24

RECENT LOCO MO TIVES.

is of course in the inside of the tubes, between which and the hemispheri-cal caps and also from the latter and the steam-drum there is a free com-munication. Owing to the inclined position of the tubes there is a rapidcirculation of the water, and, consequently, it is not surprising that theseboilers should be very efficient.

Although these engines have been working for several years, we havenot been able to get very complete information of their performance. Onedifficulty encountered was in charging the boilers with water all heated to auniform temperature of 390 degrees, which is that of steam of 220 lbs. pres-sure. Of course the water in the boiler, of whatever temperature it hap-pens to be, would rush into the tank as soon as communication was openedbetween the two. It is extremely difficult to have all the water in anyboiler heated to a uniform temperature, and therefore that, with which thetank is filled is usually below the temperature due to the pressure in theboiler. At first sight it might be supposed that hot steam could beadmitted into the water with a perforated pipe or other means, and thusheat the water ; but when this was done it was found that the upperstratum of water would thus become heated up to the temperature of thesteam, or near to it, and that enough steam would soon escape to the sur-face to make the pressure in the tank on top of the water equal to that inthe boiler, after which the flow of steam into the tank either ceased or wasvery slow, while at the same time the lower stratum of water remainedcomparatively cold. This difficulty could probably be removed by somemeans, but it is one which has been encountered and which has interferedseriously with the success of the engines. At any rate it was found diffi-cult to maintain a pressure in the tank equal to the boiler pressure aftercommunication between the two was cut off. Usually in running from thestationary boilers to the place where the engine was attached to the car,the pressure would fall from 220 to 190 lbs., but the engine would then runa distance of 3)4 miles and have 100 lbs. pressure in the tank at the end ofthat distance. With 80 lbs. pressure the engine would pull a car while thesteam was cut off at 2 in., or one-fifth of the stroke. It should be addedthat, as the city of New Orleans is built on a level plain, there are no gradesof any consequence on this line, but it. has curves of 35 and 40 ft. radius,around which the engines run without difficulty.

STEAM INSPECTION CAR.

Designed and Constructed by Mr. Jay Noble, faster Mechanic for l^essrs. ty.Buck & Co,1 St, Louis, N|o.

J ig. 111.

This engraving represents what has been called a “ steam-hand-car,” de-signed and constructed by the master mechanic of the well-known St. Louis railroad supply house in 1876. It was intended as an inspection car, and forthat purpose is certainly much more economical, and we should say moreefficient, than a locomotive with a “superintendent’s car” attached. Theconstruction is clearly shown by the engraving. The platform extendsunder the axles and is within 10 in. of the rails. The boiler is about42 x 18 in., intended to carry 140 lbs. of steam, and the cylinders are 3*4x 6 in. The frame is supported on rubber springs over the bearings. Thetwo reversible seats will accommodate three persons each. Under one isa water tank holding about a barrel, enough for 40 miles run. On oneside of the boiler is a coal-bin which will hold a day’s supply of coal.

JOY'S VALVE- GEAR.

Figs, 112 to 117.

To many mechanical engineers it will probably seem almost likedesecration to question the superiority of the link-motion over all otherforms of reversing and expansion gear for locomotives. Although the intro-duction of that mechanism was at first bitterly opposed, afterwards its victorywas so complete that mechanics have fallen into the habit of thinking thatnothing can supplant it. Nevertheless it seems probable that its days arenumbered, and that some of the new forms of valve-gear which have beenintroduced during the past few years will, possibly with some modifications,take its place. In the Railroad Gazette of April 23, 1880, there was pub-lished a very good example of the Walschaert gear (see figs. 199-204) de-signed by Mr. Charles Brown, of the Swiss Locomotive Works, Winterthur.This is very extensively used in Europe on the continent, but not in Great Britain . In this country it has not met with much favor, excepting fromMr. Wm. Mason, of Taunton, who has applied it to his double-trucklocomotives. In the Railroad Gazette of Dec. 28, 1877, a valve-gearinvented by Mr. Brown, of Winterthur, was also illustrated. This isvery similar in principle to Joy’s valve-gear, represented by the engrav-ings herewith. Mr. Joy, however, claims to have improved the gear, so asto give a more correct motion to the valve, and to have simplified themech^pism. The engravings published herewith represent a design by Mr.loy of a method of applying the gear to an outside cylinder engine of theAmerican type. The gear has been described as follows by him :

“ In this valve-motion eccentrics are entirely dispensed with. Themotion of the valve is taken direct from the connecting-rod, and, by util' 2 'ing independently the backward and forward action of the rod, due to thereciprocation of the piston, and combining this with the vibrating action ofthe rod up and down, a movement results which is employed to actuate th evalves of engines using any combination of lap and lead desired, and gi v "'ing an almost mathematically correct cut-off for both sides of the pistonfor forward and backward motion, and for all points of expansion inter-mediately. The action of the gear may be understood by reference tothe engraving, fig. 112. Figs. 113 and 114 are respectively an elevatioHiplan and transverse section on XU of fig. 112, looking forward.

