282 TELPHERAGE. 



line should be single or double and the weight to be carried by each 

 unit. The installations should be so planned that the expense will be 

 reduced to a miiiinuuii, and, further, that the track will not interfere 

 with existing machinery or buildings, taking care to avoid an excessive 

 number of curves and switches, as these add more or less to the expense, 

 particularly to the cost of erection. 



Method of operation.- -It is difficult to treat in a general way of the 

 method of operation. In automatic lines it is necessary to provide 

 appliances whereby it is impossible for an unskilled operator to injure 

 the telpher. In order, therefore, to provide for contingencies, a 

 "dead section" is placed at each end of the line, the middle of the 

 line being generally left alive. Upon closing a spring sAvitch, the 

 dead section is energized so long as the operator keeps his hand on the 

 switch, which is usually only a few seconds, during which time the tel- 

 pher passes to that portion of the line which is always aliv^e. When 

 it reaches the other end it comes upon the dead section and then either 

 slows down of its own accord, or else a mechanical or solenoid brake is 

 applied. The telpher then passes under the reversing arrangement 

 and it is therefore reversed, either with no current in the line or else 

 with a high resistance. If the telpher is at the farther end of the line, 

 the operator at the near end, by closing a switch, can bring it 1)ack to 

 him. The dead sections at the end of the line, which have current 

 only so long as the hand is held upon the spring switch, render the 

 line as safe as possible against the telpher coming in contact with the 

 terminal posts. An automatic block system prevents collision of 

 telphers. 



Carves. — The curves are solid rail and likewise the trolley track, 

 where there is a curve, especially when it has a short radius. Where- 

 ever it is necessary to pass around a curve, to take turnouts or cross- 

 overs, a resistance is inserted in the trolley circuit, where])y the telpher 

 automatically I'educes its speed while it is traversing the curve or turn- 

 out or approaching a cross-over switch. As soon as it reaches the 

 other side of the curve it receives full voltage and continues at its nor- 

 mal speed. In regular service the speed yaries from 8U<J or 800 feet 

 per miiuite up to 20 miles per hour, or even more, when required. 

 The slower speeds are used when the lines are short and where there 

 are many curves, particularly for factory and foundry work. For 

 lines running across the country a speed in excess of 20 miles per hour 

 can l)e obtained, but with the higher speeds the cost of the construc- 

 tion increases, certain special devices being necessary. Even for 

 installations which are termed "cross-country work," 15 to 20 miles 

 per hour has been foiuid amply sufficient. 



As to what the ultimate capacity on grades niay be, this has not 

 been fully determined. Experimentall}^ more than 20 per cent has 

 been reached. In actual practice the greatest grade equipped has been 

 12 per cent, and thus far there seems to be ample traction. 



