The engine wheels are four in number, made by sawing from half-inch
board four circles four inches in diameter, and from cigar-box wood
an equal number four and a half inches in diameter. Each wheel is
double, you see, to form the flange which keeps it on the track. Nail
with little brads, each larger circle on to a smaller one, so that the
former will project equally all around. Then bore a hole exactly in the
middle of each, and your wheels are ready. With lath nails fasten one
pair of wheels to the platform board at the side of the cab (flanges
inside, of course), and the other pair to the same board in front, and
so far that the rims of the two wheels on one side will be about two
inches apart.