Part 5

The electric spark is a very effective igniter for the explosive mixture, and, by properly setting cam _n_ the explosion can be made to take place just at the position of the piston that may be found the most desirable; but the points at _i_ are liable to get out of order, and the battery that actuates the induction coil _M_ and the coil itself can become a source of more or less trouble, and on that account the igniting is effected in some motors by means of a hot tube. When this is used the cam _n_, the lever _l_ and the electrical parts of the apparatus are not required. In their stead a tube is placed on the upper side of the chamber _Q_ and this tube is maintained at a red heat by means of a flame impinging against its outer surface. When the explosive mixture is compressed it rises in the interior of the hot tube, and when it reaches the portion that is hot enough to produce combustion an explosion takes place. By many engineers this arrangement is regarded as superior to the electric spark on account of its simplicity.

Gasoline motors are made with one, two or more cylinders, but in each cylinder the action that takes place is that described above. The actual construction of a motor is not so simple as might be assumed from the appearance of Fig. 1; many details are required which are not here shown. A more perfect idea of the actual construction of a gasoline motor can be had from Fig. 2, which is a working drawing of a recent European invention. In this design it will be noticed that the cylinder is cooled by radiation into the surrounding air, the exterior surface being increased by numerous circular ribs and also by extending a hollow trunk from the upper side of the piston, so as not only to increase the radiating surface, but also to allow the hot air to escape from the chamber _T_ in which the crank discs revolve. In this drawing _E_ is the explosion chamber, corresponding to _Q_ in Fig. 1, and the valve _s_ is the counterpart of _f_, while _s’_ corresponds to the valve _h_. The upper pipe _t_ is the pipe _e_ of Fig. 1 and the lower pipe _t’_ is the pipe _r_ of the same figure. Although the crank discs, connecting rods and other details are different in shape, it will readily be seen that their relation to each other is the same.

Since a gasoline motor cannot start of its own accord, it is necessary in vehicles in which they are used so to arrange the driving gear that the motor may be kept in motion all the time and always in the same direction, hence, to reverse the direction of the carriage, reversing mechanism, independent of the motor, must be provided. The most simple mechanism for a gasoline vehicle employing spur gearing exclusively is shown in diagrammatic form in Fig. 3. In this figure _A_ represents the cylinder of the motor, _B_ the crank disc chamber and _M_ the vaporizing receptacle, which is generally called the carburator. The pinion _C_, on the end of the motor shaft, meshes into a gear _D_ which is mounted upon a sleeve _E_ which revolves freely round shaft _G_. This sleeve has its ends formed so as to engage with the gears mounted upon shaft _G_, and by means of a lever, which is not shown, but which works in groove _a_, the clutch either _s_ or _ss_ can be thrown into engagement with its corresponding gear. If _s_ is thrown into gear, as shown in the drawing, the wheel _F_ will turn _H_ and the pinion _I_ will rotate the gear _J_ which is mounted upon the axle of the carriage. If the clutch _ss_ is thrown into engagement, the gear _G_ will turn _K_ and this wheel will turn _l_; but, as can be clearly seen, the direction in which _l_ will revolve will be opposite to its motion when driven through _F_ and _H_, therefore, if when _F_ drives the carriage runs forward, when _G_ drives it will run backward, and when _E_ is moved to the central position, so that neither _s_ nor _ss_ engages with their respective gears, the vehicle will stand still, but the motor will continue to revolve.

This diagrammatic arrangement is more simple than the gearing actually used and is not as complete in action as many of the devices, as it only provides means whereby the direction of rotation of the axle may be changed, while in many carriages the gearing also varies the ratio between the speed of the motor and the driving wheels. It is also quite common to combine in the train of gearing spur gears and sprocket wheels, and in some instances even belts. Fig. 4 illustrates a French gasoline automobile made by Underberg, of Nantes. The first figure is a side view, and the second is a plan of the truck and driving mechanism.

The motor, which is of the single cylinder type, cooled by radiation into the air, is located at _N_. The pinion on the end of the motor shaft engages with the wheel on the end of shaft _A_. This shaft carries four gears, which can be moved by means of lever _C_, so as to engage with corresponding gears on shaft _B_, thus providing four different speeds. The motion of _B_ is transmitted to the rear axle by means of a belt that runs over the pulleys _p_ and _P_, the latter being carried by a differential gear, so as to run the two driving wheels at proper velocities. The circular ribs surrounding the motor cylinder are well shown in the figure, in which the carburator of _C_ is also seen. The housing for the motor is open at the sides so as to give air currents free access. In Fig. 4 the speed changing gears are shown, the reversing train being omitted; but if it were also drawn in, the diagram would be far more elaborate than Fig. 3.

