1846.] 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



351 



2. The same points as above, Ihe engines of the " Spencer" being re- 

 duced in speed to assimilate, as far as practicable in power, to those of the 

 " McLaae." 



3. The same points, with the pressures of steam reduced one-half. 



4. The effect of the coosumplion of an equal quantity of fuel (2,000 lb ) 

 with similar iniiial pressures. 



The elements for a comparison of the two vessels, regarding their form, 

 &c., are as follows : — 



The hulU, euRines, and boilers were constructed from duplicate draw- 

 ings. One vessel had three and the other two masts, adapted for equal 

 surfaces of canvas. This dillerence of rig. however, could not in the least 

 have influenced the results of the trials; and especially so, as the vessels 

 were not tried under canvass. The instruments of cutting otT the steam 

 differed in some degree, — that of the " Spencer" being a slide valve, and 

 that of the " iMcLanc" a puppet. In the spaces between the grate-bars, 

 there was also a vnriante. those of the " Spencer" being the greatest, and 

 consequently effecting a greater waste of fuel. The geering of Ihe engines, 

 propellers, and wheels, was similar in its charscter (cogged wheels), the 

 only mechanical diff'erence being that necessarily due to the peculiar means 

 of propulsion. 



The bottoms of the vessels, and Ihe engines and boilers, were, as far as 

 our observation extended, aided with the iuforuiatiou received respecting 

 them, in equally good oriler. 



Respecting Ihe proportions of the different propellers, it was clearly 

 shown that they were of sufficient diameter and surface for the purpose 

 intended. There was a point, however, connected with their application 

 which in our opinion malerially interfered with the speeds of the vessels, 

 arising from the relative speeds of the engines, and each of their attached 

 propellers. Had the engines been geered so as to have worked faster 

 with equal pressures, there would have been a material increase of power 

 (as the boilers of the vessels were capable of supplying a greater quantity 

 of steam than that they were restricted to in these trials). Had this dis- 

 advantage been similar, it would alone have effected the rate of speed ; but 

 as it occurred, Ihe engines of the "McLane" were geered so as to preclude 

 the attainment of a power with similar pressure equal to that of the 

 " Spencer." The effect of this, however, is duly considered in determin- 

 ing the results given in slatemeut C. which was prepared by C. H. Has- 

 well ; as a s■lb^tltute for which, M. C. Perry submits statement D ; while 

 to those marked A and B, we refer you for details of the iuforuiatiou on 

 various points indicated in your letters. 



M. C. PtBRY, Engiiieer-in-chief U.S. Navy, 

 V. H. Haswell, 



Commodore Charles Morris, 



Chief of Bureau of Construction, Ifc, Washington, D. C. 

 From the concluding sentence it appears that a difference of opinion ex- 

 isted as to the conclusiceness of the experiments : the separate statements 

 [C] and [D] refer to those points on which a difference of opinion existed, 

 and are submitted, the former by the Engineer-in-Chief, the latter by Com- 

 modore Perry. 



[C] 

 Results of the Comparisons deduced from the Preceding Elements. 



Iq these the consumption of fuel is not considered, for reasons which 

 will appear obvious when presented. 



1. The boilers and engines being identical in capacities, the amount of 

 steam used in the engines is an exact measure of ihe expenditure of each 

 means of propulsion, which amount is estimated in the calculations of 

 power here given. 



2, The steam required was so much below the actual capacities of the 

 boilers to furnish it, and so nearly alike in its quantities, that a hurried 

 combustion of the fuel was unnecessary. Hence the waste consequent 

 upon rapid combustion was not only not incurred in either vessel, but was 

 not incurred by either means of propulsion at the risk of its economy 

 compared with the other. 



J. The omission of this element sets aside the effects of the difference 

 in the grate-bars, and of any difference iu firing by different individuals. 



The computation then, of the powers of the engines is considered a fair 

 and proper exponent of the cost of propulsion; while the cubes of the 

 speeds are taken as the measures of the effects produced, which elements, 

 (those of power and effect) being reduced for each trial, the fullowmg de- 

 ductions are furnished : — 



First. — In this trial, the application in the " Spencer" was 1'52 to 1 

 more efficient than that in the " McLane." 



Second. — In this trial, the application in the " Spencer" was ri4 to 1 

 more efficient than that iu the *' AlcLane." 



Third. — In this trial, the application in the " McLane" was 1'16 to 1 

 more efficient than that iu the " Spencer." 



Fourth. — III this trial, the application in the " McLane" was 1 to -82 

 more elhcient than lliat in the '' Spencer" 



Fifth. — In this trial the application in the "Spencer" was r04 to 1 

 more efficient than that in the " McLane." 



Sixth. — In this trial, the application in the " Spencer" was 1"03 to 1 

 more efficient than that in the " McLane." 



[D.] 



"Having stated in the foregoing papers all the particulars connected with 

 Uie experimental trials of the steamers '' McLane'' and " Spencer," 1 &a<i 



in passing them in review a diflicully in forming any definite conclusioos 

 upon the subjects under inquiry. 



