Mobil-TracSystems/MTS {4198} Caterpillar

Agricultural Tractor

35 (S/N: 8RD1-UP; 9DF1-UP; ADK1-UP; 8DN1-UP; 3HS1-UP)

45 (S/N: ABF1-UP; 3BK1-UP; 1DR1-UP; 4KW1-UP; 4DZ1-UP)

55 (S/N: 5DK1-UP; 3SM1-UP; 7DM1-UP; AEN1-UP; 6NN1-UP; 7TZ1-UP)

65 (S/N: 7YC1-UP)

65B (S/N: 7YC1-UP)

65C (S/N: 2ZJ1-UP)

65E (S/N: 1GM1-UP; 6GS1-UP)

70C (S/N: 2YL1-UP)

75 (S/N: 4CJ1-UP)

75C (S/N: 4KK1-UP)

75D (S/N: 5AR1-UP)

75E (S/N: 1HM1-UP; 6HS1-UP)

85C (S/N: 9TK1-UP)

85D (S/N: 4GR1-UP)

85E (S/N: 1NM1-UP; 6JS1-UP)

95E (S/N: 1SM1-UP; 6KS1-UP)

MT735 (S/N: AKN1-UP)

MT745 (S/N: ALA1-UP)

MT755 (S/N: ALM1-UP)

MT765 (S/N: AMS1-UP)

MT835 (S/N: BAM1-UP)

MT845 (S/N: BBP1-UP)

MT855 (S/N: BCC1-UP)

MT865 (S/N: BDS1-UP)

Asphalt Paver

AP-1055B (S/N: ABB1-UP; 8BM1-UP; A3P1-UP)

AP-1055D (S/N: FAC1-UP)

AP-655C (S/N: CDG1-UP; AYP1-UP)

AP1055E (S/N: TJF1-UP; TRS1-UP)

AP1055F (S/N: TJ51-UP; RLM1-UP)

AP255E (S/N: D8A1-UP)

AP355F (S/N: NED1-UP; NRG1-UP; NTT1-UP)

AP500F (S/N: AF51-UP; F5M1-UP)

AP555E (S/N: A5D1-UP)

AP555F (S/N: AP51-UP; M451-UP; 5F51-UP; RBM1-UP)

AP600F (S/N: JA61-UP; D6F1-UP)

AP655D (S/N: GNN1-UP; GNZ1-UP)

AP655F (S/N: 4521-UP; P651-UP; 6551-UP; MH61-UP; ML61-UP)

AP655F L (S/N: AC61-UP)

BG-2255C (S/N: CKR1-UP)

BG-2455C (S/N: B2G1-UP; ACM1-UP; 6TN1-UP)

BG-2455D (S/N: BNW1-UP; BXW1-UP)

BG1055E (S/N: FRR1-UP)

BG555E (S/N: B5P1-UP)

Combine

LEXION 465 (S/N: 3HZ1-UP)

LEXION 475 R (S/N: 7671-UP)

LEXION 485 (S/N: 8ZW1-UP)

Compact Track Loader

239D (S/N: CD41-UP; BL91-UP)

249D (S/N: AH91-UP; GWR1-UP)

259B3 (S/N: YYZ1-UP)

259D (S/N: FTK1-UP; FTL1-UP)

279C2 (S/N: KWB1-UP)

279D (S/N: GTL1-UP; PPT1-UP)

289C2 (S/N: RTD1-UP)

289D (S/N: WCT1-UP; TAW1-UP)

299D (S/N: HCL1-UP)

299D XHP (S/N: NLC1-UP)

299D2 (S/N: FD21-UP)

299D2 XHP (S/N: DX21-UP)

Engineer Support Tractor

DEUCE (S/N: 7RR1-UP)

Mini Hydraulic Excavator

All

300.9D (S/N: TGP1-UP)

301.5 (S/N: MNH1-UP)

301.6 (S/N: MY61-UP)

301.7CR (S/N: JH71-UP)

301.8 (S/N: H8X1-UP)

302CR (S/N: RHM1-UP)

304.5E2 (S/N: FXT1-UP)

Multi Terrain Loader

247B3 (S/N: TSL1-UP)

257B Series 3 (S/N: B7H1-UP)

257D (S/N: EML1-UP; EZW1-UP)

277C2 (S/N: MET1-UP)

277D (S/N: FMT1-UP; MLT1-UP)

287C2 (S/N: SSB1-UP)

287D (S/N: STK1-UP; HMT1-UP)

297D2 (S/N: BL71-UP)

297D2 XHP (S/N: HP21-UP)

Skid Steer Loader

232D (S/N: KXC1-UP; DPR1-UP)

262C2 (S/N: TMW1-UP)

Trailer

VFS70 (S/N: 7XN1-UP)

Uninterruptible Power Supply

UPS 1200Z (S/N: HDR1-UP)

Introduction

Table 1

Revision	Summary of Changes in SEBF8351
21	Added serial number prefixes for New Product Introduction.
18–20	Added serial number prefixes for New Product Introduction.
17	Added serial number prefixes for New Product Introduction. Updated introduction section.

© 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 questions when using this document, work with your Dealer Technical Communicator (TC).

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

Summary

This bulletin shows the level of track belt damage that is required for replacement and reusability. Potential causes of damage are also covered. Locate the cause of track belt damage and make necessary repairs.

References

Reference: Special Instructions, SEHS9874, "Challenger Agricultural Tractors in Scraper Applications"

Reference: Undercarriage Recondition Bulletin, SEBF9396, "Asphalt Paver Undercarriage Inspection"

Safety

Illustration 1	g02139237

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. Hazardous steps will be identified by warning symbols like the ones.

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.

Show/hide table

Do not attempt to disassemble or assemble this machine until you read and understand the disassembly and assembly instructions. Improper disassembly and assembly procedures could result in injury or death.

Show/hide table

Inspect all threaded components before use. Damaged threads may fail under hydraulic pressure. Broken threads may release flying objects that are propelled with great force. Personal injury or death can occur if struck by flying objects.

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.

Mobil-Trac System/MTS Terminology

Belt construction is made up of three primary features: Guide Blocks, Carcass, and Tread Bars refer to Illustration 2. Note the outside diameter and inside diameter surfaces for future reference. Note also the inside and outside belt edges. See Illustration 2. The inside edge refers to the belt edges closest to the machine.

Illustration 2	g02431057

Illustration 3	g02431078
General belt references.

Guide Blocks

The two most widely used belt guide block configurations have been the standard grooved guides see Illustrations 4 and 6. For the side slope non-grooved guides see Illustrations 5 and 6. There are fewer guide blocks on the standard belt than the side slope belt see Illustration 6. Guide Block components features: lead edge, groove, block base, and block top. Refer to Illustration 7.

Illustration 4	g02431098
Standard guides.

Illustration 5	g02431117
Side slope guides.

Note: The MT700 and MT800 series use 46 and 52 respectively non-grooved side slope type guides on all the current belt offerings. See Table 2.

Illustration 6	g02431137
Guide Block – standard (A) vs. side slope (B).

Illustration 7	g02431156
Guide Block Components.

Table 2

Guide block Offerings
Machine	Guide Type	Guides/Belt
Challenger 35, 45, 55	Standard	36 Grooved
	Side Slope	48 Non-Grooved
Challenger 65, 70, 75, 85, 95	Standard	36 Grooved
	Side Slope	48 Non-Grooved
Series MT700(1)	Side Slope	46 Non-Grooved
Series MT800(2)(3)	Side Slope Long Side Slope	52 Non-Grooved 52 Non-Grooved
Series AP1055B	Standard	36 Grooved
Lexion 465/475/485	Standard	38 Grooved

(1)	MT series are all equipped with side slope design
(2)	MT series are all equipped with side slope design
(3)	MT800 Extreme App belt has 135mm long blocks vs 115 mm for side slope.

Carcass

The belt carcass comes in various widths depending on the application requirements. Wider belts are used for greater flotation and to reduce ground pressure. Narrower belts may be used in row crop applications. The 0° cables lay in the direction of belt rotation. Refer to Illustration 8.

Illustration 8	g02431159
Carcass construction.

Tread Bars

There are three basic types of tread bars:

• General Ag (some versions also known as Standard)

• Low Profile (formerly known as Special Application/Heavy Duty/Scraper)

• Extreme Application (some versions also known as Extreme Service)

There are some special variations not listed, but in general, the three types are similar to one of the above families.

Application Definitions

Normal Operation is used to describe use of the machine in applications where loads being pulled are typical agricultural loads and/or operation. Operating on relatively flat ground less than 10° side slope.

Low Profile is used to describe use of the machine in certain applications such as low ground disturbance or low ground pressure. Also in situations requiring high drawbar or hitch pull with little tread bar penetration.

Extreme Service/Application is used in situations with high drawbar loads with good tread bar penetration, lots of roading time, or abrasive conditions.

Side slope Operation is used to describe use of the machine on side slopes of 20 percent or more.

Illustration 9	g02431162
Side slope operation.

Roading is operation of equipment at higher speeds on paved roads.

Slot or Cut Work/Construction generally is used when referring to pulling a towed scraper in any construction application.

