David Napier by David Napier and David Bell: Chapter VII
Chapter VII: Patents
Mr. Napier’s patents included —
No. 8044, 1839. Improvements in Iron Steam-boats, viz. the constructing of Iron Steamers with two water-tight bottoms, and applying the space between them in condensing the exhaust steam from engines. This arrangement, it was claimed, secured greater strength and safety, a saving of power in working the air-pump, and less wear and tear of boilers. Fresh water being always used, and the quantity remaining nearly always the same, accidents arising from want of water in the boilers could scarcely occur. It was recommended that in "steamers of magnitude" the double bottom be continued up the sides of vessels.
A, space between the bottoms B and C; D, inner water-tight floor, about 11 inches above C, into which sea water flowed through openings at the bows and out at the stern, thereby keeping the surfaces of C always cold; a, a, iron keelsons rivetted to B and C for the double purpose of resisting the internal pressure and strengthening the vessel.
No. 8893, 1841. Improvements in Propelling Vessels. One Part of this invention consisted in placing two wheels or propellers of equal diameter at the stern of the vessel, the axles of both above the level of the water, and one wheel further aft than the other, to permit the blades or float-boards of one wheel working nearly up to the axle of the other. These wheels, on patent drawing, had each eight oblique blades, radiating from a central disc. A further arrangement in this patent applied to side wheels. The floats, in this case, were connected at their lower edges to a heavy metallic frame, the weight of which kept the floats, all round, in a nearly vertical position.
No. 9439, 1842. Improvements in Steam-Engines and Steam-Engine Boilers. This patent covered the various forms of the vertical engine with return connecting-rod, known as the "steeple engine," one, two or four piston-rods being employed. It also included the well-known "haystack" boiler. A feed-heating apparatus was also specified, the feed water being pumped through an annular casing at base of funnel, and thence into the boiler.
No. 11652, 1847. Improvements in Steam-Engines and Steam vessels. This covered several arrangements of marine engines, securing compactness and simplicity, and permitting the cylinder to be placed immediately under the paddle shaft. Also a double bottom under the engines, forming a casing for condenser tubes, with pump to circulate condensing water when the vessel was at rest.
No. 13884, 1851. Improvements in Steam-Engines; included a rotary engine, water-tube furnace bars, forced draught, and a valve causing engines to stop, go ahead, or reverse.
No. 1044, 1852. Improvements in Steam-Engines; included heating air for boiler furnaces (an application of the "hot-blast"), suitable also for locomotives.
It may be noted that the longitudinal girder system of construction for vessels' bottoms, as specified above, dates some fourteen years before its adoption by Mr. Scott Russell in the Great Eastern.
Surface condensation was applied in the Post Boy in 1820, nineteen years prior to the above patent; and the United Kingdom, 1826, also had a surface condenser. The copper tubes used are said to have been about 12 feet long and inch diameter. The Rotary also was similarly fitted, but with a separate iron casing in the engine room, at side of vessel, to contain the tubes.
A model of Napier's side wheel is shown in the Science Museum, South Kensington. Experiments were made in several of his boats with the side and stern wheels. The steeple engine was introduced about 1831, and for a long period was, in its various forms, the favourite type of engine for passenger steamers in Britain and America. It is still used in tugs and smaller-sized paddle-boats; and in a number of passenger steamboats engines of this description are still doing good work, after forty to sixty years' constant service.
In a modern high-class Clyde steamer the original horizontal boilers were some time ago replaced by others of the "haystack" type, thereby effecting a considerable saving of weight, lessened draught of water, and a marked increase in speed.
Many varieties of rotary engine had been designed and tried before Napier's time, but none achieved any great success.
Napier's first rotary was, in 1851, fitted into a steamboat built at Millwall; and another was constructed for him, probably in 1853, by Thomas Wingate and Co, Glasgow. The former ran successfully for a considerable time, but the Clyde vessel did not prove so satisfactory. She plied for about two years, but her performances fell short of Napier's expectations, and the engine was replaced by one of ordinary type. The latter engine had its single cylinder placed on a bed-plate in the engine room, and its power was transmitted to the paddle-shaft overhead by two heavy rubber belts, said to have been each about six inches by one inch. Napier's view of the advantages to be gained by the rotary was given in the Glasgow Courier of 26th March, 1853, as follows:
"The advantages these engines have over other engines are, that they are more compact, consume about one fourth less fuel, and require no engineer. The steersman, by a peculiar valve, moves the vessel ahead or astern without communicating with any one. The furnace bars contain water, consequently the hot ashes, which are destructive to the common furnace bar, in this case tend to the production of steam. There is also a simple application of the fan to assist combustion. These two parts of the patent might be applied with advantage to most steamers. These engines are not now a matter of experiment, — a steamer was fitted with them in London above a year ago, and has been plying on the Severn with complete success, the engine being as perfect now as on the day it was made and from the far-famed workmanship of the Clyde it is expected this one will prove equal, if not superior, to the one made in London. Such steamers would be invaluable on crowded rivers like the Clyde, as running down would scarcely ever happen,—the steersman standing before the funnel, and there being no paddle-boxes to interrupt his view, he sees every object ahead and can stop or reverse the engines in an instant without leaving the wheel or applying to any second party."
