348 



FIELD OPERATIONS 



The following conditions have been found to produce excel- 

 lent results with a 4-ft. cube mixer: Each batch is mixed 

 1 min. at a speed of 10 rev. per min., making a total of 

 15 turns per batch. The time allowed for dumping, cleaning 

 and charging the mixer and for temporary stoppage of the 

 work is about 3 min., making an average time interval 

 between successive batches of 5 min., which is at the rate 

 of 12 batches per hour. Allowing only cu. yd. of rammed 

 concrete per batch, this gives for a 10-hr, day an output of 



105 cu. yd. 



R a n s o m e Mixer. 

 Another form of batch 

 mixer, called the Ran- 

 some mixer, is illustra- 

 ted in two views in 

 Fig. 2. This machine 

 consists essentially of 

 a hollow cylindrical 

 drum that is mounted 

 on a horizontal axis and 

 has a circular opening 

 in each end. As shown 

 in (a), the mixer is 

 charged through one 

 of these openings a. 

 In the other opening, 

 shown in (b), is a chute 

 b that receives the 

 mixed concrete from 

 the drum and delivers 

 it to a wheelbarrow or other receptacle. Inside the 

 drum are several steel blades arranged in such a manner 

 as to deflect the material from side to side as the drum 

 revolves. The drum is mounted on four rollers and is sup- 

 ported on a truck, which is either made stationary or mounted 

 on wheels, as required. The mixer is turned by power 

 applied to the rim of the drum either from an engine mounted 

 on the same frame or from a belt or a chain. The illustra- 

 tion shows one driven by a belt. 



FIG. 1 



