2T2 



ERICSSON'S EN'GINE. 



accounts disagree veiy matoniilly on most of the important points. 

 By personal inqiiiiy and by consnltiny- the most rclable at-coants 

 I have cndea\oui'ed to come as near to the trutli as pcissiblo. 

 The following are the principal lesults : 



No. of revolutions of wheel; per ininnte, (ac^'ording to 



Eries?on,) - 9^ 



Same, (accoi-ding to other most reliable authorities,) 9 



Speed through the water, (according to Ericsson.) 8-1- miles. 



" " (according to other authorities,) 7 " 



Working pressure in receiver, per square inch 8 lbs. 



Consumption of anthracite coal in 24 hours 6 tons. 



The two estimates of the speed through the water are quite 

 clifterent, but the number of revolutions of the paddle wheels as 

 stated by different auihorities, lies between 9 and 9j. The num- 

 ber of revolutions, about which there is but little disagreement, 

 will enable us to obtain by calculation a pretty close approxima- 

 tion to the speed. For this purpose we have the following data. 

 Diameter of the wheels from centre of pressure, to centre of pres- 

 sure, 30f- feet; paddles 32 in number, on each wheel, and lO-J- 

 feet long by 16 inches deep; dip of the wheels '44 inches. The 

 following quantities vrere obt:^ined by calculation, viz. : number 

 of paddles in water on each wheel, V; immei'sed paildle surface 

 on both wheels, 196 square feet; area of midship section, at 1 7 

 feet draft, 5'20 square feet; ratio of immersed paddle surface to 

 area of midship section, 1 to 2.653 ; same for Steamship Arctic, 

 1 to 1-662 (see Journal of Franklin Institute for Jan. 1853, No, 

 1 p. 33;) slip of wdieels of Arctic, 19-32 per cent. From which 

 we find the slip of the wheels of the Ericsson, on the trial trip 

 to have been 25'-l per cent. The dista;:ce passed over by the 

 centre of pressure of wdieels was 9-88 miles per hour. Hence 

 allowing for the slip, the speed of the ship was 7-47 miles per 

 hour, "if we allow for the less oblique action of the paddles in 

 the case of the Ericsson than in that of the Arctic, we find the 

 speed to have been 7-57 miles per hour (the slip of the wheels 

 beino- I'educed to about 23-4 from this cansc. 



There is some little uncertainty with regard to the area of the 

 midship sections Although I have not succeeded in obtaining 

 the data necessary for an exact calculation of this element, the 

 information furnished me in reference to the model of the Erics- 

 son as compared with that of the steamers of the Collins' hue, 

 has enabled me to approximate very neai'ly to a correct result. 

 The rule by wdiich the calculation was made has been tested by 

 tryino- it upon a large number of ships. It gives results, in al- 

 most every instance, a little too small ; thus for the Arctic, the 

 result is 662, and the true area is 685. The. greater "dead-rise' 

 of the Ericsson may diminish the area, as compared with the 

 Arctic, some 30 square feet; which would make it about 510 

 square feet. It in all probability, lies between 520 and 500. 



If we take it at 500, the slip of the wheels comes out 23 per 

 cent, and the speed of the ship 7-0 1"' miles. In \-iew of all that 

 has now been stated, we may conclude that the average speed of 

 the Ericsson through the water, on the trial trip covld not have 

 exceeded 71- statute miles per hour; and was most probably about 

 7^ miles. 



Horse-power of the Ericsson^s Ein/ines, developed on the 

 trial trip. Working ])ressure of air, 8 Ibs.+l 5 lbs. Supposing 

 the cut oft" to be at y (=-052) of the stroke, then the mean effec- 

 tive pressure, in each cylinder, would be C.4 ibs+15 fts.; and 

 the horse-power of both engines, calctdated by the rule given on 

 page 403, would be 311. If we take the cut oft' yi\, as it is 

 stated to bo in some accounts, then the moan effective pressure 

 in the working cylinder we find to be 6.04 lbs.+ 15 lbs., wdiile 



•If wc Inkeilic number ol rcvolulioiisol lliu paddle-wheels nl O-, iho .'■|ced 

 c imes out 7.88 mile>. 



[1853 



that in the supply cylinder remains at 6.4-|-15. With these 

 data the result obtained for the horse power is 259. 



For a niean effective pressui-e, in each cylinder, equal to ft)s., 

 the result is 292; and for 6^- fe., it is 3*10. 



The power developed by the engines on the trial trip, was un- 

 doubtedly less than the determination above obtained (311), for 

 the reasons mentioned on page 270; w-e may safely conclude 

 that it conld not have exceeded 300 horses-poceer. It was proba- 

 bly less. This is but one half of the full power of the engines, 

 according to Captain Ericsson's estimate. This estiinate supposes 

 a working pressure of 12 lbs., to be employed, whereas, by 

 reason of leakage, &c., but 8 lbs could be obtained. In fact, 

 making the calculation on the supposition of a working pressure 

 of 12 lbs., and taking the cut oft' at |- stroke, neglecting also, the 

 clearance, « hieh is not known, I find the horse-power of the two 

 engines to be 640. The allowance for clearance and other causes 

 of reduction wdiich have been indicated ( see p. 403,) may well 

 reduce this detei mination to 600. 



The powei-, but for practical difficulties, may be indefinitely 

 increased, by enlarging both cylinders, keeping their relative 

 size the same. 



It is stated that Captain Erricsson has fixed upon 12 lbs. as 

 the highest limit likely to be practically reached in the working 

 of caloric engines. This must be regarded as an indication 

 either that it is not expected the leakage will be entirely stopped, 

 or til at it is supposed that it will not be regarded as safe and 

 economical to woik at the high temperf.tui'e of 500 ° , and up- 

 wards, necessary to double the expansive force of the air. 



Consumption of Fuel, on trial trip, 6 tons of anthracite coal 

 per da}-, cr 560 lbs. per hour. This amounts to 1 "8 7 lbs. per 

 hoi'se-power per hour. If the full power of the engines (600) 

 wei'c to be developed, the expenditure would be 0-93 lbs. per 

 horse-power per hour. On the other hand, if w-e allow that the 

 excess of pressure in the receiver ovc-r that in the woiklng cylin- 

 der, on the trial trip, was fV of a pound per square inch, and the 

 excess of pressure in the supply cylinder over ihatin the receiver 

 the same, we find that, with a cut oft at |, the horse power de- 

 veloped could not ha\'e been more than 248. The expenditure 

 of fuel, answering to this determination, would be 2-26 lbs. per 

 horse-jjower per hour. 



COMPARISOX WITH THE STEAM ENGINE. 



1. Comparative consumption of Fuel. This is presented in 

 the foUowino- table. 



The second column shows the mean effective pressme of the 

 steam, or air, per square inch, on the piston ; the third the real 

 horse-pow^or actually devclo]wd by the engines of each ship; tho 

 fourth the number of pounds of bituminous coal, per horse-i)owor 

 per hour, consumed: tho fifth tho equixalcnt amount of anthra- 

 cite of coal, i. 0., the luimber of pounds that would do the same 

 work. These several quantities answer to the average perfonn- 



