tn 



M \rillNT. I >K. \\MN, 





rings is shou ii \ front elevation o| the locking arrange- 



(6). A sectiunul plan of 

 one of the nuts for the junk n -\n.\\n a 



: draw th- OH -t thi- : :\\ a ]'lan. 



one-third of which. i ( .-niplrtr. ..nc tliird t.. 



tin- junk riii-: removed, and the remaining third to he a hori/ontal 

 section through het \\een tlie packing rings. Th- |) and (e) 



need not be drawn separately > a foot. 



Mi in his 



i.'inr. ring/ gives tlie following rule 

 designing marine engine pistons : 



D = diameter of piston in inches. 

 p =cflfective pressure in 11 j>cr square inch. 



' 



Thickness of front of piston near hoss . . 0-2 x x. 



rim . . o-I7 x.r. 



hack (.f piston .... 0-18 

 bass around rod . 



flange inside packing ring . . ( 



at edge .... 0-25 y r. 



junk ring at edge . . . ( 



in-idc packing ring . 21 x a-, 



at liolt-h-.lfs . . ' . ' 



metal around piston edge . , 



nreadth of packing ring .... 0-63 x x. 



ii of j.iston at centre . . . . T4 x x. 



I.. -I], of junk ring on piston .... ol."5x;r. 



Space between piston body and packing ring 0-3 x r. 



I>iameter of junk-ring bolt* ... <>! > s+ -2." inch, 



i of junk-ring bolts 10 diameters. 



,l>erof webs in j.istc.n 



Thickness .. . . o-18x*. 



61: Design i ri.\f<>n. Calculate 



by Seaton's nil. - tin- dimensions for a marine engine piston 40 

 inches in diameter, and subjected to a; pressure of :'', lh>. 



per square inch. Then mak- -;ir\ \\<rking drawings 



piston to a scale of, say, 8 inches to a f. 



Note. Take the dimensions got by calculation to the nearest 

 MCthofaninch. 



