Page:Popular Science Monthly Volume 91.djvu/765

This page needs to be proofread.


Whirling Concrete Poles into Shape £^

THE principle of centrifugal action utilized in a machine invented by

��Centrifugal action is set up and the liquid concrete is thrown against the tubular frame

��Walter H. Lienesch, of Chicago, makes possible the production of substan- tial, attractive and inexpensive lamp poles, telegraph poles and sign posts from re- inforced concrete.

The machine consists of an outer cylin- drical frame which carries the mold and which is constructed of sheet metal, formed from two half-cylinders hinged together. Within this carrier-frame is a smaller mold-' cylinder, of tapering, rather than of true cylindrical form. This mold is likewise constructed from two half-cylinders of sheet metal, hinged together. The inner mold is supported by braces carried within the outer carrier-frame or cylinder.

Both frames are opened and concrete is poured into the inner mold cylin- der to partly fill it, reinforcing wire netting having been placed in the mold first. The mold and the outer carrier -cylinder are then bolted or latched together.

����The concrete lamp posts are unusually- attractive and are made in different styles

A motor which is connected with the carrier-frame by a flexible shaft is started up, and carrier-frame and mold are rapidly rotated axially. The resulting centrifugal action whirls the concrete compactly against the cylindrical mold sides to form a tubular pole. The operation is continued long enough to allow the concrete to harden. The machine is then stopped and the newly formed concrete pole is removed. Poles of almost every type can be thus formed.

��A telegraph pole of concrete recently erected in Milwaukee. It will probably be doing as good service as now one hundred years from today

���The mold is constructed of comparatively thin metal and is light in weight so that it can be readily removed from the carrier-frame after the pole has been completed and is ready to set up

749

�� �