THE MOTOR AFLOAT

The Romance of Modern Mechanism by Archibald Williams is part of the HackerNoon Books Series. You can jump to any chapter in this book here. CHAPTER VIII

THE MOTOR AFLOAT

PLEASURE BOATS — MOTOR LIFEBOATS — MOTOR FISHING BOATS — A MOTOR FIRE FLOAT — THE MECHANISM OF THE MOTOR BOAT — THE TWO-STROKE MOTOR — MOTOR BOATS FOR THE NAVY

Having made such conquests on land, and rendered possible aerial feats which could scarcely have been performed by steam, the explosion motor further vindicates its versatility by its fine exploits in the water.

At the Paris Exhibition of 1889 Gottlieb Daimler, the inventor who made the petrol engine commercially valuable as an aid to locomotion, showed a small gas-driven boat, which by most visitors to the Exhibition was mistaken for an ordinary steam launch, and attracted little interest. Not deterred by this want of appreciation, Mr. Daimler continued to perfect the idea for which, with a prophet's eye, he saw great possibilities; and soon motor launches became a fairly common sight on German rivers. They were received with some enthusiasm in the United States, as being particularly suitable for the inland lakes and waterways with which that country is so abundantly blessed; but met with small recognition from the English, who might reasonably have been expected to take great interest in any new nautical invention. Now, however, English manufacturers have awaked fully to their error; and on all sides we see boats built by firms competing for the lead in an industry which in a few years' time may reach colossal proportions.

Until quite recently the marine motor was a small affair, developing only a few horse-power. But because the gas-engine for automobile work had been so vastly improved in the last decade, it attracted notice as a rival to steam for driving launches and pleasure boats, and soon asserted itself as a reliable mover of vessels of considerable size. To promote the development of the industry, to test the endurance of the machine, and to show the weak spots of mechanical design, trials and races were organised on much the same lines as those which have kept the motor-car so prominently before the public—races in the Solent, across the Channel, and across the Mediterranean. The speed, as in the case of cars, has risen very rapidly with the motor boat. When, in February, 1905, a Napier racer did some trial spins over the measured mile in the Thames at Long Reach, she attained 28·57 miles per hour on the first run. On turning, the tide was favourable, and the figures rose to 30·93 m.p.h., while the third improved on this by over a mile. Her mean speed was 29·925 m.p.h., or about 23 m.p.h. better than the previous record—standing to the credit of the American Challenger. The latter had, however, the still waters of a lake for her venue, so that the Napier's performance was actually even more creditable than the mere figures would seem to imply. At a luncheon which concluded the trial, Mr. Yarrow, who had built the steel hull, said: "To give an idea of what an advance the adoption of the internal combustion engine really represents, I should like to state that, if we were asked to guarantee the best speed we could with a boat of the size of Napier II., fitted with the latest form of steam machinery of as reliable a character as the internal combustion engine in the present boat, we should not like to name more than sixteen knots. So that it may be taken that the adoption of the internal combustion engine, in place of the steam-engine, for a vessel of this size, really represents an additional speed of ten knots an hour. I should here point out that the speed of a vessel increases rapidly with its size. For example: in what is termed a second-class torpedo boat, sixty feet in length, the best speed we could obtain would be twenty knots; but for a vessel of, say, 200 feet in length, with similar but proportionately larger machinery, a speed of thirty knots could be obtained. Therefore, the obtaining of a speed of practically twenty-six knots in the Yarrow-Napier boat, only forty feet in length, points to the possibility, in the not far-distant future, of propelling a vessel 220 feet in length at even forty-five knots per hour. All that remains to be done is to perfect the internal combustion engine, so as to enable large sizes to be successfully made."

