280 



TELPHERAGE. 



Hoists. — The hoist is suspended below the telpher, or sometimes 

 from a trailer drawn by the telpher. Special attention has been paid 

 in the later designs of hoists to use as little head room as possible. It 

 was deemed best at first to combine the telpher and hoist all in one, 

 but there were so many cases where it was necessary to use the telpher 

 alone without the hoist, and also where it was advisable to put the 

 hoist on the trailer instead of on the telpher, that experience has shown 

 it is better to make the telpher and hoist two separate pieces of appa- 

 ratus. Greater simplicity has also been obtained and a correspond- 

 ingly lower maintenance reached. There are many other interesting 

 details concerning hoists, as to the speed, lift, and construction, which 

 it is necessary to omit here. 



brakes. --Two distinct types of brake are used on telphers, either 

 hand brakes or solenoid brakes, both of which are arranged to apply 



Fig. 4. — Plan of circular coal-storage 

 shed with rotating telpher track. 



Fig. 5.— Space-covering or movable 

 telpher track. 



pressure to the wheels or to grip the track. In regard to the solenoid 

 brake, it is only necessary to explain that it works automatically, the 

 solenoid being placed in series with the armature. A spring normally 

 holds the brake on the wheel or the track. If, however, from any 

 cause the amount of current passing through the solenoid is reduced, 

 whether by means of external resistance^ or ])V reason of the additional 

 counter-electromotive force generated by the armature, due to running 

 at a high speed, the solenoid becomes weakened ami the brake is applied. 

 An air cushion is arranged so that the brakes will be applied gradually. 

 Traile7'K. — It is often advisable where a large amount of material is 

 to be carried, especially over one track, to use trailers. These con- 

 sist generally of a two-wheeled truci<, l)elow which is suspended a 

 bucket or other suitable form of carrier, or even the hoist, as the case 

 may require. For heavy traflic it is customary to arrange a long train 