Illustration 10	g02431177
Construction Work.

Guide Blocks

Typical Wear Patterns/Characteristics

Typical guide block wear patterns are revealed after an initial break-in period of operation. Initial break-in can take up to the first 500 hours. The ideal operating condition for belt break-in is dry and dusty. Dust acts as a dry lubricant to prevent early hour break-in scuffing. During break-in, operate belts in dry and dusty conditions to minimize early hour scuffing.

Note: Roading a new belt for long distances prior to initial field use is not recommended and can lead to high initial guide block wear.

As shown in Illustrations 11 and 12, minor scuffing of the guide blocks can be observed during the break-in period. Minor scuffing of the guide blocks is sometimes referred to as early hour scuffing. Scuffing occurs on a new belt with new wheels, however scuffing can be found on new belts with old broken in wheels. The scuffing erosion may be as much as 1/4 inch deep during break-in.

Beyond the break-in period, some additional wear should make the break-in scuffing marks polish up and smooth over, improving the appearance. The scuffed edges become worn and less pronounced. Gradual, light wear is expected as operation hours accumulate and the guide block sides will gradually continue to erode proportionally to hours of operation.

Extra scrubbing or scuffing wear after the break-in period is not to be expected. If the belt alignment is correct, scrubbing or scuffing wear should cease, as the belt and undercarriage system settles into an operating position. While operating on a flat surface, if the temperature of the guides differs from the inside face vs. the outside face, an alignment problem could be indicated. Anytime a belt is changed, belt alignment should be checked and adjusted as needed. Refer to the Operation and Maintenance Manual (OMM) for more information on alignment. Contact your dealer if alignment is a concern.

Guide block wear patterns can help determine whether belt alignment is proper or improper and indicate the belt application use or abuse. More detailed guide block wear patterns and damage are covered in the following sections.

Illustration 11	g02431183
Typical early hour scuffing.

Note: Note the step in the carcass near the guide blocks. This step is a design feature and not a result of wear from the drive wheel.

Illustration 12	g02431197
Typical guide block break-in wear polishing in center of guide.

Illustration 13 shows typical guide block wear at the guide block base. Minor fatigue cracks appear during early hours of operation and are not a concern. Note the wear shown near the guide block top and on the leading edge. This wear is not typical, and should be monitored.

Illustration 13	g02431239
Scuffing at base of guide block typical.

Scuffing at guide block top is not typical

Illustration 14 shows minor chunking or spalling of the guide block. Sometimes sharp debris that gets caught in the undercarriage can chip rubber chunks from the guide block. Also, running over large objects can force the guide into the roller frame or bogie wheel axles causing tip damage. Check the undercarriage periodically and clean debris from components.

Illustration 14	g02431297
Minor guide block chunking or spalling.

Major Scuffing

Symptom

Guide erosion greater than 1/4 inch deep see Illustrations 15 and 16.

Illustration 15	g02431316
Moderate to excessive guide block scuffing.

Illustration 16	g02431337
Moderate to excessive guide block scuffing.

Cause of Damage

Major scuffing of belt guides is due to one of the following:

• Poor belt alignment.

• Gage adjustment incorrect.

• Steep side slope operation.

• Break in in wet or non-dusty conditions and/or excessive roading when new.

Damage Assessment/Usability

The belt is still usable, however, the problem must be corrected immediately to prevent extra wear. If too much wear occurs, the belt may become unusable.

Prevention

If the cause is poor alignment, the belt will need to be aligned as soon as possible to stop the scuffing from continuing. Refer to the Operation and Maintenance Manual (OMM) , service manual, or your Cat dealer for instructions on belt alignment.

MT series tractors: If the gage adjustment on the hard bar or the rear axle has moved, severe scuffing or reversion may occur. This damage can occur even though the front idler alignment is correct. Make sure to double check gage widths at front and back before adjusting the front idler alignment screws.

Steep side slope operation will cause accelerated wear and should be monitored. Avoid continued operation with the same side of the machine downhill. Operating the machine with same side downhill most the time will promote accelerated wear. Switch the belts from side to side, to equalize the wear on the guides.

Rubber Reversion

Symptom

Rubber reversion is a surface state of the guide block. The material has been changed from relatively hard to soft and tacky due to heat from friction. The guide can also develop recesses and cavities. Refer to Illustration 17.

Illustration 17	g02431357
Rubber reversion initial stages.

Cause of Damage

Excessive friction occurs on the guide block surface as the surface comes in contact with the idler, midwheels, or drive wheel, typically when:

1. The belt system is substantially out of alignment.

2. Operation is in severe side-slope applications.

Damage Assessment/Usability

Illustrations 17 and 18 show the early stages of rubber reversion scuffing. Observation at this stage is critical to make alignment corrections before the guide blocks are more severely damaged. Some small amount of rubber reversion on guide blocks can be normal during the break-in period of operation. Reversion seen in Illustration 18 is likely due to other causes than the initial break-in period.

Illustration 18	g02431362
Rubber Reversion major scuffing.

Notice the displaced material which has adhered to the inside belt surface in Illustrations 19 and 20.

Illustration 19	g02431365
Severe rubber reversion misalignment or side slope operation.

Illustration 20	g02431369
Severe rubber reversion- misalignment or side slope operation.

In Illustrations 19 and 20 , severe reversion has occurred. Severe reversion appears as if the rubber melts off or chunks, creating cavities and recesses in the guide blocks. Some of the material may adhere to the carcass surface, midwheels, idler, or drive wheel as a result. If damage is seen as shown below, severe reversion must be corrected immediately. If severe wear to guides as shown in Illustration 19 occurs, belt repair should be considered. Weak guides will cause belts to untrack more easily. Untracking also usually causes carcass damage. Bolt-on guide blocks would be an economical way to repair this type of failure. See section on “Repair of Missing or Damaged Guides” for more information on bolt-on guides.

Prevention

1. Periodically inspect guide blocks for signs of rubber reversion.

2. Make necessary idler adjustments if out of alignment.

3. Make sure that the proper belt is being used for the application.

4. When operating on side-slopes, avoid continual operation with the same side of the machine on the downhill side.

Grinding

Symptom

Severe guide block wear by grinding rather than scuffing.

Cause of Damage

In some situations, abrasive material can be present between the belt and the drive wheel. The material, in slurry form, lightly packs into the groove of the drive wheel and grinds the sides of the guide block. Packing has been seen in crops such as sugar cane, with certain types of sticky/abrasive soils.

Damage Assessment/Usability

As the guides grind away, the strength of the guides is reduced, making untracking more likely. With narrower belts such as 16 inch on Challenger 35/45/55, belt alignment is much more difficult to maintain. Once a large portion of the guides has been lost, the problem compounds and can rapidly erode guides away.

Illustration 21	g02431375
Abrasive wear grinding.

Illustration 22	g02431381
Abrasive wear grinding.

The belt shown may still be usable in an agricultural application but may not be usable in a side slope or construction application. After eliminating the cause of this wear, closely monitor the belt for alignment problems. A belt rendered unusable by grinding can be salvaged by using bolt-on guides. See the section titled “Repair of Missing or Damaged Guides” for more information.

Prevention

1. Make sure that the belt is aligned. See the Operation and Maintenance Manual (OMM), service manual, or your Cat dealer for belt alignment procedures.

2. When operating in fine, wet, abrasive underfoot conditions, thoroughly clean undercarriage components at the end of the day to remove packed material. Once the material is allowed to harden/dry, the material becomes much more difficult to remove.

3. Install or check adjustment and condition of guide groove scraper also known as a stinger.

Chunking or Spalling

Symptom

Guide blocks exhibit chunking or spalling where rubber chunks have chipped off the guide block surface. See Illustration 23. Chunking or spalling can occur at the top, middle or at the base of the guide block.

Illustration 23	g02431398
Serious chunking or spalling localized damage.

Cause of Damage

Sharp debris such as flint or rocks that are caught in the undercarriage can chip various sizes of rubber chunks from the guide block.

Damage Assessment/Usability

In Illustration 23, trapped debris likely worked loose after damaging only one guide block. More serious cases might have damaged all guide blocks. If any loose guide block rubber is observed, trim off the loose material. Trimming the loose material off will ensure no interference with the drive wheel or other undercarriage components.

Note: Rubber can be easily trimmed with the use of a sharp box cutter type knife. Bend back or stretch the rubber tightly, then trim the rubber with small swipes, while maintaining tension on the rubber at all times. The rubber will trim much faster and easier this way.

Prevention

1. Periodically inspect and clear material and debris from the undercarriage.

Tears/Cuts

Symptoms

Guides blocks exhibit cuts, slices, and tears.

Cause of Damage

Sharp debris caught or ingested in the undercarriage can cause the damage seen in Illustrations 24 and 25. Both photos were taken from the same belt and all guide blocks on this belt had similar damage. Mishandling of the belt such as use of a forklift, can physically damage guides as well.

Illustration 24	g02431406
Severe cut/tear physical damage.

Illustration 25	g02431411
Severe cut/tear physical damage.

