Notwithstanding the fact that one of the objections raised against the steam locomotive is that the heat energy developed in its use is not fully utilised, it has until recently remained essentially the same as when constructed by Stephenson. But the invention of new motors and their competition with steam has caused improvements to be made in the steam engine with a view to adapt it for use both for small-power -stationary and traction motors. Just as the incandescent gas light is the outcome of the fight for existence of the ordinary gas light against the electric light, so those interested in improving the steam engine have been spurred on by the results attained with gas engines and explosion motors.
Very recently yet another rival threatens the steam engine in the shape of the heat motor (Warmemotor) invented by the Bavarian engineer Diesel, and first made generally known at the Munich Power and Engine Exhibition in 1898, though a great future had already been prophesied for it by engineering experts. Although at present in the trial stage, it is mentioned here because of the brilliant prospect which its use in connection with automobiles offers for military purposes.
When the Diesel motor has proved suitable for stationary engines, its application for purposes of traffic will certainly follow. Like the explosion motors it works on the fourcycle principle, but with the difference that in this case neither electric nor incandescent tube or fuse ignition is used, but at the instant in which the fuel (coal dust or petroleum, etc.) is introduced into the working cylinder, it is ignited without explosion by coming into contact with the air in it, which has been heated to incandescence by the previous compression. In this connection it is specially noteworthy that in this new motor the energy developed out of the combustible material used is much greater than in other motors. Whereas in the best triple expansion steam engines it amounts to only 12 to 13 per cent., in the Diesel motor it is 30 per cent.
For military purposes the fact that the necessity for some special method of ignition is done away with is a great advantage. Electric ignition is quite unsuited for use in war on account of the difficulty of keeping the batteries and accumulators charged, and the incandescent tube is also unsuitable, being too liable to be affected by weather influences. Among other advantages claimed for the Diesel motor for military purposes, are:
Absence of smoke and smell, which in other motors are said to frighten horses.
Small quantity of fuel required—240 to 250 grammes (120 to 125 oz.) of petroleum per horse-power per hour. This would allow greater distance between the depots on the line of communications, and consequently it would be necessary to establish fewer of them. As no water for cooling the cylinders is required, as is the case in so many motors, the necessity for stoppages to get water and refill the cooling chambers is done away with.
Another great advantage is that the motor is always ready to start work, whereas with oil motors it requires some minutes to heat them, and with the steam engine a quarter of an hour to get up steam. The starting of the Diesel motor is effected instantly by opening a valve in the supply chamber holding the reserve of compressed air (at 40 atmospheres), which at once starts the motor. The dependence of the motor on this method of starting it prevents its use at present for carriages; and especially for military purposes, as it would be risky to expose an apparatus containing gas at such high pressure to jolting on bad roads.
Nowadays interest centres generally in the different applications of electricity. Many think of it first when it is a question of traction by mechanical means. As a matter of fact, both gas and steam motors have the disadvantage as compared with those driven by electricity, that the movement they communicate to the vehicle is by impact or shock. Whereas in the gas engine (benzine, etc., motors), which works with four-cycle cylinder, the explosion of the gas mixture causes a stroke of the piston at every other rotation of the driving shaft, in the steam engine, with every forward and return movement of the piston in the cylinder under the expansion of the steam, work is performed twice, with every revolution. In both the amount of power employed in driving the engine is different every moment, and in both dead points have to be passed, causing the movement to be jerky.
The ideal thing would be a power which would act perfectly evenly and regularly, and at every moment supply the same amount of driving power, so that no storage of live power in a flywheel would be necessary, and the transmitting of the rotation of the driving shaft to the axles of the running wheels be done either directly or by means of simple transmission.
In the steam engine, and often also in gas motors, the attainment of this object is attempted by combining several working cylinders in which the stroke of the piston, exposed to the influence of the gas and steam, takes place alternately; thus the maximum effects of the pressure relieve one another alternately. But the electric motor is superior to all these arrangements in the regularity of its action on the driving wheels; it possesses also other very valuable advantages, which make it preferable to other motors when the electric fluid is obtainable. There is no fear of explosion, the steering is done by a simple hand grip, safety valves are not required, no great heat is developed, no smoke and no smell, and a motor of this kind can on occasion be driven at much higher power than its normal working power.
For driving vehicles with electricity accumulators are necessary—the Heilmann locomotive, in which the attempt is made to combine the use of steam and electricity (dynamo), not being at present practical
Accumulators have not made much headway for use for driving vehicles on ordinary roads. They are too heavy and too much dependent on arrangements for charging; also require too much care to be of use for military purposes. They are only suitable at present for use in and near towns with light vehicles which can run from 25 to 35 miles a day with one charging.
But it may safely be said that the time is not far distant when extended use will be made of light, dry accumulators which can be safely carried, and in that case means of recharging them will be as common as coal depots are now. But, from a military point of view, of course, there can be no thought of sending accumulators back to their own stations to be recharged, and electric motor vehicles for war purposes can only be employed when the army is accompanied by power engines, like traction engines, which also carry dynamos.
Put Shortly, the present position of the motor question as regards the army is as follows:—Some of them are capable of development, but at present are incomplete, others are from the very nature of their construction too complicated at present to be thought of seriously for war purposes. The road traction engine, on the other hand, promises, with the recent improvements which have been effected in it, to prove of great value.
