116 



THE INDIA RUBBER WORLD 



[January i, 1904. 



Two roads — the Pennsylvania and the Chicago. Milwau- 

 kee and St. Paul — limit the expansion of diameter to /j inch 

 with 100 pounds pressure. The latter road also prescribes a 

 flexibility test. A similar test is also required by the Chicago 

 meat packing concern of Swift & Co., who are large users of 

 rubber hose on refrigerator cars. 



The directions for executing all of these tests are found in 

 the specifications issued by the purchasing or testing depart- 

 ment of the various railroads. A description of some of the 

 apparatus employed may be worth while. 



Expansion and Bursting Test.— In the testing room of 

 the Pennsyvania railroad at Altoona, Pennsylvania, is an ar- 

 rangement of piping for the attachment of several sections of 

 hose under test at the same time. The samples are attached 

 vertically to the pressure pipe and enclosed in a sheet metal 

 box to confine the water in case of a burst during the test. The 

 outside diameters are calipered at the middle of the section to 

 determine the expansion under 100 pounds. 



Friction Test. — There are various devices for holding the 

 sample although the test is essentially the same. At the Long 

 Island Railroad laboratory, at Long Island City, New York, 

 the sample is suspended by attaching the free end to the arm 

 of a ring-stand by a small screw clamp. The mandrel in the 

 hose section is of wood, made tight fitting and provided with 

 a small iron axis on which the test weight is hooked. [See 

 Figure I.] At the Baltimore and Ohio Railroad laboratory 



FIG. 1. FIG. 2. FIG- 3. 



the sample section is placed on an iron mandrel 6 or 8 inches 

 long, supported in a pair of iron wall brackets and the test 

 weight hooked to the free end of the sample. TSee Figure 2.] 

 The arrangment at the Pennsylvania Railroad test room con- 

 sists of a bar several feet long provided with a series of ten 

 stout hooks from which as many samples may be suspended 

 and tested. The ring for this purpose is attached to the iron 

 mandrel holding the test section, while to the free end is 

 clamped a small hand vise, into the lower end of which the 

 weight is hooked. [See Figure 3.] 



Stretching Test.— This test is credited to Mr. H. B. 

 Hodges, purchasing agent of the Long Island railroad, who 

 first suggested it as a means for determining the quality of the 



FIG. 4. 



rubber and its degree of vulcanization, as shown by the strength 

 and permanent set after test. The arrangement employed by 

 the Pennsylvania railroad for holding the rubber strips under 

 tension consists of a box-like contrivance of wood. This is 

 made to hold one sample at a time, but it is proposed to modify 

 it so as to stretch the samples in a removable frame which 

 can then be set aside for ten minutes while other samples are 

 being put under tension. [See Figure 4.] At the Baltimore 

 and Ohio Railroad testing department, the rubber strip is at- 

 tached at each end to a stout cord, one of these cords is then 

 attached to a screw eye in a table top while the other is con- 

 nected to the hook of a spring balance by which the amount of 

 the pull can be ascertained. 



Vibration Test.— The airbrake hose specification of the 

 Chicago, Milwaukee and St. Paul Railway Co. provides: 



One piece to be mounted on standard nipples, with ends rounded to 

 prevent undue cutting of the tube, will be placed on vibrating machine. 

 With a uniform air pressure of 60 pounds per square inch, the hose must 

 not fail in less than 75 hours. The test on the vibrating machine is 

 made as follows : One end of hose is held fast, the other end passing 

 through a distance, vertically, of 14 inches, at the rate of 92 strokes per 

 minute. A uniform air pressure of 60 pounds per square inch is main- 

 tained on the hose during test. [See Figure 5.] 



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 *» SE». 



Fid. 6. 



The vibrating test required on air brake hose by Swift & Co., 

 of Chicago, is performed on a machine holding the hose (four 

 at a time) vertically and with the lower end fixed working the 

 upper end forward and back, at the rate of 70 strokes per 

 minute. 



The practical value of these vibrating tests is open to serious 

 question. The conditions under which they are made are very 

 unlike those of actual service, and the results are so extremely 