Damage Assessment/Usability

Important to note the depth of cut or tear to assess the risk of continuing operation. The cuts shown are deep, however, the guide blocks are still intact enough to perform as designed.

Prevention

1. Periodically inspect and clear material and debris from the undercarriage.

2. Make sure to handle belts with care when storing or installing on machine.

Unbonding/Separation

Symptom

Guide block separates cleanly and smoothly from the carcass.

Cause of Damage

Unbonding is typically caused by a defect in materials or workmanship.

Note: There can be confusion as to the terminology when a guide block is loose. Unbonding, is when the guide comes off the carcass cleanly. Guide tearing or guide block loss, is when the guide comes off roughly and some material is still attached to the carcass. The difference is that a large portion of the guide material is still attached to the carcass and has not separated cleanly and smoothly.

Damage Assessment/Usability

Guide block separation occurs when the guide block starts to separate from the carcass, see Illustrations 26 and 27. Initial stages of separation are referred to as corner lifting. Corner lifting is normal and fairly common. Continued separation of the whole guide cleanly, though, is not typical. Eventually the guide block will break away from the carcass through continued operation and fatigue. The unbonded carcass surface will appear smooth with a light crosshatched pattern. Guide block failure of this type typically occurs within the initial 500-1000 hours of belt operation.

As guide blocks separate, the force per remaining amount of bonded surface area increases. Belts with this condition have reduced functionality due to loss of guide block attachment strength to the carcass. Belt untracking is more likely. Refer also to section titled “Missing Guide Block ”for additional information. If more than a couple guides are lost this way, a viable salvage alternative would be to use bolt on guide blocks. See the section on “Repair of Missing or Damaged Guides” for more information.

Prevention

Periodically inspect and closely monitor guide blocks that show signs of separation from the carcass.

Illustration 26	g02431418
Initial guide block separation corner lifting.

Illustration 27	g02431421
Progression of guide block separation corner lifting.

Groove Cracking

Symptom

Guide blocks split and separate at the notched groove. This type of failure only occurs with grooved guides and not with side slope non-Grooved guides.

Cause of Damage

Groove cracking occurs when the guide block begins to show signs of fracture from fatigue, initiating in the groove near the guide block base. Generally this type of damage is caused by:

• High hours of normal operation

• Prolonged side slope operation

• Operation under severe loads

• Use of standard belt on side slopes

• Belt misalignment

Note: Groove cracking should not be considered unbonding. If the guide comes off with groove cracking, there will be a fairly smooth separation at the groove. Further examination shows that the material is still attached to carcass. See Illustrations 30.

Damage Assessment/Usability

The guide blocks in groove cracking cases have good bonds to the carcass, but the guide block cracks near the base. Any of the causes are serious and require close monitoring. Continually observe the depth of cracks and the number of cracked blocks.

The guide blocks shown pose the same risk as the unbonding case. The guide blocks are still usable considering the condition of all the blocks and risk of untracking is unlikely. A good repair option would be bolt on guides, but the base of the old guide must be removed to the smooth carcass surface.

Note: Most often, groove cracking will begin on the lead edge of the guide block. That is, the front guide block edge when the machine is operated in forward motion.

Refer to Illustrations 28 through 30.

Illustration 28	g02431437
Initial stage of groove cracking.

Illustration 29	g02431457
Groove cracking advanced stages.

Illustration 30	g02431459
Severe groove cracking guide lost.

Missing Guide Block

Symptom

Guide blocks missing.

Potential Cause of Damage

• Chunking, tearing, and cutting.

• Severe rubber reversion.

• Unbonding.

• Groove cracking fatigue.

• Untracking.

• Low pneumatic idler inflation pressure, Challenger 65/65B/75 only.

Damage Assessment/Usability

Guide blocks showing signs of chunking, tearing, cutting, rubber reversion, unbonding, or groove cracking result in missing guide blocks before belt life is realized. Damage control is available for several of these types and can be managed.

1. Guide block separation due to chunking, tearing, or cutting, normally is a function of the amount and type of debris encountered in operation. If operation in heavy debris is required, guide block life can be roughly estimated through continued monitoring, and measurement of the damage over time.

2. Guide block loss due to severe rubber reversion usually suggests that the operator is not inspecting the undercarriage for proper alignment. Guide block loss may be contributed to operation on severe slide slope for prolonged periods of time. Rubber reversion damage is normally discovered before the guide blocks are missing.

3. Guide block separation due to unbonding usually occurs at low hours of machine operation. Repair with bolt-on guides. See Illustrations 31 and 32.

4. Guide blocks, which separate due to groove cracking, normally occur at high hours of machine operation through fatigue. See Illustration 33. Guide block life can be roughly estimated through continued monitoring and measurement of the damage over time.

5. Belt untracking can cause guide blocks to be sheared or torn off. Usually untracking occurs when operating in severe side-slope applications or trying to turn in a V-ditch or grade transition.

6. Guide blocks can be pinched off if pneumatic tires are not properly inflated.

Using Belts with Missing or Damaged Guides

Normal operation can continue if some guide blocks are missing. Usually in normal conditions, belt use can continue if no more than three guide blocks in a row are missing. Also, if the belt is not missing greater than (1/3) of the total guide blocks and (1/4) total guide blocks on sides-lopes.

Note: Undercarriage with drive wheels much larger than the idlers in nonside-slope applications can frequently tolerate up to 4-5 guides missing in a row.

If there are more than 3-5 consecutive missing guide blocks. Or if more than (1/3) of the total guide blocks per belt are missing and (1/4) total on sides-lopes. The belt should be repaired using bolt-on guides or possibly replaced if close to fully worn out . See the section titled “Repair of Missing or Damage Guides” for more information.

Illustration 31	g02431472
Missing guides due to unbonding.

Operator judgment must be exercised if operation is close to or beyond these criteria continue. Consideration must be given to current belt performance and safety requirements. Condition of the remainder of the blocks must also be considered.

If many of the blocks are severely damaged due to chunking, rubber reversion, or groove cracking, the risk of untracking is high. Best practice is to replace or repair the belt if this scenario exists.

Illustration 32	g02431477
Missing block due to unbonding.

Illustration 33	g02431496
Missing blocks due to groove cracking fatigue.

If slight or mild damage exists on the remaining guide blocks, use caution and continually monitor the Mobil-Trac system performance.

Summary of missing Guide Blocks:

1. Are more than three guide blocks in a row missing?

2. Are more than (1/3) of the total guide blocks/belt missing and (1/4) in the case of side slope belts?

If the answer to both of these questions is no, continued use of the belt is recommended. If the answer to either or both of the questions is yes, then repair the belt. Replace the belt if little tread bar life remains to make repair economical.

Illustration 34	g02431499
Good-normal operation. Three in a row missing, but less than (1/3) guide blocks missing.

Illustration 35	g02431516
Replace/Repair-normal operation. More than three in a row missing, but less than (1/3) total guide blocks missing.

Illustration 36	g02431522
Replace/Repair-normal operation. Three in a row missing, but more than (1/3) total guide blocks missing.

Illustration 37	g02431524
Good/Side-Slope and Heavy-Duty operation. Singular guide block missing, but less that (1/4) guide blocks missing.

Illustration 38	g02431527
Repair/Replace/Side-Slope and Heavy-Duty operation. Two or more in a row missing, but less than (1/4) guide blocks missing.

Illustration 39	g02431542
Repair/Replace/Side-Slope and Heavy-Duty operation. Singular guide block missing, but more than (1/4) guide blocks.

In side-slope and severe applications where two or more guide blocks in a row are missing, untracking risk is high. The belt should be repaired or replaced if two guide blocks or more in a row are missing. Replace or repair belt if more than (1/4) of the total guide blocks per belt are missing.

Prevention

1. Refer to sections covering chunking, tearing, and cutting.

2. Refer to section covering rubber reversion.

3. Refer to section covering unbonding.

4. Refer to section covering groove cracking.

5. Practice good operation techniques.

6. Avoid severe side-slope operation and avoid sharp, high-speed turns.

7. Keep pneumatic idlers properly inflated.

Crushed

Symptom

Guide blocks fracture and split, usually down the center of the block, in line with the track direction.

Potential Cause of Damage

Guide blocks become crushed when there is severe drive wheel packing. Guide blocks also undergo accelerated wear when packing exists. Refer to Illustration 40.

Illustration 40	g02431556
Drive wheel packing.

Damage Assessment/Usability

The guide blocks that have fractured are at risk of being torn or chunked off the belt. Packing also creates risk of 0º cable tensile failure. Immediately clear packed material or debris from the undercarriage and closely monitor progression of this type of damage. If the application typically leads to drive wheel packing, then the driver scraper/stinger should be installed and periodically checked for wear. Refer to the “Repair of Missing or Damaged Guide Blocks” section for more information on repair of severely crushed guides.

Illustrations 41 and 42 show crushed guide blocks. Note the rounded, worn guide block top and the fatigue cracks. Guide blocks will crush and split under extreme load.

Illustration 41	g02431576
Crushed Guide Blocks.

Illustration 42	g02431577
Crushed Guide Blocks.