Until quite recently the marine motor was a small affair, developing only a few horse-power. But because the gas-engine for automobile work had been so vastly improved in the last decade, it attracted notice as a rival to steam for driving launches and pleasure boats, and soon asserted itself as a reliable mover of vessels of considerable size. To promote the development of the industry, to test the endurance of the machine, and to show the weak spots of mechanical design, trials and races were organised on much the same lines as those which have kept the motor-car so prominently before the public—races in the Solent, across the Channel, and across the Mediterranean. The speed, as in the case of cars, has risen very rapidly with the motor boat. When, in February, 1905, a Napier racer did some trial spins over the measured mile in the Thames at Long Reach, she attained 28·57 miles per hour on the first run. On turning, the tide was favourable, and the figures rose to 30·93 m.p.h., while the third improved on this by over a mile. Her mean speed was 29·925 m.p.h., or about 23 m.p.h. better than the previous record—standing to the credit of the American Challenger. The latter had, however, the still waters of a lake for her venue, so that the Napier's performance was actually even more creditable than the mere figures would seem to imply. At a luncheon which concluded the trial, Mr. Yarrow, who had built the steel hull, said: "To give an idea of what an advance the adoption of the internal combustion engine really represents, I should like to state that, if we were asked to guarantee the best speed we could with a boat of the size of Napier II., fitted with the latest form of steam machinery of as reliable a character as the internal combustion engine in the present boat, we should not like to name more than sixteen knots. So that it may be taken that the adoption of the internal combustion engine, in place of the steam-engine, for a vessel of this size, really represents an additional speed of ten knots an hour. I should here point out that the speed of a vessel increases rapidly with its size. For example: in what is termed a second-class torpedo boat, sixty feet in length, the best speed we could obtain would be twenty knots; but for a vessel of, say, 200 feet in length, with similar but proportionately larger machinery, a speed of thirty knots could be obtained. Therefore, the obtaining of a speed of practically twenty-six knots in the Yarrow-Napier boat, only forty feet in length, points to the possibility, in the not far-distant future, of propelling a vessel 220 feet in length at even forty-five knots per hour. All that remains to be done is to perfect the internal combustion engine, so as to enable large sizes to be successfully made."

Boats of 300 h.p. and upwards are being built; and the project has been mooted of holding a transatlantic race, open to motor boats of all sizes, which should be quite self-contained and able to carry sufficient fuel to make the passage without taking in fresh supplies. In view of the perils that would be risked by all but large craft, and in consideration of the prejudice that motor boats might incur in event of any fatalities, the Automobile Club of France set its face against the venture, and it fell through. It is possible, however, that the scheme may be revived as soon as larger motor boats are afloat, since the Atlantic has actually been crossed by a craft of 12 h.p., measuring only forty feet at the water-line. This happened in 1902, when Captain Newman and his son, a boy twelve years old, started from New York, and made Falmouth Harbour after thirty days of anxious travel over the uncertain and sometimes tempestuous ocean. The boat, named the Abiel Abbot Low, carried auxiliary sails of small size, and was not by any means built for such a voyage. The engine—a two-cylinder—burned kerosene. Captain Newman received £1,000 from the New York Kerosene Oil Engine Company for his feat. The money was well earned. Though provided with proper navigating instruments—which he knew how to use well—Newman had a hard time of it to keep his craft afloat, his watches sometimes lasting two days on end when the weather was bad. Yet the brave pair won through; and probably even more welcome than the sense of success achieved and the reward gained was the long two-days' sleep which they were able to get on reaching Falmouth Harbour.

PLEASURE BOATS

We may now consider the pleasure and commercial uses of the motor boat and marine motor. As a means of recreation a small dinghy driven by a low-powered engine offers great possibilities. Its cost is low, its upkeep small, and its handiness very great. Already a number of such craft are furrowing the surface of the Thames, Seine, Rhine, and many other rivers in Europe and America. While racing craft are for the wealthy alone, many individuals of the class known as "the man of moderate means" do not mind putting down £70 to £100 for a neat boat, the maintenance of which is not nearly so serious a matter as that of a small car. Tyre troubles have no counterpart afloat. The marine motor dispenses with change gears. Water being a much more yielding medium than Mother Earth, the shocks of starting and stopping are not such as to strain machinery. Then again, the cooling of the cylinders is a simple matter with an unlimited amount of water almost washing the engine. And as the surface of water does not run uphill, a small motor will show to better advantage on a river than on a road. Thus, a 5 h.p. car will not conveniently carry more than two people if it is expected to climb slopes at more than a crawl. Affix a motor of equal power to a boat which accommodates half a dozen persons, and it will move them all along at a smart pace as compared with the rate of travel given by oars. After all, on a river one does not want to travel fast—rather to avoid the hard labour which rowing undoubtedly does become with a craft roomy enough to be comfortable for a party.

