THE INDIA RUBBER WORLD 



ber of a given composition and hardness will have a higher, and 

 a piece at a higher temperature, a lower tensile strength. 



A tensile test will vary as much as 25 per cent, according to 

 the type of machine upon which the test is made. The faster the 

 pull, the greater will be the tensile strength as indicated by the 

 machine. To insure an\ tiling like accurate results, a motor- 

 driven test machine should be used. 



Furthermore, the tensile test will vary according to the amount 

 the piece has been vulcanized. A compound that has been vul- 

 canized until it is very hard will have a much higher tensile 

 strength than the same compound vulcanized less. A jar with 

 high tensile strength is usually too hard and brittle to give sat- 

 isfactory service. 



The results of elongation tests will vary according to the shape 

 of the test piece, its temperature and the amount it has been 

 vulcanized. The slower the speed of the test machine, and the 

 higher the temperature, the greater will be the elongation. The 

 harder the compound is vulcanized the smaller will be the elon- 

 gation. The distance betw-een the jaws of the test machine is 

 usually taken as the basis of elongation tests. If the test piece 

 is of uniform cross section, the percentage of elongation will be 

 lower than if the test piece is of the usual shape, that is, small at 

 the center and large at the ends. There is also tlie slippage in the 

 jaws to contend with if the distance between the jaws is taken 

 as the basis. To insure accurate elongation tests, the basis should 

 really be the distance between two given points on a piece of 

 uniform cross section. 



The electrical test on a hard rubber jar is usually made by 

 placing it on a mandrel inside a frame, the mandrel and frame 

 being respectively the positive and negative poles. The results 

 here will vary according to whether the current used is alter- 

 nating or direct, the length of time during which the current is 

 applied, and, in the case of alternating current, its frequency. 

 RIGID SPECIFIC.\TIO\S REQUIRED. 



When battery manufacturers adopt specifications for hard 

 rubber goods, there is an inclination to make them too rigid. 

 Jars may be rejected that would really be more serviceable than 

 many that might pass the test. A certain specification might call 

 for a tensile strength of 3,600 pounds and an elongation of 3 

 per cent. A jar might have a much larger percentage of rubber 

 than would be necessary to meet these specifications if it were 

 cured to the degree of hardness necessary to meet them, or 

 might happen to be slightly under-vulcanized so that it would 

 have a tensile strength of only 2,500 pounds or an elongation of 

 as much as 10 per cent. Such a jar, although rejected, would 

 be more serviceable than a jar that would just meet the specifi- 

 cations. 



It will be well to add a word of caution regarding the so-called 

 flexible jars. Any rubber manufacturer can furnish a hard rub- 

 ber jar that is flexible when it is new by simply making it from 

 the compounds used in the manufacture of a rigid jar, but vul- 

 canizing it for a shorter length of time or at a lower tempera- 

 ture. Such jars were put into service as many as seven or eight 

 years ago, but their use was discontinued. They were flexible, 

 and almost unbreakable when new, but were more easily affected 

 by the acid than the ordinary rigid jar, and hardened up rapidly 

 with age and from the effect of the acid, to the point where they 

 were more brittle than if they had been vulcanized to the usual 

 degree of liardness in the first place. 



With flexible jars, therefore, the problem is to furnish a jar 

 low enough in price to be used in a commercial wav that will 

 not become brittle too rapidly with age, and that will not 

 harden so as to make it unserviceable. Whether any given jar 

 meets these requirements is something that can be determined 

 only by actual service for the ordinary life of a battery. 



Hard rubber parts as they are now used in automobiles vary 

 greatly in designs and sizes, and it is necessary that the hard 

 rubber manufacturer have an enormous investment in special 

 equipment. Costs could be materially reduced if these parts were 

 standardized. There is already considerable standardization of 

 hard rubber parts as used by railroads, and while in automobile 

 construction standardization could not be carried to the same 

 point, there is no reason why it could not be carried further than 

 at the present time. 



DISCUSSION. 



