Repair Procedure for the Lower Articulation Pin on the 24H Motor Grader {7050, 7057, 7100} Caterpillar

Motor Grader

24H (S/N: 7KK1-UP)

Introduction

The lower pin for articulation on the 24H will wear over time. If the pin becomes loose, the bores for the pin must be repaired to prevent wear of the upper pin for articulation. This Special Instruction contains the necessary procedure and information for repairing the lower pin for articulation on the 24H Motor Grader. Two different repair procedures are available. The first procedure should be used if the wear to the bore for the lower pin for articulation is minimal. The second procedure should be used if there is extensive wear to the bore of the lower pin for articulation.

Reference: Refer to Disassembly and Assembly, SENR1438, "24H Motor Grader Machine Systems", "Frames".

Prepare the Area for Welding

Clean the area that will be welded. Make sure that the substances that follow are removed from the area that will be welded.

• Oil

• Grease

• Paint

• Dirt

If the temperature of the base metal is below 0 °C (32 °F), heat the base metal to at least 21 °C (70 °F). Maintain the temperature of the base metal at 21 °C (70 °F) during the welding process.

Note: Heat distortion of the base metal is possible when you weld. Avoid excessive heating of the base metal.

Attach the welding ground cable directly to the base metal. Protect machined surfaces from sparks. Protect the machined surfaces from the weld splatter.

Weld Specifications and Qualifications

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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 kill. Read and understand the manufacturer's instruction and your employer's safety practices. Keep your head out of the fumes. Use ventilation, exhaust at the arc, or both, to keep fumes and gases from your breathing zone and the general area. Wear correct eye, ear and body protection. Do not touch live electric parts. Refer to the American National Standard Z49.1, "Safety in Welding and Cutting" published by the American Welding Society, 2501 N.W. 7th Street, Miami, Florida 33125: OSHA Safety and Health Standards, 29 CFR 1910, available from U.S. Dept. of Labor, Washington D.C. 20210.

Note: Personal breathing protection should be worn by the personnel that are welding. Personal breathing protection will prevent fumes from entering the lungs of the person that is welding. Use a 1U-8088 Type H Respirator for breathing protection.

Welders must be qualified for fillet welding and groove welding. The welders should be qualified in the use of the welding processes that follow: Shielded Metal Arc Welding (SMAW), Flux Cored Arc Welding (FCAW) and Gas Metal Arc Welding (GMAW). Refer to "American National Standards Institute (ANSI)/American Welding Society (AWS) Specification D1.1, or Specification D14.3" for information that regards the qualifications for the processes that follow: SMAW process, FCAW process, and GMAW process. The welders must have used the process at some time within the last 6 months. The welders must complete the process of certification if the welders have not used the welding processes for 6 months.

Proper Welding Procedure on Machines and Engines with Electronic Controls

Proper precautions are necessary to prevent damage to electronic controls. When you weld on a machine with electronic controls, use the steps that follow:

1. Turn off the engine. Put the key start switch in the OFF position.

2. If the machine has a battery disconnect switch, open the switch. If the machine does not have a battery disconnect switch, disconnect the negative battery cable at the battery.

3. Connect the ground cable for the welder directly to the actual machine component that will be welded. Attach the clamp for the ground cable as close as possible to the area that is being welded. This action will reduce the chance of damage from welding current to the components that follow: bearings, hydraulic components, and electrical components.

   Note: Do NOT use electrical components as a ground point for the welder. Do NOT use ground points for electronic components as a ground point for the welder.

4. Protect the wiring harnesses from the weld splatter.

Weld Specifications

Low Hydrogen Electrodes for the SMAW Process

The tables that follow list the mechanical properties of welds that are deposited by low hydrogen electrodes.

Low hydrogen electrodes must be stored in an electrode oven at 120 °C (248 °F). If low hydrogen electrodes get damp, discard or recondition the low hydrogen electrodes to manufacturer specifications.

The table that follows shows setting for the welding current for the electrode diameter.

Use a polarity setting of DC reverse polarity. Remove the slag after each pass of the welding electrode. The width of the weld should not exceed two times the electrode diameter.