Another form of variable speed gear is shown in Fig. 5. This provides for two speeds. The large wheel _E_ is on the carriage axle, and it is driven either by a pinion _F_, or by _J_. Upon the shaft _O_ there are two friction clutches _C D_, and when _C_ acts the pinion _F_ drives _E_, and when _D_ acts the pinion _G_ drives _H_, which in turn drives _I_, and this wheel is mounted on the same shaft as _J_.

Some of the best-known makers of gasoline vehicles do not employ variable gears and depend for changes in the speed wholly upon variation in the velocity of the motor. The De Dion carriages are made in this way, the gearing being substantially as illustrated in Fig. 3.

Fig. 6 shows a gasoline vehicle made by Panhard & Levassor, who are perhaps the best known French manufacturers of automobiles, as their vehicles have been the winners in all the notable races held within the past few years. The motor they use is shown in Fig. 7, and, as can be readily seen, is of the two-cylinder type, cooled by a water jacket, just as in Fig. 1. The explosion is produced by means of a hot tube, as explained in connection with the last-named figure. This motor is placed under the body of the vehicle, and is connected with the rear axle by means of a train of gearing which terminates in sprocket wheels and chains that connect with driving wheels, each one being operated by a separate chain. In Fig. 6 the sprocket wheel and chain are well defined, and forward of these can be seen the outline of the casing enclosing the gearing.

Fig. 8 shows another European design, in which a variable-speed gear is used. The plan of the truck, showing the general arrangement of the mechanism, is presented in Fig. 9, and the details of the variable-speed gear are shown in Fig. 10. The motor is located at _A_, and through a friction clutch _B_, and the variable speed gear _C_, it rotates the shaft _H_, which runs lengthwise of the vehicle. Motion is imparted to the hind axle by means of bevel gears contained within the casing _D_. The large bevel gear on the axle is of the differential type, so as to drive the wheels _R R_ at the proper velocities.

When a high speed is desired, the variable speed gear, Fig. 10, is set so that shaft _M_ drives _N_ direct, the clutch at _E_ being moved so as to interlock. _N_ is the end of shaft _H_, so that with this connection the bevel pinion, which meshes into the axle gear at _D_, revolves at the same velocity as the motor shaft. By moving the handle _V_, Fig. 9, to the right, an intermediate speed is obtained, and by moving it to the left, the carriage is run at the lowest velocity. When the handle _V_ is turned to the right, the ends _M_ and _N_, which form the clutch _E_, Fig. 10, are separated, and at the same time the lower shaft _H_ is moved toward _M_, so as to cause gear 1 to mesh into gear 2, and also 3 into 7. By this means the end _N_ of the axle-driving shaft is rotated through the train of gears 1, 2, 3 and 7. If the handle _V_ is turned to the left, the shaft _I_ is moved toward _M_, so as to cause gear 1 to mesh into gear 4, and gear 6 into 8, the latter being secured to end _N_ of the axle-driving shaft. The speeds obtained by these changes are in the ratio of nearly 1, 2 and 4.

Fig. 11 shows the plan of a light French carriage, which is equipped with a double cylinder motor, set in a horizontal position above the front axle, and arranged to impart motion to the hind axle by means of belts. The motor, which is located at _A_, turns a vertical shaft, and this, through spur gears, rotates a horizontal fly wheel, _B_. Two pulleys are mounted upon the motor shaft, and from these belts run to tight and loose pulleys on a countershaft, _S_. From the latter the rear axle is driven through two sets of spur gearing, which give two different speeds. By means of the belts, two other speeds are obtained, thus giving, in all, four different velocities. To stop and start, the belts are shifted from the tight to the loose pulleys by a belt-shifter, _f_. At _h_, a muffling chamber is located, into which the motor exhausts, so as to reduce the noise.

The elevation and plan of one of the celebrated French racing-machines, the Vallée car, is shown in Fig. 12. The motor of this machine is of sixteen horse-power capacity, has four cylinders, and is connected so as to impart motion to the hind axle by means of a single wide belt, which is marked _G_ in both the line drawings. The driving-pulley on the motor shaft is located at _H_, and the axle pulley at _H’_. Within the latter there is a train of gears for reversing the direction of rotation of the axle, and also for obtaining the differential velocities of the two driving wheels. There is no mechanism for variable speed, this being obtained wholly by changes in the velocity of the motor. The motor speed can be made to vary through a wide range by using four cylinders, with which it is possible to reduce the velocity so low that it would be likely to bring the machine to a standstill if provided with one, or even two, cylinders. The change in the motor velocity is obtained in part by the action of a governor located in a chamber at _A_, and in part by the action of the electric ignition device which is arranged so that the time when the spark is produced can be varied. The rear axle is so held that it can be moved through a short distance, horizontally, by manipulating the lever _D_, and in this way the belt _G_ can be made tight or loose, thus affording another means for varying the speed. A brake is provided which presses against the inner side of the axle pulley, _H_. This brake is used ordinarily, but in the case of an emergency another brake can be operated which presses against the outside of the wheel in the space between the two sides of the belt. It is claimed for this vehicle that by the elimination of mechanical speed-changing devices, a great deal of weight is saved, and that this is more than enough to compensate for the extra weight of the motor, arising from the use of four cylinders. In most gasoline carriages it is necessary to provide a slow-speed gear for hill-climbing, as the motor cannot put forth a sufficient effort to ascend a steep grade at the normal velocity. With this racing-machine such a gear is not required owing to the enormous power of the motor.

