Truck tests truncated

Komatsu Mining Systems builds huge off road trucks used by mining companies for hauling material from open pit mines. The company has been doing this since 1957 when the payload of its vehicles was about 30ton. Today payloads are as high as several hundred tons which is a benefit to mining companies since it allows them to make fewer trips into the pit. The Komatsu 930E, the company’s largest model, has a payload of between 285ton and 310ton, depending on how the customer has it configured. This truck is made with a majority of American-made components. It is nearly 24ft tall and 26.5ft wide. Loaded the truck weighs almost 1million pounds. Komatsu 930Es are going into service around the world in coal, iron ore, copper and other types of mines.

Because the frame supports the entire load it is essential for test engineers to evaluate metal fatigue and make life estimates by analysing data from strain gauges which measure deflection in response to loads in typical field operating situations. Three-element rosette strain gauges are placed at various places on the frame to ensure that all incoming forces are detected. These multi-axial devices are preferred over single-axis gauges because forces don’t always come from the expected direction. Unlike single-axis gauges, there is no guesswork about how to orient multi-axis gauges on the vehicle. Once the rosettes are in place and connected to the data acquisition device, the loaded truck is then driven through a course that includes the pot holes and other rough road conditions typical of mine driving.

To record the output of the sensors a data acquisition tape recorder was used, the bulk and delicateness of which required special handling and numerous preparations. Telemetry was impossible as the truck had to go around corners at a mine site. The recorder had to travel with the truck. But it was too large to fit into the cab so a special instrument cab was adapted from an old truck to house it. Due to the heat and the dust of the test site, the instrument cab required special shock absorbers and an air conditioner that was welded to the roof. The installation required an auxiliary generator to power the special components required for the test. Creating this special environment added days of set-up time to a field test. Also loading all the test equipment into the instrument cab required special machinery. The tape recorder could sample data from only 28 channels at a time. With each three-element rosette requiring three separate channels, this meant that each test run could collect data from fewer than 10 sites on the frame. As a result, many runs were needed to acquire data from the numerous locations that a standard field test samples. The load in the truck had to be checked to make sure it didn’t shift or change during the previous run. Another drawback to the tape recorder was that it stored data in analogue format. After a test, the data had to be converted into digital format for use in analysis software. This took several days.

Komatsu needed to reduce testing time to maintain its position as the leader in the highly competitive mining truck market. After considering other data acquisition systems, they chose the SoMat Model 2100 FCS (Field Computer System) from SoMat Systems UK. It was chosen because its high sampling capacity would increase the number of data channels that could be recorder during the test drive. The fact that it was small enough to fit in the cab and rugged enough to withstand the heat and jolts of mine roads meant that time would no longer be spent creating a special test instrument environment.

The increased channel capacity of the SoMat 2100 FCS led to a significant reduction in field testing time for the frame test on the Komatsu 930E. The computer was configured to sample data from 60 channels simultaneously. By more than doubling the number of channels that were previously sampled, this system reduced the need for many of the test runs that were made in the past.

Additional time savings came from the ruggedness and compact size of the SoMat 2100 FCS which meant it could be placed directly in the cab. Ease of set-up and running and the immediacy of the test results all contributed to the testing time being half that using the traditional tape method.

Unlike single-axis gauges, there is no guesswork about how to orient multi-axis gauges on the vehicle. Once the rosettes are in place and connected to the data acquisition device, the loaded truck is then driven around a course that includes all the road surfaces, such as pot holes and other rough conditions that are typical of mine driving.

The Haulpak 930E, Komatsu’s largest model, has a payload of between 285ton and 310ton. The most critical component, the frame, was tested using Somat’s 2500 series data acquisition system with 64 channels. More channels meant fewer test drives and reconfigurations were were needed to collect the necessary data.