The Wheels
of the back-yard “switchback” car must be made of thick, sound wood, and if there is a wood-working factory in your neighborhood it will save you time and trouble to go there and have the wheels sawed out with the machinery which they have built for that kind of work. But if you must do it yourself, then select a piece of two-inch plank, and after driving a tack in the centre, fasten a string to the tack and attach a soft pencil to the opposite end of the string. With this describe a circle about nine inches in diameter, or measuring about four and a half inches from the tack to the pencil.
With a hand-saw roughly cut out the wheel, using great care to only touch the circle with the saw, but in no case to cut through the circumference. You will now have an irregular wheel, with a number of flat surfaces for its edge (Fig. 123 A).
In this way you may continue to saw off the triangular corners until you reduce the wheel to a condition where it only needs the application of a sharp knife to round the edge until it corresponds with the pencil circle.
Figs. 123-126.—The Wheel.
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