The following pages show photos and illustrations of track damage and the probable cause of the damage. It is intended to be used for identifying the reason for track damage and how to avoid future track damage.
Cutting Of Steel Cords
Damage:
Embedded steel cords are cut off [Figure 30-30-1] and [Figure 30-30-2].
Replacement:
Replacement is required.
Causes of the damage:
When applied to rubber tracks under the following circumstances, tension in excess of the breaking strength of the embedded steel cords causes steel cords to be cut:
When the rubber track is detracting, the idler or sprocket
rides on the projections of the embedded metal [Figure
30-30-3].
When the rubber track is detracted, projections of rubber tracks get stuck between the frame of the undercarriage.
The rubber track is clogged with stones or foreign obstacles.
When moisture invades through a cut on the lug side rubber surface, the embedded steel cords will corrode. The deterioration of the design strength may lead to the breaking off of the steel cords.
Prevention:
The following preventions should be taken to minimize the risk of this damage:
Periodical checking on site of the recommended track tension.
Avoiding quick turns on bumpy and rocky fields.
Drive carefully to avoid having stones and other
articles clog the rubber tracks.
Driving over sharp objects should be avoided. If this is impossible, do not make turns while driving over sharp objects.
Abrasion Of Embedded Metals
Damage:
In proportion to the service time, embedded metals will gradually wear away by friction [Figure 30-30-4].
Replacement:
Replacement is required when the width of the embedded metals (D1) becomes 67% of their original width (D) [Figure 30-30-5].
Causes of the damage:
When the track rollers, sprockets and idler gears roll over the embedded metals, abrasion of embedded metals is inevitable. The following cases sometimes accelerate their abrasion:
Rubber tracks are driven with an extraordinary heavy load on them.
Rubber tracks are used on sandy fields. Prevention:
As long as rubber tracks are used under normal operating conditions, abnormal abrasion is unlikely to occur. The level of abrasion should be carefully checked when the machines are used for dozing which generate a heavy load for rubber tracks, and when they are operated under a sandy field condition for a long time.
Separation Of Embedded Metals
Damage:
Extraordinary outer forces applied to embedded metals cause their separation from the rubber track’s body [Figure 30-30-6].
Replacement:
Even a partial separation of embedded metals requires replacement of the track.
Causes of the damage:
Embedded metals are adhered between the steel cords and the rubber body. The following cases generate external forces greater than the adhesion strength, causing separation of the embedded metals:
When the idler continually rides on the projections of embedded metals, the embedded metals will eventually peel off [Figure 30-30-7].
When a rubber track is detracted, it becomes stuck between the guide or the undercarriage frame, causing the separation of embedded metals [Figure 30-30-8].
Separation Of Embedded Metals
Abnormally worn sprockets will pull embedded metals out [Figure 30-30-9].
Prevention:
Similar to the prevention against the cutting of the steel cords:
Track tension should be periodically checked.
Quick turns on bumpy and rocky fields should be avoided.
If abnormal wear of sprockets is observed, they should be immediately replaced.
Separation Of Embedded Metals Due To Corrosion
Damage:
Due to corrosion of embedded metals, the adhesion to the rubber body deteriorates, resulting in complete separation [Figure 30-30-10].
Replacement:
Even a partial separation of embedded metals requires a rubber track replacement.
Causes of the damage:
Embedded metals are bonded to the rubber body. The following operating conditions cause embedded metals to corrode, causing deterioration of the bonding, and finally resulting in separation of the embedded metals from the rubber body [Figure 30-30-11].
Excessively salty fields, like the sea shore.
Strong acidic or alkali soil conditions
Compost spread grounds
On tracks that are out of adjustment, the track rollers, idlers and sprockets will gradually wear the rubber surface at track roller side, causing exposure of the embedded metals. Consequently the embedded metals will corrode resulting in their separation from the rubber body.
Prevention:
If rubber tracks are used under such field conditions as described under (Causes of the damage). The tracks should be washed with plenty of water. After being completely dried, they should be stored correctly.
When the bonded rubber cover is separated from the embedded metal projections and the metals in the rubber body become loose, it is time to consider replacement of the rubber track.
Cuts On The Lug Side Rubber
Damage:
Cuts on the lug side rubber often occurs as one of the most typical failure modes [Figure 30-30-12]
Replacement:
When a cut on the lug side rubber reaches the embedded steel cords, it should be immediately repaired with cold vulcanization rubber.
Causes of the damage:
When rubber tracks drive over projections or sharp stones in the fields, the concentrated forces applied cause cuts on the lug side rubber surface. In case of making turns on projections, the lug side rubber surface will have an even higher chance to be cut. If the cuts run through the embedded steel cords, it might result in the steel cords’ breakage due to their corrosion. It is highly recommended to repair the cuts with cold vulcanization rubber as soon as they are observed [Figure 30-30-13].
Prevention:
Machine operators are requested to drive with great attention to the ground’s surface especially in terrains of the following type:
Construction sites
Demolition sites
Paths covered with rocks and wood
Concrete ridges
Stumpy fields
When operating on terrains as mentioned above, high speed, quick turns and overloading should be avoided.