The marine motor also scores under the heading of adaptability. A wagonette could not be converted into a motor-car with any success. But a good-sized row-boat may easily blossom out as a useful self-propelled boat. You may buy complete apparatus—motor, tanks, screw, batteries, etc.—for clamping direct on to the stern, and there you are—a motor boat while you wait! Even more sudden still is the conversion effected by the Motogodille, which may be described as a motor screw and rudder in one. The makers are the Buchet Company, a well-known French firm. "Engine and carburetter, petrol tank, coil, accumulator, lubricating oil reservoir, exhaust box, propeller shaft, and propeller with guard are all provided, so that the outfit requires no additional accessories. For mounting in position at the stern of the boat, the complete set is balanced on a standard, and carries a steering arm, on which the tanks are mounted; and also the stern tube and propeller guard, which are in one solid piece, in addition to the engine. In order that no balancing feats shall be required of the person in charge, there is, on the supporting standard, a quadrant, in the notches of which a lever on the engine frame engages, thus allowing the rigid framework, and therefore the propeller shaft, to be maintained at any angle to the vertical without trouble."[12]

The 2 h.p. engine drives a boat 16 feet long by 4 feet 6 inches beam at 612 miles per hour through still water. As the Motogodille can be swerved to right or left on its standard, it acts as a very efficient rudder, while its action takes no way off the boat.

For people who like an easy life on hot summer days, reclining on soft cushions, and peeping up through the branches which overhang picturesque streams, there is the motor punt, which can move in water so shallow that it would strand even a row-boat. The Oxford undergraduate of to-morrow will explore the leafy recesses of the "Cher," not with the long pole laboriously raised and pushed aft, but by the power of a snug little motor throbbing gently at the stern. And on the open river we shall see the steam launch replaced by craft having much better accommodation for passengers, while free from the dirt and smells which are inseparable from the use of steam-power. The petrol launch will rival the electric in spaciousness, and the steamer in its speed and power, size for size.

Some people have an antipathy to this new form of river locomotion on account of the risks which accompany the presence of petrol. Were a motor launch to ignite in, say, Boulter's Lock on a summer Sunday, or at the Henley Regatta, there might indeed be a catastrophe. The same danger has before now been flaunted in the face of the automobilist on land; yet cases of the accidental ignition of cars are very, very rare, and on the water would be more rare still, because the tanks can be more easily examined for leaks. Still, it behoves every owner of a launch to keep his eye very widely open for leakage, because any escaping liquid would create a collection of gas in the bottom of the boat, from which it could not escape like the gas forming from drops spilled on the road.

The future popularity of the motor boat is assured. The waterside dweller will find it invaluable as a means of carrying him to other parts of the stream. The "longshoreman" will be able to venture much further out to sea than he could while he depended on muscles or wind alone, and with much greater certainty of returning up to time. A whole network of waterways intersects civilised countries—often far better kept than the roads—offering fresh fields for the tourist to conquer. River scenery and beautiful scenery more often than not go together. The car or cycle may be able to follow the course of a stream from source to mouth; yet this is the exception rather than the rule. We shoot over the stream in the train or on our machines; note that it looks picturesque; wonder vaguely whither it flows and whence it comes; and continue our journey, recking little of the charming sights to be seen by anyone who would trust himself to the water. Hitherto the great difficulty has been one of locomotion. In a narrow stream sailing is generally out of the question; haulage by man or beast becomes tedious, even if possible; and rowing day after day presupposes a good physical condition. In the motor boat the holiday maker has an ideal craft. It occupies little room; can carry fuel sufficient for long distances; is unwearying; and is economical as regards its running expenses. We ought not to be surprised, therefore, if in a few years the jaded business man turns as naturally to a spin or trip on the rivers and canals of his country as he now turns to his car and a rush over the dusty highway. Then will begin another era for the disused canal, the vegetation-choked stream; and our maps will pay more attention to the paths which Nature has water-worn in the course of the ages.

To the scientific explorer also the motor affords valuable help. Many countries, in which roads are practically non-existent, can boast fine rivers fed by innumerable streams. What fields of adventure, sport, and science would be open to the possessor of a fast launch on the Amazon, the Congo, the Mackenzie, or the Orinoco, provided only that he could occasionally replenish his fuel tanks!

