in proper condition. Sixth, a gasoline engine, which is an internal combustion type, will weigh much less in ratio to the horse-power developed than a steam power plant which consists of engine and boiler, or tlie electric power plant consisting of storage battery and electric motor. Its compactness is another important advantage in its favor.
Combination Gasoline-Electric Systems
As the use of electric power offers important advantages in ease of control and as the electric motors can be applied easily as an integral part of a wheel member which will combine directive and tractive functions, combination systems have been evolved in which a gasoline engine is depended on as the prime mover and its power utilized to generate electricity, which in turn is employed to drive the vehicle. The two combination systems generally applied are shown at Fig. 2. That at A is a four-wheel drive chassis adapted for use with the heaviest types of apparatus, because all four wheels furnish traction and may be moved to steer the vehicle. The gasoline engine drives the armature of an electric generator dynamo instead of the usual gearing. The current from the generator is led to a storage battery from which the motors carried by the wheels are supplied with electricity. The advantage of providing a storage battery in this manner is that in event of an overload which might be beyond the capacity of a gasoline engine temporarily, current of sufficient value will be drawn from the storage battery to furnish positive traction.
The wheels, which are a special construction, are mounted on steering knuckles and are moved to steer the vehicle just as the front wheels of the ordinary automobile. This feature is particularly well adapted to long apparatus such as aerial trucks, water towers, etc., where it is necessary to steer by both front and rear wheels on account of the long wheel base. Of course methods of power transmission as outlined at A is wasteful of energy. In the first place there is a loss when converting the mechanical energy of the gasoline engine into electric current from the dynamo. There is another loss of power in charging the storage battery from the mechanical generator. There is further chance for diminution of the power available for traction on account of loss between the storage battery and the motors carried by the wheels and again another opportunity for waste in the speed reduction gearing employed between the wheel motors and the members they drive. A system of the form shown at A even if very carefully designed would not be more than 40 per cent, efficient, i.e., over 60 per cent, of the power available at the engine crankshaft would be wasted in transmission.
The combination system depicted at B is somewhat more efficient than that outlined at A because no storage battery is used, thus eliminating one opportunity for power loss. The gasoline engine drives a dynamo just as in the previous instance but this is connected to the one electric motor which turns the rear wheels through the medium of a countershaft and sprocket and chain drive. The system outlined at B would be 50 per cent, efficient at least. In this connection it will be well to state that the factor of efficiency is not the most important one in vehicles intended for fire service as it is in those forms adapted for commercial application where they receive constant use instead of intermittent service.
Utility and Types of Tractors
A form of automobile that was designed primarily for fire service and which is now applied successfully in several commercial applications is the tractor in its various forms. Most of the large cities have thousands of dollars invested in heavy first-class, horse-drawn apparatus, and when the automobile demonstrated its practicability the authorities did not feel justified in sacrificing equipment that had always been satisfactory for newer motor propelled forms. The tractor was evolved to make possible the application of mechanical power to replace the animal energy required to draw the apparatus. The application of the mechanical tractor is simple, as in most cases the rear wheels of the tractor replace the front wheels of the horse-drawn apparatus, the frame of which is.mounted on a turntable so the tractor can pull it around corners just as the animals would.
The various tractor systems that have received general application are outlined at Fig. 3. That at A is a three-wheeled form which does not differ radically from conventional automobile practise, as far as the power plant and driving systems are concerned. The radical departure is in the use of a single front wheel mounted in a pair of forks very similar in construction to ‘bicycle forks, except that they are heavir. The wheel carrying member passes through a steering head and oscillates on anti-friction bearings. The arrangement of the steering gear is such that the front wheel may ‘be turned so it is parallel .to the axle of the tractor instead of being at right angles to it. as in normal operation. This makes it possible to handle a tractor and its load in average city thoroughfares and the three-wheel form is much easier to turn on a narrow thoroughfare than the four-wheel types. The tractors outlined at B and C are short wheel base, four-wheel automobiles equipped with a fifth wheel or turntable over the rear axle to support the trailer. The form shown at B is a straight gasoline drive, while that outlined at C is a straight electric, four-wheel drive.
The tractor outlined at D is a combination gasoline electric form in which the driving motors are mounted on the front wheels which are movable for steering and which combine directive and tractive functions. The gasoline engine turns a generator armature and this in turn furnishes electricity to energize the windings of the motors in the wheels. A two-wheeled tractor of this form is especially adapted for those types of fire apparatus where short wheel base is desirable. The two-wheel tractor is shown applied to a steam pumping engine at D, and in this case the gasoline engine is used only for the propulsion, while the steam engine, which is favored by many conservative fire chiefs and which has demonstrated its reliability for many years, is employed for driving the pump.
Another two-wheel tractor of front drive system of the straight gasoline type is outlined at E. The power plant is carried at the front end of the chassis, but it is placed in the frame in such a wav that the crankshaft is parallel to the front axle instead of at a right angle to it as in the systems outlined at A, E and D. The motor drives a change speed gear set through the medium of a chain and sprockets and this in turn imparts the engine power to the front wheels, which may be moved to steer the vehicle and which revolves to drive it, by universal joints and drive shafts connecting the change speed gearset and the drive gearing in the wheels. Structural details of all these various tractor systems, as well as the more conventional methods of propulsion will be fully described in future instalments.
Early Steam Fire Engine Design
The illustration at Fig. 4 is made from a wood cut. which shows one of the three Amoskcag selfpropelled steam fire engines installed by the Chiicago fire department as far back as 1877. When one considers that this was fully eight years in advance of the development and first application of the internal combustion engine by Daimler, in 1885. it will be apparent that the state of the art as relates to steam fire engines was well advanced even at that early date. The engine shown was of the double crane neck type and was supplied with double pumps. The vertical boiler was thirty-two inches in diameter and the steam engine cylinders were 7 5/8 inches bore. The pump cylinders were 4½ inches in diameter and had a stroke of 8 inches. The pumps had a capacity of 900 gallons per minute and two discharge gates were provided at the pump. The overall length of the machine was about 14 feet, the heighth about 9 feet, while it was just over 6 feet in width. The weight with full equipment was four tons, and it is said the engine could maintain a speed of twenty miles an hour on good pavements. The propelling was done by the pumping engine which was provided with valve linkage, so it could be made to run forward or backward. Th power of the engine was transmitted to the rear wheels from sheaves on the engine crankshaft to larger members, which provided a reduction in speed, attached to the rear hubs. The steering was accomplished by swinging the entire front axle around, which was done by a large hand wheel convenient to the driver’s seat through the medium of reduction gearing. The poor condition of many of the most prominent streets of Chicago at that time was said to have been responsible for a number of serious wrecks accompanied by some loss of life. It will be noted that provision was made for the attachment of a pole to the front axle so that horses could be used to draw the apparatus if traction was poor. The machines were not run as self-propellers long as one of the three was changed to a horse-drawn type in the fall of 1878, and the other two machines were converted in the same way a year later. The report of the chief of the fire department for the year 1877 spoke very well of the self-propelling powers of the machines. He mentioned that they could make better time through mud and snow than any two horses drawing the same weight, and this could be accomplished at about one-half the cost of keeping two horses. Similar machines have been used in other departments, notably in Boston. Mass., and Hartford, Conn.
(To be continued.)
Ed. Note.—The next instalment will consider in detail the parts of straight gasoline chassis, will show the relation of the various members to each other and outline clearly the functions of all parts of the chassis assembly.