MacGregor Slewing Ramps Successfully Tested

For two 14,300-dwt ro/ro container vessels building at Howaldtswerke Deutsche Werft AG, Kiel, for the German owner Deutsche Dampfschifffahrtsgesellschaft "Hansa," Bremen, MacGregor has supplied a comprehensive array of ro/ro equipment.

The most spectacular item is, undoubtedly, the stern access ramp which was introduced on the market under the name MacGregor Machbridge 90 Slewing Ramp.

The reason for the worldwide interest in this type of ramp is that it represents the ultimate solution in ro/ro berthing versatility.

In addition to the classical method of using the ramp for ro/ro traffic with the ship being berthed directly stern-to a purpose- built quay, the slewing ramp allows direct ro/ro access irrespective of whether the ship is berthing with her port or starboard side along the pier.

The first vessel to be so fitted is the Reichenfels, and her slewing ramp was recently tested to the full satisfaction of the owners and of Germanischer Lloyd, the classification society responsible for the ship.

The second ramp has now been installed on the following ship, the Rheinfels, and delivery of the two vessels is scheduled for this month and November, respectively.

For those not familiar with the MacGregor slewing ramp, originally patented back in 1972, it comprises three main components: the three-section ramp itself, the turntable at the ship's stern, and the two large hydraulic driving winches. When fully extended, the ramp has a total length of about 115 feet, section 1 being approximately 66 feet long, section 2 about 36 feet and section 3 with finger flaps 13 feet long. The ramp design with a 23-foot-wide trackway allows two trailers with a maximum weight of 80 tons each to pass at the mid-point of the ramp, one entering and one leaving the ship.

The slewing ramp on the DDG Hansa ships can be placed on the pier anywhere in a range from 33 degrees off the centerline on one side through right astern to 33 degrees on the other side. In cases where it is not possible to use the fully extended ramp with the ship berthing stern-to, vehicles can enter the ship via the so-called "short ramp version," i.e., only section no. 1 will serve as a ramp, whereas sections 2 and 3 remain locked under section no. 1.

The ramp is hinged to a turntable at the ship's stern, which turns on a kingpin and runs on a ground slide ring. Slewing of the ramp is achieved by the same two winches which are provided for the lowering and raising maneuvers of the ramp. This method of operation is very similar to that of a heavy-lift derrick. Consequently, it is basically a simple arrangement and one that will be very familiar to Hansa crews.

For all operations of the ramp, the lowering/ extending, the slewing movement, and the raising/folding to stowing position can be done from either of two control stands by means of two levers only.

Lowering of the main first section of the ramp is achieved by the two hydraulic winches arranged at the port and starboard masts on the upper deck, whereas extending of the second and third sections will be done by means of two additional winches arranged one each side of the first section.

Slewing of the ramp can be started as soon as it has reached an opening angle of 30 degrees. This is done by running two main winches in opposite directions. With one winch pulling and the other paying out, the effect of this synchronized operations is to slew the ramp in the desired direction.

For a complete description of the Mac- Gregor Machbridge 90 Slewing Ramp, write to Henri Kummerman, MacGregor International, 28 Chemin Du Pommier 1218, Geneva, Switzerland, or to John A. Nydegger, MacGregor-Comarain, Inc., 135 Dermody Street, Cranford, N.J. 07016.