MOTOR LIFEBOATS

Turning to the more serious side of life, we find the marine motor still much in evidence. On account of its comparatively short existence it is at present only in the experimental stage in many applications, and time must pass before its position is fully established. Take, for instance, the motor lifeboat lately built for the Royal National Lifeboat Institution. Here are encountered difficulties of a kind very different from those of a racing craft. A lifeboat is most valuable in rough weather, which means more or less water often coming aboard. If the water reached the machinery, troubles with the electrical ignition apparatus would result. So the motor must be enclosed in a water-tight compartment. And if so enclosed it must be specially reliable. Also, since a lifeboat sometimes upsets, the machinery needs to be so disposed as not to interfere with her self-righting qualities. The list might easily be extended.

An account of the first motor life-saver will interest readers, so we once again have recourse to the chief authority on such topics—the Motor Boat—for particulars. The boat selected for experiment was an old one formerly stationed at Folkestone, measuring thirty-eight feet long by eight feet beam, pulling twelve oars, double-banked, and of the usual self-righting type, rigged with jib, fore-lug, and mizzen. After she had been hauled up in Mr. Guy's yard, where some of the air-cases under the deck amidships were taken out, a strong mahogany case, measuring four feet long by three feet wide and as high as the gunwales, lined with sheet copper so as to be water-tight, with a close-fitting lid which could be easily removed on shore, was fitted in place, and the whole of the vital parts of the machinery, comprising a two-cylinder motor of 10 h.p., together with all the necessary pumps, carburetter, electric equipment, etc., were fitted inside this case. The engine drives a three-bladed propeller through a long shaft with a disconnecting clutch between, so that for starting or stopping temporarily the screw can be disconnected from the engine. The petrol, which serves as fuel for the engine, is carried in a metal tank stored away inside the forward "end" box, where it is beyond any possibility of accidental damage. Sufficient fuel for a continuous run of over ten hours is carried. The engine is started by a handle fitted on the fore side of the case, which can be worked by two men. The position and size of the engine-case is such that only two oars are interfered with, but it does not follow that the propelling power of the two displaced men is entirely lost, because they can double bank some of the other oars when necessary.

Fitted thus, the lifeboat was tested in all sorts of weather during the month of April, and it was found that she could be driven fairly well against a sea by means of the motor alone; but when it was used to assist the sails the true use of the motor as an auxiliary became apparent, and the boat would work to windward in a way previously unattainable. Neither the pitching or rolling in a seaway, in any weather then obtainable, interfered at all with the proper working or starting of the motor, which worked steadily and well throughout. Having been through these preliminary tests, she was more severely tried. Running over the measured mile with full crew and stores on board, she developed over six knots an hour. The men were then replaced by equivalent weights lashed to the thwarts, and she was capsized by a crane four times, her sails set and the sheets made fast, yet she righted herself without difficulty. An interesting feature of the capsize was that the motor stopped automatically when the boat had partly turned over. This arrangement prevents her from running away from the crew if they should be pitched out. The motor started again after a few turns of the handle, so proving that the protecting compartment had kept the water at bay.

From this account it is obvious that a valuable aid to life-saving at sea has been found. The steam lifeboat, propelled by a jet of water squirted out by pumps below the water line, is satisfactory so long as the boat keeps upright. But in event of an upset the fires must necessarily be extinguished. No such disability attends the petrol-driven craft, and we shall be glad to think that the brave fellows who risk their lives in the cause of humanity will be spared the intense physical toil which a long row to windward in a heavy sea entails. The general adoption of this new ally will take time, and must depend largely on the liberality of subscribers to the fine institution responsible for lifeboat maintenance; but it is satisfactory to learn that the Committee has given the boat in question a practical chance in the open sea by stationing her at Newhaven, Sussex, as a unit in the lifeboat fleet.

MOTOR FISHING BOATS

It is a pretty sight to watch a fishing fleet enter the harbour with its catch, taken far away on the waters beyond the horizon while landsmen slept. The sails, some white, some brown, some wondrously patched and bearing the visible marks of many a hard fight with the wind, belly out in graceful lines as the boats slip past the harbour entrance. No wonder that the painter has so often found subjects for his canvas and brushes among the toilers of the deep.

But underlying the romance and picturesqueness of the craft there is stern business. Those boats may be returning with full cargoes, such as will yield good profits to owner and crew; or, on the other hand, the hold may be empty, and many honest hearts be heavy at the thought of wasted days. A few years ago the Yarmouth herring fleet is said to have returned on one occasion with but a single fish to the credit of the whole fleet! This might have been a mere figure of speech; it stands, at any rate, for many thousands of pounds lost by the hardy fishermen.

