1844.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



i8i 



of propeller, as it had been tried at various periods, and with as varied re- 

 sults, on the Continent, in the United States of America, and in this coun- 

 try; ' but it appeared certain that Mr. Samuel Brown, the inventor of the 

 gas vacuum engine, was among the first who applied the sub-marine propeller 

 with any practical eifect. The propeller used by him was on the principle 

 of a regular screw, and consisted of two blades, which were affixed at an 

 angle of 45° to a horizontal shaft, which was placed in the how of the 

 vessel, and he believed that it had also been used in the stern. This pro- 

 peller was driven by a gas vacuum engine, of the nominal power of 12 

 horses, and actually caused a vessel of GO feet in length, to move at the rate 

 of six or seven miles per hour. M. Sauvage of Boulogne-sur-Mer, had also 

 made several attempts at propelling vessels by the same means, and it was 

 very gratifying to find that his services had recently been acknowledged and 

 rewarded by the King of the French. It was, however, Mr. F. P. Smith who 

 first rendered the screw propeller practically useful ; for his perseverance, 

 being aided by spirited capitalists, induced the building of the Archimedes 

 steamer, the machinery of which was constructed by Messrs. G. and J. Ren- 

 nie, in the year 1839. The results obtained from that vessel were well 

 known, and caused the subsequent construction of the Priticess Royal, the 

 Great Northern, H. M. S. V. the Bee, the Rattler, and the Dwarf, formerly 

 the Mermaid, a model of which was exhibited, with the various forms of 

 screws used in the different experiments. The Great Britain not having 

 yet been to sea could only be mentioned as a projected experiment. Figs. 1 

 and 2, Plate VII. are drawings of Mr. Smith's Double Threaded Screw 

 adopted in the " Archimedes." 



The Dwarf was 130 feet in length, 16 feet 6 inches in breadth, 9 feet 

 deep, and was 164 tons burthen. The power of the engines was 90 horses, 

 making from 30 to 32 strokes per minute. Friction wheels without teeth 

 were first tried for giving motion to the propeller; but on account of their 

 sHpping and being very noisy, they were abandoned, and two spur mortice- 

 wheels with wooden teeth, working into iron pinions, were substituted ; the 

 speed thus attained was from 150 to 160 revolutions per minute. The pro- 

 peller was of cast iron, and was moulded in loam without a model, by means 

 of iron templates cut to the required curve, which was formed from a solid 

 cone revolving on its axis, during the perpendicular descent of a tracer. 

 The advantage of this form over the cylindrical screw, was an increasing 

 pitch, so formed, that while the propeller was rotating on its axis, the vessel 

 was advancing and thus producing the least po»6ible amount of " slip." 

 This was exemplified by the form of the various models on the table. The 

 principle point to he obtained in a screw propeller, was a form which should 

 offer but little obstruction to the water, and yet act upon it so as to exert 

 full power in propulsion ; a large portion of a complete screw having no 

 useful eflfect had induced the introduction of propellers with several blades ; 

 thus doing away with the useless part of the surface. A great portion of 

 the centre part of the screw of the Archimedes had been cut away, but the 

 effect had not been so good, on account of the arms of the screw obstructing 

 the free passage of the water ; the propellers with three arms were, he be- 

 lieved, preferred to those with a larger number. The Dwarfs propeller 

 consisted of three curved blades, fromed on the conoidal principle, by vari- 

 ahle curves approximating to angles of from 27" to 30°, and advancing at 

 the rate of 7 feet 6 inches per revolution. It was 5 feet 10 inches in diame- 

 ter, by 2 feet deep in the direction of its axis, and the area was about 15 

 square feet, which was nearly one-fourth of the area of the midship section 

 of the vessel at light draught ; but since the Dwarf had been transferred to 

 H. M. service, the mean draught had been increased one foot, and the area 

 of the midship section in proportion ; her speed had in consequence been 

 reduced from 12 to 11 statute miles per hour. Figs. 3 and 4, Plate VII. 

 are drawings of Mr. Rennie's Conoidal Screw Propeller. 



The following were the results of the trials made by Captain Sir Edward 

 Parry, Mr. Lloyd, and Mr. Murray, at the measured mile in Long Reach on 

 the 15th May, 1843 :— 



1st Experiment against tide 

 2nd ditto with tide 

 3rd ditto against tide 

 4 th ditto with tide 

 5th ditto against tide 

 6th ditto with tide 



General Average 



Stat. Miles. 



9-890 1 

 14-400/ 



9-7561 

 14-400/ 



9-890 1 

 14-516/ 



Mean. 

 12-145 



12-078 



12-203 



12-142 ^^^^' ^^'^^8 

 per hour. 



I The dates of the experiments on screw propellers are nearl) in the foUowiDg 



Baron Seguier 



Fulton 



Shorter 



Trevithick 



Millington 



Lowe 



Whytock .. 



Perkins 



Brown 



Woodcroft 



1828 

 1832 

 1832 

 18.36 

 1836 

 1838 

 1839 

 1839 

 1840 

 1841 



2 In a letter to Dr. Cartwright, dated Paris. February 16, 1798, Fulton says, " I have 

 just proved an experiment on moving boats, with a fly of four parts, similar to that of a 

 Braoke.jack, and I find this apply the power to great advantage, and it Is extremely 



The draught of water was 5 feet 8 inches. 



