For the larger rear wheels the lids of two canisters can be used, or, if something is required giving a more definite impression of solidity, two flat boot-polish tins can be substituted. Another piece of knitting needle passes through the centre of these, and through holes in the sides of the cab, and so acts as axle. This is kept in place by means of dabs of sealing wax.
For the stack you can use a long thin cotton reel, or, better still, you can fix on another small tin by the method shown in Fig. 81.
The turning of the front wheel can be regulated by means of two strings passing from the two right-angle strips through a hole into the cab. If you can fix the strings to a piece of wood as shown in Fig. 82, you will be able to steer properly. A hole in the bottom of the cab, and a piece of wood stretched tightly across the top, should enable you to set up the steering apparatus.
_A Working Motor Boat._--To construct a motor boat that will travel a considerable distance is not really a difficult matter. All that is necessary is a piece of board for a hull, a wood or metal propeller, and a yard or two of strong elastic: these, carefully adjusted, will do all that is necessary.
For the hull, a piece of 5/8 in. or 3/4 in. board, about 18 in. long will do. This can be cut to the boat shape by means of a pocket knife or a spokeshave, and finished off with glass-paper. It should be sharp-pointed at the bows, about 3 in. to 4 in. at the centre, tapering down to a width of 2 in. at the stern. In the centre of the hull nail a block of wood, and to it glue two funnels (Fig. 83). For these, the odd lengths cut off from bamboo curtain poles will do admirably; or, if these be not obtainable, a couple of incandescent-mantle cases will suffice.
The adjustment of the motive power is the difficult task. First, you will need to purchase a couple of yards of suitable elastic: this is sold at most large toy shops, and costs usually a penny a yard. To fix this into place beneath the hull you will need to construct two metal supports. If you can get an old tin box made from metal sufficiently stout, that will do; if not, then you had better buy a piece of sheet brass, No. 20 gauge: 6 in. by 4 in. will be ample. Draw out these supports as shown in Figs. 84 and 85, and bend them into shape as in Figs. 86 and 87--one for the bow and one for the stern. Screw on the bow one about 1-1/2 in. or 2 in. from the point, and the stern one in the middle of the end.