TIRED METALS.

Hokitika Guardian, 17 September 1921, Page 4

TIRED METALS.

(13v fin ICntiincoi') ; It is not gem-lady known that ttiela,ls—iron mul steel in p' r: ii-nlnr—siro subject to fiitigue alter constant, strain, and need an occasional rest, iust ms :in overwork'd human being requires a. holiday every new and then to recuperate from his 1011. . A ease in point occurred recently at Wappiiifi Station, where two lives were lost thiough a runaway good-nan-an coll id i tie; with a stationary motor train. The disaster was caused by ihe drawbar hook coupling- the wagon to the remainder of she goods train breaking n m adieut. leaving the " a you free Id run hack on its course with increasing impetus. Experts who oxamimd the broken pieces of the liook eonld find no flaw of any kind in the metal, and were unanimous in declaring that the metal, brittle through fathom, had collapsed i a'!i excessive shock, oossihly re(eivol during shunting alterations. h was impossible to know betorehaad that the hook needed !i rest, although had fate ordained that the wagon should he held up lor a lew days, the rested metal would in all probability have recovered and the catastrophe have been averted.

A good rest will work womlers with a piece of metal suffering from fatigue and give il a new lease of usefulness. A few years agn a liossrnier steel rail collapsed under the weigh! el a goods train and broke into several pieces. It was found that the rail had done gallant service I'm 22 years and badly needed a rest. Had it been replaced by another rail and lain aside for a le ■ tr.entus. it would have returned to its normal state and done duly for many more yea is. Lord Kelvin was tin- lirsi In make this discovery, and, hv expel intents, prove its inidi. By keeping iron wiser. :u a -late ol constant o.eillattoti lor st.r .. i s nr discovered that they had he ; a _ <:’■!- siderahle amount of their elasticity. A dav's resl was given, when the v.ites weie found to Lave returned in their original condition. Hcpcatcd exp - in.cuts pr.oed this result to hi' an absolute I'.iel " ith regard to wrought iron and steel. Singularly oncegh. alllmugh * 'wrought iron Lai will locovcr HI paw c out in elasticity alter a three we ks’ ri'.pite froin hard work, east iron improve'- in strength il siihjeeli'd to c cnistatit shocks -so in m-1 1 Sl , that expel imculs have demoii-tratc'd tliat eastiron bars will gain as much a.- lift per cent in strength after being td'j Ucl to a succession of shocks. There Lave been instance", in the past of buildings giving way through the' sudden rail.ipse ol a suppcuting i.order owin' to ti c - ltm easing st:nnt Ihe metal lms had to . I t". llappilv, in thi- age ol • mad steel. slit'll cas. s are re m;’Ai! listd nowaday- is ittvtt'"" lr -i '•'> . ilh'ianil a far i.'.reatec than .1 ■ 111 I , ailed up. nto ht" "i• '! Tit • . h 'lee has ta ! edl'* t 'ipe-d lice iiavellin;.; p'd" • I'adwav < outpaces now took-’ r i-.cn! of taking tip the mi!.- on ail tise-.l lin-s .'very lev, years give •he old nietal- a needed f"" and restore their elasticity for another period m years. , „