Procedure for Replacement Grouser Bars {0679, 4172, 4173, 7950} Caterpillar


Procedure for Replacement Grouser Bars {0679, 4172, 4173, 7950}

Usage:

D6D 01Y
Caterpillar Products
Machines with Grease Lubricated Track with Swage
Machines with Greased Lubricated Track (GLT)
Machines with Positive Pin Retention (PPR) Track
Machines with Positive Pin Retention 2 (PPR2) Track
Machines with Rotating Bushing Track
Machines with Sealed Positive Pin Retention (PPR) Track
Machines with Sealed Track
Machines with Sleeve Bearing Track
Machines with SystemOne Undercarriage
Machines with non-PPR Sealed and Lubricated Track
Track Drills
MD5150C (S/N: SEY1-UP)

Introduction

Table 1
Revision  Summary of Changes in SEBF8556 
22  Added serial number prefixes for New Product Introduction. 
19–21  Added serial number prefixes for New Product Introduction. 
18  Added serial number prefixes for New Product Introduction.
Updated introduction information. 

© 2019 Caterpillar All Rights Reserved. This guideline is for the use of Caterpillar dealers only. Unauthorized use of this document or the proprietary processes therein without permission may be violation of intellectual property law. Information contained in this document is considered Caterpillar: Confidential Yellow.

This Undercarriage Reconditioning Bulletin contains the necessary information to allow a dealer to establish a parts reusability program. Reuse and salvage information enables Caterpillar dealers and customers to benefit from cost reductions. Every effort has been made to provide the most current information that is known to Caterpillar. Continuing improvement and advancement of product design might have caused changes to your product which are not included in this publication. This Undercarriage Reconditioning Bulletin must be used with the latest technical information that is available from Caterpillar.

For technical questions when using this document, work with your Dealer technical Communicator (TC).

To report suspected errors, inaccuracies, or suggestions regarding the document, submit a form for feedback in the Service Information System (SIS Web) interface.

Summary

Reconditioning worn track shoes is performed by either replacing the shoe with a new pad, or a fabricated grouser bar attached to the existing shoe. This bulletin addresses the replacement of grouser bars using mechanized or semi-automatic welding equipment. Replacement grouser bar stock is available from an outside supplier. Using the recommended procedure will extend undercarriage life.



Illustration 1g02375817
Example of reconditioned track shoe with new grouser bar

Note: Caterpillar recommends removing shoes from sealed and lubricated link assemblies because of potential seal lip damage caused by exposure to temperatures of 71 °C (160 °F) or higher. Under certain conditions, this option does not apply. Therefore, special precautions must be taken when welding shoes on link assemblies to assure seal integrity. Refer to sections "Preheating" and "Welding Procedure (Shoes on Link Assembly)" for the appropriate welding procedure.

Safety



Illustration 2g02139237

------ WARNING! ------

Personal injury or death can result from fumes, gases and ultraviolet rays from the weld arc.

Welding can cause fumes, burn skin and produce ultraviolet rays.

Keep your head out of the fumes. Use ventilation, exhaust at the arc, or both, to keep fumes and gases from your breathing area. Wear eye, ear and body protection before working.

Protect yourself and others; read and understand this warning. Fumes and gases can be dangerous to your health. Ultraviolet rays from the weld arc can injure eyes and burn skin. Electric shock can cause death.

Read and understand the manufacturer's instructions and your employer's safety practices. Do not touch live electrical parts.

See "American National Standard Z49.1, Safety in Welding and Cutting" published by the American Welding Society.

American Welding Society
2501 N.W. 7th Street
Miami, Florida 33125

See "OSHA Safety and Health Standards, 29 CFR 1910", available from U.S. Department of Labor.

U.S. Department of Labor
Washington, D.C. 20210

Most accidents that involve product operation, maintenance, and repair are caused by failure to observe basic safety rules or precautions. An accident can often be avoided by recognizing potentially hazardous situations before an accident occurs. A person must be alert to potential hazards. This person should also have the necessary training, skills, and tools to perform these functions properly.

This bulletin may contain hazardous steps. A safety alert symbol like the one below is used to indicate a hazard.

Warning messages identify a specific, imminent, latent, hazard that has a reasonable probability of resulting in personal injury or death if the warning is ignored.

Canceled Part Numbers and Replaced Part Numbers

This document does not include all canceled part number and replaced part number information. Use NPR on SIS for information about canceled part numbers and replaced part numbers. NPR will provide the current part numbers for replaced parts.

Required Tooling

Table 2
Required Tools 
Part Number  Description 
8T-3054  Clean 'N Strip' Disc 

Preparation



Illustration 3g02375819
Clean rust away with wire brush and 8T-3054 Clean 'N Strip' Disc

The track shoe and chain assembly must be cleaned before any welding takes place. Foreign matter (packed mud, dirt, oil, grease, and paint) must be removed and the track washed. If washing is not practical during field repairs, effort should be made to clean as much dirt away as possible.

Rust and dirt residue should be removed using a wire brush and an 8T-3054 Clean 'N Strip' Disc. During welding, rust and dirt will cause the weld to be brittle and crack if exposed to external stress and thermal contraction.

Welding



Illustration 4g02375836
Cross-section demonstrating cutting face drag
(A) Kerf width
(B) Drag
(1) Cutting tip
(2) Work piece
(3) Drag lines

When mechanized welding equipment is used, worn grouser bars are trimmed leaving a 25.4 mm (1.00 inch) projection from the shoe pad. Trimming is performed using a gas/oxygen cutting torch. Fuel gases include acetylene, propane, propylene, or natural gas. Dealers should consult welding suppliers for gas/oxygen recommendations.