When the boats have been made fast, the fish, if already disentangled from the nets, is usually sold at once by auction, the price depending largely on the individual size and freshness of the "catch." Now, with the increase in the number of boats and from other causes, the waters near home have been so well fished over that much longer journeys must be made to the "grounds" than were formerly necessary. Trawling, that is, dragging a large bag-net—its mouth kept open by a beam and weights—along the bottom of the sea for flatfish, has long been performed by powerful steam vessels, which may any day be seen leaving or entering Hull or Grimsby in large numbers. Surface fishing, wherein a long drift-net, weighted at its lower edge and buoyed at the upper edge to enable it to keep a perpendicular position, is used for herring and mackerel, and in this industry wind power alone is generally used by British fishermen.

The herring-boat sets sail for the grounds in the morning, and at sundown should be at the scene of action. Her nets, aggregating, perhaps, a mile in length, are then "shot," and the boat drifts along towing the line behind her. If fish appear, the nets are hauled in soon after daybreak by the aid of a capstan. The labour of bringing a mile of nets aboard is very severe—so severe, in fact, that the larger boats in many cases employ the help of a small steam-engine. During the return voyage the fish is freed from the meshes, and thrown into the hold ready for sale as soon as land is reached.

Fish, whether for salting or immediate consumption, should be fresh. No class of human food seems to deteriorate so quickly when life is extinct as the "denizens of the deep," so that it is of primary importance to fishermen that their homeward journey should be performed in the shortest possible time. If winds are contrary or absent there may be such delay as to need the liberal use of salt, and even that useful commodity will not stave off a fall in value.

It therefore often happens that a really fine catch arrives at its market in a condition which spells heavy loss to the catchers. A slow return also means missing a day's fishing, which may represent £200 to £300. For this reason the Dogger Bank fishing fleet is served by steam tenders, which carry off the catches as they are made, and thus obviate the necessity for a boat's return to port when its hold is full. Such a system will not, however, be profitable to boats owned by individuals, and working within a comparatively short distance of land.

Each boat must depend on its particular powers, the first to return getting rather better prices than those which come "with the crowd." So steam power is in some cases installed as an auxiliary to the sails, though it may entail the outlay of £2,000 as first cost, and a big bill for upkeep and management. "Small" men cannot afford this expense, and they would be doomed to watch their richer brethren slip into the market before them had not the explosion motor come to their aid. This just meets their case; it is not nearly so expensive to install as steam, occupies much less room, is easier to handle, and therefore saves the expense of trained attendants.

Fishermen are notoriously conservative. To them a change from methods sanctioned by many years of practice is abhorrent. What sufficed for their fathers, they say, should suffice for them. Their trade is so uncertain that a bad season would see no return for the cost of the motor, since, where no fish are caught, it makes little difference whether the journey to port be quick or slow.

However, the motor is bound to come. It has been applied to fishing boats with marked success. While the nets are out, the motor is stopped, and costs not a penny more till the time comes for hauling in. Then it is geared up with a capstan, and saves the crew much of their hardest work. When all is aboard, the capstan hands over the power to the screw, which, together with the sails, propels the vessel homewards at a smart pace. The skipper is certain of making land in good time for the market; and he will be ready for the out voyage next morning. Another point in favour of the motor is that, when storms blow up, the fleet will be able to run for shelter even if the wind be adverse; and we should hear less of the sacrifice of life which makes sad reading after every severe gale.

As to the machinery to be employed, Mr. F. Miller, of Oulton Broad, who first applied the gas-motor to a fishing smack—the Pioneer—considers that a 12 h.p. engine would suffice as an auxiliary for small craft of the class found in the northern parts of Great Britain. The Norfolk boats would require a 30 h.p.; and a full-powered boat—i.e. one that could depend on the motor entirely—should carry a three-cylinder engine of 80 h.p. In any case, the machinery must be enclosed and well protected; while the lubrication arrangements should be such as to be understood easily by unskilled persons, and absolutely reliable. Owing to the moisture in the atmosphere the ordinary high-tension coil ignition, such as is used on most motor-cars, would not prove efficient, and it is therefore replaced by a low-tension type which makes and breaks the primary circuit by means of a rocking arm working through the walls of the cylinder. Lastly, all parts which require occasional examination or adjustment must be easily accessible, so that they may receive proper attention at sea, and not send the vessel home a "lame duck" under sail.

