BODY 3H6250 - Caterpillar

No matter how good tires are or how well the machine is maintained, if loading practices are poor, optimal tire life can never be achieved. There are many ways to identify this including, visually observing machines as loading occurs. The payload should be centered fore-aft in line with the payload indicator on the body. The images in Illustration 1 show proper load placement versus poor load placement in the fore-aft direction. The position of the pile in the right image is too far forward as indicated by the pile centerline of the payload indicator. The rocks up on the canopy and lack of material on the tail of the body are also indicators. This load puts excessive weight on the front tires causing excessive heating and wear.
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Payloads can also be placed improperly from side-to-side. In Illustration 2 the position of the pile is too far toward the left. Often times, an unbalanced load (such as the one shown) results from improperly sized loading tools or poor positioning of the machine under the shovel. This load puts excessive weight on the left tires, especially on the single left front tire. The result on the tires under this condition is excessive heating and wear. The payload should be placed directly in the center of the body to balance the load side-to-side.Load placement accuracy can also be determined through more scientific scale studies. The scale studies involve weighing each of the machine corners individually. A perfectly placed payload will not change the side-to-side bias of the empty machine.
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Many times during scale studies, machines can have each payload scanned to help measure payload accuracy. These scans can be correlated to the actual machine data so that comparisons can be made between weight splits and payloads. The information can be used to ensure that the empty machine, specifically the struts, are set up correctly. A centered payload should have evenly distributed corner weight splits. Illustration 3 shows examples of payload scans and the corresponding front axle splits.
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Finally, another benefit to scale studies and payload scans is that a scan can identify whether carryback is an issue at site. Carryback results in extra weight being carried during empty runs. This issue decreases tire life as more weight is carried by the tires during the overall haul. Illustration 4 shows an example of a machine with carryback in front right corner of the body.
There are many contributors to payload placement, foremost are both the truck and loading tool operators. The truck operator must properly place the machine under the loading tool so that the material can be centered on the machine. Placing the truck too far away from the loading tool results in a bias load towards the shovel. Next the loading tool operator must properly spot the truck and load the truck over the load indicators so that the material is correctly distributed. Also, both operators should be responsible for ensuring the payload is loaded to target weights. Proper training of