walls of the test flume. This simple attachment 

 was possible because of the limited weight of 

 the debris screen and appurtenances, or struc- 

 ture, and the limited water pressure (loading 

 value*) against it. Vertical suspenders of 9.6- 

 mm chain were clamped to the main cables at 

 2.1-m intervals. The suspenders carried the 

 longitudinal stiffening members used as a base 

 for mounting the track, the carriers, and the 

 cable-formed screen. 



The velocity of the water passing through 

 the screen directly affected the loading value — 

 with an increase in water velocity, the loading 

 value increased. The effect of increased load- 

 ing values on a traveling debris screen is not 

 as important as that on a traveling fish screen, 

 as the former has a great amount of open area, 

 resulting in reduced drag. 



Stiffening members and cables Longitu- 

 dinal stiffening members used as a base for 

 mounting the endless track, the carriers, and 

 the cable-formed screen consisted of a series 

 of 1.2-m long brackets spaced at 2.1-m intervals 

 along the length of the structure. 



The longitudinal stiffening members were 

 given vertical support at 2.1-m vertical inter- 

 vals by suspenders of 9.6-mm chains clamped 

 to the two main cables. Turnbuckles in the 

 suspender chains provided for adjustment of 

 the vertical alignment of the track, walkway, 

 and the longitudinal stiffening members. Water 

 forces against the screen were so minimal that 

 counter-resistance was not required. 



Track design and support The endless 



track, 43 m in circumference (Figure 3), was 

 composed of a 19.2-mm black pipe through 

 which was passed a 16-mm prestressed cable. 

 By tightening this cable, the track became 

 snugly interlocked for smooth travel of the car- 

 riages. The track at either end was shaped 

 to conform to the curve of the end turns and 

 then welded into place. 



Mechanical Aspects 



The mechanical design included all traveling 

 assemblies such as the power-drive units, the 

 bull wheels or sheaves, haul line or traction 



line, carriages and cable connectors, and man- 

 ner of screen attachment. 



Drive system.— A central hydraulic drive 

 system powered the two bull wheels installed 

 at opposite ends of the structure. The hydrau- 

 lic drive system included a 10-hp gasoline-pow- 

 ered engine, a pressure relief valve, and a man- 

 ual two-way flow control valve. The two hy- 

 draulic orbit motors, each with a sprocket at- 

 tached to the drive shaft, were mounted beneath 

 the bull wheels on adjustable plates. Each 

 sprocket was fitted into a No. 50 roller chain 

 attached along the inside circumference of the 

 bull wheel. When each hydraulic orbit motor 

 was driven by oil forced under high pressure 

 into the motor, the sprocket rotated in the mesh 

 of the roller chain and turned the bull wheel. 



Bull wheels — The bull-wheel design was 

 patterned after those on conventional ski-tow 

 systems. The two bull wheels were 1.2 m in 

 diameter, and the 10.2-cm wide, flat outside 

 surface of each wheel, around which the haul 

 line passed, was faced with rubber to prevent 

 spillage and wear of the haul line. 



Haul line. — The haul line was formed of a 

 9.6-mm diameter flexible steel cable held under 

 863-kg tension by coiled springs. The haul 

 line formed a complete circuit about both bull 

 wheels. 



' Either wind or water pressure against a traveling 

 screen and its appurtenances is considered a "loading 

 value." The loading value can be affected by the 

 amount of debris impinging on the screen. 



Figure 3. View of track and carriage system of travel- 

 ing debris screen. 



Screen and Support System 



The endless cable-formed screen was 2.6 m 

 high and 43 m in circumference. The support 