The Dioarf, under the command of Lieutenant Nicholls, left Greenhithe 

 in company with the Hecate, Captain Bower, on the 14th January, 1844, 

 and reached Portsmouth on the following day ; on the 20th she left Ports- 

 mouth accompanied by the Hecate, and although it was necessary to reduce 

 the speed of the engines to 26 revolutions, in order to keep with her consort 

 during the night, they reached Falmouth on the 21st, after an additional run 

 towards the Scilly Islands, making a distance of 200 miles in 23 hours, 

 having burned 10 tons of coals in 27 hours, from the time of getting the 

 steam up. The two steamers left Falmouth on the 23rd, and reached Bear 

 Haven on the following day, having run 1351 knots, or IS^miles by the 

 log, in rough weather in 12 hours, and with bad coal; the engines making 

 from 28 to 29^ revolutions per minute. She anchored during the night at 

 Bear Haven, and on the following day, (the 26th,) reached Tarbert, the total 

 distance from Falmouth being upwards of 400 miles. 



Mr. Galloway said, that it was extremely difficult, if not impracticable, to 

 arrive at the true amount of the " slip " of the propeller, because from' its 

 position abaft, or in what is termed the deadwood of the vessel, it acted in 

 a current which was continually flowing to fill up the cavity, which would 

 otherwise be formed by her progress through the water. The relative 

 motion of a stream through the arches of a bridge, and in the wake of its 

 piers, was an apt illustration of what unquestionably took place, (and from 

 the same law,) in the case of a moving vessel. The screw, therefore, when 

 acting in this current, might be compared to what would occur, if a paddle- 

 wheel steamer was supposed to be moving in still water, while the floats 

 acted in side canals, which flowed in the same direction as the vessel. 

 Whether the benefits derived from this following current giving resistance 

 to the screw, were not counteracted, by the deduction of so much of what 

 is termed minus pressure from the ship itself, was not at present under con. 

 sideration. His object was to show, that an accurate estimate of the amount 

 of "slip" of a screw, could not be arrived at, until the rate of the following 

 current, was first ascertained. That the " slip " must be much greater than 

 Mr. Grantham assumed, would, he thought, be admitted, both from the cir- 

 cumstance he had stated, and from the fact that screw propellers, when 

 worked with the vessels at their moorings, invariably moved at a ratio at 

 least equal to one-half the speed obtained when running. It was clear, 

 therefore, that the " slip," which was dependent on the proportion of the 

 resistance of the screw, compared to that of the vessel, must always exist in 

 a degree ; but that, it might in the screw, be reduced below that of the 

 paddle-wheel, was evident, because in the best modifications of wheels, or 

 where the immersed segment was small, the paddle must turn in the water, 

 in effecting a change of position from its angle of entrance to that of its 

 emersion, and this unavoidable angular action, even when the upper edge of 

 the float coincided with the rolling circle, was still so much "slip" inevitably 

 encountered ; this " slip " too became very considerable when the vessel was 

 in a sea-way; but the " slip" of the screw decreased with its magnitude, 

 and in the like proportion, its action approached that of a screw moving in 

 a solid. It appeared, therefore, to him, that if the " sHp " was small, the 

 spiral or increasing pitch, would be a disadvantage, because a true screw 

 would under those circumstances create little or no disturbance ; while the 

 spiral in. that case, would have the contrary eflTect, for the same reason that a 

 helix would pass with facility through a solid, in which a spiral or untrue 

 thread would become fixed, or would move with difficulty. In the absence 

 of all " slip," or in so small a slip as Mr. Grantham assumed to have taken 

 place in his experiments, the effect of a propeller witn an expanding pitch, 

 would be like that of a curved plate, moving through the water in a right 

 line ; while the true helix would have acted like a flat plate moving in the 

 direction of its own plane ; that is to say, the opposing forces would merely 

 consist of edge resistance and surface friction, which were common to every 

 kind of propeller. The advantage too, which was assumed to arise from this 

 spiral propeller, merely affected the question of magnitude, for it was clear 

 that, whether the screw acted upon a large body of water at once, or gave a 

 second impulse to a lesser quantity, the result would be similar, as to the 

 sum of the effect upon the vessel. It was true that in certain kinds of fish 

 (he would instance the electrical eel), the impulse produced by the ventral 

 fin, was by an increasing spiral, the length of the curves becoming greater 

 towards the tail ; yet it appeared probable, as we coiUd only see this eel in 

 confinement, that the pecuharity he alluded to, was only developed in pro- 

 ducing a change from rest to motion, for which it was well adapted (because 

 the "shp" was great and the progress small,) and that when in rapid 

 motion, it was probable, that the fin acted in a true spiral. 



Mr. Rennie stated that the "slip" of the screw of the Dtearfwis from 

 Jth to ^th. That with respect to the general question of ths " slip," he 

 conceived that it depended upon the comparative resistance between the 

 vessel and the propeller. The case was similar to the immersed plane sur- 

 faces of the paddle-wheels of a steamer and of the vessel itself; the re- 

 sistance of the midship section was reduced by the forms given to the fore 

 and after bodies, which gave the vessel what might be termed more " mobi- 

 lity." According to the experiments of Mr. Peter W. Barlow, read before 

 the Royal Society, May 29th, 1834,* the "mobility" of several of Her 

 Majesty's steamers was found to vary from -^th or jijth of a plane surface, 

 equivalent to the area of the midship sections ; or in other words a plane float 



a " An Investigation of the Laws which govern the motion of Steam Vessels, deduced 

 from Experiments, by Peter W. Barlow, C.E." Phil, Trans., 1834, p. 309, 