Prevention

1. Install scrapers/stingers between drive wheels. See service literature or your parts book for more information.

2. Avoid operation in under-foot conditions where packing is likely.

3. Periodically inspect and clear material and debris from undercarriage.

4. Make sure that the proper belt is being used for the application.

Deformed Guide Block

Symptom

Guide block deformation. Refer to Illustration 43.

Potential Cause of Damage

Guide block deformation occurs when belts are improperly stored.

Damage Assessment/Usability

When belts are folded over, twisted up, or strapped down for extended periods of time, the guide block material takes a set permanently. Damage as seen in Illustration 43 is not acceptable for operation. This guide should be trimmed off at the damaged edge and then continue to run.

Use of the belt with deformed guide blocks may cause damage and excessive wear to rollers, idlers, and the drive wheel.

Prevention

1. Ensure proper belt storage practices. See section titled “Storage of Belts” for information on correct storage practices.

2. Make sure that belts are stored and handled properly.

Illustration 43	g02431596
Deformed guide blocks.

Repair of Missing or Damaged Guides

Caterpillar has replacement guide blocks available that can be bolted on a belt carcass. Bolt-on guides should be used where the guide wear has dictated the life of the belt, and the tread bar wear is not significant. Bolt-on guides are an economical solution to extend belt life. Refer to Special Instruction, REHS0151, "Repair Guidelines and Procedures for Mobil-Trac System belts (MTS) that have Missing or Worn Guide Blocks" for information on this repair procedure. The procedure, depending on the level of repair needed, can range from 1-12 hrs.

Individual guides are purchased as well as the bolts/nuts/washers. Remove the damaged guides. Drill holes in the belt to allow the bolts to go through the guides and carcass. If any significant guide wear has occurred on the remaining guides, all the guides should be removed and replaced with bolt-on guides. Otherwise, the change in shape as the guides meet the wheels will cause undue stress on the bolted guides. Again, this process allows uniform stiffness between all guides so undue stress will not occur. The referenced special instruction has more details on replacement criteria and installation procedures.

Carcass

Typical wear patterns and characteristics

As the belt accumulates early hours of operation, the belt will reveal surface blemishes on the outside diameter (O.D.). and the inside diameter (I.D). These blemishes will include cuts, scrapes, scratches, nicks, surface cracks, and slits. Illustrations 44 and 45 show typical belt wear.

Illustration 44	g02431597
Typical nicks and scratches on outside diameter.

Illustration 45	g02431598
Typical nicks and scratches on inside diameter.

Monitor the wear so that maximum belt life can be realized.

Exposed Breaker Sheet Wires

Symptom

Breaker sheet wire exposure on the belt.

Potential Cause of Damage

1. Normal operation at full belt life.

2. Operation in fine, abrasive soil, or rocky underfoot conditions.

3. Operating in fields with hard stubble.

Damage Assessment/Usability

As a belt wears in normal operation, the breaker sheet wires will eventually be exposed as the full belt life is realized. Exposed breaker sheet wires are not considered cause for immediate belt replacement.

In most wear conditions, the tread bar will wear off nearly all the way before loss of traction is noticed. Operation in fine abrasive or rocky underfoot conditions or in stubble fields will accelerate belt carcass and tread bar wear relative to guide block wear. Breaker sheet wires will rust when exposed. Rust will corrode and weaken the wires, eventually causing breakage.

Illustration 46 shows significant wear due to chunking. The belt should still have life remaining.

Illustration 46	g02431599
Exposed breaker wires, wear, and chunking.

Broken Breaker Sheet Wires

Symptom

Broken breaker sheet wires.

Potential Cause of Damage

1. Normal operational wear at full belt life.

2. Operation in fine abrasive soil or rocky conditions with worn tread bars.

3. Operating in fields with hard stubble.

4. Gashes, slices, gouges, and punctures can penetrate and cut through the breaker sheet layers when operating in ground containing sharp rocks or refuse.

Damage Assessment/Usability

Broken breaker wires pose the same consideration as exposed wires. Broken breaker wires weaken the lateral strength of the belt and can cause the belt to lose alignment. Lateral belt strength affects untracking resistance. Breaker sheet wire damage is less critical than 0° cable damage. Wear should be monitored closely.

Loss of traction exceeding 10% is an indicator that the belt is worn to the point of replacement. Illustration 47 shows breaker sheet wires that have been worn through between the tread bars. The tread bars, in this case, are also worn down considerably and the belt is approaching replacement. Breaker sheet wire exposure is typically seen when tread bar height remaining is less than 1/2 inch.

Illustration 47	g02431601
Breaker wire damage caused by fine abrasive soil, rocky conditions, or hard stubble.

Broken breaker sheet wires due to gashes, slices, gouges, punctures. can be serious if other damage exists. Illustration 48 shows a belt gash or gouge which penetrates and breaks only the outer breaker sheet layer. The belt is still usable . Monitor corrosive effects of rust, due to prolonged exposure where breaker sheet wires have been cut.

Illustration 48	g02431616
Breaker sheet cut.

Prevention

1. Avoid operation in underfoot conditions that can accelerate wear.

2. Use the appropriate belt for underfoot application.

Sheet Separation

Symptom

Outer rubber layer and/or breaker sheets separate from the carcass.

Potential Cause of Damage

1. Edge and/or carcass damage.

2. Defect in material or workmanship.

Damage Assessment/Usability

When the carcasses outside diameter and/or edges are worn or damaged to the point where the breaker sheet wires are exposed, sheet separation can occur. Belts demonstrating this separation characteristic have been used longer than recommended and should be replaced.

Note: The smooth separation of rubber from the wires. See Illustrations 49 through 52. If the sheet unbonding is localized to one small area, cutoff the loose material. Continue to run the belt and watch for any signs of further unbonding. If the sheet unbonding becomes enough to affect the operation, the belt should be replaced.

Prevention

Periodically inspect and closely monitor belts for signs of sheet separation from the carcass.

Illustration 49	g02431644
Sheet separation single area/treadbar.

Illustration 50	g02431637
Sheet separation.

Illustration 51	g02431646
Sheet separation causing loss of tread bar.

Illustration 52	g02431647
Sheet separation loss of tread bars and outside diameter rubber.

Edge Wear/Damage

Symptom

Edge is worn or damaged.

Potential Cause of Damage

1. Normal operational wear at full belt life.

2. Operation in raised material ridges.

3. Operation in fine, abrasive soil, or rocky underfoot conditions.

4. Operation in hard stubble.

5. Gashes or slices from sharp debris or material can cut or chunk the belt edge.

6. Material packing around undercarriage or final drives.

7. Operation of tractor at narrow gauge in high debris or muddy conditions.

Damage Assessment/Usability

Some form of edge wear can be found in every application.

1. Under normal operation, the belt edge is designed to wear at the same rate as the guide blocks and tread bars. Full edge life is expected at the point where the full belt life is realized. Edge wear tends to be smooth and rounded.

2. Operation in beds with raised material ridges can cause wear on the edges of the belts and eventually round off the edges.

3. Operation in fine abrasive, rocky underfoot conditions or in hard stubble will accelerate belt edge wear relative to guide block wear. Edge wear tends to be smooth and rounded. Refer to Illustrations 53 and 54. Also shown in the figures is initial exposure of the 0° cable as a result of this wear. This example shows good bonding, and the belt still has remaining life.

Illustration 53	g02431648
Edge Wear-exposed 0° cable from fine abrasive conditions.

Illustration 54	g02431652
Edge Wear-exposed 0° cable from fine abrasive soil.

Operation in sharp debris or rocky soils will cause edges to be chipped, chunked, or torn. Belt edges can be cut if sharp turns are made while pulling tillage implements. Usually the outside edge gets damaged in that case. Untracking can damage the inside edge of the belt. Pulling a scraper bowl in a slot slightly smaller in width than the outside width of the belts can cause belt edge fold-over or creasing damage. Illustrations 55 and 56 show considerable edge wear (chunking/spalling) possibly due to belt untracking or turning too sharply causing implement interference.

Packing between the final drive and the belted undercarriage may also wear the belt edge. The packing material gets between the tractor and the belt. Packing material can cause wear to the belt and drive wheels.

Illustration 55	g02434576
Edge Wear-chunking/spalling.

Illustration 56	g02434577
Edge Wear-chunking/spalling.

Illustration 56 shows worn edges and unbonding at the edges.

Prevention

1. Avoid operation in underfoot conditions such as sharp rock or refuse.

2. Use the appropriate width and type of belt for underfoot application in raised material ridges or slots.

3. Practice good machine operation habits. Know the minimum turning radius of the machine without causing implement interference.

4. Clear accumulated final drive and undercarriage material.

Inner Diameter Damage Chunking/Chipping

Symptom

Cuts, gouges, or chunking of inner diameter rubber.

Potential Cause of Damage

1. Abrasive or rocky material in soils.

2. Build up on cast iron slotted drivers.

Damage Assessment/Usability

Some shallow cuts and small chunking is to be expected in most applications. Sometimes, more extreme amounts of repeated cutting or gouging can be an indication of a more serious problem. See Illustration 56. In rocky soils, the ingestions of sharp rocks such as flint or other debris can cause cutting or gouging. This damage can be seen on the tread bars as wear.

