In Part 2, we built a small A-Frame Gantry for a practice session. In this article, we will put the gantry to work to move a load. As should be noted for any kind of technical rescue training, these techniques should be performed under the supervision of an experienced rescue instructor. Furthermore, should be watching the load at all times while it is suspended and at no time should anyone be permitted to work under the load unless it is properly cribbed.
With that little safety reminder, we will return to our a-frame to prepare for the move.
- (2) Shovels (to dig holes)
- (2) Gusset plates, if ground is soft
- (2) Pinch bars
Dig a hole for each foot, about one to two inches bigger in each direction and as deep as the dimension of the lumber (4x4, dig down 5 to 6 inches, dig it 6x6). The feet should be inserted into these holes to create a pivot point for the gantry.
As lifting begins, the force in each of the gantry legs will be about equal to the load. Spotters must use pinch bars to help guide the feet into the bearing points and to help resist the lateral forces while the gantry moves into position. In soft ground, it may be necessary to use gusset plates (12-inch x 12-inch plywood) to spread the load at each foot.
The gantry structure being complete, the haul and belay lines rigged and the entire system in position, it is time to hook the load onto the lifting rig, insuring that the load will lift evenly and that the load will not engage until the gantry is over 45-degrees. Again, this is not a load rigging discussion, but consideration needs to take place regarding the position of the load and taking into account the load's center of gravity. When the load is lifted, it is important to insure that the load doesn't roll into a new position and throw off the weight distribution. Connect the lifting rig to the anchor sling of the gantry. As mentioned earlier, we have found that having a way to adjust the length between the anchor sling and the load sling makes the whole job a lot easier. A chain hoist or come-along works great in this situation. It's time to put this machine to work and move some stuff.
Moving The Load
Assign one person to oversee the operation and act as safety officer. This person should have a pinch bar or picket, the purpose of which we will discuss later. There should be one person stationed at each foot, also armed with pinch bars. One or more persons should be stationed at the belay device.
Finally, the balance of your personnel should be prepared to act as the haul team; one person should be on the running end of the entire haul system, the others should take up station at the apex of the gantry. The number of personnel required depends on the size of the load and the gantry, but we have done this plenty of times with six man teams.
With the assistance of the Haul Team at the apex, the "Foot Team" should move the gantry to guide the feet into the holes. The Haul Team should have a short 4x4 nearby. The reason for this 4x4 is that as the Team Leader orders the Haul Team to lift the apex toward the 45 degree position, the 4x4 can be placed vertically as a column under the apex to support the gantry if it has to be eased down, or if adjustments need to be made. As the gantry is lifted to 45 degrees, the lone haul team person on the rope should tension the line, taking care to insure the progress capture device is holding the gantry from going back to ground. The belay line should be slack.
The haul team should, on order of the Team Leader to lift, walk the gantry up until it is at 45 degrees, then someone has to take all of the slack out of the chain hoist (or whatever arrangement was made for adjusting the length between the anchor sling and the load sling). The haul line again should be maintaining as much of the gantry weight as possible. That being done, the haul team now should move (quickly) to the haul line and on order, haul the load.