1842.J 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



181 



THE "ANTI JOHN SCOTT RUSSELL" STEAM BOAT. 

 ( IFith an Engraving, Plate J^Il.j 

 In our last number we slightly alliulpd to the performance of this 

 Tessel, and then stated that we deferred gis'ing the drawings of the 

 engine and the boiler patented by Mr. Beale until we had an oppor- 

 tunity of making a second trial. Since then we have had another 

 trial, when her performance was equally as good as in the tirst trip- 

 The boat is a small iron vessel, .53 ft. long by ti ft. beam, and 3 ft. 3 in. 

 deep, and draws 17 in. at stern, and 13 in. fore, or 15 in. mean. The 

 paddle-wheels are 6 ft. 5 in. diameter, out and out, with 10 float boards 

 on each wheel, 2 ft. 9 in. by 74 in. She is propelled by one rotary 

 steam engine patented by Mr. Beale, and which is delineated in the 

 annexed engraving Plate VII, Fig. 1, drawn to a scale of li in. to a 

 foot. The cylinder is 14 in. diameter, and 9i in. long (measured 

 transversely) in the clear of the casing. The drum is 12 in. diameter, 

 Laving 3 indents for the reception of 3 rollers 4i in. diameter, and 

 '-•a in. long: these perform the office of the piston. At the top is the 

 steam pipe : when the aperture is opened, as shown in the figure, the 

 steam passes down the pipe, and acts against the back of the roller, 

 and presses it forward until it reaches the aperture on the opposite 

 side, where the steam is allowed to escape into the eduction pipei 

 and thence into the condenser, as indicated by the arrows. It will be 

 observed that the apertures are always open, one for the reception of 

 the steam, and the other for its exhaustion. The admission is regu- 

 lated by a throttle valve in the steam pipe, before it enters the casing 

 of the engine. The reversing of the engine is extremelv simple : it 

 is done by turning the screw, or by a lever which pushes forward 

 the D slide valve, when it reverses the flow of the steam, which passes 

 through the cylinder in the contrary direction of the arrows. The 

 engine generally makes from 250 to 300 revolutions per minute, and 

 by this rapid motion the centrifugal force causes the rollers to press 

 against the outer casing, and allows the steam to act upon the 

 back of them, as before explained. To the engine of the above boa' 

 there are 2 air pumps 8 in. diameter, and 11 in. stroke. The condense'' 

 forms a pedestal in the bottom of the boat, upon which the engine 

 and pumps are placed. 



The boiler, it will be perceived, is as compact as the engine. The 

 drawing, Fig. 2 in the Plate, is drawn to a scale of f of an inch to the 

 foot. It is cylindrical, 2 ft. G in. diameter, and 7 ft. high over all, and 

 contains numerous small tubes about one inch diameter, and an inch 

 apart, through which the heat and smoke pass from the furnace to the 

 chimney immediately over. The area of the grate is about 4 square 

 feet, or half a foot per horse ; the water occupies onlv a verv small 

 height of the boiler, the other portion forms a receptacle for the steam. 

 We should think it would be better if the water was kept up to the 

 second cock, otherwise great heating surface is lost. The steam is 

 generally generated to a pressure of 40 to 50 lb. in the boiler. The 

 consumption of coke is stated to be about GO lb. per hour, depending 

 upon the speed. The air for the supply of the furnace is driven in 

 by the aid of a fan. 



For communicating motion to the paddle-wheel there is a pinion 

 wheel on the outside of the shaft or axis of the engine, which drives 

 a larger wheel upon the shaft of the paddle-wheels, in the proportion of 

 1 to 4^, so that when the engine makes 270 revolutions per minute, 

 the paddle-wheels make 60 revolutions. The total weight of the 

 engine, condenser, air pumps, paddle-wheels, boiler, and water, is 

 2i tons. 



Having thus described the engine, we shall next proceed to give 

 the particulars of her performance. The first trip we made was from 

 Westminster Bridge to the Old Swan at Chelsea, when she performed 

 the distance (2i miles) in 20 minutes, against the tide when slack, and 

 back again in IS minutes, the tide being both ways just upon the turn 

 at low-water. We then went down the river imilx the tide, and per- 

 formed the distance from Westminster Bridge to London Bridge 

 (2 miles) in 19 minutes ; from London Bridge through the Pool to 

 Greenwich Hospital (5 miles) in 39i minutes. We then tried a 

 measured mile (where the river was clear, from the 4iS to 5A miles 

 mark), which was done in 6 minutes with the tide. 



