1. It requires only a two-hoist drum crane.2. It provides accuracy in locating leads in all batterpositions.3. It provides rigid control of the leads duringpositioning operation.4. It allows batter angles to be set and accuratelymaintained.5. It allows for the use of short boom angles thatincreases the crane capacity.6. The boom can be lowered and leads folded underfor short hauls over the road when a crane with adequatecapacity is used This operation depends on the lengthof the lead and boom and the configuration of the crane.DISADVANTAGES.— Some disadvantages ofusing an extended four-way lead are as follows:1. It is the heaviest and most expensive of the threebasic lead types.2. It is more troublesome to assemble.Spud LeadsA spud lead is a steel wide flange or H-beam usedin place of pile-driving hammer leads. The pile-drivinghammer rides on the flange of the beam through spudclips bolted to one side of the pile-driving hammer (fig.12-58).Depending on the design of the spud lead, the spudcan be used as a swinging and underhung lead orequipped with a sheave head assembly as an extendedfour-way lead An advantage of this type of lead is thatit bears the whole bottom of the pile cap to the pilingespecially when sheetpiling is being driven (fig. 12-59).PILE-DRIVING HAMMERSThe three principal types of pile-driving hammersare the drop hammer, the steam, or pneumatic,hammer, and the diesel hammer.A drop hammer is a block of metal hoisted to aspecific height and then dropped on a cap paced on thebutt or head of the pile. Drop hammers weigh from1,200 to 3,000 pounds.WARNINGThe noise generated by a pile drivingoperation can cause hearing loss. Hearingprotection must be worn by personnel in thevicinity of pile driving operations.Figure 12-58.-Spud clips mounted to one side of the pile-driving hammer.Figure 12-59.-Sheet pile driving with spud leads.12-41
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