708 



Popular Science Monthly 



proceeding being not unlike that of feeding 

 cartridges from a belt or clip to a machine- 

 gun. 



A Car Can't Be Safely Stopped in Less 

 Than Two Miles 



The stations at which the cars arrive are 

 similarly constructed. Each solenoid is 

 energized at the moment when the middle 

 of the car has passed its middle and is de- 

 energized when the rear of the car has 

 passed through. The stations must be 

 some two miles long in order that the cars 

 may be stopped gradually. 



What will be the speed of such a system? 

 My experi- 

 ments have 

 given me the 

 data neces- 

 sary to cal- 

 culate the 

 amount of 

 attract! o n 

 between the 

 core of an 

 electromag- 

 net and an 

 ar mature 

 separated at 

 a considera- 

 ble distance 

 from it, so 

 that I have 

 been able to 

 fix the maxi- 

 mum speed 

 attainable . 

 That maxi- 

 mum depends on the maximum attractive 

 force of the electromagnets which can be 

 developed to overcome the centrifugal 

 force on the curves. 



Assuming electromagnets of reasonable 

 size and currents of reasonable strength I 

 found on the basis of my aforesaid experi- 

 ments that with curves having a radius of 

 two tho.usand feet it would hardly be pos- 

 sible to attain a speed of more than five 

 hundred miles an hour. But think what 

 that means! New York would be no more 

 distant from Chicago than it is now from 

 Philadelphia, so far as relative times are 

 concerned. Florida might easily become a 

 kind of winter Coney Island for all New 

 York. A journey from New York to San 

 Francisco would occupy only half a day. 



Lifting an Ordinary Train off the Rails 

 While the vacuum tube is an electrical 



This is the experimental apparatus which Prof. Wein- 

 berg used in working out the details of his proposed elec- 

 tromagnetic vacuum system of passenger transportation 



possibility, it is more likely that some 

 method of transportation proposed here, 

 or one like that proposed by Emile Bachelet 

 a few years ago, will be more seriously con- 

 sidered first. Bachelet did not propose 

 the propulsion of a car in a partial vacuum 

 so as to cut down air resistance, but he did 

 propose the idea of overcoming gravity by 

 the use of alternating-current electromag- 

 nets. Every amateur electrician knows 

 that an electromagnet through which an 

 alternating current is passed has the curious 

 property of repelling a light metal object 

 brought near it. Bachelet intended to 

 build his cars with aluminum bottoms. 



When the 

 cars ran over 

 the magnets 

 successively 

 they were to 

 be repelled — 

 literallylifted 

 off the rails. 

 The system is 

 objection - 

 able because 

 very much 

 power is 

 wasted per 

 mile (con- 

 trary to my 

 system where 

 the waste of 

 energy is in- 

 significant) 

 and the pas- 

 sengerswould 

 be very un- 

 comfortably heated by the action of the cur- 

 rents from below. In my opinion an 

 electric system, such as that which I have 

 here outlined, but without the vacuum 

 tube and with approximate (not complete) 

 neutralization of gravity would be safer, 

 cheaper, and simpler. The loss in speed 

 due to the resistance of the air would not 

 be excessive if the cars were properly de- 

 signed, and might be compensated for by 

 cutting the electromagnets out just as the 

 front of the car left them one after the 

 other. In this way the electromagnets 

 would not only sustain the car but would 

 also accelerate its speed. Moreover it 

 would be much simpler to run on wheels 

 instead of moving freely through space, 

 gravity being only so far neutralized that 

 the wheels would barely touch the tracks 

 and a pressure would be exerted that 

 would be almost negligible. 



