1841.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



251 



from front to rear, and outside of it are five more lines of way for the 

 luggage trucks. Along the front of the carriage house^, and at right 

 angles with the rails is a pair of rails laid to a gauge of 7 ft. 4 in., and 

 9 inches below the lines, of way, upon which runs a carriage, shown in 

 figs. 10 and 11. On the top of this carriage, and on a level with the 



Fig. 10, Plan of Truck. 



-y 



0; 



n 



^ 



n ' 



^ 



TJ 



Fig. U, Section of Truck. 



^ 





'^^^:!^^^^M^^^^^m^^m 



rails of the main line are corresponding rails supported on timber 

 framing, which is suspended to the axles of six cast iron wheels, 20 

 inches diameter. These wheels run on the 7 ft. 4 in. gauge for the 

 purpose of removing the carriage or truck which is put upon the frame 

 to any pair of the reserve rails in the carriage-house. This saves the 

 trouble and expense attendant upon turn tables opposite to each pair 

 of rdils. 



The engine house is 

 a polygonal building 

 containing twelve lines 

 of way, in the middle 

 of which is a turn table 

 communicating with 

 the whole. The con- 

 struction of the points 

 is shown in the an- 

 nexed figure 1"2. 



Glass Cloth Weaving.— A most ingenious artist, a Mr. Barker, from Ossett- 

 street-side, is nuw e.\liil<iting the process uf this novel species of manufactere, 

 in a room in the Philosoi'hical Hall, Halifax. He has lately forwarded a 

 most splendid apron, and a pair of shppers, to her Majesty the Queen, which 

 have been most graciously received, nith the strongest approbation. We 

 have seen some very beamii'ul specimens o' the ingenious inventor's skill, and 

 consider them as spJendi 1 novelties. We particularly noticed a piece of 

 waistcoating, two and three ijuarters yards long, and half a yard in width, 

 which he states to be the fi.st of the kind he has been able to bring to any 

 degree of perfection, and has been woven in Hiiddersfield. It is beautifully 

 figured like damask or fancy work. One remarkable circumstance in glass 

 cloth is that it will stand washing. We were shown a piece of pure i\hite. 

 which has six times undergone that process. We hope the ingenious and 

 persevering man wdio has already spent two years and a halt in bringing his 

 invention io a state fit to meet the pubfic eye, will reap his reward for his 

 invention. — Halifaj: Guardian. 



ON THE ECONOMY OF FUEL IN LOCOMOTIVES CONSE 



QUENT TO EXPANSION AS PRODUCED BY THE 



COVER OF THE SLIDE VALVE. 



Sir — With a view to economy of fuel, locomotives are now generallr 

 constructed so that the slide valve shall have what engineers call 

 "cover on the steam side," the effect of which 

 is, that steam is admitted to the cylinder during 

 only a part of the stroke of the piston, and during 

 a part of the remainder that steam by expanding 

 to occupy a greater volume propels the piston ; 

 ■^~"i "■^-ij which expanding increases the work performed 

 by a given quantity of steam to an extentdepend- 

 ing on the ratio of that part of the stroke, during 

 which the steam is adtnitted to the cylinder, and 

 y^^ 11 that part of it during which the steam is expaiid- 



'^!'TTnffjTf(.700 ing; and as the consumption of fuel is dependent 

 on the work performed by a given quantity of 

 steam, an analytic investigation of the cover of 

 the slide valve is the object of the following. 



In the figure* let F' G, represent the connecting 

 rod, F' E the engine crank, E A' the eccentric 

 crank, F E the engine crank when the piston com- 

 mences its stroke, and E A the corresponding 

 position of the eccentric crank, B C, D C valve 

 levers. Put E A' = a, E F' ^ rf, cover of valve =: 

 c, lead of valve =;, B C = D C. To diminish 

 complication neglect the radiation of the eccen- 

 tric rod and connecting rod, which may be done 

 wdtliout sensible error, since their length is great 

 in proportion to the lengths of the cranks. 



Diavv L E perpendicular to E B, and any angle 

 LEA has its sine proportional to the distance 

 that the valve is from its position when L E A =:: o. 

 When the piston is commencing its stroke the 

 valve is open, the quantity (0, and therefore it 

 has travelled the quantity (I -\- c) from its position 

 when L E A =: ; hence a X sin. L E A := i -|- tf 



' + c 



. • . sin. L E A = , and cos. L E A ^ 



a 



l\ 



\.: 



Again, if the engine crank travels owr any 

 ^ angle (<p) from its position, F E the descent or 



progress (y) of the piston is equal to rf X ver- 



sin-p, .-. cos. ,.= l-|,andsin,), = ^A/('-^-|sY The tr.ivel 



(x) of the valve corresponding to the travel (y) of the piston, is equal 



to (asin. (LEA + <p) — asin. LEA), .-. ^ = sin. LEA cos. 9+ cos. 



LEA sin. <p — sin. L E A, and by substituting for the functions of th e 

 angles their values found above, and reducing we get 





2y 



m equation expressing the relation of (x) and (y) in terms of known 

 quantities. 



When the piston begins its stroke the valve is a little open, and 

 steam continues to enter until the valve in its retrograde motion shuts 

 the passage; expansion then cotnmences and continues until the educ- 

 tion pa.ssage is opened. When the eduction passage is opened on 

 one side of the piston it is sliut on the other, wdiich gives rise to the 

 compression of steam on the educted side of the piston, and this cimi- 

 pression continues until the valve opens for the lead of the next stroke. 

 In figure let ABC D' be a steam cylinder, 

 stroke = A D= -2 rf,a' = distance from com- 

 mencement of stroke to commencemfiit of ex- 

 pansion, 6= distance from commencement of 

 stroke to end of expansion ; c'= distance from 

 commencement of stroke to position of [dston 

 when the valve opens for the lead of next 

 stroke. To find by the above equ.ition the 

 travel of the valve corresponding to the travel 

 (a') of the piston substitute x= — /, for the 

 travel corresponding to (b) x= — {l+ c), and 



the line should be draun iioui /' Lo< 



2 M 2 



* The figure is not quite correct 

 and not from/' to a'. 