Notwithstanding the care with which the trials were made under the 

 skilful management of Captains Fraser and Howard, very little of a satis- 

 factory character was elicited. On Ihe contrary, the results tended rather 

 to confuse than to elucidate: certainly ihey furnished no criterion by which 

 to determine the relative properties of the propeller and the side wheels, 

 and the causes may, in my judgment, be justly ascribed to the defective 

 form of the bottoms of the vessels. 



It may be assumed by some, that as the models and dimensions of the 

 two vessels were precisely alike, and the steam force exeited upon their 

 respective propelling power was the same, the results ought to be conclu- 

 sive of the superiority of the propeller — but such is not my opinion. 



Captains Fraser and Howard both affirmed, and I give much weight te 

 their professional opinions, that neiilier vessel would stand up under can- 

 vas, that they would not stay under ordinary circumstances, and it was 

 difficult to wear them within any reasonable space, or to keep them to the 

 wind in heavy weather — that in fresh breezes, on the wind, the lee wheel 

 of the '■ McLane" would he immersed almost to its axis ; in a word, that 

 they were unmanageable at sea, and in their belief would be unsafe if 

 thrown upon a lee shore in a heavy gale, even if assisted by steam 

 power. 



It is plain, therefore, that no application, whether of steam power or 

 sails, or both combined, to vessels of such unusual model, could by possi- 

 bility pioduce any satisfactory results, illustrative of the question of reW 

 five merits of the two modes of propulsion : and this opinion is strength- 

 ened by the fact, that on the occasion of their first day of trial in the 

 Sound, when there was a strong double reef topsail breeze from the north- 

 ward and westward, they were so slow in their movements, that all 

 agreed that any fair sailing vessel would have worked from New York to 

 Falkner's Islaud, and made the run baek, in a less space of time than was 

 occupied by the fastest of the two steamers in accomplishing it." 



The general result of the experiments is given in the following table »( 

 the Elements of Comparison of the various Trials : — 



The distances given are in nautical miles. 



Trials 1 and 3 — Speed and consumption of fuel with equal pressures, 

 and under various circumstances of wind and weather. 



OUT. IN. 



Spencer. McLaac. 



Average* pressure of st^am in pounds, per 

 square incll .. 



Average revolutions of engines per minute 



Time of running, in hours and minutes .. 



l>istanceran ttirougli tlie water in miles, 

 ttie elfect of ttie tide (2 Icnots} being esti- 

 mated .. 



.Speed in miles per hour 



Consumotion of fuel in pounds per hour .. 



Power of engines in horses 



Spencer. 



423 

 415 

 4 31 



24-25 

 54 



1224 

 186 



47- 

 24-6 

 6 42 



2775 

 4 14 



928 

 l.'» 



42- 



42- 

 3 33 



22-85 

 6-48 



8«D 

 192 



45- 

 28- 

 3 »7 



22-4 



5-e7 



1176 

 147 



Trials 3 and 4 t — Out. — Speed and consumption of fuel, the pressure of 

 steam in the " Spencer," being reduced in order to assimilate the 

 power of the engines to those of the " McLane." 



/».— Speed and consumption of fuel, the pressure of steam in both 

 vessels, being equally reduced to 22-5 lb. per square inch. 



Average pressure of steam per square inch 



in pounds .. 



Average revolutions of engines per minute 

 Time of running, in h urs ami minutes .. 

 Distance run through the water in miles .. 

 Speed in miles pep hour 

 Consumption of fuel in pounds per hour .. 

 Power of eogines in horses 



IN. 



Trials 5 and G.** — Out. — Speed and duration of operation with similar 

 quantities of fuel — 2000 pounds of coal being allowed to each vesael. 



In. — Speed and consumption of fuel uuder equal pressures aod 

 various circumstances of wind and weatber. 



IN. 



ATerage pressure of steam in pounds per 



square inch . . 

 Average revolution of engines per minute. 

 Time ul running, in hours and minutes . 

 Distance run thruu;^h the water in milei . 

 Speed in miles per hour 

 L'onsumptioti ot futl in pounds per hour . 

 Power 01 engines in horses ., 



It will be observed that these *' elements'* do not include the amount ©f 

 steam evaporated during the experiments. The formula given above for 



* In these trials, the cut-off of the starboard engine of the *' Spencer" was cot used, 

 the effect of which, however, is estimated, and the consumption of fuel given is in ac- 

 cordance with it. 



t The throttles of the " Spencer's'' engines were constantly closed, to reduce the revo- 

 lutions in the run out. The effect of this is fully ttstimated, as the revoluiions of the 

 engines of this vessel were ascertained at such pressures as were necessary to deter- 

 mine it. 



** In these trials the wheels of the " McLane" were reduced in diameter 16 inches. 



I In this tiidl the distames run, and the limes of running (equal distances), were very 

 nearly alike, the difference being inappreciable. One of the engines of ihe "Spencer" 

 continued working for several minutes after alt the oth«r6 had slopped, which increased 

 the time ot running of ih;it vessel beyond the other. 



t While coal lasleiJ 960 lb. 



S While coal lasted b;*u lb. 