At the second trial, she performed the distance from Westminster 

 Bridge to Greenwich Hospital (7 miles) in 37 minutes, with the tide. 



During the above trips the paddle-wheels varied from 45 to 58 

 revolutions per minute. 



We will now analyse the power of the engine. 



The radius of centre of pressure is apparently about 6-75 in., say 

 diameter 13-5 in., and circumference = 42-39 in. bv 225 turns per 



9537-75 , 

 minute = — jj— = ' 94-8 feet, say 795 feet per minute. 



Area of piston! or exposed part of roller appears to be 2 in. x 9^ 

 = 19 in. area, although it is doubtful if the steam does not enter the 

 space he/iind the roller, and exert its force on that part of the machine. 

 Su])pose we take it at 19 in. area, we have for power, at 7 lb. per inch 

 nominal, 



19 X 795 X 7 



33,000 ■ = '^■^ ''""^^ P°"«''- 



But this rule is not applicable, as the steam used is as high as 50 lb. 

 or 40 lb., say mean 45 lb. in boiler, perhaps 40 lb. in cylinder or drum. 

 With this pressure the vacuum is probably not more than 20 inches, if 

 so much, but that is matter of experiment only, as it depends on cir- 

 cumstances not before us ; suppose it be 20 inches, it will then be 

 equal to 10 lb. We have, Steam pressure = 401b. ) 



Vacuum 



and 



19 X 795 X 50 



= 10 lb.) 



=50lb.eifective 



=: 23 horses, which may be considered as actual 



33,000 



power, and if this engine is expected to exert double its nominal 

 power, as the common reciprocating marine engine does, we have 



23 



— = lU horses power. Mr. Beale, however, calls it only & horse 



power; but this difference doubtless arises from our not having hit 

 upon the proper pressure and vacuum, and which experiment only 

 can determine, that is by a steam and vacuum gauge, for we apprehend 

 the common indicator is inapplicable to this engine. The consump- 

 tion of coke is stated to be about 130 lb. per hour, this for nominal 

 power is equal to a-2 lb. per horse per hour, and for actual power = 

 2-6 lb. per horse per hour, which is a very small consumption. 



The paddle-wheel is 6 ft. 5 in. diameter, boards 7A incites deep, 

 inner diameter of wheel = 5-2 feet; taking the mean diameter at 50 

 turns per minute, the velocity will be lOJ miles per hour. 



The amount of tear and wear is a question of practice, but the good 

 workmanship which is now common, would obviate many difficulties 

 formerly experienced. The engine is certainly very simple compared 

 with previous patents of the same kind, and is also very powerful in 

 working, and must be very economic in its construction, particularly 

 when used as a non-condensing engine. 



Besides the engine on board tlie "Anti John Scott Russell," Mr. 

 Beale has one of a similar size and description at his manufactory at 

 East Greenwich, worked at the low pressure of 4 to 6 lb.; it stands 

 on the ground, and is hardly perceivable among the numerous ma- 

 chinery in the shop, although it drives the blast fan of a foundry, and 

 sets in motion numerous lathes, planing machinery, drills, &c. 



THE VARIATION OF THE COMPASS. 



Observations made at the Royal Observatory, Greenwich, 

 G. B. Airy, Astronomer Roval. 



Mean Magnetic. 



Variation. 



1841. June '• 23 IG 16 



July 23 15 34 



August ' 23 19 1 



September 23 24 17 



October \ 23 12 18 



November ' 23 17 7 



December ' 23 11 5 



1842. January ' 23 11 54 



February 23 15 23 



Dip 

 at 9 A.M. 



Dip 

 at 3 P.M. 



69 

 69 

 69 

 68 

 68 

 G8 

 58 

 68 

 68 



12 

 9 

 7 

 43 

 43 

 25 

 22 

 46 

 38 



69 IJ 



69 14 

 69 2 



68 38 



68 35 



68 37 



68 27 



68 42 



68 44 



