SAFETY IN WINDING OPERATIONS. 21 5 



After preaching the gospel of tliis safety brake to a leading 

 " safety-first " financier the other clay, the author was immediately 

 asked the question, " What is it gouig to cost?" In looking into 

 this important matter, it has to be acknowledged that the extra 

 cost is serious, bringing up the price of an A.C hoist, fitted with 

 E.C brake, to just about that of a Ward-Leonard set. Mr. 

 Chambers stated that the cost of the E.C. brake for a five-ton 

 hoist, with a rope speed of 3,500 per minute, was £2,000. Mr. 

 J. H. Rider, at the Institution of Electrical Engineers, 1915, in 

 his paper on " The Power Supply of the Central Mining Rand 

 Mines Group," gave the cost (with the motor, generator, etc.) as 

 nearly two-thirds that of the winding motor. He also stated that 

 ail expenditure of energy at the rate of about 45 K.W. in the 

 field magnet system of the E.C. brake obtained a result equal 

 to a rate of about 1,600 K.W . in the case of counter current 

 braking. 



This comparison invites the author to make a few closing 

 remarks v/ith respect to electric winding. 



The A.C. hoist can j^robably be made as safe as the Ward- 

 Leonard, and doubtless when normal times return further steps 

 will be taken in this direction, 'ilie author was present at tUc 

 tests varried out on the A.C winding hoist at the Village Deep, 

 Ltd., when, witli an unl)alance(l load of y,ooo lbs., the speed was 

 reduced from 3,000 to 250 feet ])er minute in a few seconds, one 

 d(jzen being al)out the figm-e. \\'ith a \\'ard-Leonard set at the 

 Consolidated J.anglaagte, he had the privilege to witness an 

 important test, of which the following details give the description. 

 The winding motor was accelerated as quickly as possible, until 

 a normal rojje speed of 2,500 feet ])er minute was reached; the 

 driver was then taken off the platform and the hoist allowed to 

 com])lete the wind with only the safetv-gear controlling it. The 

 cams l)rought the winding drmns to an almost imperceptible 

 cree])ing speed, and when this speed had caused a sufiicient 

 jiressm-e to bear on the brake trigger gear, the brakes were 

 ap])lied, the current cut oft", and the lioist brought to rest. This 

 test, the antlior is informecl, is ap])lied to the Ward-Leonard hoists 

 of this ])articular group once a week. 



If a thi'ee-])hase hoist be installed where the winding c\cle 

 IS sucli. in ordinary l)alance winding, that the upward load always 

 overbalances the downward load, then if failure of current takes 

 jflace, it is obvious that before the hoist could run awav the rope 

 direction nnist be reversed, and the load which before the failure 

 was l)eing wound ]n an ujnvard direction nmst change to a down- 

 ward direction. ( )l)viously, then, at some moment the load will 

 1k' stationary, and therefore the automatic application of the 

 I)rakfs will ])ull the hoist u]>, and no runaway will take place; 

 whereas if the downward load overbalanced the ui)ward load, and 

 a failure of power took place, the direction of hoisting will not be 

 reversed, the speed will be accelerated, and the ai)plication of the 

 brakes w ill l)e ineft'ectual. With the Ward-Leonard lun'st. although 



