April, 1910 NEW SHEAR LEGS AT UNION IRON WORKS CO. SAN FRANCISCO. MONG the numerous structures that suffered damage by the earth- quake and fire which visited San Francis-. coin April, 1906, leaving behind a trail of wreck and ruin having no parallel in modern times, were the heavy shear legs at the plant of the Union Iron Works Co. at Portrero, San Francisco. The legs were thrown from their foundations and so badly damaged that it was decided to entire; ly renew the structure from the foun-. dations up. By courtesy of the Union Iron Works Co., we are enabled to present herewith a halftone and line engravy- ings of the new legs, which were de- signed by Hugo P. Frear, superinten- dent of hull construction for the com: pany, and erected under his supervi- sion. Since their completion they have been subjected to a number of full load capacity tests and have prov- en entirely satisfactory. The total lifting capacity is 100 tons, by means of two hoists, each electric- ally driven. The main hoist has a capacity of 80 tons and the auxili- ary hoist 20 tons. The hoisting speed, with full load, is 4 ft. per minute and the racking, or horizontal, travel speed is 0.23 ft. per minute. It will be seen that these speeds are exceedingly moderate compared with other recent examples of shear legs of similar capacity. The extreme over- hang of main hoist is 44 ft. from the center line of front piers and of the auxiliary hoist 53 ft, and from the face of the fender piles 37 ft. and 46 ft. respectively. The general arrangement and con- struction of the shear legs are very clearly shown in the illustrations. A novel feature of the design is the stepping of the front legs on steel piers at a height of about 46 ft. above the mean water line and 32 ft. 6 in. above the wharf level. This construction allows of a large over- hang without excessive length, but it _ will be readily observed that the chief advantage lies in the ability to reach well beyond the midship line of a large ship without resorting to crotch- ing out from the wharf, as is frequent ly the case with high-sided ships where the legs are stepped directly at the wharf level. The halftone shows the legs placing a spar in steamship Mexican immediately after launching, | with a free board of about 40 ft. The foundation consists of three cylindrical steel sheathed piers, each 10 ft. diameter. Each front pier rests on twenty 80-ft. fir piles and "'TAE Marine. REVIEW cop ee oe me SELL hee ee ek hot oe ee Be =F, oe Aap ek eee = Se ley ae RS eT a Inert =et-eT a= eer Rita tae Sears eae Te 4 La a --a7 Sree ah et Front ELevATion OF SHEAR Lecs For UNION Iron Works Co. 149