There are quite a number of gasoline automobiles manufactured in this country, and, as in the case of the steam and the electric carriages, they compare most favorably with the best European products, in so far as the artistic effect is concerned. That such is the case can be realized at once by an examination of Figs. 13 and 14. We regret our inability to illustrate the mechanism of these vehicles, but the truth is, that the manufacturers appear to be unwilling to make public the details of their designs. In the phaeton shown in Fig. 13, a single-cylinder motor is used, and it is so arranged that it can run at different velocities, so that no variable speed mechanism is required, except a single train of gears, which is thrown into action when running uphill. The motor itself can be run at any velocity from 200 to 800 revolutions per minute, thus giving a speed variation of four to one. A carriage of this make competed in the last international automobile race from Paris to Lyons, France, and although it failed to come in first, it made a remarkable showing, which might have been considerably improved if it had not been for an accident which compelled it to retire from the contest.

The vehicle shown in Fig. 14 is of small size and light construction, although amply strong for the purpose for which it is intended. The power of the motor, which is located under the seat, is transmitted through friction wheels. In looking at the illustration it will be noticed that the hind wheels have a circular rim attached to the inner side, and of a diameter somewhat smaller than the wheel itself. Two small friction wheels are placed so that either one may be pressed against the inner surface of this rim. The shape of the rim, as well as that of the small wheels, is such that they hug each other firmly, so that the rim is carried around in a direction which corresponds with the direction of rotation of the friction wheel. In operating the carriage the motor is set in motion, and then one or the other of the two friction wheels is pressed against the rim on the driving wheel, according to whether it is desired to run forward or backward. While this arrangement might not operate with entire success if applied to a heavy vehicle, it appears to be all that could be desired for a light carriage.

Three-wheel vehicles have been used, but there is a difference of opinion as to their value, as the construction has disadvantages as well as advantages. It is evident that such a vehicle can be steered with greater ease than one running on four wheels, but on country roads, where the wagon wheels roll down a smooth surface, and leave the space between in a rough condition, it is equally evident that the third wheel, in passing over this uneven surface, would jolt the vehicle to a considerable extent. On a smooth pavement the three-wheel vehicle will run fully as well as the four-wheel; but, on the other hand, on such a pavement the latter can be steered with as little effort as the former, so that the question of superiority of design is one that probably depends upon individual taste.

From the descriptions of automobiles given in this and the two preceding articles, it will be seen that although many of them are used, especially in France, they are not entirely free from objectionable features. The electrical vehicles are provided with the most simple and durable machinery, and, being noiseless, odorless and free from smoke, are all that could be desired in so far as their operation is concerned; but they are heavy and can only be used in places where the batteries can be recharged. The steam vehicles are light, have simple mechanism and can run anywhere; but they exhaust steam into the air, which is clearly visible in cold or wet weather, and the heat from the engine and boiler is an objection, at least in summer time. The gasoline vehicles run well, but are noisy, and the odor of the gasoline is disagreeable as well.

SOME SCIENTIFIC PRINCIPLES OF WARFARE.

BY WILLIAM J. ROE.

As in boxing, fencing, saber and bayonet exercises, there are comparatively few postures, guards, thrusts and strokes, so in warfare, whether the numbers be large or small, the arms most modern or ancient, there are just a few principles to whose steady adherence and skilful manipulation all success is due. In order that these may become apparent without irksome study of military details, let us imagine a command of say a thousand men, fairly well drilled, of good ordinary intelligence and engaged in a cause worthy of being fought for. We have been in camp for some time, but an order has now come to join the main army. This is a long distance off, the railway communications have been broken, and the intervening country, though possessed of good roads, is more or less in the hands of the enemy.

