Engineering and Contracting . HOISTS USED IN CHICAGO FOUNDATION SHAFT SINKING. A standard method of foundation construction for tallbuildings in Chicago is to sink circular shafts throughthe overlying clay blanket 50 to 100 ft. thick to ledgerock or hardpan and fill these shafts with concrete. Gen-erally there is a shaft for each foundation column sothat for a large building many shafts are required andthe task of excavation becomes one of importance in themere matter alone of handling the spoil out of shaft. Theusual hoisting outfit is of the type shown by Fig. 1; sev-eral of these hoists in
Engineering and Contracting . HOISTS USED IN CHICAGO FOUNDATION SHAFT SINKING. A standard method of foundation construction for tallbuildings in Chicago is to sink circular shafts throughthe overlying clay blanket 50 to 100 ft. thick to ledgerock or hardpan and fill these shafts with concrete. Gen-erally there is a shaft for each foundation column sothat for a large building many shafts are required andthe task of excavation becomes one of importance in themere matter alone of handling the spoil out of shaft. Theusual hoisting outfit is of the type shown by Fig. 1; sev-eral of these hoists in a row are commonly driven by anendless steel cable operating over the driving is obvious from inspection that, should driving cableslip off a sheave while the bucket is being hoisted, thepull would reverse the rotation of the sheave and thebucket descending the shaft would fall on the workmen atthe shaft bottom. To safeguard against this mishap thesafety brake shown by Fig. 2 has been devised and put on t-eSwMShck. Lerel v/////////////////////////////- steel ffinefs Fig. 1—Head Frame Hoist. the market by French & Allen, manufacturers of con-tractors equipments, 508 S. Canal St., Chicago, 111. Between the timbers which carry the sheave and withinhead shaft is bolted a casting A within which runs abrake wheel B keyed to the shaft. The two slots, C, C,in the casting are eccentric with respect to the brakewheel; they provide for the brake shoe D as to the drawing, the shaft usually revolves inthe direction shown by the arrow, and so revolving thebrake shoe rides up on the wheel with very little of the direction of revolution, as would resultfrom a falling bucket, carries the brake shoe down and the eccentric slot C causes it to wedge and stop thewheel. It the normal operation of the shaft is the re-verse of that indicated the brake shoe is shifted to the
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Keywords: ., bookcentury1900, bookdecade1900, bookpublisherchicago, bookyear19
