The whole of the wood-work above ground must be planed, and the edges neatly rounded off. It is the custom to burn or char the surface of that part of the timber which has to be let into the ground, to prevent it from rotting, but a good coat of gas tar answers the purpose very well.
PORTABLE FRAME FOR TRAPEZE, RINGS, OR SWING.
2 Norway spars trimmed, 14 feet long, at 5_s._ 10 0 6 ft. 2 in. iron tube, at 7-1/2_d._ per foot 3 9 2 Elbows for iron tube, at 1s. 4-1/2_d._ 2 9 100 ft. 3/8 in. iron wire rope 10 0 1 Coupling Screw 5 0 4 Stakes 3 ft. 3 in. square 1 4 ------------ £1 12 10 ============
Fig. 4 represents a very simple way of forming the uprights for a swing. It consists of two scaffold poles, or more correctly speaking, Norway spars (the same as used for ladder-making when they have been sawn down the centre). They may be procured at any ladder-makers, with the bark taken off and properly trimmed. The top should be 2 in. in diameter, and the bottom 3-1/2 to 4 inches. The cross-piece (B) to which the ropes are fastened is formed of 2-in. gas barrel, _i.e._ iron tubing, and is measured by the calibre or inside diameter, therefore 2-inch gas tubes will measure about 2-1/2 inches outside diameter. The elbows, which are bought already screwed, would have to be fitted with iron staples riveted to them, to fasten the wire rope to, and two hooks also riveted through the tube, made of 1/2-in. diameter iron, 18 inches apart, for attaching the swing.
Cut the iron rope into four lengths of 25 ft. to form the stays (C C C C). One of these stays must be fitted with a coupling screw, for tightening the whole, when fixed. Most telegraph-posts are stayed in this manner; they would, therefore, be a good guide for you to see how the wire ropes are fastened.
The two uprights are not let into the ground; it is best to let them stand on some hard substance, such as a stone or a block of wood, to prevent their sinking when the stays are strained.
The next illustration (Fig. 5) represents another method of constructing a portable frame. This has the advantage of the uprights being readily removed, as the whole consists of tube-iron. The Norway spars are here represented by two 14-feet lengths of 2-inch gas tube. If, however, the length be a difficulty, then get four 7-feet lengths of 2-inch gas tube, two of which may be screwed together to form one upright. The screwed sockets, by means of which the tubes are joined, are supplied with them. A horizontal bar (D) may be added by introducing the [T] pieces (A A), which should be 2-1/2 inches, to slide up and down the iron tube, and a hole drilled through the [T] piece and into the tube will enable it to be fixed at the requisite height.