- Pipelayer: All
- Track-Type Loader: All
- Track-Type Tractor: All
- Track-Type Loader: All
Introduction
This special instruction provides information pertaining to material packing (debris/soil/rock) in the link box to the extent that the sprocket tooth and idler tread cannot make full penetration into the track chain.
Effective Track Frame Guarding
Whether a machine has a SystemOne, Heavy Duty, Sealed and Lubricated, Rotating Bushing or any other type of track, packing of the track produces excessive forces on the undercarriage. Effective guarding of the track begins with shedding of material away from the top of the track roller frame (TRF) and idlers to minimize the possibility of the material getting into the link box. Next is guarding from below the TRF to prevent material from entering the link box. Lower guarding must not be used for mud packing conditions. Lower guarding should only be used in conditions where rock and free flowing debris are entering the track roller area. The Custom Track Service Handbook (PEKP9400) gives guidance on packing and the use of roller guarding.
If the link boxes are packing enough, the track will be forced away from the sprocket. This action may cause track jumping of the sprocket. If the link boxes are packed enough, the idler is forced into the extreme recoil position. When the chain is forced away from the sprocket and the idler is forced to the extreme recoil position, great load forces are put on the undercarriage. These forces are strong enough that the forces can break idler mounting blocks, idler shafts, and in some cases, the track can separate.
Underfoot material, machine application, and operator technique all contribute to debris entry and packing into the link box.
Underfoot Material
Wet, pliable debris/soil that can be "pushed" or "extruded" through the link openings in the track link box have relatively low potential to pack into the link box. Materials such as wet sand or clay have small aggregate that will pass though the track link holes.
Damp and dry materials such as incompressible debris/soil/rock that cannot be "pushed" or "extruded" through holes in the track link box has higher potential to pack into the link box. Materials such as clay/rock mixtures, rock, wood chunks, trash and metal, or sod like materials have aggregate that is too large to pass through the track link holes.
Machine Application
Low Potential for Packing: Fine grading
Moderate Potential for Packing: Damp clay/sand/rock mixture such as residential construction site, "V" ditch grading, slope work
High Potential for Packing: Forestry work, aggregate stock piling, ice, and rock, steep slope work, land fill
Operator Technique
High Potential for Packing: Sharp turns in free flowing material which allows material to collect at the idlers above the TRF
Guarding Guidelines
Effective track frame guarding must:
- Shed debris from the top of the track frame
- Guard debris from entering below
Recommendations for Oval Track Machines:
- Primary coverage - Guards at the bottom side of the idlers and the sprocket that will prevent the ingestion of material that is between 25.4 mm (1 inch) and 152.4 mm (6 inch) in size.
- Secondary coverage - Primary coverage plus full-length roller guards that prevent material from entering the link boxes between the rollers, idler, and sprocket.
- Full coverage - Primary and Secondary coverage plus "tent" type guards. Guards sit on top of the roller frame and shed material away from the idlers and rollers.
Recommendations for Elevated Track Machines:
- Primary coverage - Guards at the bottom side of the front and rear idlers that will prevent the ingestion of material that is between 25.4 mm (1 inch) and 152.4 mm (6 inch) in size.
- Secondary coverage - Primary coverage plus full-length roller guards that prevent material from entering the link boxes between the rollers and idlers.
- Full coverage - Primary and Secondary coverage plus "tent" type guards. Guards sit on top of the roller frame and shed material away from the idlers and rollers.
Note: Lower guards must only be used in conditions where rock and free flowing debris is entering the track roller area. Lower guards should not be used for mud packing conditions.
The use of roller guards should be based on the need to keep rocks and/or other foreign debris from entering the roller areas. Roller guards should be used in conditions where there is a danger of rocks and debris entering the spaces between rollers. These conditions can cause structural damage for rollers, idlers, links, bushings, or sprockets.
Roller guards should only be considered when working in the following types of materials and when structural damage to rollers, idlers, links, bushings, and sprockets may be a problem:
- Rocks or gravel between 25.4 mm (1 inch) and 152.4 mm (6 inch) in size
- Tree limbs, branches, or other non-extrudable wood products, or waste materials
- Sanitary landfill and demolition materials only if large metal, wood, or other high strength objects of 25.4 mm (1 inch) to 152.4 mm (6 inch) in size, are frequently encountered.