Janl-akv 1, 1913.) 



THE INDIA RUBBER WORLD 



189 



The tension test, which is the most widely applicable for soft 

 rubber products, is used to determine strength, ultimate elonga- 

 tion, and elasticity or recovery. The results of tests are 

 influenced by : 



1. Shape and size of test pieces. 



2. Method of preparing and measuring same. 



3. Design of grip. 



4. Direction in which test pieces cut (in straight specimens). 



5. Temperature. 



6. Previous stretching. 



7. Time allowed after extension and release before measuring 

 set. 



8. Speed at which rubber is stretched. 



Other important considerations affecting test pieces are : Prepa- 

 ration and measurement; design of grip; direction of cutting; 

 temperature; influence of previous stretching on strength and 

 elongation; increase of ultimate elongation and strength. 



An objection to the practice of attempting measuring and re- 

 marking specimens immediately after release, is the influence thus 

 exercised on the second set by the few seconds interval which 

 necessarily takes place. 



The author's aim has been to deal with uniform methods of 

 testing, no attempt having been made to treat the general sub- 

 ject of physical testing in an exhaustive manner. 



TESTING OF AIR BRAKE HOSE AND ACTUAL 



SERVICE. {Abstract.) 



By G. E. Bishop. 



""THE above subject is treated by the author in two sections — 

 ■^ air brake hose and steam heat hose. In the former two 

 sizes are considered — V/g. in. .x 22 in. and IJ^ in. -x 22 in. The 

 first of these is for use in passenger service and the second on 

 freight cars only, the hose being specified to stand a bursting 

 pressure of 500 pounds per square inch for 10 minutes. Ai 200 

 pounds pressure it must not expand in diameter more than one- 

 quarter inch, or change more than one-quarter inch in length. 

 It has also to stand a friction test of such a nature that with a 

 weight of 25 pounds suspended from the end, the separation 

 would be uniform and regular; the average speed not exceeding 

 6 inches in ten minutes ; as well as a stretch test, between marks 

 two inches long on a piece half an inch wide. This is quickly 

 stretched until the marks are 10 inches apart and released; then 

 re-marked as at first and again stretched to 10 inches ; remain- 

 ing ten minutes without breaking. After release the distance 

 between the marks must not show a permanent set of more than 

 one-quarter inch. 



Several interesting tables are appended to the paper, showing 

 in the first place the performance of 1^ in. air hose during the 

 year from November, 1911, to November, 1912. The table in- 

 cludes the number of hose removed for all causes, classified 

 under the general causes for removal and the life of the hose. 

 The total number of hose purchased of each of the eight makes 

 used during a period of three years is also shown as an indica- 

 tion of the proportion of the different makes of hose in service. 

 This point is illustrated by the numbers of each make inspected 

 and rejected. 



A large portion of the hose was removed on account of being 

 damaged in service ; this being largely attributed to the auto- 

 matic connector, which increased the chafing and cutting of the 

 hose. The results given by the eight makes are criticized in 

 detail. 



Another table deals with similar particulars as to the XYg. in. 

 air hose, the two tables constituting a detailed history of the per- 

 formances of the two sizes of air-hose during the twelve months 

 ending November, 1912. 



In the second part of the subject, steam heat hose If^ in. x 

 24 in. is dealt with, used on passenger cars, locomotives and 



tenders, with an automatic connector, as referred to under the 

 discussion of air hose. The tests include the elongation and 

 ultimate tensile strength of a piece of the inner tube. A friction 

 test provides for the pull at which the duck will start to unwind, 

 while the sample is likewise subjected to saturated steam at a 

 pressure of 45 pounds per square inch for a period of forty- 

 eight hours. After cooling, the tests are repeated, when the 

 stretch test must not show a deterioration of more than 30 

 per cent, and the tensile friction not more than 20 per cent. 

 Inspection of the hose after removal from the digester must not 

 disclose swelling, blisters or loosening of inner tube. 



A performance table records the results on the same prin- 

 ciple as those shown for air hose. 



In conclusion, the fact is referred to that purchasing under 

 proper specifications has decreased consumption of hose per car 

 per year from 4.3 pieces to 2.5 pieces. 



It is thought that better steam hose can be procured by in- 

 creasing the friction and stretch test. A specification is now 

 being tried with the requirements, after the digester test, in- 

 creased to what thcv were before that test. 



RAILROAD AIR BRAKE HOSE. {Abstract.) 

 By J. S. Sheafe. 



WHILE the requirements prescribed by the Master Car 

 Builders' Association are intended to insure uniformity 

 of standard in railroad equipment, the air brake hose now being 

 manufactured does not comply with those requirements in other 

 than the physical tests. 



The M. C. B. specifications prohibit the use of rubber substi- 

 tutes. Neither pure rubber nor a fair grade of rubber can be 

 used at the price paid. 



Air brake hose to-day are poorer than formerly, for which 

 both the railroads and manufacturers may be blamed ; the for- 

 mer for continually hammering down the price asked for an 

 honest article, and the latter for consenting to attempt the manu- 

 facture of an article at a price below that which they know can 

 be fairly met. The quality of air hose must be improved by the 

 co-operation of manufacturer and consumers. 



Air hose is sold as low as 30 cents a foot and as high as 50 

 cents, there being thus a difference of 66 per cent. How much 

 can be expected of a quality costing the minimum? The cost 

 of replacing poor hose would make up for the extra price of a 

 good quality. 



The largest number of failures has resulted from outside 

 injury, not attributable to inherent weakness of the hose. 



There can be no doubt of the deterioration of the average 

 air hose within six months of manufacture. The makmg of 

 hose to wear well, is the most important part of the manu- 

 facturers' problem. Rubber manufacturers could make a last- 

 ing hose by compounding a tube and cover with just as 

 much or little flexibility as would be necessary for long life. 

 If the manufacturers will produce a hose with an inner tube 

 and cover able to withstand the action of time and weather for 

 36 months at a commensurate price, the whole situation will be 

 greatly improved. 



CONTRACTS. (Abstract.) 



By Artltur If. Stedman. 



/'^OMMON law presupposes that, in making a contract, both 

 ^' parties have agreed upon the same thing. A contract should 

 be so drawn as to be enforcible by law, and should embody a 

 consideration, whether in the form of some actual object or 

 service, or under the guise of "one dollar and other good and 

 valuable consideration." 



The chief points to be defined are: First, an agreement as to 

 what is being purchased; second, an expressed or understood 

 standard of quality, and third, delivery at a certain time and 