“ From a point A, fig. 112, on the connecting-rod, motion is impartedto a vibrating-link B constrained at its lower end H to move vertically bythe radius-rod C which is pivoted at I. From a point D on this vibratinglink B horizontal motion is communicated to the lower end of a lever Lfrom the upper end of which lever the motion is transmitted to the valve-spindle by the rod G. The centre or fulcrum F of the lever E partakesalso of the vertical movement of the connecting-rod to an extent equal to theamount of its vibration at the point A ; the centre F is for this purposecarried vertically in blocks which slide in slots in the links JK which atecurved to a radius equal to the length of the rod G connecting the lever fto the valve-spindle. These links are attached to a shaft Z, figs. 113 and114, corresponding to the ordinary lifting-shaft of a link motion. Thecentre of this shaft corresponds to the position in which the fulcrum F<&the lever E is represented in fig. 113. The shaft Z and the links can b epartially rotated on the centre of the former, so that the slots in the linkswill be inclined over to either side of a vertical position, as shown atand X. This is done by means of an ordinary reverse lever connected tothe upper arm M attached to the shaft Z. When the links are thusinclined, the vertical movement of the lever E causes the blocks in thelinks and the centre F to traverse a path inclined to a vertical centre line ;and to diverge from it to either side. The centre F therefore, has a hor-izontal movement, the extent of which depends upon the degree of inclin-ation of the links, and the direction of which is governed by their posi-tion.

“ The forward or backward motion of the engine is governed by giv-ing the slots this inclined position on one or other side of the verticalcentre-line ; and the amount of expansion depends on the amount of theinclination, the exactly central or vertical position being ‘ mid-gear.’ 1°that position steam is admitted at each end of the stroke to the amountonly of the lead ; and this is done exactly equally on each side of thecentre-line, the amount of lead being constant for forward and backwardmotion, and for all degrees of expansion. Thus when the crank is set atthe end of the stroke either way, the centre F of the valve-lever coincideswith the centre of the slot, and therefore the slot may be moved overfrom forward to backward gear without affecting the valve at all.

“It will be seen at a glance that if the lower end D of the lever E wereattached directly to the point A on the connecting-rod, it would travel i°the path of the ellipse A lY represented by dotted lines, and there wouldbe imparted to the centre F of that lever an unequal vibration above andbelow the centre of the links JK. The extent of inequality would betwice the versed-sine of the arc described by the lower end F> of the leverF; and this would give an unequal port and unequal cut-off for the twoends of the stroke. But this error is corrected by attaching the lower endID of the lever E to the vibrating linkZy for while the points in theconnecting-rod is performing a nearly true ellipse, the point D in thevibrating link B is moving in a figure DOPQ like an ellipse bulged out onthe lower side, and this irregularity is so set as to be equal in amount tothe versed-sine of the arc described by the lower end Z> of the lever F., thuscorrecting the above error, and giving an equal travel to the centre F 0 fthe lever above and below the centre of the slot. At the same time theerror introduced by the movement of the end of the valve-rod G is cor-rected by curving the slots or links J K to a radius equal to the lengthof G.

Referring again to the equalizing of the traverse of the centre F ofthe lever E in the slot J K, the unequal traverse may be either under cor-rected or over corrected by shifting the point D in the vibrating-link 1 ’nearer to or further from A j by this means a later point of cut-off may b cgiven to either end of the cylinder at will, and the engine may thus havemore steam admitted to one side of the piston than to the other, if re-quired. The same thing may be done for the lead. By altering theposition of the crank for which the lever centre F coincides with the centreof the slots J K, an increased or diminished lead may be given. Thecentral positions and exact connections are, however, in all cases standardand equal.

“ Hitherto the centre F of the lever E which gives motion to thevalve-spindle, has been described as carried in curved slots. - This plangiven as the most simple to manufacture, but if preferred the centre fmaybe carried by a radius-rod so that its vibration will make the centreof the lever E describe identically the same arc as if moving in the slot /■

In locomotives with small wheels the link 6’may come so low down a 5to be in danger of being knocked off. For such cases—and for otherswhen it may be considered desirable—Mr. Joy has proposed the ph irl