A gin pole consists of an upright mast which is guyed at the top to maintain it in a vertical or nearly vertical position and is equipped with suitable hoisting tackle. The vertical mast can be timber, a wide-flange steel beam section, a railroad rail, or similar members of suffient strength to support the load being lifted. The load can be hoisted by hand tackle or by the use of hand- or engine-driven hoists. The gin pole is predominately used in erection work because of the ease with which it can be rigged, moved, and operated, and it is suitable for raising loads of medium weight to heights of 10 to 50 feet where only a vertical lift is required. The gin pole can also be used to drag loads horizontally toward the base of the pole in preparation for a vertical lift. It cannot be drifted (inclined) more than 45 degrees from the vertical or seven-tenths the height of the pole, nor is a gin pole suitable for swinging a load horizontal y. The length and thickness of the gin pole depends on the purpose for which it is installed. It should not be longer than 60 times its minimum thickness because of the tendency to buckle under compression. A usable rule is to allow 5 feet of pole for each inch of minimum thickness. Table 6-2 lists values for the use. of spruce timbers as gin poles with allowance for normal stresses in hoisting operations.
NOTE: Safe capacity of each length shears or tripod is seven-eighths of the value given for a gin pole.
1. Rigging. When rigging a gin pole, lay out the pole with the base at the exact spot where it is to be erected. To make provisions for the guy lines and tackle blocks, place the gin pole on cribbing for ease of lashing. Figure 6-50 shows the lashing on top of a gin pole and the method of attaching guys. The procedure is as follows:
Figure 6-49.-A steel picket holdfast.
Table 6-2.-Safe Capacity of Spruce Timber as Gin Poles in Normal Operations.
a. Make a tight lashing of eight turns of fiber rope about 1 foot from the top of the pole, with two of the center turns engaging the hook of the upper block of the tackle. Secure the ends of the lashing with a square knot. Nail wooden cleats (boards) to the pole flush with the lower and upper sides of the lashing to prevent the lashing from slipping.
b. Lay out guy ropes, each one four times the length of the gin pole. In the center of each guy rope,
Figure 6-50.-Lashing for a gin pole.
form a clove hitch over the top of the pole next to the tackle lashing, and be sure the guy lines are aligned in the direction of their anchors.
c. Lash a block to the gin pole about 2 feet from the base of the pole, the same as was done for the tackle lashing at the top, and place a cleat above the lashing to prevent slipping. This block serves as a leading block on the fall line which allows a directional change of pull from the vertical to the horizontal. A snatch block is the most convenient type to use for this purpose.
d. Reeve the hoisting tackle and use the block lashed to the top of the pole so that the fall line can be passed through the leading block at the base of the gin pole.
e. Drive a stake about 3 feet from the base of the gin pole. Tie a rope from the stake to the base of the pole below the lashing on the leading block and near the bottom of the pole. This is to prevent the pole from skidding while it is being erected.
f. Check all lines to be sure that they are not tangled. Check all lashings to see that they are made up properly, and see that all knots are tight. Check the hooks on the blocks to see that they are moused properly. The gin pole is now ready to be erected.
2. Erecting. A gin pole 40 feet long can be raised easily by hand, but longer poles must be raised by supplementary rigging or power equipment. Figure 6-51 shows a gin pole being erected. The numbe of men needed depends on the weight of the pole. The procedure is as follows:
a. Dig a hole about 2 feet deep for the base of the gin pole.
b. Run out the guys to their respective anchorages and assign a man to each anchorage to control the slack in the guy line with a round turn around the anchorage as the pole is raised. If it has not been done already, install an anchorage for the base of the pole.
c. If necessary, the tackle system used to raise and lower the load can be used to assist in raising the gin pole, but the attaching of an additional tackle system to the rear guy line is preferable. Attach the running block of the rear guy line tackle system (fig. 6-52) to the rear guy line end which at this point is near the base of the gin pole. The fixed or stationary block is then secured to the rear anchor. The fall line should come out of the running block to give greater mechanical advantage to the tackle system. The tackle system is stretched to the base of the pole before it is erected to prevent the chocking of the tackle blocks during the erection of the gin pole.
d. Keep a slight tension on the rear guy line, and on each of the side guy lines, haul in on the fall line of the tackle system while eight men (more for larger poles) raise the top of the pole by hand until the tackle system can take control.
e. The rear guy line must be kept under tension to prevent the pole from swinging and throwing all of its weight on one of the side guys.
When the pole is in its final position, approximately vertical or inclined as desired make all guys fast to their anchorages with the round turn and two half hitches. It is often advantageous to double the portion of rope used for the half hitches.
g. Open the leading block at the base of the gin pole and place the fall line from the tackle system through it. When the leading block is closed, the gin pole is ready for use. If it is necessary to move (drift) the top of the pole without moving the base, it should be done when there is no load on the pole unless the guys are equipped with tackle.
3. Operating. The gin pole is perfectly suited to vertical lifts. It also is used under some circumstances for lifting and pulling at the same time so that the load being moved travels toward the gin pole just off the ground. When used in this manner, a snubbing line of some kind must be attached to the other end of the load being dragged and kept under tension at all times. Tag lines are to be used to control loads being lifted vertically. A tag line is a light line fastened to one end of the load and kept under slight tension during hoisting.