CARTRIDGE GP-TURBOCHARGER 3509781 - Caterpillar

Purpose
A stringline provides an accurate, parallel reference for elevation (grade) and alignment (steering) control of automated fine grading and paving machines.The most important steps in determining the accuracy and smoothness of the finished pavement are:1. Preparation of the stringline.2. Setup of a particular machine to the stringlineTo maintain an accurate elevation reference, the stringline must be the same elevation above each survey hub. If there are cut or fill hubs, the distance between the stringline and the survey hub may vary at each stringline stake. The height of the stringline should be a constant distance above the top of the pavement.
Elevation ReferenceSurvey hubs (2) are placed by the survey crew on one or both sides of the roadway a maximum of 15 m (50 ft) apart. Stringline stakes and arms (1) are then set up by the stringline crew so the bottom of the stringline is the specified distance above the top of each survey hub. Distance A is normally between 450 and 750 mm (1.5 and 2.5 ft).To maintain an accurate alignment reference, the stringline must be the same distance from the centerline of the roadway.
Alignment ReferenceAfter the survey crew has placed the survey hubs, they use instruments to precisely mark the specified distance from the centerline. That distance is indicated by driving tack (3) into the top of each hub.
Tack Placement for Centerline DistanceTack (3) may not always be the same position on the top of each hub, but it is always the same distance from the centerline.Equipment
Stringline equipment is generally available in sets of various lengths. Each set provides stringline, stakes, holders and blocks, take-up reels, and storage reels for the specified length based on 15 m (50 ft) spacing between the stakes.The tension of the stringline is controlled by the take-up reels. In the assembled position, the take-up reels are anchored by metal stakes driven through the winch body. The unused portion of the stringline is stored on tripod-mounted storage reels.Placement
During construction of a new roadway, a stringline is sometimes needed for multiple layers. All users of the stringline should agree on the stringline survey and stringline setting needs.A decision must be made where to place the stringline in relation to the roadway. Factors to be considered are:* The terrain* Delivery of material* The type of road building machines to be usedIt is very important that users agree upon and understand the relationship between each layer of the roadway and the elevation reference provided by the top of the survey hub. The road builder must know precisely how far above or below the survey hub to place each layer.Elevation and Depth
Elevation is the relationship of the pavement surface, base, or subgrade to the survey hub. Depth is the relationship of the roadway layer to the layer below it.The elevation of the pavement surface is always in the same plane at a specified distance from the survey hub.The depth of a roadway layer depends on the accuracy of the surface below that layer. If the