Cracks On The Lug Side Rubber Due To Fatigue
Damage:
Small cracks around the root of the lug as a result from operation fatigue [Figure 30-30-14] and [Figure 30-30-15].
Replacement:
When the cracks reach so deep that they expose the steel cords, track replacement is required.
Causes of the damage:
Because of wound stress applied to rubber tracks around the undercarriage parts during operation, the fatigue especially causes cracks on the lug side rubber surface. Once the cracks occur, they gradually deteriorate with even small external cracks. When operating near seashores or under cold temperatures, rubber tracks are more likely to suffer from ozone cracks.
Prevention:
Rubber tracks are designed with special rubber compounds to prevent cracks due to fatigue. External injuries on the lug side rubber sometimes cause more chance of cracking. Machine operators should observe soil conditions when driving, so as not to cause external injuries to the lug side rubber. In order to minimize the occurrence of ozone cracks, attention should be paid to the following instructions for maintenance:
Avoid exposing stored tracks to direct sun light.
Avoid exposing stored tracks to direct rain and snow fall.
Store tracks in well ventilated warehouses.
Use the tracks at least once a month.
Lug Abrasion
Damage:
As its service time proceeds, the lug side inevitably undergoes abrasion [Figure 30-30-16] and [Figure 30-30-17].
Replacement:
No replacement is required.
Causes of the damage:
Lug abrasion is inevitable. Even if lug abrasion is proceeding, the rubber track can be used. As the traction performance deteriorates accordingly, it is highly recommended to replace the abraded tracks with new ones when the lug height becomes less than 5 mm (0.197 in).
Prevention:
In order to prevent the rubber track from abnormal or premature abrasion, following operating conditions should be avoided:
Making quick and repeated turns on concrete and asphalt roads
Driving up and down hilly paths with slippage
Making frequent turns on paths covered with rocks and wood
Cracks And Cuts On The Lug Side Rubber
Damage:
Sometimes cracks and cuts on the lug side rubber at the edges of the embedded metals can be observed [Figure 30-30-18].
Replacement:
No replacement is required unless the cuts on the lug side rubber are discovered all around the edges of the embedded metals, as this will result in a complete cut off.
Causes of the damage:
When rubber tracks drive over sharp projections, intensive stress is applied to the lug side rubber surface, especially at the edges of embedded metals, causing cracks and cuts in the area around the embedded metals [Figure 30-30-19].
Prevention:
To avoid extensive stress applied to the lug root where metals are embedded, machine operators are requested to avoid driving over stumps and ridges.
Abrasion Of The Track Roller Side
Damage:
The rubber surface on which track rollers run is gradually abraded. It will end in the exposure of the embedded metals [Figure 30-30-20].
Replacement:
It is recommended to replace the rubber track when more than half of the embedded metals are completely exposed.
Causes of the damage:
The abrasion of the track roller side rubber surface occurs because of sand and gravel being clogged between the rubber and the outside surface of the track rollers. The stress pushes the sand and gravel against the side of the rubber track to cause the abrasion [Figure 30-30-21].
The level of abrasion is highly dependent on terrain conditions. A higher level of abrasion will occur when the rubber tracks are operated in fields covered with many stones and gravel. Small stones hardened with mud, stuck to the track rollers increase the abrasion level. After an extended period of abrasion, it will be more likely for exposed embedded metals to catch moisture through the inside steel cords, which can cause breakage of steel cords and separation of the metals from the rubber body.
Prevention:
After operation in wet fields containing many small stones, wash off the mud that is stuck to the track rollers completely. When operating on gravel paths and stony grounds, machines should be driven slowly and the turning radius should be big enough to prevent stones and gravel from getting stuck to the track roller side rubber.
Cuts On The Edges Of Track Roller Side
Damage:
Both edges of the rubber track have no special reinforcements. It sometimes occurs during operation that they are cut or torn off [Figure 30-30-22] and [Figure 30-30-23].
Replacement:
In such case, the rubber track does not have to be replaced.
Causes of the damage:
This damage is caused by objects on the field or by interference with the machine frame.
In case of damage by objects on the operating ground:
The edges of rubber track are often deformed largely due to a bumpy ground surface, stones and other objects, which cause extensive stress on the edges resulting in the damage. When a machine drives over concrete ridges, this type of damage easily occurs [Figure 30-30-24].
In case of damage by interference with the machine frame:
If a machine continues operating with rubber tracks being detracted, the rubber tracks may get caught up in the machine frame or undercarriage parts resulting in damage. When a machine travels along side slopes, the rubber tracks are deformed so much that they come into contact with the machine frame and undercarriage parts, which causes cutting, gouging and rubbing of rubber tracks in the end [Figure 30-30-25].
Cuts On The Edges Of Track Roller Side (Contโd)
Prevention:
When traveling, a machine operator should be careful not to drive over any projections on the ground. He should also prevent rubber tracks from coming into contact with concrete walls, ditches and ridges. If rubber tracks are detracked, the machine should be stopped immediately for retracking.
