Explosives . -runners work-ing on a stone it is more usual tohave iron runners work-ing on an iron bed-plate ;of course iron must notwork upon stone, or viceversa, on account of thedanger of genera ting-sparks. In the most usualtype of mill the runnersare G or 7 feet in diameterand about 15 inches wide,and weigh about 4 tonseach. They rotate on theopposite ends of a hori-zontal shaft, which iscarried by a cross-head,which again is attached to a vertical shaft making about eight revolutions a minute. Usually the twoedge-runners are mounted at different distances from the central sh
Explosives . -runners work-ing on a stone it is more usual tohave iron runners work-ing on an iron bed-plate ;of course iron must notwork upon stone, or viceversa, on account of thedanger of genera ting-sparks. In the most usualtype of mill the runnersare G or 7 feet in diameterand about 15 inches wide,and weigh about 4 tonseach. They rotate on theopposite ends of a hori-zontal shaft, which iscarried by a cross-head,which again is attached to a vertical shaft making about eight revolutions a minute. Usually the twoedge-runners are mounted at different distances from the central shaft sothat one works the outer part of the charge and the other the inner, but theirpaths overlap. There are two ploughs of wood covered with leather, whichare fixed to the shaft and travel round with it. These continually pushthe charge away from the centre and the curb respectively, and bring itunder the edge-runners again. The mills make 1\ or 8 revolutions per minute. 1 P. ,t >.. \<»1. iii., e. Fig. 7. Gruson Gunpowder Mill. EXPLOSIVES In the Grusou mill (Fig. 7) the iron runners do not rest on the bed but are•nded a short distance above it, so that there is no danger of a very thinlayer of powder being subjected to great friction. The bearings are bopended that either runner can travel upwards independently of the other when an extra thick portion of charge comes underneath it. The runnersweigh about 5| tons each and rotate equidistantly round the main verticalBhaft. The ploughs are made of phosphor bronze, and each runner is alsoprovided with a Bcraper to prevent the charge being thrown off the bed. Thedrive is by mean- of a la: _ lied gear-wheel, which may be arranged either above the machine or below it. In Germany iron runners are not allowed to work on an iron bed-plateunless they are suspended, as in the Gruson mill. If they actually rest uponthe bed. it must be made of wood fastened down with brass screws. By the action of the runners the ingredients a
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Keywords: ., bookcentury1900, bookdecade1910, bookidexp, booksubjectexplosives