As an alternative, use Flux Cored Arc Welding (FCAW) with E71T-1 H8 (ANSI/A5.20) welding electrode. Use shielding gases that are specified by the manufacturer for inside welding. The H8 implies that the electrode is designed to provide less than 8 ml/100 g of diffusible hydrogen in the weld deposit. The weld that is deposited by the flux cored welding electrode will have the following minimum mechanical properties:

Flux Cored Welding Electrode for the FCAW Process

The table that follows lists the mechanical properties of welds that are deposited by the flux cored welding electrode.

The table that follows shows setting for the welding current for the flux cored welding electrode that has a diameter of 1.3 mm (.051 in).

Note: The settings for the welding current can vary due to the position of the weld. Also, the settings for the welding current can vary with the manufacturer of the welding electrode.

Use a polarity setting of DC reverse polarity. Remove the slag after each pass of the welding electrode. The fast freezing characteristics of flux cored welding electrode increases the possibility of evolving gas that is trapped in the weld. Control the size of the weld to reduce the possibility of evolving gas that is trapped in the weld. The volume of the fillet weld should not exceed 8.0 mm (.315 in).

Arc Welding Electrodes for the GMAW Process

The table that follows lists the mechanical properties of welds that are deposited by the GMAW Process.

The welding parameters will vary with the position of the weld and with different electrode manufacturers.

Weld Inspection

The weld should not have any of the conditions that follow:

• Cracks

• Porosity

• Undercut

• Incomplete Fusion

To verify the quality of the weld, refer to"American National Standards Institute (ANSI)/American Welding Society (AWS) Specification D14.3".

Procedure 1 (Minimal Wear to the Bore)

1. Split the machine. Refer to Disassembly and Assembly, SENR1438, "24H Motor Grader Machine Systems", "Frames".
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   Illustration 1	g01683114

2. Remove bolts (6) and washers (5).

3. Remove pin (7).

4. Remove bolts (4), washers (3), and spacers (2). Discard spacers (2) if equipped. Old machines may not be equipped with spacers.

5. Remove plate (1). Discard plate (1).
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   Illustration 2	g01687397
   Fabricated part (8) ( A) 75 mm (3 in) (B) 89.881 ± 0.013 mm (3.53861 ± 0.00051 in) press fit. Do not create center hole until Step 8. (C) 200 mm (8 in) (D) 18 mm (0.71 in)

6. Fabricate plate (8) with 11 mm (0.43 in) thick steel. The following steel should be used to fabricate plate (8).

   • ATSM A570 Grade 45

   • JIS G3106 Grades SM490A, SM490B, or SM490C.

   • CSA CAN3-G40.21-M Grades 300W, 350W, 300WT, or 350WT.

   Note: Pin associated with dimension (B) is installed with a nominal press fit of 0.076 mm (0.003 in). Do not create center hole until step 8.

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   Illustration 3	g01683273

7. Align holes (D) and weld fabricated plate (8) to the existing plate on the frame with a continuous fillet weld.
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   Table 7

   Weld Tolerances
   Weld	Description
   (W1)	12.0 mm (0.47 in) fillet weld with 1.5 mm (0.06 in) of penetration

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   Illustration 4	g06078710

8. Line bore (E) and (G) as per requirements below. Press fit is desired for proper fit of the pin.

   To reuse 117-2027 Pin, bore diameter (E) is 89.881 ± 0.013 mm (3.53861 ± 0.00051 in) and diameter (G) is 89.881 ± 0.013 mm (3.53861 ± 0.00051 in).

   To use the new 271-1421 Pin, bore diameter (E) is 109.882 ± 0.013 mm (4.32605 ± 0.00051 in.) and diameter (G) is 89.881 ± 0.013 mm (3.53861 ± 0.00051 in).

   Note: Reference Reuse and Salvage Guidelines , SEBF8401 for lower hitch dimension. The lower bore of the lower hitch applies to machines using either the 117-2027 or 271-1421 Pin. The upper bore dimensions for the lower hitch are for machines that have updated to the 271-1421 Pin.

