12 BULLETIN 831, U. S. DEPARTMENT OF AGRICULTURE. 



a large scale to quickly discharge large volumes of water. The cost 

 of installation and operation is a large factor in discouraging their 

 use. They are useful as a means of entirely emptying a reservoir in 

 case of accident or to scour out silt when they are placed low for 

 these purposes, and they should be provided only as an additional 

 safeguard and not when the passage of flood water in excess of the 

 safe flow is required. Examples of outlet gates and the elaborate 

 towers necessary for their installation are shown in figures 1, 2, and 3, 

 Plate VIII. 



TAINTOR OR RADIAL GATES. 



Taintor or radial gates are usually set between piers as buttresses 

 and on the crest of a spillway to provide additional storage. They 

 can be operated with the expenditure of less power and time than the 

 other types of gates. They have cylindrical surfaces and are so 

 connected as to revolve on an axle usually connected to the curved 

 face by means of arms or braces, the axle being set parallel to the 

 center line of the crest on which the gate is mounted. 



Two examples of radial gates are shown in figures 1 and 2, Plate IX. 

 The curved or cylindrical surface may be of wood, steel, or reinforced 

 concrete. Where radial gates are mounted to pass drift over the crest 

 of the spillway in large openings and there is danger of the axle 

 catching debris and clogging the passage, the long axle is eliminated 

 and in its place bearing tubes are placed in the sides of the piers, and 

 into these pins are set to form pivots or hinges. The radial arms of 

 the gates are connected to these pins, so that the only forces to be- 

 overcome to lift them are the weight of the gates and the friction on 

 the pins or pivots and on the faces of the buttresses or piers, because 

 the pressure has been, of course, transmitted to a single point instead 

 of being distributed over an extended bearing face, as in the case of 

 the ordinary sliding gate. 



The main objection to the use of the radial gate is that it lacks 

 automatic control, unless its specifications of installation more prop- 

 erly conform to the class following, and the fact that it is seldom 

 watertight where it comes in contact with the crest of the spillway 

 or the sides of the opening. 



TILTING OR COUNTERWEIGHTED GATES. 



Tilting or counterweighted gates are among the number of in- 

 genious types of automatic gates which have been designed and in- 

 stalled on spillway structures in this country and in Europe where 

 it is necessary or desirable to maintain a relatively constant head 

 under fluctuations, floods, or changeable use of water. Three types 

 of these are shown in figures 1 and 2, Plate X, and in text-figure 3. 



They are usually patented, vary in form of construction and in 

 method of operation, and are satisfactory only to 'a certain extent. 



