Rensselaer Republican, Volume 19, Number 24, Rensselaer, Jasper County, 17 February 1887 — How Iron Breaks. [ARTICLE]

How Iron Breaks.

Hundreds of existing railway bridges which carry twenty trains a day with, perfect safety would break down quickly under twenty trains per hour, writes a British civil engineer. ' This fact was forced on mv attention nearly twenty years ago by the fracture of a number of iron girders of ordinary strength under a five-minute train service. Similarity, when in New York last year, I noticed, in the case of some hundreds of girders on the elevated railway, that the alternate thrust and pull on the central diagonals from trains passing every two or three minutes had developed weakness which necessitated the bars being replaced by stronger ones after Very short service. Somewhat the same thing had to be done recently with a bridge over the River Trent, but the train service being small, the life of the bars was measured by years instead of months. If ships were always among great i waves, the number going to the bottom would be largely increased. It appears natural enough to every one that a piece, even of the toughest wire, should be quickly broken if bent backward and forward to a sharp angle; but perhaps only to locomotive anct marine engineers does it appear equally natural that the same result would follow in time if the bending were so small as to be qnite imperceptible to the eye. A locomotive crank 'xle bends but one-eighty-fourth inch, and a straight driving axle a still smaller amount under the heaviest bending stresses to which they are subject, and yet their life is limited. During the year 1883 one iron axle in fifty broke in running, and one in fifteen was renewed in consequence of defects. Taking iron and steel axles together, the number then in use on the railways of the United Kingdom was 14.848, and of these 911 required renewal during the year. Similarly during the past three years, no less than 228 ocean steamers were disabled by broken shafts, the average safe life of which is Said to be about three or four years. Experience lias proven that-a Tery moderate stress, alternating from tension to compression, if repeated about 100,000,000 times, will cause fracture assurely as a bending to an angle repeated only ten times. It is not worth while to think too much about doing good. Doing the best we know, minute by minute and hour by hour, we insensibly grow to goodness as fruit grows to ripeness.