C '72 ] 



of the lift is reduced in time thereby. With the bucket empty 

 and the platform horizontal, the load at the free end can 

 be varied from 160 Ibs. to 362 Ibs. without disturbing the 

 equilibrium, whilst with a load of 247 Ibs. in the bucket, equal 

 to 24*7 gallons of water, the platform remained horizontal, 

 though the loads at the working end varied between 58 Ibs. 

 and 275 Ibs. Taking the mean between the two extreme 

 values to be the actual weight required to balance the plat- 

 form, it is possible by taking moments about the centre, to 

 determine the only force acting on the platform which is not 

 measured, viz., the weight of the empty bucket and ropes 

 acting with a leverage of 2^443 to i. With the bucket un 

 loaded, the weight works out as 65*4 Ibs. and when loaded, 

 62 Ibs., a remarkably close agreement. The lift was worked 

 during the trial by a bullock weighing 7oolbs. and a man 

 weighing nylbs. The rate of working was Si lifts per hour 

 from a well 18 feet i inch deep. The average quantity of 

 water brought up by the bucket, as measured into a tank 

 was 23*5 gallons, and the useful work done per hour amount- 

 ed to 344,210 ft. -Ibs. The mechanical efficiency of the lift 

 can be ascertained by multiplying the fall of the front end 

 of the platform by the force required to set it in steady 

 motion when lifting a bucket full of water. The total height 

 the bucket had to rise to discharge its contents was 22 feet 

 and the end of the platform therefore fell 9 feet and the 

 work done was 584x9 = 5,256 ft.-lbs. To raise the platform 

 back to its initial position, the free end then falls 5'i8 feet and 

 the load on it is 362 Ibs. and the work done is equal to 

 1875 ft.-lbs. The total work therefore done in a single lift is 

 7,131 ft.-lbs. and the useful work given to the water is 

 4,245 ft.-lbs. ; so that the mechanical efficiency when just 

 working is 59*6 per cent ; at the normal rate of working it is 

 much lower, probably not more than 50 per cent. 



