[ '68 ] 



214. The Double mot. The following data occur for an 

 experiment with the Double mot conduced in Madras : 



FIG. 37. THE DOUBLE-MOT (PLAN), 



FIG. 38. THE DOUBLE-MOT (SECTION THROUGH AB.). 



"The buckets were of iron with leathern discharging trunks 

 and were in good order and discharged an average of 28 

 gallons per bucket as measured into a tank. The trial lasted 

 3 hours, and in that time 200 buckets of the water raised. The 

 mean lift was 22-125 ft. and the useful work done per hour 

 was 413,000 ft.-lbs. The circumference of the drum of the 

 whim was 12 ft. ui"and the circumference of the circle in 

 which the bullock walked was 60 ft. 9," so that the velocity ratio 

 was 4*67. The pull on the dynamometer at the ordinary speed 

 of working was 90 Ibs. and the pull to just prevent a full 

 bucket descending, 59 Ibs. and the pull to just raise a full 

 bucket 81 Ibs. The mean between these last two quantities, 

 70 Ibs., is the force at the end of the lever arm required to 

 balance a full bucket of water when friction is eliminated. 

 Multiplying by the mechanical advantage, the unbalanced 

 weight is 327 Ibs., a result probably not very much in error 

 as the water in the bucket weighed about 300 Ibs. The 

 mechanical efficiency of the lift just moving is therefore 74 



