caps. The buffer nut bumpers absorb the recoil of theBelleville springs.RAM-PISTON OVERSTRIKE.— The length offree travel (maximum stroke) of the ram from the bottomof the stroke to the safety catch lip at the top is 109 inches(fig. 12-65). When the ram is recoiled high enough, theram rings will engage the safety catch lip and prevent itfrom going out of the top. If the upward force of the ramis too great, the whole hammer will be lifted off the pile,possibly causing the rings to shear. To prevent thisdanger, watch the projection of the ram above thehammer and reset the throttle when necessary.Pile-Driving CapsA pile-driving cap is a block (usually a steel block)that rests on the butt or head of the pile and protects itagainst damage by receiving and transmitting the blowsof the hammer or ram. In the steam, or pneumatic,hammer, the cap is a part of the hammer. The cap witha drop or diesel hammer is a separate casting with thelower part recessed to fit the head or butt of the pile andthe upper part recessed to contain a hard cushion blockthat receives the blows of the hammer. The cap is fittedwith a wire rope sling so that the cap, as well as thehammer, may be raised to the top of the leads whenpositioning a pile in the leads.On the DE-10 hammer, you place one cushion blockin the drive cap and lash the cap to the hammer front andFigure 12-66.-H-beam pile-driving cap.back with two pieces of 1/2-inch wire rope and clips.You must allow 3 to 4 inches of slack in the wire rope.The cap is normally lashed to the hammer after thehammer is placed in the leads.NOTE: The top of the cushion block should be kepthigh enough to prevent the hammer shroud from foulingon the rim of the drive cap pocket.Pile-driving caps are available for driving timber,concrete, sheet, and H-beam piles. Figure 12-66 showsa pile cap designed for driving a H-beam pile.Placing Hammer in LeadsPlacing the pile-driving hammer in the leads isperformed two ways: while the leads are horizontal orvertical.Leads are not always used in pile-drivingoperations. Pile hammers can be used as a flyinghammer, using special adapter caps attached to thehammer (fig. 12-67). This is far the most dangerous ofall types of pile-driving operations and should beattempted only by experienced personnel.Figure 12-67.—Pile driving using a flying hammer.12-47
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