low pressure tires may not retain the boom during deployment and 

 retrieval, and (2) the PAU may not prevent the pilings, camel log, 

 or other projections on a pier from scraping the boom. To overcome 

 these difficulties, two modifications of the PAU were carried out. 

 First , a vertical, boom retaining channel member was bolted on each 

 side of the low pressure tire assembly and a horizontal boom retaining 

 channel member was welded to the upper edges of the two vertical 

 boom retaining members, Figure 1. This modification ensured that the 

 boom would be retained on the low pressure tires under all 

 circumstances. Second , a chute was bolted to the PAU to protect the 

 boom from the pilings. These modifications are shown in Figures 2, 3, 

 and 4. The design drawing of the entire PAU modification is shown in 

 Figure 5. 



The chute of the PAU is such that it can be assemJsled during use 

 and removed from the main PAU unit during storage. The chute design 

 was based upon the stipulation that the PAU should be firmly located 

 on the pier; therefore, to clear protrusions on the pier, the chute 

 must hang over the edge of the pier. However, an examination of the 

 pilings showed that to clear the pilings and the camel log, the chute 

 attached to the PAU would have to be very large , which would make the 

 PAU unstable. To overcome this difficulty, a smaller chute was 

 fabricated and the PAU was rigidly fixed to the pilings, as shown in 

 Figures 3 and 4. 



Operation 



There were three difficulties noted in the PAU operation. First , 

 the foot control. Figure 6, requires that it be pressed to stop the 

 tires in an emergency. A more reasonable, and safer design would 

 require that it be kept pressed during rotation of the tires . In the 

 safer design, any emergency or operator distraction will cause the 

 operator to step off the control thereby automatically stopping the 

 tires from rotation. Second, there is no neutral gear to permit the 

 tires to rotate freely during deployment of the boom. Therefore, 

 physical removal of the drive chain was necessary for each boom 

 deployment operation. This procedure is cumbersome, time consuming, 

 and there is an ever present danger of losing the small chain parts 

 during their installation and removal procedures. It is, therefore, 

 recommended that the PAU be modified to permit free rotation of the 

 tires to assist deployment of boom. Third, during operation of the 

 PAU, the boom and the line from the boom kept getting stuck between 

 the tires. This problem could be solved if the four tires are replaced 

 by a long rubber coated cylinder. 



During deployment and retrieval of boom using the PAU, it was 

 found necessary to have a flat, nonskid surface around the PAU as a 

 walkway for the crew because the PAU was not resting on the pier. 

 During tests, this surface consisted of a 4 ' x 8' x 3/4" plywood 

 sheet. It was felt that a surface of this type could be useful on 

 all types of pier surfaces. 



