SOLID LOG WHEELS.
In Mexico, Chili, Tartary and elsewhere, rough discs of timber (Fig. 1) are sawed or chopped off from large trees. A hole is made in the centre to receive the axle. These wheels answer well enough for countries where time is of no value, mercy to draught oxen unthought of, and where the inhabitants would rather hear a dry wheel grate on its axletree than take the trouble to grease it. “Evil spirits dread a creaking wheel,” say they, and so the primitive contrivance is allowed to revolve noisily. A wheel of this kind might be made much more efficient by leaving a nave or boss in the centre, sheathed with hard wood or raw hide, and by binding it with the latter material let into a groove cut round the circumference in place of a tire; an endless band cut out of the hide of a rhinoceros, hippopotamus, elephant, or giraffe, put on wet, and allowed to shrink and dry before it was much used, would be almost everlasting.
WHEEL BUILT IN SEGMENTS.
A very neat and serviceable barrow wheel may be thus built: Take a piece of deal 4in. wide, 3in. thick, and 14in. long; set a pair of compasses to a radius of 8in.; and, fixing the centre leg 4in. from the block, describe on it the segment of a circle; draw this on both sides, and cut the block truly to the outline; then saw it down into six thicknesses of somewhat less than ½in.; lay three of these together, so that their chords form an equilateral triangle, each angle being 60°, and their segments will complete the circumference of a true circle. Then take the other three, and lay them on so that the centre of each shall cover the ends of each pair of the lower series; then bore holes and screw or nail them together (inch copper boat nails, with rooves for clenching them, are the best for this purpose), and you will have a wheel ¾in. thick, and 16in. diameter. Take a 1in. bar of wood 3in. broad, half check it into the opposite triangles where there is but one thickness of wood, strengthen it by bars from the other angles, bore a hole in the centre, and insert an axle of hard wood or iron. If you have a piece of iron hoop, reduce it, and rivet the ends together, so that it forms a tire that will just not go on; punch half a dozen holes in at intervals, heat it, put it on quickly, hammer it into place, and cool it with water; then put nails or screws through the holes, to keep it from working off, or tire it as before with an endless band of raw hide; or bore holes through it 1in. or 2in. apart all round, at about 1in. from the edge, and lace thongs of raw hide through these and round the edge, so as to preserve it from splitting, or being worn by contact with the ground.
THE CONSTRUCTION OF A WAGGON WHEEL.