Cast iron slotted drivers require an inside protected belt, which has extra breaker and rubber layers. Chipping on the inside diameter of the belt may be due to buildup on the cast iron slotted drivers. This chipping occurs on the inside diameter of the belt. The inside diameter breakers will be the first damaged. The damaged breakers can reveal small wires protruding through the rubber surface. This damage will occur less if the belt is the proper belt for the application. Buildup can occur on any part of the cast iron slotted wheel. See Illustration 58. Small amounts of buildup will not be detrimental, but any buildup over 3.0 mm (0.12 inch) high may start to cause damage. See Illustration 57. Important to keep drive wheel mud scrapers adjusted correctly. Illustration 57 shows the initial stages of rubber pinching. This damage can progress into 0° cables being exposed once the rubber is damaged enough to separate from the cables.

Illustration 57	g02434598
Inside diameter belt damage caused by cast iron slotted driver buildup initial stage.

Illustration 58	g02434616
Cast iron slotted drive wheel buildup.

Prevention

When in harsh soils, avoid turning sharply. Turning sharply will allow material to get into the inside diameter of the belt.

If equipped with cast iron slotted drivers, make sure that you have drive wheel scrapers installed and adjusted correctly. Keep the drive wheel scrapers adjusted 3.0 mm (0.12 inch) to keep the material off the drive wheels preventing buildup. The buildup will cause the inside diameter rubber to start to be pinched on each revolution. The rubber eventually starts to separate from the zero cables in sheets. The area of separation corresponds with the area of buildup. Frequently the worst buildup occurs on the inside wheel, as this scraper is less frequently adjusted.

Note: A total of four scrapers are installed on both the inside and the outside of the cast iron slotted drive. Make sure all are adjusted correctly to a clearance of 3.0 mm (0.12 inch). Adjustments should be checked daily. See the Operation and Maintenance Manual (OMM) or service manual for details on adjustments of scrapers. Check with your dealer for the latest scraper design. Recent material improvements have lengthened the time between typical adjustments.

Illustration 59	g02434700
Sheet separation caused by buildup on cast slotted driver early/middle stage.

Illustration 60	g02434717
Sheet separation caused by buildup on cast slotted driver later stages.

Illustration 61	g02434736
Sheet separation caused by buildup on cast slotted driver later stages.

Surface Cracks

Symptom

Cracks in the rubber surface, inside or outside diameter.

Potential Cause of Damage

1. Belt fatigue.

2. Exposure to the sun and environment.

Damage Assessment/Usability

As shown in Illustration 62, surface cracks may appear. These cracks are commonly referred to as ozone cracks. Ozone cracks are typically found on aging belts. This cracking is not serious. This cracking surface should be inspected periodically.

Prevention

Protect belts from sun and environmental elements when storing. See (Storage of Belts) for more information on extending belt life.

Illustration 62	g02434639
Surface Cracks/Ozone Cracks.

Exposed 0° Cable

Symptom

Exposed 0° Cable

Potential Cause of Damage

1. Rubber drive wheel packing with fine, abrasive material.

2. Cast iron slotted drive wheel buildup.

3. Rocks or sharp debris in undercarriage.

4. Implement damage.

5. Untracking.

6. Prolonged slot operation.

7. Over tensioning Versatile Flotation Systems (VFS) series trailer belt.

8. Excessive belt to driver slip.

Illustration 63	g02434657
Edge wear initial exposure of 0° cable.

Damage Assessment/Usability

Exposure of the 0° cable is more serious than the exposure of the breaker sheet plies though the belt can still be used.

Drive wheel packing is when material gets caught between the drive wheel and belt during operation. Fine, abrasive material which gets packed can completely strip the rubber layer from the carcass inside diameter. Illustrations 64 and 65 show extensive carcass inside diameter wear and 0° cable exposure. Wear is shown along the entire circumference of the belt on one side of the guide blocks. This wear is the likely result of abrasive material that adhered to the drive wheel and/or idler. Packed abrasive material acts like a grinder, grinding off the inner rubber layer when the machine is in operation. Midwheel lockup may also cause this damage. This belt is still usable as the 0° cables have not been broken. Cables will likely rust when exposed to moisture in the environment. Also, loss of belt to driver traction may result. Exposure of the 0° cable may wear the drive wheel and idler excessively. Periodically inspect for any progressive damage.

Illustration 64	g02434678
Exposed 0° cable along entire circumference.

Illustration 65	g02434696
Exposed 0° cable along entire circumference.

When rocks or sharp debris get caught in the undercarriage, more severe damage can occur. Illustration 66 shows carcass inside diameter damage and 0° cable exposure due to chunking of the rubber sheet. More serious damage can occur as large objects get caught between the drive wheel and belt. The chance of 0° cable breakage failure increases.

Illustration 68 shows 0° cable exposure in a single location. This exposure is a possible result of implement damage since the location is close to an edge. The bite in the edge could also be due to rock or debris becoming caught between the idler or drive wheel.

Untracking of the belt causes damage when the inside edge makes contact against the machine.

Slot operation causes belt creasing on the belt edge that contacts the slot edge.

Illustration 66	g02434738
Exposed 0° cable chunking.

Illustration 67	g02434741
Exposed 0° cable on inside diameter.

Illustration 68	g02434742
Exposed 0° cable near edge.

Over tensioning of the VFS50 and VFS70 series trailer belt, especially the tread bar version can result in the cables being pulled through the rubber. Refer to Illustration 69.

Illustration 69	g02434777
Exposed 0° cable over tensioning VFS series trailer bel.t

Over tensioning is due to the application. A result of build-up on the idler wheels causes over tensioning of this lighter construction belt. If this type of problem is encountered, the belt should be replaced with a heavier carcass version such as the circumferential ribbed belts. These types of belts have more cables and more inner rubber.

Illustration 70 shows an example of 0° cable exposure possibly due to untracking or prolonged slot operation. The edge foldover or creasing can be observed over most of the belt inside diameter. In this case, exposure or cracks in the rubber close to the edge will be seen along the entire circumference of the belt.

During some slot operations, the difference in the belt width to slot width is great enough that the belt actually creases or folds over during operation. These creases or folds are observed on the inside diameter of the belt in from the edges causing carcass cracking and 0° cable exposure.

Closely monitor belt edges when operating in these conditions to make sure that cables are not exposed or broken.

Illustration 70	g02434779
Exposed 0° cable near edge.

Prevention

1. Periodically inspect the undercarriage and clear packing material.

2. Make sure if equipped with cast iron slotted drivers to adjust the scrapers to prevent build-up.

3. Periodically inspect and clear rock and sharp debris caught in undercarriage.

4. Practice good machine operation habits. Know the minimum turning radius of the machine without causing implement interference.

5. Practice good machine operation to avoid untracking. Inspect guide blocks to make sure that adequate guides are in place. Use the appropriate belt for the application.

6. Make sure that operation in a slot does not cause belt creasing or folding by pulling the correct width bowl or by using the correct width belt.

Illustration 71	g02436040
Broken 0° cable tensile failure.

Broken 0° Cable

Broken 0° cable is caused by these situations: tensile failure, punctures/gashes/tears. The most serious case is from tensile failure.

Broken 0° Cable Tensile Failure

Symptom

Broken 0° cable torn across belt.

Cause of Damage

1. Severe packing.

2. Rocks or debris caught between the drive wheel and belt.

Damage Assessment/Usability

Tensile failure generally occurs when there is severe drive wheel packing and the 0° cable breaks. Illustration 71 shows this damage.

Prevention

Periodically inspect the undercarriage and clear packing material, rock, and sharp debris.

Broken 0° Cable Puncture/Gash/Tear

Other serious failures are puncture, gash, or tear on either inside or outside diameter of the belt. Belt puncture is defined as penetration through the belt where both the 0° cable and breaker sheet plies are cut/broken and is not on an edge. A gash is defined as penetration, but not through the belt, though the breaker sheet plies or 0° cable may be broken. A tear is defined as 0° cable damage on the belt edge.

Symptom

Broken 0° cable in a localized area

Potential Cause of Damage

1. Sharp rocks or debris caught between the drive wheel and belt or caught in the guide block V groove can puncture the belt from the inside diameter.

2. Operation over sharp rocks or debris can puncture the belt from the outside diameter.

3. Belt untracking/tear.

4. Implement interference/tear.

Damage Assessment/Usability

Illustration 71 could have been the result of a rock getting caught between the drive wheel and the belt. In that case the cables stretched until the cables break. The belt could have been pierced while driving over sharp objects. Illustration 72 shows a puncture where the cables were cut by a sharp object.

Illustration 72	g02436044
0° cable break belt puncture.

Illustrations 73 and 75 show tears and gouges where the 0° cable is exposed and broken. Likely caused from debris caught in the undercarriage or contact with the frame during untracking that cut and penetrated belt surface during operation. This type of failure can also be caused by build-up on cast iron slotted drivers.

