. Train resistance : a consideration of its elements and a discussion of experiments made with the university dynamometer car . ich is as near perfect lubrication as it is possibleto have. V/e see from plate ] that between pressures of 100 and 500pounds per square inch the resistance is practicallyjconstant. There-fore between these pressures we have practically perfect lubrication Pressures found on freight car journals may be estimatedfrom the following table of weights kindly furnished by a prominentwestern railroad(and which represents average practice. Kind of Oar Weight Pressure per sq.
. Train resistance : a consideration of its elements and a discussion of experiments made with the university dynamometer car . ich is as near perfect lubrication as it is possibleto have. V/e see from plate ] that between pressures of 100 and 500pounds per square inch the resistance is practicallyjconstant. There-fore between these pressures we have practically perfect lubrication Pressures found on freight car journals may be estimatedfrom the following table of weights kindly furnished by a prominentwestern railroad(and which represents average practice. Kind of Oar Weight Pressure per sq. in. on Jour. lbs. Empty Loaded 20-ton capacity box 26600 95 lbs 258 lbs or tt ft m ^ u 27500 81 228 22 ii 29700 88 264 25 „ furnit. 30000 88 236 1° „ 35800 105 282 20 ,, stock 24900 go 232 OC ii H ft •••••••• «-/<-►-/ ~5 „ 26800 70 226 30 u 32000 04 271 20 „ fri*it 29200 10d00 54. 201 50 20300 66 236 40 ■ 28700 64 242 ■ coal 24100 36 ... 229 25 ■ 25300 74 *22 30 » ■ 26600 7S 255 40 » ■ 31300 71 265. 16 This table gives average values for pressures on journal3 :for emoty cars 85 pounds per sq. in,, for loaded cars 245 pounds persq. in. ,-approximately a ratio of 1 to 3. Tower found (see ) forthese pressures and a speed of 24 miles per hour,the and respectively,corresponding to resistances of per ton. How nearly these values obtain in actual practice is notdefinitely known; when estimates are made, the part of the totalresistance which is journal friction is assumed on -ere common theory is that al1 the resistance which arises about thewheels is journal friction. This amounts to saying that the lubrica-tion on cars is about one-sixth as efficient as a bath of oil,or ispractically that obtained by Tower for a pad which gave an oil filmon the journal barely perceptible to touch. That car lubricationis better than this can not be doubted; in fact for passenger cars and well kept
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