Napier retained his confidence in the principle of rotary engines, and, four years later, wrote that he was going on with another of this type, but no particulars of it have been found. Rankine, in 1859, stated that the number of rotary engines that had been patented in Britain alone was upwards of two hundred, but that very few had been brought into practical operation, and these to a limited extent only. "The most successful," he added, "appear to have been the Earl of Dundonald's and Mr. David Napier's."
It will be seen that there were few of the essential improvements found in the modern steamship, engine or boiler which Napier did not anticipate or foreshadow in his patents. The screw-propeller, although not patented, appears to have suggested itself to him as far back as 1820, as indicated by the following letter:
MILLWALL, September 17th, 1841.
SIR,
It is upwards of twenty years since I came to London to take out a patent for propelling vessels on the screwing principle. On my arrival I found that a Mr. Shorter in the Borough had made experiments of that kind nearly twenty years before that, of which I had ocular demonstration by Mr. Shorter turning out of his cupboards and presses perfect models of vessels with machinery and springs attached. A few years afterwards I was introduced to Mr. Perkins of steam-gun notoriety, who shewed me a deviation on Mr. Shorter's (for which he had obtained a patent), exactly the same as a Mr. Ericsson tried a few years ago on a boat called the Robert F. Stockton, which went to America. Seeing that I could not be considered the Inventor, as I at first thought I was, it cooled my ardour in prosecuting the matter, until, about three years ago when I came to reside here, I found all the world agog about it as a thing that had never been thought of or tried before. Learning that none of the new experimenters had any connection with Mr. Shorter, the original inventor, and that he was in all probability dead, being an old man when I first saw him, I considered the field open for resuming the subject. As I was of the opinion that, although attended with many advantages, there was a considerable waste of power having the wheel or propeller entirely immersed, I have taken out a patent for working two wheels astern, the lower part only immersed, by which I expect to get a greater resisting surface; and the wheels of such a diameter as to enable the engines to be connected directly to the propellers. I have made several trials on a small steamer called Rocket; after many harassing alterations we have attained a pretty fair speed (about 12 miles an hour). With this information, if you think our joint efforts will be of any use I shall be most happy to meet you. I am going to Dover to-morrow, - I expect to be at home Tuesday and Wednesday, when I hope the Rocket will be again ready to take the field. She got her propellers damaged by a buoy getting among them; we are reversing the motion, so that she will expel articles floating on the water, instead of grabbing them in.
I am, Sir,
Your obedient Servant,
(Signed) DAVID NAPIER.
The copy letter here quoted does not show to whom the original was addressed.
Edward Shorter, in February 1800, patented a "machine or engine for working and causing the progressive motion of ships and vessels of every description . . . without the assistance of sails or oars."
He proposed (1) an arrangement of endless chains carrying duck-foot blades or paddles; and (2) "angular blades" fitted to the end of a spar or shaft projecting over the vessel's stern, the lower end immersed to a suitable depth in the water, with a floating buoy to prevent it sinking too deep. The upper end of this shaft to have a universal joint connecting it to an inboard shaft, put in motion by wheel and chain driven by a capstan or by a steam-engine if such available. This arrangement, it was claimed, would "have the effect of an endless screw." It was further suggested that the immersed propelling blades could be drawn by guy-ropes to either side to assist in steering the ship.
Opposite page 64 is a reduced facsimile of a document found amongst Mr. Napier's papers, and probably given to him by Mr. Shorter at the interview referred to. From this it appears that Shorter's propeller was tried in the Government vessel Doncaster in 1802, and found to be useful.
- David Napier by David Napier and David Bell
- David Napier by David Napier and David Bell: Chapter VI
- David Napier by David Napier and David Bell: Chapter VIII
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Sources of Information