Illustration 74 shows a tensile failure that was likely caused by large amounts of material build-up around one side of the drive wheel and idler. This tensile failure can cause a few of the cables in the belt to take all the load.

Illustration 73	g02436051
Exposed cable gash.

Illustration 74	g02436056
Exposed 0° cable tensile failure.

Illustration 75	g02436057
Exposed 0° cable tears.

Illustrations 75,76, and 77 show edge tear examples. Damage in Illustrations75and77are most likely due to untracking, if on the inside of belt next to machine. Marks on the final drives or guards can also help determine the cause.

Illustration 76	g02436059
Broken 0° cable edge tear.

Illustration 77	g02436062
Broken 0° cable edge tear.

Broken 0º cables from tensile failure, punctures, slices, gouges, gashes, tears, and rips must be quantified to assess belt usability. The size of the break and location of the break are significant in judging belt usability.

When broken 0º cables are discovered, count the number of broken cables within the drive wheel contact area. If more than five cables in a row are broken or cut the belt should be evaluated to see if a replacement is needed. The belt alignment should be checked as the loss of cables could alter the tracking of the belt. If, the cables are torn in the center of the belt and not from the edge the belt will continue to align and operate for an extended amount of time. Make sure that no cables are protruding to damage the rest of the undercarriage.

If a length of broken cable is sticking out of the belt, cutoff the broken cable and rubber at the belt surface. Cutting off the broken cable and rubber will prevent further damage of the belt or other undercarriage components during operation.

Monitor and measure the cable for unraveling. If the cable begins to unravel during continued operation, the belt should be replaced or undercarriage damage could result. Unraveled cable could wrap around a final drive or wheel.

Prevention

1. Install drive wheel scrapers and stingers if buildup is a problem.

2. Periodically inspect and clear material and debris from the undercarriage.

3. Avoid operation over sharp objects.

4. Practice good machine operation to avoid untracking. Inspect guide blocks to make sure that adequate guides are in place. Use the appropriate belt for application.

5. Practice good machine operation habits. Know the minimum turning radius of the machine without causing implement interference.

Rubber Edge Strip Separation

Symptom

Rubber strip separates from the carcass.

Potential Cause of Damage

1. Normal wear.

2. Chunking.

3. Unbonding.

Damage Assessment/Usability

Belts manufactured before October, 1987 were constructed with rubber edge strips. Today, most belts are constructed without rubber edge strips. Special circumstances still require rubber edge strips on belt construction.

As Illustrations 78 and 79 demonstrate, rubber edge strip wear and chunking. Rubber edge strip wear and chunking are likely to be seen after moderate belt use in most applications and conditions. The belt is usable if the rubber edge strip is worn or torn off. Unbonding can occur but is not commonly found.

Illustration 78	g02436066
Rubber Edge Strip separation chunking.

Illustration 79	g02436067
Rubber Edge Strip separation chunking.

Prevention

Monitor the belt edge for continued wear.

Emergence of 0° Cable Core Wire

Symptom

0° cable core wire breaks belt may be undamaged.

Potential Cause of Damage

Fatigue

Damage Assessment/Usability

0° cable core wire emergence occurs when the core wire of the 0° cable separates from the cable bundle. After separation the core wire works up through the carcass surface inside or outside diameter. Refer to Illustration 80. This problem happens infrequently and only with belts which were made before May, 1995 (date code 0595). Changes in construction on later belts eliminated this problem. Simply clip the exposed wire at the carcass surface. This spiral core wire that penetrates the surface does not reduce the strength of the cable or belt.

Illustration 80	g02436068
Spiral Core Wire penetrates the surface.

Kinked Carcass

Symptom

Belt carcass has kinks.

Potential Cause of Damage

Poor storage practice

Damage Assessment/Usability

Belt breaker wire and 0° cable may fatigue and fracture due to carcass kinking. Also, kinked carcasses may not be easily installed or may not ride smoothly. The belt should be watched closely to see if the problem continues.

Prevention

When storing belts, be careful not to keep the belts bound and strapped where the belts might become kinked. See also section “Storage of Belts” for proper belt storage.

Tread Bars

Typical Wear Patterns/Characteristics

As with guide blocks and the belt carcass, tread bars also demonstrate wear patterns. Illustration 81 shows typical tread bar nicks, cuts, and chunking.

Illustration 81	g02436080
Tread Bar nicks, cuts, and chunking.

Illustration 82	g02436081
Tread Bar nicks, cuts, and chunking.

Illustration 83 also shows cracking around the perimeter of the bonded tread bar. This cracking is normal and should not be a concern unless the tread bar unbonds from the carcass. This belt shows typical high hour wear.

Illustration 83	g02436082
Cracking around perimeter of Tread Bar.

Calculating Tread Bar Wear

Table 3 indicates the values needed to estimate the tread bar wear. Use this table to estimate wear rates in your particular application.

Table 3

Tread bar Design	0% Worn/New Height	100% Worn Height
Low Profile/Spec Applications	38.10 mm (1.5 inch) - 40.64 mm (1.6 inch)	12.70 mm (0.5 inch)
MT Series General Ag	68.58 mm (2.7 inch) - 71.12 mm (2.8 inch)	12.70 mm (0.5 inch)
MT Series Extreme App	76.20 mm (3.0 inch) - 78.74 mm (3.1 inch)	12.70 mm (0.5 inch)
Standard Ag Tread	63.50 mm (2.5 inch) - 66.04 mm (2.6 inch)	12.70 mm (0.5 inch)
VFS Ribbed Belt	25.40 mm (1.0 inch) - 27.940 mm (1.1 inch)	7.62 mm (0.3 inch)
Paver	38.10 mm (1.5 inch) - 40.64 mm (1.6 inch)	10.16 mm (0.4 inch)

Note: Many times belts can be used past the 100% wear point. The deciding factor is the amount of traction lost due to wear of the tread bar. Loss of traction exceeding 10% is an indicator that the belt is worn to the point of replacement.

Cupping or Uneven Wear

Symptom

Tread bars show uneven wear or wear in one part of the tread much quicker.

Potential Cause of Damage:

Extended operation on hard soils or roads.

Damage Assessment/Usability

Illustration 86 shows tread wear heavy to one side only. This tread wear is common when operating consistently on side-slopes or in slot applications, or when frequently roading with a heavy load. The side showing the most tread bar wear will be found closest to the tractor. The belt is still usable as long as the operator perceives the belt as not losing traction. Illustration 84and 85 shows significant cupping of the tread bar. This cupping is due to the heavy loads imposed on the belt by the midwheels when operating on a hard surface.

The belt can continue to run. The tread bar will tend to equalize the loads as when the wear gets to a certain point.

Prevention

Uneven wear and cupping can be minimized by limiting the amount of time on hard surfaces. Lightening the load on the machine when operating on hard surfaces will reduce cupping.

Illustration 84	g02436096
Tread Bar cupping paver.

Illustration 85	g02436097
Uneven wear agricultural.

Tread Bar Erosion

Symptom

Tread bars are severely eroded across the whole bar uniformly.

Potential Cause of Damage

Operation in hard soil, clods, and rocks. See Illustrations 86 and 87.

Damage Assessment/Usability

The belt can continue to run. Operation in these soils will continue to do damage the belt.

Prevention

Avoid operating in these conditions.

Illustration 86	g02436116
Tread Bar Erosion later stages.

Illustration 87	g02436117
Tread Bar Erosion early stages.

Tread Bar Leading-Edge Erosion

Symptom

Tread bars are eroded across the front leading edge.

Potential Cause of Damage

Heavy drawbar loading in abrasive soil conditions or in hard packed soil

Damage Assessment/Usability

When belt tread bars are used in abrasive soils at high drawbar loads, the tread bar is bending. Bending occurs during the transmitting of the load to the ground. The high strains occur at the backside of the tread bar while on the ground. When, operating in abrasive or hard rocky soil the tread bars erode at the high load areas. These high load areas on the leading edge of the tread bar. See Illustration88.

Prevention

1. Run machine at a higher speed with reduced drawbar loading.

2. Consider upgrading to a Special Application or Extreme Application belt if a significant percentage of machine work is done in these conditions.

Illustration 88	g02436121
Tread Bar leading-Edge Erosion

Inside Edge Damage

Symptom

Tread bars are damaged only on the inside edges of each belt

Potential Cause of Damage

1. Contact with tractor due to partial or full untracking event. Refer to Illustration 89.

2. Debris or mud packing in fenders.

Damage Assessment/Usability

Depending on the damage of the belt can continue to run. If the belt will align properly, loose cables are trimmed, the belt can continue to be used. The belt should be monitored closely.

Prevention

1. Avoid events that can cause untracking.

   Note: Refer to Special Instructions, SEHS9874, "Challengers in Scraper Applications" for more examples and tips to avoid untracking.

2. Keep the tractor clean from packing material and debris.

Illustration 89	g02436141
Inside Edge Damage.

Outside Edge Damage

Symptom

Tread bars are damaged on the outer edges of each belt.

Potential Cause of Damage

Contact with sharp debris when turning. Contacting the implement while turning sharp. See Illustrations 90 and 91.

Damage Assessment/Usability

The belt can continue to be used.

