350 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[Nov. 



of " HanlerV ami " Loper's" propellers, deduced from llie performances 

 of a rt'Veuue sleamcr fitted io the first experiment with tlie former of these 

 propellers, and subseq'icntly with the latter of tiiem. 



The secoad report compares the effect of I^oper's propeller with that of 

 Ihe ordiuary paddle-wheel fitted into two vessels of exactly the same size 

 and dimensions. The section fig. 1, plate XVI. will show the plan of 

 gearing on board the .S/)cncfr (the screw vessel). The steam cylinder is 

 horizontal, and the conuecling rod drives a horizontal bevil wheel, which 

 lakes into a vertical bevil wheel on the same with the screw propeller. 

 The propellers are therefore two in number; they project from either 

 qu-trter of tiie vessel. The mode of [gearing here adopted seems to possess 

 peculiar advantages. It is well known to engineers that bevil wheels run 

 lighter than the ordinary spur-wheels, and indeed it may be shown theore- 

 lically that they have, cceteria pnrihns, less friction ; moreover the teeth of 

 the former will generally, come in contact more gradually and consequently 

 with less concussion and noise. This mode of gearing has also the ad- 

 vantage of compactness and affords peculiar facilities of construction where 

 Ihe cylinders are horizontal. 



The vertical wheel contained 75 wooden cogs and the horizontal wheel 

 no iron cogs. There seems a slight error of detail in making the numbers 

 of cogs in each wheel bear the relation here stated. In general the re- 

 tpective number should be prime to each other, that is, should not contain 

 a common measure. The greatest common measure of 75 and CO is 15, 

 and consequently instead of each tooth in Ihe one wheel coming into con- 

 tact with each tooth in the other duiing successive revolutions, it happens 

 that by the time one wheel has revolved 4, and the other 5 times, the con- 

 tact of the same teeth commences again. 15y the contrivance of a " hunt- 

 ingcog," that is, an additional tooth, in the smaller wheel the numbers 

 (75 and 01 j become prime to each other, and this disadvantage is avoided. 

 Cog-wlieels driving screw propellers are subject to so much wear and tear 

 that no expedient for diminishing the evil ought to be neglected. 



The plan of gearing on bnard the McLane, fitted with paddle-wheels, is 

 eihibiled in fig. 2, plate XVI. The cylinder is horizontal as before. On 

 the engine shaft is a pinion of 47 teeth taking into a wheel on the upper 

 «haft of 72 wooden teeth ; the wheel and pinion are io diameter 7 feet and 

 4{ feet respectively, and concussion or jar is diminished by forming each 

 of two similar wheels b inches wide with the teeth off set. The pinion and 

 the wheel driven by it have therefore each a face 10 inches wide. The 

 fallowing extract from the reports will give the remaining particulars. 

 Dimensions of Vessels, Engines, Propellers, Ifc. — Vessels (iron). 

 Length between perpendiculars . . 143 feet. 



Beam at knuckle ..... JgJ „ 

 Beam at water line . , . . 22 „ 



Deptii of hold H „ 10 inches. 



Uis/)/(itemeH/ at load line . . . 400 tons. 



Area of immersed sfc/ion . . . 160 feet. 



Engines — Two, non-condensing; cylinders, 24 inches diameter, by 3 ft. 

 stroke of piston ; steam, cut off at halt stroke ; one boiler containing 1,450 

 square feet of heating surface cotndustion, anthracite coal aided with a 

 blast. 



Power. — The h orses power of the engines is estimated by the formula — 

 ^X(I'-/+l4-7) 



vToJu > "''^''^ ^ represents velocity of piston in feet per mi- 

 nute. P, means effective pressure upon cylinder piston in pounds, per 

 square inch ; and /, the friction of the engines, equal J of pressure upon 

 steam gauge. 



^^ Spencer." — Two screiv propellers. 8 feet in diameter, having four 

 blades each, with an area of II J square feet on each side. Angle of 

 blades at hub, from plane of axis, 3U° ; at edge of blade, 54°. Kevolu- 

 tions of propellers, I^ for each revolution of engines. Draft of water, 

 g feet 8 Mil hes. 



'• ^ytLin.f."— Two siJe wheels, 10 feet 5 inches in diameter, in trials 1, 

 2, S,and 4, and 15 feet I inch in trials 5 and 0; 14 buckets in each Hheel, 

 10 inches by 5 feet 11 inches each. Immersed area of buckets, in each 

 wheel, 24 square feet. Heroliiliiins of wheels, 05 for each 100 of engines. 

 Draft of water, 9 feet 8^ inches. 



The two vessels being almost identical in form, allowed a comparison 

 by meansjof simultaneous experiments which were accordingly commenced 

 in April by Capt. 1'kaser, under the supervision of Mr. Haswell, engi- 

 neer-in-chief of the navy, and Commodore Perrv. From Capt. Eraser's 

 report we make the following extract: — 



(Jreat care was taken to trim both vessels as much alike as possible. 

 The coal to be used was the best quality, anthracite, from the same mines, 

 (Beaver Meadow). 



