THE INDIA RUBBER WORLD 



[October 1, 1920. 



long hampered their activities and are once more on a properly 

 functioning basis, is a matter that time only can decide. It is 

 fair to presume, however, that, in the meantime, the business of 

 truckportation will have become a recognized, standardized in- 

 stitution, fulfilling a field of usefulness from which it will be 

 difficult to dislodge it. 



THE AMERICAN RAILWAY EXPRESS COMPANY IN 

 TRUCKPORTATION 



The status of truckportation with respect to the .\mericaii 

 Railway E.xprcss is a different matter. This company, by reason 

 of the forced consolidation of all the express companies of the 

 country into its one organization in 1918, operates on every rail- 

 road in the country. It handles a million shipments a day. It 

 has a working force of 135,000 people. It is equipped to do a big 

 business, and it is going to do it, truckportation or no. It has 

 fleets upon fleets of motor trucks of its own operation at 

 terminals for delivery of goods to its express cars. 



Competing with itself, and in order to try out the possibilities 

 of all motor express transportation, the .\merican Railway Ex- 

 press Company has been experimenting with a line of its own 

 between New York and Passaic and Paterson, New Jersey, re- 

 spectively 16 and 22 miles away. A fleet of 10 new 3>2-'o" 

 trucks with "Van" bodies was assigned to this service; and, 

 when operations have been conducted for a sufficiently long 

 period this organization will know something about truck- 

 poi^ation, its costs and its usefulness. 



ELASTIC CORD FOR AIRPLANE SHOCK ABSORBERS 



ANVO.NE who has experienced the thrill of landing in an air- 

 plane recalls the swift upward rush of the earth to meet the 

 craft and the disproportionately slight shock of the actual con- 

 tact of earth and plane. One invariably feels braced for a more 



racking shock 



and the absence 

 of jolting is a 

 matter of won- 

 der. Almost the 

 first conclusion 

 reached about 

 the science of 

 aviation was that 

 the safety of an 

 aviator depends 

 in great measure 

 on the landing. 

 This fact was 

 unscientifi c a 1 1 y 

 stated long ago 

 by the small boy 

 who observed 

 that falling did 

 not hurt him but 

 it hurt when he 

 stopped, and in 

 order that Un- 

 cle Sam's avia- 

 tors shall not be 

 hurt when they 

 "stop," much 

 careful study has 



been given by manufacturers of aircraft to the problem of lessen- 

 ing the shock of landing. The result has been the rubber shock 

 absorbers with which the landing wheels of all Government air- 

 planes are now fitted. Ordinary automobile springs and shock 

 absorbers were out of the question because of their weight, and 

 an ingenious contrivance utili/int; nibber cord was used instead. 



It is due to the remarkable <|uality of India rubber that spe- 

 cially constructed elastic cords are successful in heavy airplane 

 construction to secure the cushioning effect when landing. The 

 wheel supports, at both front and rear of the machine, are pro- 

 vided with steel tubes that slide within each other. The rubber 

 cords supply the necessary tension to the sliding supports, so that 

 when the machine is on the ground the weight is cushioned 

 by the tension of the rubber cords, and when flying they are 

 relaxed. Sixteen of these cords to a machine are generally used, 

 but that depends, however, on the weight and style of the air- 

 plane. 



Great care is given to the quality of the rubber cords used in 

 shock absorbers on all government planes. The rubber used 

 is a compound containing at least 90 per cent by weight of the 

 best quality wild or plantation rubber. This gives a very 

 "lively" compound, which is also free from ingredients known 

 as "oil sub.stitute." The organic acetone extract does not exceed 

 S'/i per cent of the weight of the rubber and the free sulphur 

 content does not exceed one-half per cent of the total compound. 

 The weight of the non-volatile ash does not exceed 5 per cent 

 of the compound. 



The elastic cord varies in width according to its use, but the 

 appearance and construction are the same for all sizes. It is 

 composed of multiple strands of rubber tightly encased within 

 two layers of cotton braid. The rubber strands are square, of 

 equal size (0.05 — 0.035-inch), and are thoroughly treated with 

 soapstone or talc to prevent them from adhering to each other 

 Ml the finished cord. The number of strands varies according 

 10 the diameter specified, which always means the over-all diam- 

 eter of the braid with rubber strands enclosed. A tolerance of 

 plus J^:(-inch is allowed in the over-all diameter but there must 

 be no minus variation. The double covering of braid is very 

 strong, each thread of it having a tensile strength of from 4 to 

 5]4 pounds by test. Both the inner and outer braids are wrapped 



over and under 

 with three or 

 four threads. 



In consequence 

 of the care used 

 in material and 

 manufacture an 

 elastic cord of 

 great durability 

 and tensile 

 strength is pro- 

 duced, which is 

 well fitted to en- 

 dure the strain of 

 use in airplane 

 shock absorbers. 

 Two inches of 

 the rubber cord 

 used by the Gov- 

 e rn m e n t will 

 stretch to 16 

 inches before 

 breaking, over 

 700 per cent ex- 

 tension. After 

 aging in dry 

 heat for seven 

 days at a tem- 

 perature of 160 degrees F., a two-inch specimen will still stretch 

 to 9 inches, an extension of 350 per cent. 



In order to test its fitness a 6-inch sample of cord is stretched 

 to double its normal length and the weight of the load measured. 

 To give this 100 per cent extension in a cord of J/^-inch diameter 

 a load of from 145 to 180 pounds should be required. If the 



Airplane Kquu'pf.d with Rubber Shock Aii.^okuKu.^ 