Prevention

Avoid turning sharply.

Illustration 90	g02436142
Outside Edge Damage implement contact.

Illustration 91	g02436143
Outside Edge Damage implement contact.

Illustration 92	g02436144
Outside tread bar damage implement contact.

Delamination

Symptom

Rapid tread bar wear in thin sheets.

Potential Cause of Damage

Defects in materials or workmanship.

Damage Assessment/Usability

Delamination is where the tread bar rubber exhibits spiral peeling effect during normal operating conditions. Delamination has been seen in some belts manufactured before January 1994 (date code 0194). This condition is not serious, though delaminating tread bars will wear faster than newer belt tread bars. Refer to Illustration 93.

Belts with delamination should continue to run until useable life has been reached.

Illustration 93	g02436197
Initial stage of tread bar delamination

Prevention

Closely monitor tread bars that show signs of delamination.

Tread Bar Internal Reversion

Symptom

Pockets develop in tread bar and eventually burst open. These pockets are on the row of tread bars closest to the tractor.

Potential Cause of Damage

This type of wear is due to excessive buildup of heat in the tread bars that can be due to a combination of the following:

• Heavy three point hitch loads.

• Extended time spent roading.

• High ambient conditions.

• Poor tractor balance “tail heavy”.

• Excessive tractor weight.

Note: Internal reversion is more evident on narrow belts because of less tread area. Internal reversion is also found on row crop-wide gage tractors. Row crop tractors tend to have higher loads on the inside tread bars.

Damage Assessment/Usability

Tread bars with internal reversion may be softer than intended. These tread bars will stop the internal reversion process once the operation that is conducting the heat input has ceased. These belts can continue to be run. The reason for the reversion must be avoided. See Illustrations 94 through 96.

Illustration 94	g02436199
Tread Bar Reversion initial stages.

Illustration 95	g02436200
Tread Bar Reversion initial stages.

Illustration 96	g02436202
Tread Bar Reversion later stages.

Prevention

Avoid roading in high ambient conditions. If roading is required, reduce the weight of the machine. Drive on cooler surfaces or reduce speed to avoid heat build-up in tread bar. Improve the balance of the machine to distribute the load across the undercarriage. Run at narrower gage when possible to reduce the amount of load on the inner tread bars.

Note: There is a maximum operating weight for any application. If that weight is exceeded, then shortened belt life can be expected. Excessive weight will also damage the midwheels and the drive wheels.

Drive Wheels

Typical Wear Patterns/Characteristics

Drive wheels are not usual wear items and are intended to last the life of the machine in most applications. Wear should be viewed with concern and troubleshooting should be done immediately to find the source of any problem.

Traction of a friction drive system relies on the sharpness of the edges of the drive wheel rubber. This sharpness will wipe the mud and moisture out of the inside diameter of the belt. Anytime the edge is damaged or rounded the inside belt traction is diminished.

Drive Wheel Chunking

Symptom

Pieces of the drive wheel rubber are missing or lost.

Potential Cause

Operation in abrasive hard soils.

Damage Assessment/Usability

See Illustration 97.

Illustration 97	g02436236
Drive Wheel Chunking.

Prevention

Avoid conditions in which the abrasive soil can get into the belt. Minimize the amount of spot turning. Avoid getting in deep cuts or slots which can cascade material into the belt.

Drive Wheel Severe Wear

Symptom

Rubber is worn off the drive wheel.

Potential Cause

1. Build up of debris in the undercarriage.

2. Low belt tension.

Damage Assessment/Usability

A drive wheel that has encountered this type of wear becomes less effective in cleaning the inside diameter of the belt. If only one side of the drive wheel is worn and the other is not, the belt alignment can be affected.

If, material is allowed to build up in the undercarriage the rubber on the wheel can be ground off. See Illustration 98. If build-up in this area is a problem, debris guards and scrapers are available. See your parts book for more information.

If the tension on the belt is low or operating in heavy clay or mud, the wear can be caused by belt to driver slip.

Illustration 98	g02436256
Drive Wheel Wear due to build up debris on frame.

Prevention

1. Periodically inspect the frame for build-up and remove. Clean these areas at the end of the day so the build-up cannot harden overnight causing wear the following day. Make sure that all guards and scrapers are in place. Using narrower belts help, which tend to reduce the amount of material recirculation.

2. Make sure that belt tension is correct. Minimize operation in muddy conditions.

Drive Wheel Cracking

Symptom

Drive wheel rim develops radial cracks.

Potential Cause of Damage

High vertical drawbar loads.

Damage Assessment/Usability

Drivers with small cracks can continue to be used. Monitor drive wheels. Replace if the cracks get too large. See Illustrations 99.

Illustration 99	g02436258
Drive Wheel Cracks

Illustration 100	g02436259
Drive Wheel Cracks

Midwheels

Typical Wear Patterns/Characteristics

Midwheels can last the life of the machine if operated in normal applications. Operations which speed and weights are not excessive will extend life. The main factors in extending life are total load and amount of physical damage.

Illustration 101	g02436264
Typical Midwheel Wear

Illustration 102	g02436265
Typical chunking or chipping

In Illustration 101, a set of midwheels is shown with thousands of hours of use. Rubber is worn from the edges. Although, the wear is evident the midwheels are still performing as intended and have considerable life remaining.

Typical wear patterns are numerous. Small nicks, chunks, and small sections with rubber loss are seen in normal wear patterns. A slight amount of rubber separation at the edges would be typical wear. See Illustration 102.

Severe Chunking

Symptom

Sections of the midwheel rubber are missing or lost.

Potential Cause of Damage

Midwheels that have significant nicks or chunks missing can continue to operate for a substantial amount of time. See Illustration 103. Life of the midwheel may be reduced if the cuts have progressed through the rubber to the steel wheel below. Then the rubber slowly unbonds due to fatigue and rock or dirt grinding at the bond surface. See Illustration 104.

Operate midwheels until such time that one of the following occurs:

• 1/3 of the roller width from either side or any area where rubber loss extends across roller width.

• Midwheel no longer turns freely.

• Mud starts to build up on the midwheel due to lack of rubber.

Illustration 103	g02436268
Midwheel Chunking early stages

Illustration 104	g02436269
Chunking later stages

Prevention

Avoid operation in rocky or abrasive soil. If operation in these conditions are required, make sure to balance the machine and avoid excessive weight.

Midwheel Rubber Separation

Symptom

1. Midwheel rubber separation starts from the outer steel rim edge.

2. Midwheel rubber separation starts from the inner steel rim edge, next to guide blocks.

Potential Cause of Damage

1. Excessive heat build-up.

2. Improper belt alignment.

Damage Assessment/Usability

Midwheel bonds can fail from excessive heat. Heat is generated in the following situations:

• High-Speed Roading

• High Ambient Conditions

• High Temperature Material (Pavers)

• Heavy Vertical Loads

• Belts Misaligned

The belt can fold and rub against the outside edge of the midwheel. Heat can be generated and cause the midwheel to separate. See Illustration 105.

Once separation gets to the flat part of the midwheel, material can build up underneath the rubber. This build-up will erode away the rubber across the midwheel until complete rubber separation occurs. See Illustration 106.

Illustration 105	g02436277
Midwheel Rubber Separation early stage

Illustration 106	g02436278
Midwheel Rubber Separation later stage

In Illustration 105 and 106 the midwheels are both still useable. Although the midwheel in106should be watched for signs of build-up.

Prevention

1. Use only enough weight for the job.

2. Make sure that the tractor is balanced correctly.

3. Use the right belt for the job.

4. Avoid high-speed roading at elevated weights and during high ambient conditions.

5. Maintain proper belt alignment.

Maximizing Mobil Track Systems Life on Machines

General guidelines for increasing the life of the belt have been included in the preceding section. Sometimes, specific guidelines may be optimal depending on the application. The following paragraphs discuss some detailed descriptions of things that can be done in specific applications and with specific belts to improve life.

Asphalt Pavers

Factors affecting track life

Items which may cause reduced life are the following.

1. Extra hopper weight using hopper inserts and pushing elevators or material transfer vehicles.

2. Propelling at travel speed for extended time and distance.

3. Use of diesel or other solvents to clean the tracks or parts around the tracks. All solvents including Biodiesel will soften rubber. The softer the rubber, the easier for wear and cable migration.

4. Low track tension. If the driver slips on the inner carcass, it is likely to accelerate rubber wear on the inner carcass. Driver slipping may even tear the rubber on the inner carcass.

5. Misaligned tracks. Tracks out of alignment generate heat which can soften the rubber on the tracks, driver, idler, and even the bogie wheels. Heat will build quickly.

6. Working on milled surfaces. The rough surface usually wears the grousers or outer surface of the belt. Watch for track slippage on the surface. Any slippage will reduce the life of the belt tread bars.

7. Excess asphalt material flowing into the tracks either from auger feed system or spillage from haul trucks or elevator bleed through. Pulling aggregate into the tracks creates build up which may stretch the tracks or affect track tension. The aggregate also causes wear on the drive wheels and inner carcass of the tracks.