Taking into cuusideratioa the very defective model of these vessels, and 



that the engines were constructed for, and particularly adapted to Hunter's 

 submerged wheel, rendering it necessary to use ctig wheel geering, no 

 proper estimate of the speed attainable by the side wheel or propeller can 

 be arrived at. Still, their relative value in speed and consumption of fuel 

 may be very satisfdcl(trily determined. It must be borne in mind that the 

 diameter of the propeller, and consequently its ellective power, is limited 

 by the draft of water, in order to keep it entirely submerged, and at the 

 same time atiove the line of the keel, while the diameter of the side wheel 

 may be increased by raising the shaft, thereby increasing the speed. 



In the McLane, however, Ihe diameter of the wheels is as great as de- 

 sirable for sea service. 



Both vessels, as exhibited in Ihe annexed drawings, are precisely similar 

 in model and dimensiiuis, and each is furnished with two high-pressure 

 horizontal engines : diameter of cylinder 24, and length of stroke 3G 

 inches. 



A ske'ch of the half cross section of the vessels is hereunto appended, 

 which will clearly exhibit to practical men, that speed under steam, or 

 stability under canvas, are unattainable objects. Plans of the propellers 

 and mode of gearing, are likewise given. 



Each vessel is furnished with a single boiler, having 1,450 feet fire sur- 

 face. The Spencer is furnished with two of Loper's propellers, one pro- 

 jecting from each quarter, and the McLane with side wheels, having 14 

 buckets each. All the dimensions of the propellers and wheels are here- 

 after given, and the draft of water, dip of bucKets, &c., are exhibited iu 

 tabular form, with each day's trial. The buckets of the side wheel were, 

 at Ihe sug::estion of Messrs. Haswell and Coney, moved eight inches 

 towards the centre, before making the trial on the last day. 



It will be perceived by reference to Ihe drawings, that the relative revo- 

 lutions of the engines and wheels of the McLane, are as 1 of the former 

 to 'Oj'JS, while the relative revolutions of the engines and propellers of the 

 Spencer are as 1 to I'25. The greatest care was exercised in weighing 

 the coal, and the pressure of steam, revolutions, times, &cc., were carefully 

 noted every fifteen minutes. The distances, set, and velocity of the tides, 

 are given upon the authority of the superintendent of the coast survey, 

 and the time of slack water, noted in each day's work. 



The trial on the first day, from New London to Kalkner's Island, and 

 returning, was under, as nearly as possible, an uniform pressure of steam, 

 and the safely valve was loaded with 45 pounds to the square inch. On 

 Ihe second day, the trial was made by conlining the number of revolution! 

 of the engines as nearly as possible to 35, and returning under 22j pounds 

 pressure of steam. 



On the third day, as before mentioned, the buckets of the side wheels 

 were moved eight inches towards the centre, increasing the revolutions 

 under the same pressure, in order to ascertain whether the increased speed 

 attained was commensurate with the increased consumption of fuel, and at 

 the same time to ascertain what distance each %essel could be propelled 

 with 2,000 pouu'ls of coal. This poition of the trial was quite interesting. 

 The second propeller of the Spencer did not stop until the steam gauge 

 exhibited a pressure of but two pounds. 



On the first day a strong gale pie\ailed from the westward, with a tur- 

 bulent head sea, reducing all the sailing vessels in sight, which were 

 working to windward, to double reefs, and the great diflferences exhibited 

 in consumption of fuel and speed, between the passage from and returuing 

 to the light boat, was doubtless produced by the resistance offered by the 

 wheel houses of the McLane, when steaming head to the wind, and the 

 assistance alibi ded when before it, as well as the inethcieut opeialioD of 

 wheels of so small diameter in a sea way, while the propeller being sub- 

 merged was exercising the same effort at all tunes, and under all circum- 

 st.tnces. 



A trial of the sailing qualities was not deemed important, for experience 

 has hitherto shown, that by the wind, this model has neither speed or sta- 

 bility. 



A full and detailed journal of the trials is next given, but it is not neces- 

 sary to make an abstract uf it, as the general results are included in the 

 official reports of the Engineer-in-chief and Commodore Perry. The joiot 

 report of those gentlemen is as follows : — 



Washington, D. C, May 18th, 1846. 

 Sir, — In the execution of instructions contained in your letters of the 

 Ctli ultim ), the undersigned proceeded to New London, Conn., for the pur- 

 pose of witnessing some experiments that were to be made by order of the 

 'I'reasury Department, with the lievenue Steamers "Spencer" and " Mc 

 Lane," the former fitted with two of Loper's propellers (screw), the latter 

 witli the ordinary side wheels. 



Upon our arrival at that place, we were met by Capt. A. V. Fraser, 

 temporarily iu command of the " Spencer," under whose directions the 

 experiments were to be made — and also by Capt. W. A. Jfoward, in com- 

 mand of the *' McLane," who, iu conjunction with the former, atlbrded us 

 every practicable facility in the prosecution of the object uf uur attend- 

 ance. 



The necessary preliminary arrangements being made, and the two ves- 

 sels having been brought to a similar draft of waier, and provided with 

 similar fuel (auihracile), it was decided that the trials made, should be to 

 determine the following points : 



2. The relative speed of the vessels, and consumption of fuel, with equal 

 pressures of steam, wheu ruuuiug under various ciicuuistauces of wind 

 and weather. 



