BRB. The BRB sweep obstructor is 8 feet 5-1/2 inches long, 25-1/2 inches in maxi-mum diameter, and weighs 2,200 pounds. When assembled for laying; it resembles very closely a BM 1000 with tail fairings attached.

Figure 128 – Anti-Sweep Device

Component parts as follows:

The Anchor. This is a steel cylinder with an ogival nose, resembling the case of a BM 1000. It is 62 inches long and weighs about 1,000 pounds. Approximately 865 pounds of cement are cast into the forward part, the after end of the casting being formed to pro-vide (1) positioning seats for two cutters and (2) a mooring-cable drum.

The following fittings are bolted to the after end of the casting:

1. A wooden block which serves as a float seat

2. A circular, cut-away rubber buffer pad which is believed to serve as a shock ab-sorber upon impact.

The Float. This component has the appearance of two cones welded together at their bases. It is 32 inches long over-all, 21 inches in maximum diameter, and has a positive buoyancy of about 65 pounds. The mooring cable is attached to a lug at one end.

The Tail. This consists of a truncated cone fitted with four radial fins which are en-closed by a shroud ring, 8 inches long and 25-1/2 inches in diameter. The conical section is 43-1/2 inches long, 25-1/2 inches in diameter at its forward end and 8 inches in dia-meter at its after end. The tail is attached to the after end of the anchor by eight bolts.

The Cutters. These are standard mechanical cutters, two in number, secured to the mooring cable three feet and nine feet respectively, below the float.

The Mooring Cable. This consists of a 125 foot length of 5/8 inches steel wire. One end is attached to the float and the other end to a short length of chain which, in turn, is attached to a bolt on the anchor case. The chain serves to prevent the mooring cable from parting as a result of chafing on the anchor. Prior to laying, the cable is wound around the cement casting in the anchor.

Figure 129 – BRB Anti-Sweep Device – Cross Section

Operation. Impact with the water shears the tail. The buoyancy of its case and the expelling effect of the rubber buffer pad cause the float to rise toward the surface as the anchor sinks. As the anchor continues to sind, the entire length of mooring cable pays off the mooring drum and the float and cutters take depth according to the depth of the water.