January i, 1904.] 



THE INDIA RUBBER WORLD 



115 



PAPERS ON AIR BRAKE HOSE— II. 



HOSE SPECIFICATIONS AND TESTS. 



T^HE former general and unsatisfactory practice of pur- 

 chasing air brake hose on twenty-four months guaran- 

 teed service has given way, in recent years, to the prac- 

 tice, by the leading railway companies, of requiring the 

 rubber manufacturer to furnish air brake hose in accordance 

 with specifications and prescribed tests. By this means it is 

 hoped to secure goods better adapted to the trying conditions 

 of service ; also greater ultimate economy. The comparatively 

 short service of air brake hose and the disasters liable to at- 

 tend its failure, render extremely important the determination 

 of the matter of the quality and make up best suited to the ser- 

 vice required. Naturally there is much similarity in the vari- 

 ous specifications already issued. The numerous specifications 

 consulted in the preparation of this paper practically cover the 

 entire field and embrace all the essential requirements. 



Most of the railway authorities are inclined to impose exac- 

 tions on the manufacturer which are of questionable value in 

 securing greater service from the goods, while they unneces- 

 sarily add to the cost. For example the excessive 25 pound 

 friction test; the vibrating test under 60 pounds air pressure ; 

 and the complicated attempt to figure quantitative relations 

 between friction, tube, and cover. These, however, become of 

 minor concern to the manufacturer if they are provided for in 

 the price of the goods. In general, it may be said that the 

 specifications are not over exacting, considering the object to 

 be attained. It is to be observed that the importance of the 

 air brake hose problem has led the Association of Railway 

 Master Car Builders to study the subject, with the result that 

 the association has issued a standard specification recom- 

 mended as general practice. This specification will doubtless 

 come into extended use through the operation of the Master 

 Car Builders' rules regulating the interchange of car repairs. 

 They are thus of special interest and are therefore given in full 

 so far as they relate to the subject of air brake hose. 



MASTER CAR BUILDERS' SPECIFICATIONS. 



In 1901 the following specifications and tests for air brake 

 hose were adopted as " recommended practice " : 



1. All air brake hose must be. soft and pliable and not less than 3 ply 

 nor more than 4 ply. These must be made of rubber and cotton fabric, 

 each the best of its kiDd made for the purpose ; no rubber substitute or 

 short fiber cotton to be used. 



2. Tube must be hand made, composed of three calenders of 3^ inch 

 rubber. It must be free from holes and imperfections in general, and 

 must be so firmly united to the cotton fabric that it cannot be separated 

 without breaking or splitting in two. The tube must be a high quality 

 of rubber and must be of such composition as to successfully meet the 

 requirements of the stretching test given below ; the tube to be not less 

 than /j inch thick at any point. 



3. The canvas or woven fabric used as wrapping lor the hose to be 

 made of long liber cotton loosely woven, and to weigh not less than 22 

 ounces per yard, and to be from 38 inches to 40 inches wide. The wrap- 

 ping must be frictioned on both sides, and must have in addition a dis- 

 tinct coating or layer of gum between each ply of wrapping. The can- 

 vas wrapping to be applied on the bias. 



4. The cover must be of the same quality of gum as the tube and 

 must not be less than ^ to J^ inch. 



5. Air brake hose to be furnished in 22 inch lengths. Variations ex- 

 ceeding J^ inch in length will not be permitted. Hose must be capped 

 on ends with not less than j 1 ff inch or more than y% inch rubber caps. 

 Caps must be vulcanized on, not pasted or cemented. 



6. The inside diameter of all 1% inch air brake hose must not be 

 less than i 1 ^ inches or more than l-fc inches, except at the ends, which 

 are to be enlarged /j of an inch for a distance of 2 3 / inches, the change 

 from the smaller to the larger to be made tapering. The outside diam- 

 eters must be kept within the folloviog dimensions : The main part of 

 hose 1 Y% inches to 2 inches ; the enlarged ends 2 T V inches to 2y 5 inches. 

 The hose must be finished smooth and regular in size throughout, as 

 stated above. 



7. Each standard length of hose must be branded with the name of 

 mm lfactu-er, year and month when made, serial number, the initials of 

 the railway company, also have a table of raised letters at least ^ inch 

 high to show date of application and removal, thus : 



Each lot of 200 or less hose must bear the manufacturer's serial num- 

 ber commencing at 1 on the first of the year and continuing consecutively 

 till the end of the year. For each lot of 200 or less one extra hose must 

 be furnished free of cost for test. All markings to be full and distinct 

 and made on a thin layer of white or red rubber, vulcanized, and so ap- 

 plied to be removed by cutting with a knife or sharp instrument. 



8. Test hose to be subjected to the following tests : 



Bursting Test. — Test hose must stand for 10 minutes a pressure of 

 500 pounds before bursting. Each hose must stand a shop test of 200 

 pounds. 



Friction Test. — A section I inch long will be taken from any part ot 

 the hose and the friction determined by the force and time required to 

 unwind the hose, the force to be applied at right angles to the line of sepa- 

 ration with a weight of 25 pounds suspended from the separated end, 

 the separation must be uniform and regular and when unwinding the 

 average speed must not exceed 6 inches in 10 minutes. 



Stretching Test.— A one inch section of the rubber tube or inner lining 

 at the lapped or thickest part. Marks 2 inches apart on the test piece ; 

 it will then be stretched till the marks are 10 inches apart and released 

 immediately. The piece will then be remarked as at first and stretched 

 10 inches or 400 per cent, and will remain stretched 10 minutes. It will 

 then be released and the distance measured between the marks 10 min- 

 utes after the release. In no case must test piece show defective rubber 

 or show a permanent set of more than \± of an inch between the 2 inch 

 marks. Small strips taken from the cover or friction will be subjected 

 to the same test. 



9. If the test hose fails to meet the required tests the lot from which 

 it is taken may be rejected without further examination. If the test 

 hose is satisfactory the entire lot will be examined and those complying 

 with the requirements herein set forth will be accepted. All rejected 

 hose will be returned to manufacturers, they paying freight charges both 

 ways. 



RAILWAY COMPANY TESTS. 



The majority of roads purchasing air brake hose on specifi- 

 cations require the tests cited in these M. C. B. specifications. 

 There is also a strong tendency to favor enlargement of the 

 ends of hose. This form adapts it with far less strain to the 

 taper of the nipple and shank of the coupling, and consequent- 

 ly lessens the liability of injury to the tube and overstraining 

 the fabric. . 



