Page:Popular Science Monthly Volume 91.djvu/386

 �Here's the Air-Propelled Unicycle

Some mechanical misgivings about a fantastic invention

��in the transmission of the engine is small. The resistance in the wheel spindle-bearings is evidently insignificant compared with that to be looked for in the corresponding bearings of the unicycle, which are those of the three roller disks shown in the engine- carrying frame, subject to constant side pressure from a bevel-pinion drive. The loss of engine power in the transmission of the unicycle is enormous. There are con- stantly in mesh a large number of elements. At turns, there are, in addition, two hand- operated worm-gears for turning the T- shaft of the air-screw upon its vertical pivot-pin (against a considerable resistance when the screw is going), and this further operates a train of three spur-gears to make the front wheel participate in the turn and — when it is on the ground — help in directing or stopping the big wheel.

The loss of efficiency due to the many transmission gears is small, however, com- pared with that of the air-screw, which cannot be more than three and one-half feet in diameter so each blade is less than twenty inches long. An air-screw of these dimensions, at the present stage of knowl- edge, has about one-fifth of the efficiency and one-tenth of the capacity of- a screw, with forty-inch blades and can scarcely absorb more than fifteen or utilize more than two-horsepowers at the utmost ve- locity that can be imparted to it through gears. On hills, the machine would be reduced to very low speed with high fuel consumption.

An air-screw even so small as three and one-half feet in diameter would be dan- gerous to bystanders and wayfarers; a larger and more efficient one would be entirely out of the question on the road.

Ordinarily the front wheel, which some- what spoils the unicycle idea, is supposed to hover in the air when the machine is running, the driver sitting on a sliding seat, balancing his weight against that of the front structure by pushing the seat to the balancing position. The claim is made that by shifting his seat he can make the air-screw inoperative, but nothing is shown to substantiate this assertion. To the front wheel a brake mechanism is secured, to be operated with a long rod, and the inventor believes that this brake

��DO you remember the old "Star' bicycle? If not, ask your father. He will tell you that it had a little wheel in front, and behind a very large wheel over which you sat. The little wheel in front was supposed to prevent you from taking "headers."

Show your father the accompanying il- lustrations of A. F. d'Harlingue's air- propelled unicycle and he will say at once: "Why the man has simply put an air- propeller and an engine on a big old Star!"

But the difference between the old "Star" and this curiously ingenious and yet most impractical invention is this: The old "Star" was a simple, operative invention; the air-propelled unicycle is much too complicated to operate success- fully.

The Popular Science Monthly has not pictured every one of the businesslike gears and elaborate controls which are supposed to adapt this machine for high- speed travel and racing. It's unnecessary to do so. But it has emphasized the two fanciful and fundamental features, namely, the unicycle design intended to result in a vehicle running normally on one wheel only and, secondly, the use of an air-screw for propulsion. The fascination of com- bining these features may have arisen from the recognized difficulty in applying engine power in a unicycle by ordinary mechanical means, so that the use of an air-screw came to appear as the happy solution of a problem.

Compare this construction with a motor- cycle and especially with a pace-making machine having the driver's seat at the extreme rear. With the motorcycle, the practical speed is limited only by the driver's ability to endure the jolts or his willingness to take chances. The wastage

��370

�� �