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   Illustration 5	g01685105

9. Install pin (7).

   Note: Lower the temperature of pin (7) to −75 °C (−103 °F) prior to installation.

10. Install a new 117-2028 Plate (11).

11. Install washers (3) and bolts (4).

12. Install washers (5) and bolts (6).

13. Ensure that the top portion of the pin (7) is tight against the top piece of the frame. Add shims (10), as required. Refer to Disassembly and Assembly, SENR1438, "24H Motor Grader Machine Systems", "Frames" for the correct procedure.

Procedure 2 (Extensive Wear of the Bore)

1. Split the machine. Refer to Disassembly and Assembly, SENR1438, "24H Motor Grader Machine Systems", "Frames".
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   Illustration 6	g01685913

2. Remove bolts (6) and washers (5).

3. Remove the lower pin for articulation (7).

4. Remove bolts (4), washers (3), and spacers (2). Discard spacers (2).

5. Remove plate (1).
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   Illustration 7	g01047797
   Location of the worn sections of bore

6. Line bore the worn sections of bore.

   Note: The line bore must have a common axis with the upper articulation joint.

   Note: The rear frame for the 24H is now serviceable using the 24M rear frame and lower hitch pin. This line boring procedure will require the new 271-1421 Pin.

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   Illustration 8	g01685935
   Dimension (A) and (B) will vary depending on the diameter of the pin. For 271-1421 Pin, Bore dimension (A) is 109.882 ± 0.013 mm (4.32605 ± 0.00051 in) and bore dimension (B) is 89.881 ± 0.013 mm (3.53861 ± 0.00051 in). A press fit of 0.094 mm (0.00370 in)is desired. Do not bore holes until step 9. Dimension (C) will vary depending on the amount of material that is removed from the bore. Dimension (D) 80 mm (3.15 in). Dimension (E) 34 mm (1.34 in).

   Note: Dimensions (A) and (B) will not be the same measurement.

7. Fabricate ring plates (8) and (9). Dimension (A) and dimension (B) should not be created now. Use the following types of steel when you fabricate the ring plates (8) and (9).

   • ATSM A570 Grade 45

   • JIS G3106 Grades SM490A, SM490B, or SM490C.

   • CSA CAN3-G40.21-M Grades 300W, 350W, 300WT, or 350WT.
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   Illustration 9	g01686673

8. Weld ring plates (8) and (9). Use a continuous fillet weld around the entire circumference.
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   Table 8

   Weld Tolerances
   Weld	Description
   (W1)	12.0 mm (0.47 in) fillet weld with 1.5 mm (0.06 in) of penetration

9. Line bore dimension (A) and dimension (B) in ring plates (8) and (9).

   Note: Reference Reuse and Salvage Guidelines , SEBF8401 for lower hitch dimension.

   Note: The line bore must have a common axis with the upper articulation joint.

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   Illustration 10	g01687144

10. Use a new 178-9481 Plate As (10) as a guide to mark the hole positions for ring plate (9).

11. Use a 14.25 mm (0.561 in) drill to drill holes (11) to a depth of 44.0 mm (1.73 in). Use a M16 X 2 tap to tap holes (11) to a depth of 38.0 mm (1.50 in).
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    Illustration 11	g01687220

12. Install a new 271-1421 Pin (7).

    Note: The rear frame for the 24H is now serviceable using the 24M rear frame and lower hitch pin. This line boring procedure will require using the new pin 271-1421 Pin.

    Note: Lower the temperature of pin (7) to −75 °C (−103 °F) prior to installation.

13. Install a new 178-9481 Plate As (11).

14. Install washers (3) and bolts (4). Torque the bolts to 200 N·m (148 lb ft).

15. Install washers (5) and bolts (6). Torque the bolts to 200 N·m (148 lb ft).

16. Ensure that the top portion of the pin (7) is tight against the top piece of the frame. Add shims (10), as required. Refer to Disassembly and Assembly, SENR1438, "24H Motor Grader Machine Systems", "Frames" for the correct procedure.