The Road Analysis Control (RAC) is an attachment for all off-highway trucks. The RAC module samples data at a rate of ten times per second. Then, the RAC module calculates the relative severity of each haul cycle. The RAC module calculates the stress that is present on major components of the truck as a way of monitoring the condition of the haul roads. This calculation indicates when repairs to the haul road are needed. This information can be used to assess the various design configurations of the haul road. This information can be used to determine the design configurations that have the least effect on the life of the truck.
Note: For additional information on the Road Analysis Control, refer to the Systems Operation, RENR2636, "RAC (Road Analysis Control) Application Manual".
Note: The “Caterpillar 10/10/20 Payload Rule” for off-highway trucks states that no more than 10 percent of the payloads may exceed 1.1 times the truck's maximum target payload. No single payload shall exceed 1.2 times the maximum target payload.
The target payload is based upon the Gross Machine Weight (GMW) of the truck. The GMW is a function of the truck's configuration. The GMW includes the weight of the tires, rims and body.
The "Payload Distribution Reports" of VIMS Supervisor will indicate overloading by an individual truck or a fleet of trucks. An acceptable Payload Distribution is one that shows that the number of loads that exceed 110 percent of rated payload does not exceed more than 10 percent of the total loads that were hauled. No loads exceed 120 percent of rated payload. Refer to Illustrations 1 through 4.
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| Illustration 1 | g00772051 |
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| Illustration 2 | g01061802 |
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| Illustration 3 | g01061860 |
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| Illustration 4 | g01061942 |
The second key factor that affects the payload is the proper front to back placement of the load in the body of the truck. CAT trucks are designed for a typical load weight distribution for 33 percent of the Gross Machine Weight (GMW) to be on the front axle. The typical load weight distribution is 66 percent of the GMW for rear axle. The best way to determine the actual load placement is with a certified scale truck.
- The loading tool should position the bucket over the Load Placement Arrow.
- Center the load from the side to the side in the body of the truck.
Incorrect placement of the payload in the truck's body can affect the life of different components. Incorrect placement of the payload includes the situations that are listed below:
- The payload is placed too far to the front of the truck's body.
- The payload is placed too far to the rear of the truck's body.
- The payload is placed off-center of the truck's body.
This may also contribute to inaccurate payload measurements. Later trucks use a marker in order to show the center of the load that is mounted on the side of the truck's body. The marker is an arrow. Older trucks may be retrofitted with a marker in order to show the center of the load.
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| Illustration 5 | g00670357 |
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The 175-2624 Markers are available through the machine order system. For information on proper placement of the marker on the truck's body, contact your Caterpillar Dealer. Your Caterpillar Dealer will need the information that is listed here: the serial number of the truck, the part number of the truck body, the sequence number of the truck body and the information on any modifications that were made to the truck's body (1) Marker that shows the center of the load | |
A centered load improves the accuracy of payload measurement. Centering the load in the truck's body is referred to as the payload bias. The Payload bias can be determined by observing the position of the load in the truck's body. A better indicator uses the VIMS/TPMS data of the suspension cylinder pressure. Typically, the problems that occur with centering of a load are the result due to the improper positioning of truck under the loading tool. Loads that are off-center have the potential for causing RAC events, because one side of the truck carries more weight than the other side of the truck. This may reduce the service life of the truck.
The loading floor should be kept as level as possible. A loading floor with an excessive slope may affect the accuracy of the payload.