808 REPORT— 1888. 



wheel connected direct to the moving or upper millstone by a vertical spindle, 

 thus avoiding much friction. 



The author concludes by pointing out how interesting it would be to ascertain 

 whether another specimen of this mill is to be found in the British Isles, and why 

 it has given place to the more complex vertical breast or overshot wheel, to again 

 be reproduced in the most efficient form of turbine ? 



MOJVBAY, SEPTEMBER 10. 



The following Papers were read : — 



1. On the ajjpUcatimi of Electricity to the worlcing of a 20-ton Travelling 

 Crane} By W. Anderson, M.Inst.C.E. 



One of the travelling cranes in the foundry of the Erith Ironworks was 

 originally constructed to be worked by hand, but preparations had been made to 

 apply wire rope driving at some future time. 



The crane is 39' 6" span, and consists of a pair of wrought-iron girders resting 

 on end carriages running on an elevated line of rails. The gearing for hoisting 

 and for longitudinal and cross traverse is secured on to the top of the main girders, 

 the hoisting chain passes from the barrel at one end over a pulley at the other, then 

 back to the pulleys in the cross traversing carriage, which runs between the main 

 girdei's, through a falling block, and thence to an anchorage under the barrel at the 

 extreme end of the main girders. By this arrangement the crane occupies a 

 moderate height, and the hook can come within three feet of each wall. 



The inconveniences and wear attending the employment of rope-driving gear in- 

 duced the writer to try whether electricity might not be used with advantage. Messrs. 

 Elwell Parker, of Wolverhampton, were communicated with, and the.se gentlemen 

 Undertook to supply the dynamo and a motor suitable for the peculiar requirements 

 of a heavy crane. The dynamo, which was intended to give 50 amperes at 120 

 volts with 1,200 revolutions, was fixed in the main boiler-house of the works, and 

 was driven by a small horizontal engine by means of a link belt. The leads from 

 the boiler-house up to the conductor in the foundry are of 6 B. W. G. copper 

 wire, while the conductor is formed of an angle-iron bar 2" x 2" x i", extending 

 the whole 350-feet length of the shop, and has one face roughly ground and pro- 

 tected from rust by vaseline. The return current travels along one of the rails 

 on which tlie crane runs. The motor, which is shunt wound, and constructed for 

 100 volts and 50 amperes, is fixed on the working platform of the crane beside one 

 of the main girders. Its driving spindle carries a steel pinion which gears into a 

 double helical spur wheel keyed on to a shaft which runs longitudinally on the 

 top of the girder, and is connected by nests of three bevil wheels, with friction 

 clutch connections to the three shafts which command the several movements of 

 the crane, the means of using the hand-power being still retained. 



Two sets of speeds are arranged for each of the movements, namely : 



Hoisting . . slow .3'4 feet per minute, fast 10 feet per minute 



Cross traverse . . „ 25 „ „ „ 105 ,, ,, 



Longitudinal traverse „ 78 ,, „ „ 213 ,, „ 



To provide against undue strains upon the motor, an automatic magnetic cut- 

 out is fixed on the crane, and for the purpose of varying the power and. .speed to 

 meet the requirements of the foundry, a set of resistance coils is provided, governed 

 by a special switch by means of which diiferent resistances can be introduced into 

 the armature circuit of the motor, or the current can be cut off altogether, but so 

 that it must be done by steps, and not sixddenly. The connection between the 

 motor and the conductors is by means of brushes pressed again.st them by elastic 



' Printed in extenso in Engineering, vol. xlvi. p. 268. 