The advantages of the motor are so great that the Scotch authorities have taken the matter up seriously, appointing an expert to make inquiries. It is therefore quite possible that before many years have elapsed the motor will play an important part in the task of supplying our breakfast tables with the dainty sole or toothsome herring.

A MOTOR FIRE FLOAT

As a good instance of this particular adaptation of the explosion engine to fire-extinction work, we may quote the apparatus now in attendance on the huge factory of Messrs. Huntley and Palmer, the famous Reading biscuit makers. The factory lies along the banks of the river Kennet, which are joined by bridges so close to the water that a steamer could not pass under them. Messrs. Merryweather accordingly built the motor float, 32 feet long, 912 feet beam, and drawing 27 inches. Two engines, each having four cylinders of a total of 30 h.p., drive two sets of three-cylinder "Hatfield" pumps, which give a continuous feed to the hose. Engines and pumps are mounted on a single bed-plate, and are worked separately, unless it be found advisable to "Siamese" the hoses to feed a single 112-inch jet, which can be flung to a great height.

One of the most interesting features of the float is the method of propulsion. As its movements are limited to a few hundred yards, the fitting of a screw was considered unnecessary, its place being taken by four jets, two at each end, through which water is forced against the outside water by the extinguishing pumps. These will move the float either forward or astern, steer her, or turn her round.

So here once again petrol has trodden upon the toes of Giant Steam: and very effectively, too.

THE MECHANISM OF THE MOTOR BOAT

In many points the marine motor reproduces the machinery built into cars. The valve arrangements, governors, design of cylinders and water-jackets are practically the same. Small boats carry one cylinder or perhaps two, just as a small car is content with the same number; but a racing or heavy boat employs four, six, and, in one case at least, twelve cylinders, which abolish all "dead points" and enable the screw to work very slowly without engine vibration, as the drive is continuous.

The large marine motor is designed to run at a slower rate than the land motor, and its cylinders are, therefore, of greater size. Some of the cylinders exhibited in the Automobile Show at the London "Olympia" seemed enormous when compared with those doing duty on even high-powered cars; being more suggestive of the parts of an electric lighting plant than of a machine which has to be tucked away in a boat.

Except for the reversing gear, gearing is generally absent on the motor boat. The chauffeur has not to keep changing his speed lever from one notch to another according to the nature of the country. On the sea conditions are more consistently favourable or unfavourable, and, as in a steamboat, speed is controlled by opening or closing the throttle. The screw will always be turned by the machinery, but its effect on the boat must depend on its size and the forces acting in opposition to it. Since water is yielding, it does not offer a parallel to the road. Should a car meet a hill too steep for its climbing powers, the engines must come to rest. The wheel does not slip on the road, and so long as there is sufficient power it will force the car up the severest incline; as soon as the power proves too small for the task in hand the car "lies down." In a motor boat, however, the engine may keep the screw moving without doing more against wind and tide than prevent the boat from "advancing backwards." The only way to make the boat efficient to meet all possible conditions would be to increase the size or alter the pitch of the screw, and to install more powerful engines. "Gearing down"—as in a motor-car—being useless, the only mechanism needed on a motor boat in connection with the transmission of power from cylinders to screw is the reversing gear.

Though engines have been designed with devices for reversing by means of the cams operating the valves, the reversal of the screw's movement is generally effected through gears on the transmission apparatus. The simplest arrangement, though not the most perfect mechanically, is a reversible screw, the blades of which can be made to feather this way or that by the movement of a lever. Sometimes two screws are employed, with opposite twists, the one doing duty while the other revolves idly. But for fast and heavy boats a single solid screw with immovable blades is undoubtedly preferable; its reversal being effected by means of friction clutches. The inelasticity of the explosion motor renders it necessary that the change be made gradually, or the kick of the screw against the motor might cause breakages. The clutch, gradually engaging with a disc revolved by the propeller shaft, first stops the antagonistic motion, and then converts it into similar motion. Many devices have been invented to bring this about, but as a description of them would not be interesting, we pass on to a consideration of the fuel used in the motor boat.

