1 7
and dangerously unsteady. This is illustrated by an or ^ are p} ace d nearwheels of which, in order to pass around short curves runn j n g rapidly
together, and it therefore acquires a peculiar leaping nro same thing
over frogs, switches, or other uneven places on the tra ^j_ gwitc hi n g cars onmay be observed on four-wheeled locomotives, use ^ and switching
ordinary steam railroads. The speed of bot s re unsteadiness is
locomotives is, however, comparatively slow, so ra dange rous, and
of little consequence. At higher speeds it wou _ ^ never used on
for this reason four-wheeled locomotives are se ose except that of
ordinary steam roads in this country for any other p Pswitching cars or other slow traffic.
FOUR-WHEELED SWITCHING LOCOMOTIVE.
order to secure the desired steadiness of locomotives by providinguse”^ Wllee *~ base > and at the same time avoiding the evils attending theare ° ax * es placed far apart and held rigidly parallel to each other, whatthis Wn aS “ b °S ies " or *- rucks have come into almost universal use inSucl C ° Untry ^° r ab l° com °ti ves intended to run at high rates of speed.
1 trucks consist of one or two pairs of wheels and axles attached to awh' arate ^ rame ’ w hich is connected to the locomotive by a centre-pin,1C a Ho\vs the whole truck to vibrate or turn around the pin—similar toe movement of the front axle of a common road-wagon or carriage—to C ° nsequent ly> the wheels and axles of the truck can adjust themselves
0 the curvature of the track, no matter what the length of the wheel-basemay be
Jne general arrangement of such an “American” locomotive is showna h a ge 16. ] n the plan cf the wheels a, b, c, d are the driving-wheels,e -I,g , h the truck wheels, o the centre about which the truck turns,m > n > m t »' a curved track. It is apparent from the diagram that, bytr k^ ° n t ^ e centre "P‘ n > the truck can adjust itself to the curvature of’ and the wheels of the truck being comparatively near together, itsth Ce ^ )ase ' s short, and, therefore, their angle to the rails is very small ;
en gine is therefore guided by wheels which are at all times very nearlyParallel to the rails.
-but to keep a truck on the track it has been considered necessary to!t with about one-third the weight of the locomotive, lessening
load
th ereb y the load on the driving-wheels, and, in the same proportion,is CaPaCUy tbe en S' ne f° r drawing loads. Therefore, when the truckUs ed. in the ordinary way one-third of the adhesive weight of thef ^ lne ^ lost, so that the “ American ” locomotive, which weighs thirtyWhhout the tender, will not pull any more than one with four wheels,
ton
,ik e thebut has
«U i, s wight Oh the drmog-whee S . In t hetatt, ^ ^
if all the weight is thus utilized, ie p f rames and consequently
stated.be short, the axle * be ^ ^ w Lel-base is lengthened, the action*the engme is very unsteady , or, it • al experience has decided,
of the wheels is injurious to the trac . £ tlie opinion, that
and a majority of railroad engineers in t is cou gained by using a
the increased steadiness and eaSG ° f p^els compensates for the
long wheel-base and a truck for the S locomotives now m
loss of adhesive weight, and, therefore, near port ion of the weight
From what has been said, it is evident that if a "ould be
structed so that the whole weight of the boi er an £ _ w ^ ee i e d switch-
carried on the driving-wheels, as it is in the case o a. . ^ and a truck
ing engine, and at the same time the wheel-base v. ere m m ^ ne( j i n one
added, that thus the advantages of each wou . ^ illustrated by
machine. This has been done in the p an 0 * ag t p e y a re in the
simply arranging the different parts of the locomo £ rame s beyond the
four-wheeled switching engine, and then extending t p e water-
fire-box and putting a truck underneath them, and p a *^ ase is extended
tank or fuel-bin, or both, on top. In this way t e w re flexibility to
so as to steady the engine, and as the truck ias erse direction to
adjust itself to curves, by running the engine m - n £ ront to guide
that in which locomotives ordinarily run, the true withe otVif»- —
obvious, then, that locomotives constructed in this way will have all thesteadiness on the track, and will pass around curves as easily as anordinary American locomotive, and at the same time they will have amuch larger proportion of their weight on the driving-wheels, andconsequently more adhesion and greater capacity for exerting trac-tive power. In short, such locomotives, of the same weight, will domore work, or they may be of lighter weight and do the same work asthose in ordinary use. By the plan described, the whole weightof the boiler, machinery, etc., which is permanent or unchangeable , iscarried on the driving-wheels, where it is available for adhesion, andthe weight of the water or fuel, or both, which is variable, is onthe truck. Much importance is assigned to this feature. Ifthe weight on the driving-wheels consists partly of that of thefuel and water carried, it will either be excessive with a fullsupply, or, as these are consumed, the adhesion will be insufficient.If, however, the fuel and water are carried on the truck, and theweight of the boiler and machinery on the driving-wheels, thenthe adhesion is due to the permanent weight, and is, therefore,constant , while at the same time the wheel-base is sufficientlylong and flexible to give the requisite steadiness and to pass
around the curves easily. *
The advantage which this system gives will be shown bycomparing the weight of a common American locomotive andtender, with that of the Tank locomotive described and shown.Their weights are as follows :
_ , . • . , . , Weight without
Total weight with W eight on water or fuel inwater and fuel, driving-wheels. boiler of tender _
Lbs. I.bs. Lbs.
Eight-wheeled locomotive and tender.102,000 40,000 74,000
Tank locomotive.72,000 44,000 50,000
Difference in favor of tank locomotive. 30,000 4,000 24,000
From this comparison, it will be seen that, while the weight of a tanklocomotive of this kind will be only 72,000 pounds, or nearly thirty percent, less than the others, it h^s, at the same time, about ten per cent, moreweight on the driving-wheels ; and after deducting the weight of the waterand fuel carried by both, the tank engine weighs 24,000 pounds less thanthe American engine and tender. This latter weight represents thedifference in the quantity of material of which the two engines are made ;and as the cost of the locomotive bears a close relation to the material inthem, it is evident that the tank locomotives will be much cheaper thanlocomotives of the ordinary kind. The proportion of the whole weight ofthe engines on the driving-wheels is 39.2 per cent, of that of the Americanengine, and 61.1 of the tank engine.
There is also another incidental advantage gained by reducing theweight, besides the saving in cost. As the load which a locomotive drawsis its own weight and that of the train , it is obvious that, if that of theformer be reduced 30,000 pounds, that of the latter may be increased alike amount, and the total load remain the same. Or, in other words, ifthe weight of a locomotive is 30,000 pound less, and its capacity be notdiminished, the quantity of paying freight which it can draw will be 30,000pounds more.
By comparing the American and the Tank locomotives, it will be seenthat the position of the truck in relation to the driving-wheels is the samein both cases ; but in the Tank locomotive that of the boiler in relation tothe wheels is reversed from the usual position. Therefore, in order that
C.WRIGHT.N. 1
other wheels
as
it does in engines of the “ American ” type. It is
TANK LOCOMOTIVE.
the truck may lead or guide the other wheels, locomotives of this planmust be run with the fire-box in front, and the chimney behind, as indicatedby the position of the cow-catcher in the Tank locomotive. This, ofcourse, reverses the position of the boiler and machinery, and makes whathas heretofore been regarded as the front the back end. Owing to thefact that locomotives have always been run the other way, this feature, atfirst, is apt to be regarded unfavorably, but the objections to it will befound to be more apparent than real. In fact, there are some incidentaladvantages in running in that way, as it gives the locomotive runner anunobstructed view of the track ; and the position of the chimney and