CRANES. A variety of improved and novel forms are illustrated.
Swtxotso CRANE:S.-Fig. 1 represents a 30-ton swinging crane, built by Messrs. Sellers & Co., Philadelphia—the peculiar feature of the construction being that anything suspended from the hook can be brought quite close to the center, there being no brace to interfere.
Fig. 2 represents a 40-ton wharf-crane, of English construction, designed chiefly for lifting marine engines and boilers in or out of ships. The engine-cylinders, the position of which is shown on Fig. 3, are 7 in. bore and 10 in, stroke. When the crank-shaft rnns at 200 revolutions per min., loads up to 7 tons can be raised at a speed of 13 ft. per min., and heavier loads at 4 ft. per min. The brake has frill control of the heaviest loads, and can be worked either by hand lever or screw. The latter enables the attendant to keep the load suspended for any of time, without interfering with the engines working for clewing. The slowing is effected by a train of gearing from the crank-shaft, and a pinion on a vertical shaft working into the circular rack fixed on the foundation.
The Great Steel Derrick at the Brooklyn (N. Y.) Navy-Yard is carried on a pontoon 60 ft. wide by 63 ft. long. The tower is built of steel I-beams and rods, and contains 63 tons of metal.
The king post is 65 ft. high ; 14 ft. 7 in. from its base it passes through the crown casting. Just above the crown casting the front and back booms are connected to it. The back boom is a box-girder made up of plates and angle irons, and is 2 ft. sq., weighing tons. The two members of the front boom are 16i in. 1-heams, spaced far enough apart for the sheaves and tackle to work between. The object of the back boom is simply to afford a point of attach ment with advantageous leverage for the hack-stays. The upper surface of the members of the main boom has planed upon it sliding-ways for the carriage which supports the sheaves. This carriage hears two lifting-tackles. One is a gant line or single fall, for light work : the other is a 16-fold purchase, for heavy lifting. The hoisting-engine has two cylinders, 8 by 14 in., and by a system of warm gearing and clutches actuates any of the different windlass
drums required. The hoisting-gear alone weighs 1:14. tons. The lower main hoisting-block with its H sheaves, each 26 in. in diameter, and working on a 2.4-in. steel pin, rind receiving 1i-in. steel-wire rope, 2.000 lbs. The load-limit is as follows ; with the lmek-stay secured to the after-edge of the pontoon. 75 tons can be lifted : with the sliding-earriage at two thirds the length of the, boom and at full-boom length, 50 tons can l' lifted : with back-stay brought into t ha ball-carriages at the base of the tower, 30 tons eon be lifted at two thirds boons length, and :to tons at full-boom length.
OvEit t Ca N Pig. 4 represents it 1504 on steam t ravel ing-era lie. erect ed at Woolwich Arsenal, England,. It will Iift 150 tons on a Nem of 65 ft. from center to center of the rails. The crab consists of side-frames of steel plates and angles, running upon five double-flanged wheels on each side, securely connected together, and carrying the steam-engine and gearing for all the movements, with a steam-boiler, coal-bunker, and feed-water tank, the whole cov ered by a corrugated iron house with angle-iron framing. The cylinders are 10 in. diameter by 10 in. stroke. The speeds vided are as follows: floistuvr, 2 ft. per min. for 150 tons, and ft. and 6 ft. per min. for lighter loads; cross-traverse, 15 ft. per min.; longitudinal traverse, 15 ft. per min. for full load, and 30 ft. per min. for lighter loads. The maximum range of lift is from 3 ft. to 24 ft. from the ground to the bottom of the hook, with the top of the gantry rails 26 ft. above ground, giving a lift of 21 ft. The maximum cross-traverse is 54 ft.
A Sovel Form of Om•erhead Crane, of Belgian construction, is illustrated in plan and side eleva tion in Fig. 5. It is designed for situations where both light and heavy loads have to he lifted ; as, for instance, in foundries. where much time is often lost in hoist ing light molding - boxes with slow gear.