Rack Locomotives are used ou roads where
the grades are too steep to be operated by the
ordinarj' traction locomotive. The adhesion be-
tween the wheel and the rail of such an engine
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Fig. IG. GEARED LOCOMOTIVK POH LOGGING EAILWAY.
cannot be taken at more than 25 per cent, of the weight on the drivers. Hence when the grade l)e- comes so .steep that the resultant of gravity act- ing parallel to the wheels becomes equal to 25 per rnt. of the weight on the driving wlieels it will iio impossible for the locomotive to advance. Such a grade is reached when the rise is 1.320 feet to the mile. Practically it is much less tlian this. So on a grade of one-luilf of this the engine could at best only hold, not haul, itself and a load equal to its own weight. Hence for roads climbing mountains where the gradient is neces- sarily very steep the rack locomotive is used. Such an engine is shown in side elevation in Fig. 17. The weight of the locomotive is car- ried on smooth rails in the ordinar.y manner, and while the grade lies within the limits of its weight to overcome, it is propelled by driving wheels like other engines. But when the grade becomes too steep, the gear-wheel is brought into mesh with a rack rail laid in the centre of the track between the other two. The teeth of this gear engage with those of the rack and propel the engine independently of the power which is developed at the driving wheels and which would be in- sutticient to do the work. Between the two main driving axles is another driving axle, carrying a gear-wheel, which meshes with the rack.
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Fig. 17. LocoMOTrvE for rack bailwat.
This gear-axle is driven tlirough reducing gear- ing by a pair of inside c.vlinders. In addition to the two main axles there is another rear
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PEisaPAL Dimensions of Recent Heavy Freight Locomotives Illinois Central 12-wheel Rrooks 4 ft. 9 ins. 15 tt. 9 ins. 2(1 ft. 6 ins. 193,200 lbs. 232.200 lbs. 364,900 lbs. Simple 23 X 30 ins. 6 ft. 8 ins. 210 lbs. lift. X3ft. 6 ins. 424 2 ins. 14 ft. »% in.s. 3,237 sq. tt. 3,500 sq. ft. 3^V2 sq. ft. 7,000 Kalloiis 28.800 lbs. Illinois Central Consolid.ltlon Holers 4 ft. 9 ins. 16 ft. 3 ins. 24 ft. 5 ins. 194.000 lbs. 214,000 lbs. Union Consolidation Pittsburg 4 ft. 6 ins. 15 ft. 7 ins. 24 ft. ins. 208,000 lbs. 230,000 Ihs. 334,000 lbs. Simple 23X32 ins. 6 tt. 8 ins. 200 lbs. 10ft.X3 ft. 4 ins. 355 2Vi ins. 15 ft. 3.117 sq. ft. 3,322 sq. ft. 331^ sq. ft. Great Northern Tvpe 12-wheel Builder . Brooke 4 ft. 7 ins. Wheel-base, driving 15 ft. 10 Ins. 26 ft. 8 ins. Weight on drivers 172.000 lbs. 212.750 lbs. En;;ine and tender.... Cnmpoiind or simple 308.7.i0 Ihs. Simple 2;! X 30 ins. 6 ft. 6 ins. 210 lbs. 11 ft. X3ft. 6 ins. 417 2 ins. 13 tt. 2,951 sq. ft. 3,203 iiq. ft. 381A sq. ft. 6,000 gallons .Simple 1 21 X ,i4 ins. 6 ft. 6 ins. 210 lbs. 10 ft. 4 ins. X 3 ft. 4Vj ins. 376 214 ins. 13 ft. 10% ine. Heatins surface, tubes... Total 3,043 8(1. ft. 3,280 sq. tt. Grate area 34 sq. ft. Coal on tender 22.400 lbs. Railway Southern Pacific 12-wheel Scheuectadj 4 tt. 7 ins. 15 ft. 6 ina. 26 tt. 5 ins, 155,000 lbs. 192,000 lbs. 291,635 lbs. 2-cvrder, comp'd. 23 and 35 X 32 ins. 6tt. 200 lbs. 10 tt.X 3 ft. 6 ins. 332 iVi ins. 14 ft. 6 in.s. 2,819.34 .sq. ft. 3,n25.'<5 sq. tt. 35.00 sq. ft. 4,500 gallons. 22,400 lbs. Northern Pacific 12-wheel Schenectady 4 ft. 7 ins. 15 tt. 6 ins. 26 ft. 4 ins. 150,000 lbs. 186,000 lbs. 270,020 lbs. 2-c.v!'(ier comp'd. 23 and 34X30 Ins. (i ft. 200 lbs. IOtt.x:Ut. 6 ins. 332 2J< ins. 14 tt. 2,721.60 sq. tt. 2.94:1.41 sq. tt. 35.00 sq. ft. • 4.000 callous 15.000 lbs. C, C, C. and St. L. Consolidation Richmond 4 ft. 8 ins. 10 ft. 3 ins. 24 ft. 2 ins. 102,000 lbs. lso,0(]0 lbs. 300,000 lbs. Simple 22 X 30 ins. 6tt. 200 lbs. 9ft.llin.x3ft.5in. 376 2 ins. 13 ft. 5 ins. 2.6i'?.0O sq. ft. 2.80O.0O sq. ft. 33.88 sq. ft. 6.000 gallous 22,400 lbs. But., K. & Pitts. 12-wheel Brooks 4 tt. 7 Ins. 15 tt. 6 ins. 25 ft. 5 ins. 148,000 lbs. 175.000 lbs. 265.000 lbs. Simple 21 X 26 ins. 5 ft. 6-'Vi Ins. 180 lbs. 9%ft.X3ft.2V4ins. 324 2 ins. 12 ft. 7^V ins. 2,106.0 sq. ft. 2,331.0 sq. ft. 30.4 sq. ft. 4,500 gallons. 18.000 lbs. P., B. 4 L. E. Type Consolidation Builder Pittsburg DrivinK wheels Wheel-base, driving Total 4 ft. 6 ins. 15 tt. 7 Ins. 24 ft. 4 ins. 225.000 lbs. 25ll.3(«) lbs. Kiiffiiie and tender,,,. Compound or simple 391.40D lbs. 24X32 Ins. 7 ft. 4 ins. 220 Ills. Fire-box llft.Xi:it.6>iill. 406 Diameter 214 Ins. Length 15 ft. Heatlne surface, tubes Total S.5M sq. It. s.sns sq. ft. 36 S sq. ft. Water in tank 7.500 gallons 28,000 lbs.
