LOCK GATES AND VALVES. 197 



cally in another, the general design being similar. Under these conditions it is 

 believed to be best to use equal arms and to provide gearing powerful enough to permit 

 one man to control the opening or closing at any point without unusual effort. 



In one example, on the Kentucky River, where the wicket was 4! feet wide and 

 6 feet high, with a head of 15^ feet (measured from the bottom of the wicket), the pitch 

 diameter of the large gear-wheels was 39 inches and of the pinions 7^4 inches. The 

 ratio of the power at the end of the operating lever to the turning force delivered at 

 the circumference of the wicket shaft was i to 600, friction being neglected. Under the 

 full head one man could operate it, but with difficulty, but with the head reduced to 

 about 13 feet the operation was easy. On other locks with similar conditions, but 

 less powerful machinery, two or more men were needed for the maneuver, and where 

 additional help was not available, serious injury sometimes resulted to the operator 

 because of the wicket getting beyond his control. It is much better therefore to have 

 an excess of power than to have a deficiency. 



The fit of the gear-wheels on their arbors and on the shafts should not be a 

 "machine-shop," but should be a little looser, or it will be very difficult to get them 

 apart for repairs. 



Gridiron Valve. Another style of gate valve is the gridiron or sliding valve, in 

 which the valve is pierced with rectangular openings. It is usually worked by a rack 

 and worm, but it is an undesirable type, as it is slow in operation and small in area of 

 discharge, although permitting but little leakage. 



Drum Valve. The drum valve, known in France as the Fontaines valve from 

 the name of its inventor, consists of a cylindrical ring 4 to 6 feet in diameter, and 

 about 1 8 inches high, sliding up and down in a second ring above, the latter having a 

 closed and water-tight cover. The culvert, which has a circular orifice, opens under 

 the ring, and the latter rests when closed upon the edges of this opening, cutting off 

 the water. To permit the passage of the water the ring is pulled up by machinery on 

 the wall and slides up in the second ring, thus uncovering the culvert. This is the easiest 

 valve to operate, as the water-pressure balances itself on all sides, but it is costly and 

 requires large openings in the masonry, so that the water can have a free approach all 

 around. Examples of the type are to be found in America on the Muskingum, the 

 Kentucky, and the Big Sandy rivers. 



This type can also be arranged with little extra expense so that the water-pressure 

 will operate it, and some ingenious patents have been devised to accomplish this end. 



The height to which the valve should lift should be not less than one-quarter of 

 the diameter of the culvert, in order to secure the full capacity of the latter. 



An improvement on the ordinary type of drum valve would be to put the closed 

 cylinder on the inside and the open sliding cylinder on the outside, making the former 

 stationary, as shown on the accompanying drawing. This would simplify the con- 

 struction, and would do away with the necessity of water-tight pipes for the 

 valve-rod. 



