August 1, 1917.] 



THE INDIA RUBBER WORLD 



645 



Bowers' Specific Gravity Tables. 



THE determination of the weight of rubber articles is a mat- 

 ter of calculation well known to every rubber mill super- 

 intendent. It is upon these figures that factory costs are 

 based and are therefore fundamental factors in the manufacture 

 of mechanical rubber goods. According to the usual method 

 the respective volumes of the articles to be produced are com- 

 puted. Then the weight is determined for each article accord- 

 ing to the specilic gravity of the particular stock to be used in 

 the goods. These determinations require a high order of 

 technical as well as practical knowledge in the calculation of 

 dependable figures. Moreover, the amount of time consumed 

 is considerable, and human fallibility ever supplies the possi- 

 bility of costly error in making complex computations. 



A set of tables has been carefully designed to simplify the 

 necessary calculations in determining the weights in ounces or 

 pounds of rubber solids of regular dimensions, including disks, 

 cylinders, square strips and sheets. As a short-cut method these 

 tables will be of decided value to superintendents of rubber 

 mills and by their use intelligent salesmen will be able promptly 

 to answer customers' questions regarding the weight of a desired 

 article. 



The complete table with instructions, and several concrete 

 examples of the method to be observed in computing the weights 

 of disks and kindred articles are here shown. The tables for 

 cylinders, square strips and sheets will be published in subse- 

 quent issues. 



Various bases are used to reduce the number of decimals and 

 still retain a true proportion throughout the table. 



The stated base of the disk table is 62.40 pounds per cubic 

 foot. The unit used is .00OGO1731 ounce, equals a disk 1/64 in. 

 diameter 1/64 in. thick — Specific gravity 1.00. 



.000001731 ounce X (12 X 64)" 



■ ■ = 62.40 pounds. 



.7853982 X 16 



Weight of one cubic foot of water — 39.1° F. (maximum dens- 

 ity) — 62.425 pounds. (Kent, 1916 edition, page 27.) 



To convert disk table into weights according to above stand- ■ 

 ard, multiply by 1.00044- or divide by 0.99958-f-. 



The disk table is constructed to read from 1/64 in diameter 

 to 48 in. diameter (and above) as follows: 



1/6-4 in. to 3 in. by 64ths in ounces 



1/32 in. to 6 in. by 32nds in ounces 



1/16 in. to 12 in. by 16ths in pounds 



y^ in. to 2*1 in. by 8tbs in pounds 



% in. to 48 in. by 4ths in pounds 



The volumes of two similar solids are to each other as the 

 crijes ot their linear dimensions. (Kent, 1916 Edition, Page 62.) 



1 1/64 in. 



1/32 in. 



.007313475 ounce 



4 



.029253900 ounce 

 4 



4 1/16 in. = .117015600 ounce = .007313475 pound 

 2 ■ 4 



8 ',3 in. 



.029253900 pound 

 4 



16'i in. = .117015600 pound 



The scope of the disk table is partly shown in the following ex- 

 amples that are intended to demonstrate the method employed 

 when using the table which will be found on another page. The 

 samples selected for computation include gaskets of two different 

 sizes, a square flange ring, a valve, a washer, a liall valve and 

 corks and plugs. 



SAMPLE. 



Gasket — 15 ^ in. diameter, 41 in. hole, ^g in. thick. Specific Gravity 1.62. 



C0MPUT.\T10N 



4514 in. = 11 5/16 in. 



41 in. = lO'i in. 



— .056709291 pound 



= .046556976 



45 ;4 in. .\ 41 in. x 1/64 in. 



.010152315 

 16 



60913890 

 10152315 



.162437040 



1.299496320 

 1.62 



2598992640 

 7796977920 

 1299496320 



2.10518403840 pounds, or 210'/^ 

 pounds per 100. 



SAMPLE. 



Gasket — 23'8 i.-i. diameter, 20 in. hole, 3/il in. thick. Specific Gravity 1.68. 



CoMPUT.XTION. 



23's in. = It 9/16 in. ' = .059243475 pound 



= .044313600 



20 in. = 10 in. 



23 "-I in. X 20 in. x i/M in. = 



.014929875 

 4 



.059719500 

 6 



.358317000 

 1.68 



2866536 

 2149902 

 358317 



.60197236 pound, or 60 



pounds per 100. 



SAMPLE. 



Square Fiance Ring — 1 1 ;.j in. diameter, 11 in. hole. '4 in. square flange. 

 Specific Gravity 1.7l. 



.136397260.S0 pound, or 13H 



pounds per 100. 



For round flange rings. — The use of 80 per cent of the weight 



of its circumscribing square flange ring will be fnund practical. 



SAMPLE, 

 Valve — 5?;; in. iliameter. ■« in. thick, 1]/% in. hole. Specific Gravity 1.67. 

 Computation. 



5-i-4 in. 

 11/16 in. 



40/64 in. 



.014651184 pound 

 .000209451 



.014441733 ' 

 40 



.577669320 

 1.67 



404368524 

 346601592 

 57766932 



.9647077644 pound, or 96 "/S 



pounds per 100. 