Petrol has the upper hand at present, yet heavier oil must eventually prevail, on account both of its cheapness and of its greater safety. The only objection to its use is the difficulty attending the starting of the engine with kerosene; and this is met by using petrol till the engine and carburetter are hot, and then switching on the petroleum. When once the carburetter has been warmed by exhaust gases to about 270° Fahrenheit it will work as well with the heavy as with the light fuel.

Since any oil or spirit may leak from its tanks and cause danger, an effort has been made to substitute solid for liquid fuel. The substance selected is naphthalene—well known as a protector of clothes against moths. At the "Olympia" Automobile Exhibition of 1905 the writer saw an engine—the Chenier Leon—which had been run with balls of this chemical, fed to the carburetter through a melting-pot. For a description of this engine we must once again have recourse to the Motor Boat. The inventors had decided to test its performance with petrol, paraffin, and naphthalene respectively. "The motor, screwed to a testing bench, was connected by the usual belt to a dynamo, so that the power developed under each variety of fuel might be electrically measured, and was then started up on petrol. As soon as the parts were sufficiently warmed up by the exhaust heat, the petrol was turned off, and the motor run for some time on paraffin, until sufficient naphthalene was thoroughly melted to the consistency of a thick syrup. The naphthalene was then fed to its mixing valve through a small pipe dipping into the bottom of the melting-pot, and thence sprayed into the induction chamber to carburate the air therein. Hitherto, the motor had given an average of 12 electrical h.p. at 1,000 revolutions per minute, and it was noticed that as soon as the change was made, this was fully maintained. This test, when continued, bore out others which had previously been made by the firm, and showed the consumption of each of the three fuels to be a little over 12 lbs. per hour for the 12 electrical h.p. given by the motor. Still, the paraffin and naphthalene worked out about equal as to cost, and considering that the latter was in its purest form, as sold for a clothes preservative, we have yet to see how much better its commercial showing will be with lower grades, assuming beforehand that its thermal efficiency and behaviour are as good.

"On the ground of convenience naphthalene, as a solid, is a very long way in front of its liquid rival, kerosene. Its exhaust, too, was much freer from odour, and it appears that, unlike paraffin, it forms neither tar, soot, nor sticky matter, but, on the contrary, has a tendency to brighten all valves, cylinders, walls, etc., any little deposit being a light powder which would be carried into the exhaust."

THE TWO-STROKE MOTOR

In the ordinary "Otto-cycle" motor an explosion occurs once in every two revolutions of the crank. With a single cylinder the energy of the explosion must be stored up in a heavy fly-wheel to carry the engine through the three other operations of scavenging, sucking in a fresh charge, and compressing it preparatory to the next explosion. With two cylinders the fly-wheel can be made lighter, as an explosion occurs every revolution; and in a four-cylinder engine we might almost dispense with the wheel altogether, since the drive is continuous, just as in a double-cylindered steam-engine.

The two-stroke motor, i.e. one which makes an explosion for every revolution, is an attempt to unite the advantages of a two-cylindered engine of the Otto type with the lightness of a single-cylindered engine. As it has been largely used for motor boats, especially in America, a short description of its working may be given here.

In the first place, all moving cylinder valves are done away with, their functions being performed by openings covered and opened by the movements of the piston. The crank chamber is quite gas-tight, and has in it a non-return valve through which vapour is drawn from the carburetter every time the piston moves away from the centre. There is also a pipe connecting it with the lower part of the cylinder, but the other end of this is covered by the piston until it has all but finished its stroke.

Let us suppose that an explosion has just taken place. The piston rushes downwards, compressing the gas in the crank chamber to some extent. When the stroke is three-parts performed a second hole, on the opposite side of the cylinder from the aperture already referred to, is uncovered by the piston, and the exploded gases partly escape. Immediately afterwards the second hole is uncovered also, and the fresh charge rushes in from the crank case, being deflected upwards by a plate on the top of the piston, so as to help drive out the exhaust products. The returning piston covers both holes and compresses the charge till the moment of explosion, when the process is repeated. It may be said in favour of this type of engine that it is very simple and free from vibration; against it that, owing to the imperfect scavenging of exploded charges, it does not develop so much power as an Otto-cycle engine of equal cylinder dimensions; also that it is apt to overheat, while it uses double the amount of electric current.