Minimize the kerf to maintain squareness of the cut edge. Drag influences edge quality and optimum edge quality results from zero drag. To stay at zero drag, the oxygen stream must enter and leave the cut in a straight line. Oxygen pressure and torch travel speed must be adjusted for obtaining a “drop-out” (a clean, fully severed edge).

If grouser bar fabrication is performed in the field, usually the worn grouser is not trimmed. During field fabrication, the worn grouser bar should be cleaned and the pre-formed bar welded into place.

Preheating

Preheating the piece parts before welding is an effective method to reduce cooling rates of the weld and Heat Affected Zone (HAZ). Preheating also controls distortion, residual stress, and arc input required for weld deposit. Preheating prevents cracking in hardenable steels and increases the HAZ width. Without preheat, the HAZ can result in a brittle metallurgical structure. Track shoe grouser trimming provides preheat for the pad. The replacement grouser bar requires preheat also. The preheat temperature for alloy or high carbon steel should be 149 °C (300 °F).

Types of Equipment



Illustration 5g02375823
Typical submerged arc grouser welding in process.

Several types of welding equipment are used for grouser bar fabrication. Mechanized equipment has stations for grouser bar trimming, welding, and replacement bar. One mechanized grouser bar welder is the WTC model CG-3 Grouser Welder.

Grouser Bar

Replacement grouser bars should be made from 10B35 material. The material will assure a heat treat of 50 Rc hardness for the grouser countour. Core hardness should average 47 Rc. Grouser bars must be available in cut-to-length sizes and in non-heat treated 6 m (20.0 ft) lengths. This quantity provides for good field performance.

Welding Parameters

Table 3
Mechanized Welding Equipment 
Process  Sub Arc - Tiny Twin  Sub Arc - Single Wire 
 
Parameters  Wire Type 
Wire  Lincoln L-60 5/64 diameter  Lincoln L-60 1/8 diameter 
Flux  Lincoln 760 or Lincoln 780  Lincoln 760 or Lincoln 780 
Wire Feed Speed  250 to 350 I.P.M.  90 to 115 I.P.M. 
Amperage  1000 to 1400  700 to 800 
Voltage  35 to 40  35 to 40 
Stickout  31.8 mm (1.25 inch)  31.8 mm (1.25 inch) 
Polarity  Reverse  Reverse 
Travel Speed  15 to 25 I.P.M.  10 to 15 I.P.M. 

Table 4
Semi-Automatic Welding Equipment 
Process  Flux Cored  Sub Arc 
 
Parameters  Wire Type 
Wire  Lincoln NS-3M 3/32  Lincoln L-60 5/64 diameter 
Flux/Gas Shielding  --  Lincoln 760 or 780 
Wire Feed Speed  230 to 275 I.P.M.  240 to 265 I.P.M. 
Amperage  400 to 450  450 to 500 
Voltage  31 to 32  34 to 38 
Stickout  69.9 mm (2.75 inch)  28.58 mm (1.125 inch) 
Polarity  Reverse  Reverse 
Travel Speed  16 to 22 I.P.M.  12 to 15 I.P.M. 
No. of Passes  1 to 2  1 to 2 

The recommended welding parameters are a guide to fabrication. During grouser bar welding, adjustments may be made to maintain weld quality. The consumables are examples used by Caterpilar dealers. All welding consumables meet American Welding Soceity specifications.

Welding Procedure (Shoes Removed)

  1. With mechanized grouser welders, track shoes are removed from the chain assembly and then cleaned and trimmed.

  2. Not necessary to tack weld grouser bars into position when using mechanized welding equipment capable of hydraulic clamping. When no clamping mechanism is available, the replacement grouser bars must be tack welded into place using E7018 1/8 diameter electrode.

  3. Track shoe/replacement bar should be preheated to 149 °C (300 °F). No welding should occur if the temperature falls below 65 °C (149 °F).

  4. Use the recommended welding consumables and parameters outlined on Table 3 and Table 4.

  5. Avoid gaps between the track shoe and grouser bar. Weld penetration can cause burn-through. When required, fill the gap using E7018 electrode or a multi-pass weld.

  6. Cracking can occur if current is too high or travel is too fast. Cracking will also occur if arc voltage is too high and the grouser bar is welded cold without preheat.


Illustration 6g02375838
Reconditioned track assembly after welding

Welding Procedure (Shoes on Link Assembly)

  1. Field fabrication does not allow trimming. Grinding, however, will smooth uneven surfaces, remove contaminants and deformed material, and allow for better bar fit-up.

  2. Tack weld replacement grouser bar using an E7018 1/8 diameter electrode or comparable semi-automatic welding process.

  3. Preheat the replacement grouser bar and shoe to 37 °C (99 °F). Preheating is important to reduce cracking susceptibility. A lower temperature is allowed to reduce heat input in the seal cavity of the link.

  4. Use the recommended welding consumables and parameters outlined on the table 3 and table 4. Cracking can occur if current or voltage is too high.

  5. Weld one side of the grouser using two passes to keep heat input low. Do not fill the entire groove with one pass.

    Note: Keep the temperature of the link counterbore area below 71 °C (160 °F). Temperatures at or above 71 °C (160 °F) will cause permanent seal lip damage.

  6. Let the weld and shoe cool to 37 °C (99 °F) prior to welding the opposite side of the grouser.

  7. Weld the opposite side using two passes.

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