The traction engine has the advantage over other motors of many-sided utility, and this point is a most important one in its favour. It transports in the rear of the army material of the most varied kind, at the railway termini it serves for unloading wagons, in camps intended to be used for some time it furnishes electric light, and does all the pumping necessary for supplying the water-tanks. Thus the army; would possess in the traction engine a transportable power engine capable of being used in a variety of ways, whereas in the case of oil motors their use is confined exclusively to carrying loads and persons, and when not required for this purpose they are useless.
Of late renewed impetus has been given to the movement1 for using mechanical traction in the army. Mention has] already been made of the difficulties connected with the supply of the enormous armies of modem times, even in the | case of campaigns conducted in rich countries where supplies1 can be requisitioned freely. In such cases the ‘perfected conserves,* or preserved foods, invented by Professor Emmerich of the University of Munich, combined with the use of mechanical traction in the army, enable it to dispense entirely with supplies of live cattle for slaughter; thus it can carry larger supplies, including other war material, more rapidly and for longer distances than formerly. This means greater freedom in operating for the troops in the fighting line, since supplies can be sent to them quickly from depots at greater distances than formerly.
Another important advantage offered by the traction engine is that when attached to the army supply corps they enable the latter to bring in supplies from a more extended district than that actually occupied by the army. As already mentioned, in such cases horse traction is unsatisfactory, as their day’s march is too short, they consume too much of the supplies, and are subject to outbreaks of epidemic disease; in addition to this, the requisitioning of horses and carts in a country in which everything it required has already been requisitioned by the army on its march, presents great difficulties, and to get teams and carts from home means great delay. The traction engines of obsolete construction used by the German army in 1870 proved that steep ascents, bad roads, and narrow streets presented no insurmountable difficulties.
An accident which may have had some effect in creating prejudice against the traction engine took place at the village of Maupertius, near Coulommiers, when the brake of a transport train with a load of 700 cwt gave way, the engine being unable to hold such a weight on a paved street on an incline of 1 in 10. But according to reports of eyewitnesses the cause of the accident was defective construction in the vehicles requisitioned; in any case no one was hurt and but little delay caused.
The road traction engine requires coal as fuel, but can use wood if necessary, things not required by the troops on march, and which therefore may be requisitioned, or without great difficulty supplied from home, as they keep indefinitely in store, is. are not like perishable stores. It is therefore to the interest of the army to obtain in peace time as large a number of traction engines and trucks as possible, and to arrange for a proper staff of trained driven. To do this it is necessary that such means should be regularly employed for army transport in peace time. Other advantages would then be apparent, including economy of work and expense.
Calculations as to the comparative cost of horse and mechanical traction vary according to whether those who make them are prejudiced in favour of one or the other. But at present there is no basis for such comparison, as we do not know the extent of work, or the ‘life' of the improved modern traction engine, and so cannot get at its earning power and the percentage of return on the capital employed in it. But its durability is a very important factor; for instance, the two Fowler traction engines used, as already mentioned, in the war of 1870, have been in use ever since, and now, thirty years after, are employed as steam ploughs.
For a regular daily traffic probably horse traction is cheapest, but if the traffic is occasional, as is the case in the army in peace time, horse service is not economical, i.e. if they are kept purposely; and if hired the expense is great, and there are other drawbacks. Under such conditions the traction engine can be employed with advantage, as it costs little when not in actual use, and yet permits the retention in service of a competent staff of men.
A special mechanical traction corps could thus be formed, in which, under proper officers, a staff would be trained for working steam and other automobiles for military purposes, and establishing repairing shops. It would be advisable to combine animal and mechanical traction, since both have to be employed either together or separately in forwarding supplies; at one time horses would be used, at another traction engines if available. For this reason this special corps would be attached to the artillery train rather than to the railway corps. The traction engine has only in appearance any relation to the engines of the railway supply corps. The Russian experiences are instructive as regards this point, since they showed that ordinary locksmiths managed the traction engines better than the drivers and firemen of railway engines. It is well known that there is so much difference between the ordinary railway engine and the field railway engine, that drivers of the former require a considerable time to learn how to drive the latter properly. Every type of engine has, as it were, an individuality of its own which the driver and fireman must thoroughly understand before they can work the engine economically and properly.
It is not to be expected that such a traction park would pay like a joint stock company. All the same it would be available for a variety of services for which otherwise vehicles would have to be hired; for example, in foraging and fatigue service, for which cast army horses are employed, which must be fed from the stores of horse forage required by the army generally.
For making earthworks in and around fortresses, transport of guns, etc., the traction engines, held in readiness for war, could be utilised. At manoeuvres, the tactical handling of large bodies of troops could be carried out more independently of billeting, by the forwarding of the necessary bivouac supplies. Where it was necessary to make use of barracks, they could be established away from the large towns where land could be had more cheaply, and within easy distance of the drill ground.
In other special ways traction engines could be used in peace time: e.g. transport of heavy siege guns in foot artillery exercises, transport of the material of the balloon corps, for which they could also be used as power engines, either with or without dynamos; as engines for working and moving targets at field artillery firing practice in the country. At the permanent target practice grounds it is customary to use stationary engines to bring movable targets into range between the fixed ones, to represent all phases of a battle with artillery. With target practice in the open country, on the other hand, it has been necessary to employ horse power to draw the targets on sledges— a very unsatisfactory method. Apart from the fact that the artillery horses are used up and liable to get overstrained at this work, the resistance of the targets, especially against a wind, is so great that they must be very slightly constructed, or else moved very slowly.