Our scouts have kept us informed as to the condition of the country for several miles around; our first day’s march is, therefore, not hampered with any especial dread of surprise. We move quickly and at ease. Safe as everything appears to be, the commander relaxes none of the needful precautions; at least fifty men, under command of an experienced officer, are sent quite far to the front, the distance varying with the nature of the country--the farther, the more broken it may be. The best roads are followed; the men are allowed to march at ease, though always preserving-their company organization, while the officers are always more or less on the alert. There is a small rear guard, but it is upon the advance that the main responsibility falls. Of the fifty thrown forward, about half will remain together; the rest are scattered; some far to the front along the highway; others on either side of the route, riding up the hills on either hand, making sure that no deep gorge, dense growth of forest or thicket, nor even a field of grain conceals an enemy. It is upon the alertness of those vedettes on front and flanks that the safety of the force in great measure depends. History records many relaxations of this principle of precaution, and for lack of it sudden ambushes and deplorable disasters. It was thus, in spite of Washington’s repeated warnings, that Braddock fell into a cunning ambuscade, and thus (not to multiply examples) that Custer and his command were massacred to a man among the high Rockies.

On the annexed map the men may be located at ‘A’ marching from ‘D’ in the direction of the village, ‘F’. The advance is at ‘B’, the rear guard at ‘C’. The commander rides with the main column, near the front. The black dots, with pennons, indicate the general position of the vedettes at this point, though, of course, they are continually advancing. The commander has noted on his map a foot path, beginning at ‘D’, leading over the rugged hills. By taking this path a considerable distance could be saved; but it is quite impracticable for the wagons, and the troops, therefore, continue along the high road. The valley is gently undulating, with a gradual slope from the low hills towards the stream.

The projecting hills near the head of the column form an especially dangerous point. What easier than for an enemy to plant batteries here on either side of the road. A sudden, heavy fire would throw a negligent force at once into disorder; a situation to be taken instant advantage of by a vigorous adversary; a charge of horse concealed behind the hill at ‘O’, and nothing might be left except flight, with great loss of life, and surrender with loss--if not of honor, at least of reputation as a safe leader.

Happily, we shall avoid both alternatives. Our scouts have explored most thoroughly every possible vantage ground. They have not been content with any mere glances; their instructions are to take nothing for granted. That field, marked ‘G’, looks innocent enough, but the tall, thick rye or corn may cover a skilfully placed battery. The plot marked ‘M’ may be simply a vineyard; but it does no harm to inquire. The inhabitants of the country are friendly, and, therefore, the chances are not favorable to this sort of surprise; but in war it is often not the likely, but the unexpected that happens; the commander who knows his business guards against the remote possibility.

Though we have imagined a force of a thousand, it must not be lost sight of that the same kind of precautions should be employed for very much larger numbers; indeed, you need only alter the scale of the map, imagine additional roads, a railway line or two, increase to thousands, if necessary, the fifty of our vanguard, and the result is but an application of the very first principle of warfare: Eternal vigilance is the price of safety as well as of liberty.

The troops have been in camp for some time; their condition is excellent for a long march. As the corn and rye are not yet gathered, the time is early summer. The roads are in prime condition. They set out by sunrise and halted for perhaps two hours at noon. It is by thus sparing his troops during the heat of the day that the colonel will have a body of men fresh enough at nightfall to march, if necessary, all night. But no such urgency exists; it is nearing sunset, and preparations are now being made to encamp. By his map the colonel has informed himself in the matter of distances, and has decided that they shall pitch their tents somewhere in the vicinity of the village (‘F’). The scouts report an eligible location for camp at ‘S’, and this is finally chosen. It has several advantages, being comparatively level, and yet upon high ground, and has in close proximity several wells of good water. The train containing provisions and ammunition is parked in the safest locality, the horses picketed, and the guns--perhaps two or three field pieces and machine guns--placed where they can be most easily handled.

By all means, give the men as good a supper as the neighborhood affords. It will be wise not to encroach upon the rations, but rather draw supplies from the village; there are, no doubt, purveyors of one sort or another to be found ready enough to supply us, the more so that they will be amply paid.

Refreshed by their supper the men are ready to turn in at tattoo; by the time ‘taps’ have sounded most are soundly sleeping. But some are awake; if doing their full duty, wider awake than ever they are likely to be in times of peace. The same attention to the bodily comfort of his men which impelled the colonel to give them a long rest at midday and a comfortable meal, applies with increased force to those detailed early in the morning for the night’s guard; during the march these have been spared as far as possible, even being allowed a lift now and then in an ambulance. Such privileges are not granted by a commander who knows his craft as a concession to the laziness, but rather as a preparation for the effectiveness of his men. This is a principle of action, and may apply to business as well as war, that the strong head never withholds reasonable and proper indulgence; the better, it may be said, to enforce at needful times reasonable and proper exertions.