

THE INDIA RUBBER WORLD 



I.I i iv 1, 1915. 



PUBLICATIONS OF THE SOCIETY OF AUTOMO- 

 BILE ENGINEERS. 



T5 i i iv of Automobile Engineers, or the S \ I .. as 

 it i:- generally called, publishes in pamphlet form the 

 - read, and the recommendations of it- standards com- 



mittees submitted at it- semi-annual meetings. At the last meet- 

 ing, held June 14-17. nearly a score of pamphlets were issued. 

 The) included printed reports of the various division standards 

 committees on the following subjects: Iron and steel, springs. 

 electric vehicles, electric equipment and carbureter fittings. The 

 papers read at that time, and also published in pamphlet form, 

 included "The Size and Inflation of Pneumatic Tires. v 

 by P. W. Litchfield, factory manager of the Goodyear 

 Tire & Rubber Co.. of Akron; "Pressed Steel Wheels 

 Eoi Pleasure Cars." by Orrel A. Parker; "Farm 

 Tractors and Their Motors," by Philip S. Rose; "Au- 

 tomobile Clutches," by F. YV. Herst ; "Automobih 

 Lubrication," by C. \V. Stratford; "Spiral Type Bevel 

 Gears for Automobile Drives." by A. L. Stewart: 

 "Aeroplane Engines," by Neil Mac Coull, Jr.: "Alum- 

 inum Alloy Pistons," by Eugene Gruenewald ; "Spring 

 Design," by C. H. Gleason ; "Road Tractors." by 

 Frank H. Trego, and "Rational Method of Determin- 

 ing Mileage of Electric Vehicles." by T. H. Schoepf. 

 The paper by Mr. Litchfield on the "Size and In- 

 flation of Pneumatic Tires" is of interest to tire manufacturer-, 

 as well as to automobile manufacturers and users of motor 

 Mr. Litchfield's theory is that a pneumatic tire is prac- 

 tical!} incapable of supporting compressive stress so that any 



pressure in the tire, and consequently the flattening of the tire 

 on the ground varies with the load, except in so much as the 

 element of air pressure 

 intervenes to prevent this 

 flattening. It is there- 

 fore possible to regulate 

 the distortion 

 or flattening 

 ot a tire by 

 \ arying t h e 

 a i r pressure 

 and the load. 



Regardless of the size of a tire, for a given weight 

 pneumatic tires cover approximately the same surface 

 of contact on the ground, but the smaller the tire 

 the greater the distortion it must undergo to cover 

 this given surface. A smaller tire will therefore have 

 to distort itself more than a larger one in order 

 to support a given weight. The greater the distor- 

 tion the greater the wear on the tire. When the 

 owner of a car finds that his tires are flattening too much, and 

 therefore suffering extraordinary wear, he naturally will en- 

 deavor to prevent this by pumping more air into the tires to 

 make them harder. This means a reduction of the resiliency 

 of the tires, hard riding and the consequent undue wear of the 

 machine and its mechanism. But tires must not be too big, for 



ivel) large tires not only mean unnecessary cost, but 



father increase fuel consumption and w-ear and tear on the car. 



Mr. Litchfield treats at length the relation between tire wear 



and weight carried, tire dimensions and pressure of inflation. 



He submits general approximate laws of tire wear 



and a logical schedule showing the proper relation 



between air pressure, tire size and weight carried. 



Fully 33 per cent, of American cars are turned out 

 by their manufacturers equipped with tires doomed to 

 be overloaded This is a mistake that costs car own- 

 ers millions each vear. 



load which is supported bv the tire must be carried by a variation 

 of the tension of the side walls of the pneumatic. The flattening 

 of the tire on the ground relieves the tension on the walls of 

 the flattened portion, but by increasing the air pressure in the 

 other parts of the tire, this flattening increases the tension on 

 the walls of the rest of the tire. The area of contact of a tire 

 on the ground equal to the load multiplied by the air 



UNDERWRITERS' LABORATORIES 1915 BULLETIN. 



The Underwriters' Laboratories, Inc., whose work 

 in connection with the testing of materials and ap- 

 pliances used in the prevention of suppression of 

 tires is well known to all manufacturers engaged in 

 this line of production, has just issued its 1915 bulle- 

 tin. The work of this organization is carried on 

 under the general direction of the National Board 

 of Fire Underwriters, its principal plant being located 

 at Chicago, where it occupies a three-story and base- 

 ment building containing about 45,000 sq. ft. of floor space, and 

 valued, with equipment, at approximately $200,000. It maintains a 

 branch plant in Xew York City for the examination and testing of 

 electrical devices, besides offices in the principal large cities of 

 the United States, in Canada and in England. The pamphlet is 

 illustrated throughout with reproductions of photographs of the 

 Chicago plant .tv,i\ the equipment of it- various departments. 



