Feuruary i, 1904.] 



THE INDIA RUBBER WORLD 



149 



PAPERS ON AIR BRAKE HOSE— III. 



AIR BRAKE HOSE IN SERVICE. 



ELABORATE investigations have been made by the ex- 

 perts of many American railways, to determine the 

 duration of service and the causes of failure in air 

 brake hose. A matter of considerable expense de- 

 pends on the relative economy of high grade specification hose 

 and the ordinary twenty-four months' guarantee hose. Such 

 of these investigations as are available prove to be very inter- 

 esting and valuable. Abstracts and summarized conclusions 

 derived from the reports of certain of these investigations will 

 be given here. 



Recent tests and comparisons made on the Atchison, Topeka 

 and Santa Fe railway system extended over a period of four 

 months, and included the history of 5372 pieces of 1% inch, 4 

 ply, air brake hose, costing 41 cents per foot and guaranteed for 

 24 months' service. Analysis of the data obtained shows that 

 of the total number of pieces under test, 39.5 per cent. (21 16 

 pieces) fulfilled the guaranteed two years' service ; 6.5 per cent. 

 (349 pieces) were serviceable beyond the guaranteed limit ; and 

 54 per cent. (2907 pieces) failed for various causes, of which 

 two thirds were Urgely preventable on the part of the railway 

 authorities. 



The following table gives a classification of causes of failure: 



FAILURES DUE TO INFERIOR HOSE. 



Failures which makers must replace 414 



Failures not recoverable from makers, owing to neglect to can- 

 cel dates on hose 560 



Total ~ 974 



FAILURES CHARGEABLE TO ABUSE. 



Malicious cutting 103 



Run over by carwheels 86 



Mashed by buffers or couplers 76 



Cut by gravel or cinders under nipple 194 



Using hose for other purposes 168 



Trains parting with hose coupled 162 



Chafing 262 



Kinking on angle cock 118 



Hose being painted 86 



Burnt in wrecks, etc 11 



Cut by nipples while being mounted 60; 



Undeterminable causes 66 



Total 1933 



SUMMARY. 



Failures due to inferior hose 34 per cent. 



Failures chargeable to abuse 66 per cent. 



The Santa Fe report discusses very (airly the preventable 

 causes of the failure of air brake hose, with recommendations 

 designed to greatly reduce the reckless waste of over 50 per 

 cent. Its general conclusions are thus summarized : 



The average life of the he ;'hich failed to give 24 months' 

 service, was nj^ months. verage of all hose removed on 



the system (including that foreign cars — i. e., cars from 



other roads) was 23 8 months. Certain superior grades were 

 found to average 38, 51, and 61 months. This high grade hose 

 came from foreign cars and failed from abuse and old age. If 

 a marked improvement cannot be effected in the matter of 

 reducing the amount of abuse inflicted on the hose, it would 

 hardly be advisable to purchase a better grade of goods. The 

 final conclusion is : " If, however, we can stop the slaughter, we 

 can save money in the long run by buying a better grade"— in 

 other words, a grade better than that ordinarily furnished under 

 24 months' guarantee of service. 



About a year ago a series of careful tests of various makes 

 of air brake hose was completed by the Testing department of 

 the Chicago, Burlington and Quincy railroad, of which the fol- 

 lowing is a condensed account: 



The test consisted in obtaining and placing in service on sub- 

 urban trains, where the hose could be carefully watched, 12 

 samples of each of six leading makes of hose (72 samples in all). 

 Care was taken to select different grades, as well as different 

 makes, including some of the most expensive as well as some of 

 the cheapest hose on the market, also several samples repre- 

 senting intermediate and varying values. One piece of each 

 make was subjected to careful laboratory tests, such as are or- 

 dinarily employed, showing the bursting pressure, friction, 

 stretch, and set of rubber, and the remaining samples were put 

 into service. At the end of six months one piece of each make 

 was removed and retested, with the idea of determining the rate 

 of deterioration in service, and this process was repeated at in- 

 tervals of six months until all of the test hose had been re- 

 moved. 



During this test, which extended over 2j4 years, it was neces- 

 sary to remove 40 per cent, of the hose on account of its being 

 worn out and injured ; thus 60 per cent, was actually removed 

 and retested. It is probable that if none of the hose had been 

 removed for testing a considerably larger percentage would 

 have been removed on account of being worn out before the 

 test was completed. It seems safe to conclude that in a period 

 of 2 l / 2 years, at least 50 and perhaps 60 per cent, of the air brake 

 hose has to be replaced on account of being worn out. The 

 samples so removed are worn out by mechanical injury and not 

 on account of decay, either of rubber or canvas. This was 

 equally true of the low priced as well as the high priced hose. 



The tests indicated that there was not a very great falling off 

 in the bursting pressure or the stretch of the rubber tube in the 

 course of 2% years, although there was considerable difference 

 between the results obtained in the tests of the hose of differ- 

 ent grades. It also developed the interesting fact that, al- 

 though some of the more expensive brands, when new, showed 

 a very high friction test, this deteriorated very rapidly and in 

 most cases had fallen very low within one year's time of ser- 

 vice. The tests also indicated that the cheaper grades of hose, 

 having originally low friction, and low stretch of rubber, held 

 up in the bursting pressure as well as the samples of higher 

 priced hose that originally showed high friction and high 

 stretching tests. 



The conditions of the samples when removed showed that the 

 life of air brake hose is determined in practically every case by 

 mechanical injury, and not by deterioration of the hose, and the 

 conclusions from this test were that it is not necessary or de- 

 sirable, from the standpoint of expense, to buy hose showing 

 high friction and high stretching qualities, since such hose 

 costs considerably more than ordinarily well made hose, with- 

 out giving much if any increased service. 



In this connection it is interesting to note a few specimen 

 facts brought out by the tests. Just as good service was ob- 

 tained from a hose which showed a friction of 1% seconds in 

 the original piece as from a much more expensive hose which 

 showed a friction test of 40 minutes. Also, the hose which 

 gave an original friction test of 40 minutes showed at the end 

 of a year only 35 seconds ; while the hose which gave an origi- 

 nal friction test of 1 }& seconds, gave a friction test of one second 



