Fig. 244.
Fig. 245.
To enable the front sled to turn properly, get out two pieces of 2" plank, as shown in Fig. 244, about 3" wide and as long as the width of the sled, one being tapered toward the ends on the under side. The tapering is important, as it diminishes the friction when the front sled is turned. Screw one of these pieces firmly across the top of the front sled and the other across the lower side of the seat-board (see Screws), a hole being bored through the centre of each cross-piece (as well as through the seat-board and the top of the front sled) for the king-bolt upon which the front sled turns. Find these centres accurately and bore carefully with a bit 1/16" larger than the king-bolt (see Boring). The front sled should turn very freely and easily, and have plenty of play, but the bolt should not fit loosely enough to make the double-runner rickety.
A washer can be inserted between the cross-pieces. Sometimes a thick rubber washer is used to lessen the shock (Fig. 245).
Fig. 246.
To give the ends of the rear sled freedom to play up and down (without turning sideways) in passing over the inequities of the surface the arrangement shown in Fig. 243 (and enlarged in Fig. 246) is good. Do not make this of 7/8" stock. Pieces of plank should be used, the dimensions being so arranged that the seat-board will be equally raised from the front and rear sleds. The pins at the ends of the cross-piece should be not less than 1" in diameter (1¼" is better) and should be carefully cut (see Paring and Rounding Sticks). The best way is to have them turned to fit the holes in the rocker-shaped pieces. The latter should be long enough (about 1') to prevent danger of the wood breaking apart near the hole and to allow for screwing firmly to the seat-board.
Fig. 247.