MOTOR BOATS FOR THE NAVY

A country which, like England, depends on the command of the sea for its very existence may well keep a sharp eye on any invention that tends to render that command more certain. In recent years we have heard a lot said, and read a lot written, about the importance of swift boats which in war time could be launched against a hostile fleet, armed with the deadly torpedo. The Russo-Japanese War has given us a fine example of what can be accomplished by daring men and swift torpedo craft.

For some reason or other the British Navy has not kept abreast of France in the number of her torpedo vessels. Reference to official figures shows that, while our neighbours can boast 280 "hornets," we have to our credit only 225. In the House of Commons, on August 10th, 1904, Mr. Henry Norman, M.P., asked the Secretary of the Admiralty whether, in view of the proofs recently afforded of trustworthiness, speed, simplicity, and comparatively low cost of small vessels propelled by petrol motors, he would consider the advisability of testing this class of vessel in His Majesty's Navy. The Secretary replied that the Admiralty had kept a watch on the recent trials and meant to make practical tests with motor pinnaces. In view of the danger that would accompany the storage of petrol on board ship, the paraffin motor was preferable for naval purposes; and an 80 h.p. four-cylindered motor of this type has been ordered from Messrs. Vosper, of Portsmouth.

Mr. Norman, writing in The World's Work on the subject, says: "There can be no question that such high speed and cheap construction (80 h.p. giving in the little boat as much speed—to consider that only—as eight thousand in the big boat) point to the use of motor boats for naval purposes in the near future. A torpedo boat exists only to carry one or two torpedoes within launching distance of the enemy. The smaller and cheaper she can be, and the fewer men she carries, provided always she be able to face a fairly rough sea, the better. Now the ordinary steam torpedo boat carries perhaps twenty men, and costs anything from £50,000 to £100,000. A motor boat of equal or greater speed could probably be built for £15,000, and would carry a crew of two men. Six motor boats, therefore, could be built for the cost of one steamboat, and their total crews would not number so many as the crew of the one. Moreover, they could all be slung on board a single vessel, and only set afloat near the scene of action. A prophetic friend of mine declares that the most dangerous warship of the future will be a big vessel, unarmoured and only lightly armed, but of the utmost possible speed, carrying twenty or more motor torpedo boats slung on davits. She will rely on her greater speed for her own safety, if attacked; she will approach as near the scene of action as possible, and will drop all her little boats into the water, and they will make a simultaneous attack. Their hulls would be clean, their machinery in perfect order, their crews fresh and full of energy, and it would be strange if one of the twenty did not strike home. And the destruction of a battleship or great cruiser at the cost of a score of these little wasps, manned by two-score men, would be a very fine naval bargain."

Mr. Norman omits one recommendation that must in active service count heavily in favour of the motor boat, and that is its practical invisibility in the day or at night time. The destroyer, when travelling at high speed, betrays its presence by clouds of smoke or red-hot funnels. The motor boat is entirely free from such dangerous accompaniments; the exhaust from the cylinders is invisible in every way. The very absence of funnels must also be in itself a great advantage. The eye, roving over the waters, might easily "pick up" a series of stumpy, black objects of hard outline; but the motor boat, riding low and flatly on the waves, would probably escape notice, especially when a search-light alone can detect its approach.

It may reasonably be said that the Admiralty knows its own business best, and that the outsider's opinion is not wanted. The "man in the street" has become notorious for his paper generalship and strategy, and fallen somewhat into disrepute as an adviser on military and naval matters. Yet we must not forget this: that many—we might say most—of the advances in naval mechanisms, armour, and weapons of defence have not been evolved by naval men, but by the highly educated and ingenious civilian who, unblinded by precedent or professional conservatism, can watch the game even better in some respects than the players themselves, and see what the next move should be. That move may be rather unorthodox—like the application of steam to men-o'-war—but none the less the correct one under the circumstances. We allowed other nations to lead us in the matter of breech-loading cannon, armour-plate, submarines, the abolition of combustible material on warships. Shall we also allow them to get ahead with motor boats, and begin to consider that there may be something in motor auxiliaries for the fleet when they are already well supplied? If there is a country which should above all others lose no time in adding the motor to her means of defence, that country is Great Britain.

FOOTNOTE:

12. The Motor Boat, March 16th, 1905.

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