1843.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



269 



Diameter of cylinder 9 inchesr^SS'G square inches. 



Length of stroke, 1 foot ; number of strokes per minute, 100 to 



110— say 200 feet per minute. 

 Pressure of steam, 90 to 100 lb. per square inch— say 901b. 

 Fuel — coke. 



Then we shall have the engine power 



63-0 x '200 x 90 



:34-7 



33,000 



horse power on the piston, which if taken in the same proportion as 

 low condensing engines, the nominal power of which is taken at only 

 71b. pressure, or about half the effective piston power, we shall have 

 the nominal power of the engine equal to 17 horses, the consumption 

 of which may be taken at about 101b. of coal, or e lb. of good coke per 

 horse per hour, which will give for the consumption of the above 

 engine 17x8= 136 lb. per hour, or 12 cwt. per day of 10 hours. 

 If we take the cost of the coke at 35s. per ton. delivered at the works, 

 we shall have the cost of the fuel 21s., then the cost of working the 

 machine per day may be stated thus : — 



s. d. 



Coke 21 



Oil, tallow, &c 2 



Engine tender 6 



Man on the stage 5 



1 labourer assisting 3 G 



Sundries 2 



Cost per day 40 



This will be the cost for removing 500 cubic yards of earth, but 

 exclusive of repairs, depreciation, interest on cost of machine. The 

 cost of making one of the machines we estimate at 1200/. The cost 

 of manual labour may be taken for " getting and filling " (See Journal 

 Vol. V., p. 187) at iid. per cubic yard, then, 



500 cubic yards at 4.§d. — 9/. 7s. Gd. 

 We have here a difference of 71. 7s. Gd. between the cost of engine 

 and manual power ; and if we make an allowance for the repairs of 

 the machine, depreciation, interest, &c, 21. per day, there will be a 

 saving of 5/. 7s. Gd. We may, therefore, set down the actual cost of 

 engine power at 2d. per yard, which would give 4/. 3s. id. per day, 

 for 500 yards, thus clearly showing that the steam excavator must 

 ultimately supersede manual labour on account of its cost and ra- 

 pidity in execution for all extensive cuttings, either for railways, 

 canals, or docks; but if we make our calculations according to the 

 report of the American engineers, allowing the duty of the machine 

 to be 1050 cubic yards per day, the calculation will stand thus: — 



£ s. d. 



1050 cubic yards by manual labour at 4irf. 



Deduct — Working of engine per day 21. 



Repairs, depreciation, interest 



ler day 21. ) 

 t, &c, 21- ) 



19 13 

 1 



Saving 15 13 9 



By this calculation the cost of excavation is not quite \d. per yard. 



The following testimonials, from engineers in America, will show 

 their opinions of the machine. 



Engineer's Office, Western Railroad, 

 Sprinr/fitld, October, 9, 1841. 



Dear Sir, — In reply to your two letters of the 1st and 22nd September, 

 I have to state, in relation to the Steam Excavator of Carmichael, Fairbanks, 

 and Otis, that it has been most successfully and advantageously in use for 

 the last three years on this road. I have often witnessed its operating in all 

 kinds of excavation, except rock, and in every case I consider it to work to 

 better advantage than men with picks and shovels could. We have expe- 

 rienced great advantage in the expedition with which excavations are made 

 by this machine. Of course, like all other modes of excavation, it will per- 

 form the greatest amount of work in a given time in the easiest kind of ex- 

 ca»ation, that is, in coarse sand; it has removed often as much as one 

 thousand yards per day in such ; but I consider it of most importance and 

 advantage in the kinds of excavation where the ordinary modes experience 

 the greatest difficulties, for instance, in stiff clay and in very coarse gravel, 

 where it is difficult to penetrate with the common shovel. 



I consider this machine of great value, and it can be used with great 

 advantage whenever the quantity will justify the first cost. It is a simple 

 machine, easily managed, and not costly. 



Respectfully, your obedient servant, 



George W. Whistler, Engineer, W. R. R. 



Springfield, September 6M, 1841. 



Dear Sir, — In reply to your letter of the 1st instant, I have to state 

 that the Excavating Machine of Carmichael, Fairbanks, and Otis, has been 

 in use on the Western Railroad upwards of three years. I have witnessed 

 its operations in stiff clay, in compact gravel, mixed with boulders of dif- 

 ferent sizes, in quick sand, and in common sand and loam. In all these 

 various soils, the machine has worked advantageously, and the most so I 

 consider in the cases which present most difficulty when the ordinarv modes, 

 of excavation are resorted to — to wit, in the clay and the quick-sand. 



I have not at hand the means of stating the amount of material excavated 

 per month in the several soils enumerated, but I recollect that in August 

 1840, in sand and gravel in the section, it excavated 19,000 



cubic yards in twenty-five working-days, and 1000 yards per day were 

 excavated for several days in succession. I consider the machine of great 

 value, susceptible of being applied advantageously wherever earth in any 

 quantity is to he removed, easily kept in repair, and by no means a costly 

 engine. 



It is now, as you are aware probably, applied exclusively to work on terra 

 firma, but the engine may readily be placed upon a scow, and used with 

 great effect in dredging. 



Respectfully, 



W. H. Swift. 



APPARATUS TO REGULATE THE SUPPLY OF WATER 

 TO BOILERS. 



It is becoming a very common practice, and there can be no doubt 

 as to its being attended with great advantage, to use steam of fifteen 

 and twenty pounds pressure per square inch, instead of two and three 

 pounds per inch, as is usual with the Boulton and Watt engines, and 

 to reduce its elastic force, previous to its passing to the condenser, by 

 allowing it to expand within the cylinder. Having lately been 

 called upon to fit an expansive apparatus to an engine uf this class, it 

 of course became necessary to make considerable alteration in the 

 apparatus previously employed to regulate the supply of water ad- 

 mitted into the boiler. To effect this alteration in accordance with 

 the principle of the old apparatus, it would require a feed-pipe some 

 thirty feet high, with the usual complement of rods, levers, counter- 

 weights, &c, to communicate motion from a float upon the surface of 

 the water within the boiler to a stop-valve at the top of the feed 

 head. This principle is, however, in some instances adhered to, to 

 a very great extent, but in the present it would have created a fright- 

 ful " monument," too much so to be tolerated by a town which once 

 boasted great engineering skill. In order to avoid this, I contrived 

 an apparatus which answers the purpose beautifully, and has such a 

 remarkably simple outward appearance as to induce me to take the 

 liberty of submitting it to the readers of the Journal. 



The accompanying engravings consist of two views of my appa- 

 ratus. Fig. 1 is a side elevation, and fig. 2, a vertical section. The 

 parts distinguished by letters are as follows : — T, the top of the 

 boiler; W, the water level; V, the valve-chest, cast on the end of 

 the pipe P; C, a compensation valve; F, a float, encircling the pipe 

 P (made of sheet copper) ; R, three small rods descending from the 

 float to the three ends of the crossbar B, which are shown flatwise in 

 fig. 3 ; E, the pipe to convey water from the feed-pump ; S, a small 

 rod for connecting the valve C with the crossbar B ; D, a door, fixed 

 by four screws to the side of the chest, which may be readily removed 

 in case of examining the valve. 



With this simple arrangement, it will be observed, there is not a 

 packed joint of any kind through which the steam can escape, and 

 here we get rid of that very common and disagreeable hissing of the 



