Figs. 201-203.—Details of Axle and Belt Shaft.
The Upper Shaft shown in [Fig. 201] supports a spool pulley like the one on the front axle, and its screw-eye bearings should be screwed into the top edge of the sides of the box ([Fig. 200]), directly over the front axle. Slip a silk-spool on to each end of this shaft to keep its ends from slipping out of the screw-eyes.
The Belts. As you will see by [Figs. 200] to [202], the upper large pulley is belted to the motor pulley, and another belt extends from the upper shaft down to the pulley on the front axle. Rubber-bands make the best belts. Cut a hole through the bottom of the cigar-box for the belt extending from the upper shaft to the front axle to pass through. Screw the toy motor to the cigar-box with its pulley directly in line with the upper shaft pulley. Wrap the spool pulleys with bicycle-tape, to keep the rubber-band belts from slipping.
Fig. 204.—Two Home-made Battery Cells Connected in Series.
The Battery. A dry battery is too heavy for the motor truck to carry; so we must make a special two-cell battery like that shown in [Fig. 204]. Two glass tumblers to hold the solution, a pair of battery zincs, a pair of carbons, and a bi-chromate of potash solution, are needed. Old battery zinc pencils with several inches of the eaten end cut off ([Fig. 206]) will do for the zincs, and the carbons from worn-out dry-battery cells cut to a corresponding length will do for the carbons. Fasten together the zincs and carbons with rubber-bands, as shown in [Fig. 207], after wrapping a piece of bicycle-tape around the upper end of the carbon and inserting a small wad of it between the lower ends of the carbons and zincs, to keep them from touching one another.
[Figure 205] shows a completed cell, and [Fig. 204] how the two cells are connected in series, that is, with the carbon of one connected to the zinc of the other. Twisting the connecting wires into coils, as shown, is a good method of taking up the slack.