8. Propelling over hot asphalt on a consistent basis. Hot asphalt on the tracks softens the rubber allowing the tread bars to wear at a quicker rate.

Inspection items (suggest every 250 hrs)

Track items to inspect to determine wear and remaining life.

1. Review travel and paving distances on advisor display ECM if available.

2. Inspect tread bar wear for grouser style belts.

3. Inspect overall carcass thickness if smooth belt used.

4. Inspect inner carcass for wear.

5. Inspect condition of belt for cuts, damage, or exposed cables.

6. Inspect guide blocks for damage and or misalignment.

7. Inspect track tension.

8. Inspect for air in tension cylinders.

9. Inspect drive wheel wear.

10. Inspect front idler wear.

11. Inspect stroke length on the tension cylinders.

12. Inspect track length (as needed if other inspections show issues).

13. Inspect bogie wheel condition.

Techniques to improve track life

Ways to increase track life are the following.

1. Rotate tracks on a yearly basis or if uneven tread wear is observed on the inner or outer carcass surface.

2. Minimize extended travel at high speeds especially with weight in the hopper. Slow down if possible. Travel at high speed with extra weight is the largest contributor for cable migration to the belt surface.

3. Regularly check track tension to avoid driver slip on inner carcass.

4. Minimize material overflow from auger feed system to avoid material build-up and wear on inner carcass. Typically ½ auger height will minimize material flow towards the tracks.

5. Maintain proper track alignment which will minimize heat buildup.

6. Avoid propelling on hot asphalt.

7. Avoid applying any solvent on or around the tracks and undercarriage.

8. The best way to extend belt life is by operation techniques. End dumping is the easiest on belts because the hopper is not always full and there is no loose material on the ground. Using a windrow elevator is a good way to extend belt life if the pickup of material is clean. A hopper insert tends to be the hardest on belts. The insert has a substantial weight that accelerates wear due to the extra loading on the wheels. Turning no matter what the paving method, has an impact on belt life as well. Belt life is affected by operating with a full hopper and complete a counter-rotate spot turn. A better technique is to make more gentle turns when operating with a full hopper.

9. The crew also should minimize the materials the paver passes over when windrow paving. If there is any leakage of material, a portion of the track will end up on top of hot materials. This will accelerate belt wear and can cause belt slippage. Stopping on hot asphalt can give the same results.

10. Avoid getting hot asphalt on the belt and do not try to clean the belt. The belts are self-cleaning and flex during operation. The belt will eventually shed excess asphalt. Do not attempt to clean the belts with diesel fuel. Diesel fuel is hard on belts, mid rollers, drive wheels, and idlers. Avoid having diesel fuel contact any of the Mobile Track System components.

11. In paver applications hours are not always a measure of belt life. High production jobs such as interstate work equal 1 mile of travel for every 2 hours logged on the meter. Commercial applications might take 3.5 hours to cover 1 mile. The surface plays a role in wear. Belts last longer working on smooth surfaces as opposed to milled or abrasive surfaces.

The following table lists hours of belt tread bar wear life experienced by a sampling of customers in those applications. This table should only be used for general reference. This can be helpful when communicating general experience in specific applications. There is no guarantee that your belt will meet or exceed the indicated hour range. This table gives you an idea on which types of operations and applications result in higher wear rates.

Table 4

Operation	Application	Lower range	Upper range
Commercial	End dump truck	2,000h	4,000h
Highway	Windrow elevator	1200h	2500h
MTV (Material Transfer Vehicle) hopper insert		1200h	2500h

Several internal improvements to belts, mid wheel construction, and the addition of a bogie undercarriage system have increased belt and midwheel life. Make sure to follow the basic information outlined above to maximize the MTS system life.

Combines

Combines are heavy and this weight can be detrimental to MTS component life.

Here are some general points to help improve MTS component life.

• Do not road with hopper full.

• Minimize roading on paved hard surface.

• Avoid operation in deep mud that is mixed with rocks. This type of operation can accelerate midwheel and drive wheel chunking and cause belt inside diameter damage.

• Avoid continual operation on steep side slopes with the same side of the machine on the downhill side. If the same side of the machine must be downhill most of the time, rotate the belts from one side of the machine to the other to balance side slope wear. Rotate the belts even if the machine is equipped with a sidehill leveling system.

Agricultural Tractors

Many of the guideline examples and photos are from agricultural tractors. These examples describe many of the situations belts can encounter. The following points should again be emphasized:

• Always make sure that belts are aligned properly. Periodically check belt alignment.

• Avoid operation in material that will build up inside the MTS system.

• Make sure that the tractor is properly balanced and not overloaded.

• Avoid extended roading on paved surfaces. This operation wears tread bars at a high rate.

• Avoid getting stuck. Read the O&MM for specific guidelines on how to get a machine unstuck or belt tearing can occur.

• If equipped with a midwheel air spring, make sure to maintain the pressure in the range of 50-90 psi. Lower pressures cause more weight to be carried by the driver and idler increasing in belt wear. Poor balance can result which can decrease belt life.

• Localized circumferential/longitudinal wear can occur over time from operation on specific row crop stubble spacing. Swapping belts side to side can prolong belt life by moving the localized wear area caused by row crop stubble spacing. Installation of aftermarket “stalk stompers” on the combine header can also reduce this wear.

Note: Special Note on Challenger 35" Belts

Challenger 35 inch belts on tillage tractors offer a unique pairing of benefits and shortcomings. The belt is wider offering lower ground pressures and higher flotation than other belts. The belt is offset to the outside of the tractor (non-centered). This belt center of pull is outside of the centerline of the undercarriage. The belt can pull more load around a corner than the centered belt. The belt seems to minimize ground disturbance due to the curling up of the outside edge in a turn.

Since the outer edge of the belt is unsupported on the outer overhang, the outer edge of the belt will wear at a different rate than the inner area over the undercarriage rolling stock. In some conditions, this belt can lead to little wear on the outer edge of the belt, when the inner area is 100% worn. This condition can lead to excessive belt induced vibration during roading or on hard ground conditions. Shaving off the outboard edges of the tread bars to reduce vibration has proved effective often. Because the center of pull is outside of the centerline of the undercarriage, alignment problems can be encountered more often on this belt than the centered belt.

The benefits of this belt are considerable. Shortcomings should be considered when this belt is selected as well as cost.

DEUCE

When operating the DEUCE in slot work, keep the slot width a reasonable amount bigger than the machine. Avoiding debris accumulation in the undercarriage will extend the life of the undercarriage.

Make sure that all the latest equipment for monitoring belt tension is installed. Verify that all undercarriage guards are installed and adjusted correctly.

Versatile Flotation Systems/VFS Trailers

The VFS trailer is one of the few applications in which the MTS system is unpowered. Many of the problems due to slippage or excessive bending loads in high drawbar applications do not apply here. The VFS may have other problems.

The most frequent problem is excessive loads imposed on the belts. The recoil system is not as robust as the powered machine system and as a result do not have as much recoil available. The lack of any rubber on the midwheels and idlers can cause more load to go into the belt carcass. The VFS does not tend to self-clean as well as a powered unit. When there is material build-up, the VFS can get to the point of running out of recoil in severe conditions. The resulting over tensioning will damage the belt internally. The VFS chevron tread bar design can cause the cables to pull through. See Illustration 107. In applications with this type of risk the circumferential ribbed belts should be the belt of choice.

Illustration 107	g02436297
Exposed 0° cable over tensioning (VFS Trailer)

Cable pull through failure is due to the application. A result of build-up on the idler wheels will cause the over tensioning of this lighter construction belt. If this type of problem is encountered, the belt should be replaced with a heavier carcass version such as the circumferential ribbed belts. These types of belts have more cables and extra inner rubber.

To keep build-up out of the system, there are special wheel scraper plate designs available. Reference Service Magazine, SEPD0599, "A Procedure for Fabricating Mud Scraper Plates for the Rear Idlers on Versatile Flotation Systems"

Storage of Belts

Rubber component life in storage on or off the machine can be improved through following good storage practices.

The belt may be shaped for storage. Back bending is allowed as long as the minimum bend radius is at least 200mm. See 108.

Illustration 108	g02436336
Belt storage back bending shown in center

For extended storage, the ideal condition is a cool, dry, and dark location free from air currents. High room temperatures over 86ºF/ 30ºC are detrimental and should be avoided.

Particular care should be taken to store MTS components away from electric motors. The electric motors generate ozone which can cause more rapid aging. Keep the storeroom dark or at least free from direct sunlight. It is not recommended to store rubber components outside. Where this storage is necessary the belt or wheels should be protected from direct sunlight with an opaque or UV resistant covering.

Additional Information

If any belt wear or damage issues are discovered which do not readily fall into a section covered in this reusability guide. Contact the appropriate Caterpillar service representative. Make sure to obtain the following information before contacting the service representative:

• Belt serial number and wheel date codes.

• Number of hours in service.

• Application.

• Photographs of the undercarriage and close up of damage.

Illustration 109	g02436338
Belt Date Code (1002) and serial number (10390.)

Illustration 110	g02436337
Wheel Date Code (03/2002.)