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Page:Popular Science Monthly Volume 89.djvu/584

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��Popular Science Muiitlili/

���Fig. 3. The spring on rear wheel must be wound up at each stroke

��Fig. lo has a ratk- and-pinion ar- rangement to take advantage of this heel pressure. So also has the one shown in Fig. 3, but with greater complication, since a spring on the rear wheel must be wound up at each stroke. The spring keeps unwind- ing and is thus supposed to

���CUSHION STRING

��All of the methods just mentioned are open to the objection that tiiey use fine gearing at a point where great stress is imposed. Gear-teeth are likely to shear off under such conditions and the small l)earings to wear excessively. However, the several mechanical move- ments are decidedly interesting for their ingenuity. The skate illustrated in l-'ig. 4 uses a ratchet and pawl at the rear hub but is operated by a long le\er reach- ing to the center of the skate, to which lever the foot-rest is attached. This skate has large wheels and a low center of gravity — both desirable features. A handle just ahead of the foot-rest oper-

��Fig. 4. Large wheels, a low center of gravity and a brake on the front wheel

propel the ri<ler at a steady gait. In the machine of Fig. 8 the rider's foot must in- cline at an angle with each forward stroke. The heel in descending makes a pawl catch in a cog^vhecl and thus drives the skate.

It is impossible lo get more power out of a machine than you put into it. The inventions discussed fail to allow for that fact.

The skate shown in l"ig. 2 uses a .sort of pantograi)h-ni()lion. In descending ihe fool moves a lever downward. This engages a ratchet arrangenunl inside the hub and causes the rear wheel to revolve, thus driving the skater forward at a proportionate rate of speed.

���SOf£ fLATE

��Fig. 5. A single large bicycle-like wheel to be fastened to each of the rider's legs

��ates a brake on the front wheel through the meil- ium of a connect- ing rope.

Other skates are difficult to classi- fv. For instance there is the one shown in l-'ig. 9, a kind of me- chanical centi- pede. It has nine rollers per skate, arrang- ed in single and double rows, the ob- ject of the sin- gle rows being to give more of knife-edge

���Fig. 6. Skate propclcd by taking strokes in the usual simple way

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