. The design of the Chicago and Northwestern Railway train shed . materialpassing over a l/4 screen, the fome r being 28^ and the latter21,5^. Universal Portland cement is used throughout the entirework. At first two kinds of concrete mixers were in use, the Drakeand the Ransome mixers. The first consists of blades fastenedto a shaft ahout 6 feet long revolving in a semi-cylindrical dry materials are placed in the trough at the machine end anddriven forv/ard to the discharge. Water is supplied from a perfora-ted pipe running along the top edges of the trough. The arrange-I ment of t
. The design of the Chicago and Northwestern Railway train shed . materialpassing over a l/4 screen, the fome r being 28^ and the latter21,5^. Universal Portland cement is used throughout the entirework. At first two kinds of concrete mixers were in use, the Drakeand the Ransome mixers. The first consists of blades fastenedto a shaft ahout 6 feet long revolving in a semi-cylindrical dry materials are placed in the trough at the machine end anddriven forv/ard to the discharge. Water is supplied from a perfora-ted pipe running along the top edges of the trough. The arrange-I ment of this machine is shown in fig. 12. This machine was notvery effective and finally abandoned in favor of the Ransome. Nodescrii>tion ofthis mixer is necessary as any engineering periodicaladvertises and illustrates it, and also because one of them isshown in fig. 13. The arrangement of mixers is an important itemin that on the arrangement depends the facility with which the con-crete is mixed. As a geneal rule it may be said, that the materials - 31 ~7. should be put into the mixer v/ith as little handling as to fig. 12, the method of delivering to the Drake mixeris seen. This method is very poor in that the material has tobe lifted about 3 feet with shovels from the platform into themixer. This handling could be eliminated by having the platformon a level v/ith the top of the trough or even better, by havinga hopper at the machine end cind dumping the wheelbarrows directlyinto it. Then with a trap door arrangement the materials could be :fed to the mixer as needed. V^ith the mixer arranged as shown 24men hauling about 100 feet put in 40 yards of concrete in 8 hoursat a cost of | per yard. Pig, 13 shows a Ransome mixer, and illustrates the methodof delivery advocated above for the Drtike machine. Here the ma-terials are dumped directly from the wheelbarrows into the machine, and water is fed by bucket, insuring a more uniform mixture. Thematerials
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