R. J. Nightingale, sales manager, Willard Storage Battery Co., 

 Cleveland, Ohio, then said : "We use the test on hard rubber stor- 

 age battery jars exclusively, not so much to test the (luality of the 

 jar as to find the defects in workmanship. It has been our ex- 

 perience that the greater percentage of leaky jars was caused 

 by breakage in transit to us from the jar manufacturers or fail- 

 ure of the jar where the workman had rolled the seams. The 

 high voltage test does find defective seams and breaks, as well 

 as thin spots in the walls of the jars. 



WIIV WOUD SEl'.\R.\TOKS .\RE USED. 

 •We have been told by the speaker that, because .if their cost 

 storage battery manufacturers do not use rubber separators' 

 1 tiis IS not a fact. Wood separators are used in preference to 

 wooden and rubber sheets, or all rubber separators, because the 

 cell IS ot higher internal resistance with the rubber sheet or rub- 

 Der separators. If we were to construct a starting battery with 

 wooden separators and rubber sheets, it would be necessary for 

 the car manufacturer, in order to maintain the same voltage 

 characteristics at the lower temperatures, to purchase a batterv 

 ot 50 per cent greater capacity than is the one he now has in 

 which only wooden separators are used." 



S. A. E. ELECTRICAX VEHICLE DIVISION CONSIDERS BATTERY-JAR 

 DIMENSIONS. 



A meeting of the electric vehicle division was held on Feb- 

 ruary 25 in the offices of the Society of Automobile Engineers 

 29 West Thirty-ninth street, \ew York City. Aside from mem- 

 bers of the division and the standards committee staff, there 

 were present representatives of five of the leading storage bat- 

 tery manufacturers. 



The chief work of the meeting was in regard tu dimensions 

 of storage battery jars, as a preliminary to standardizing dimen- 

 sions of trays to facilitate the interchange of batteries. 



The work of the meeting was tentative, and has not been 

 formally approved by the division. The suggested dimensions 

 were as follows: 



Heights, high-rib jars 135.^ inches. 



low-rib jars 12 7/16 inches. 



^^'i'lt'i 6'4 inches. 



1 hickness of walls i,g inch. 



No conclusion was reached as to the length, which is variable, 

 depending upon the number and thickness of plates. This prob- 

 lem was discussed at length, and plans were formulated for a 

 tabulation of present practice to be submitted in an attempt to 

 arrive at a reasonable list of standard lengths. This tabulation 

 has now been prepared by a member of the division. It shows 

 forty-five variations in the length between 2 and 8'/i inches. It 

 is suggested that the list be reduced to 27 lengths with 234-inch 

 sediment space, and to 15 lengths with 1^-inch sediment space. 



The division is thus making real progress toward a standard 

 which promises to be of great value to the electric vehicle 

 industry. 



Another matter before the division is a revision of the iiresent 

 standards for charging receptacles consisting in a lengthening 

 of the sleeve and insulating members. 



S. A. E. ADOPTS STANDARDS RELATING TO RUBBER. 



.■\t a meeting of the Society of Automobile Engineers held in 

 New York City, January 5-6, recommendations for new and re- 

 vised standards were made. Those on insulated wire and cable, 

 rubber hose and clamps, industrial truck tires and solid tire 

 diameters were published in detail in The Indi.\ Rubber World, 

 February 1, 1916. These recommendations have now been 

 adopted in their entirety by the letter ballot of the voting mem- 

 bers, which was closed on March 6. 



A PILLOW VENTILATOR. 



A pillow full of light, fresh feathers affords an 

 comfortable head-rest, but the feathers are apt to 

 become heavy and matted owing to lack of ventila- 

 tion. A device designed to afford the necessary inlet 

 of air consists of a small spool-like ventilator made 

 of rubber, with holes at each end. In use several of 

 these are sewed in each end of the pillow ticking. 

 [The H. O. Canfield Co.. Bridgeport. Connecticut.] 



Replete with information for rubber manufacturers. — Mr. 

 Pearson's "Crude Rubber and Compounding Ingredients." 



