Tests were conducted near Lake Tahoe for 2 days during September 2005. The tests were conducted in a gravel pit where conditions could be controlled. Once the effectiveness of the conveyor system was established, additional tests were conducted in areas that had been thinned. Tests were designed to examine productivity, performance on slopes, effectiveness of moving wood chips and raw slash, and any problems that might arise when the conveyor sections were not connected in a straight line.

The portable conveyor system supplied by Miniveyor Systems Inc. consisted of six electrically powered sections (each 10 feet long) and one hydraulically powered section (20 feet long) with accessories (table 1). The 15-inch-wide belts were fabric-reinforced PVC with cleats. A single portable generator powered the 10-foot sections, while a hydraulic power pack ran the 20-foot discharge section.

The first test was conducted in a gravel pit with the conveyor line following a gradual horizontal curve up a steep grade. A portable chipper fed chips into the conveyor's loading hopper at the lower end of the line. The final 20-foot discharge section of the conveyor ran faster than the 10-foot sections so it could throw material into a dump truck backed under the uphill end of the conveyor line. This test examined the conveyor's ability to carry wood chips effectively.

The second test also was conducted in the gravel pit, but the chip hopper was removed and raw slash was loaded onto the belt. This test's objective was to document productivity and performance removing slash under controlled conditions. Three experienced members of a thinning crew picked slash from a 1,500-pound pile and loaded the belt. Part way through this test, the conveyor sections were realigned to reduce hangups and lost material. This test was repeated with the same slash pile positioned slightly farther from the belt's loading point.

Additional tests were conducted in a thinned stand with hand piles. A five-person piling crew brought slash from piles to the conveyor line. The test area was about 0.22 acre and had 11 separate slash piles. The average distance from the piles to the conveyor was 40 feet with the farthest pile 114 feet away. The six electric-powered sections of the conveyor were deployed into the unit with the final 20-foot section carrying material up a fill bank to the shoulder of the road. The average grade of the conveyor line in the forest was 17 percent. A portable chipper at the roadside chipped the residue and deposited the chips in a single pile. The volume and density of the pile was measured to get an estimate of productivity.

During these tests, the alignment of conveyor sections, the distance slash had to be moved when loading it on the conveyor, and similar concerns were tested under controlled conditions.

Moving Chips—This test examined the technical performance when a chipper loaded the conveyor. To configure the conveyor to carry chips, each section has to be overlapped by a foot, shortening the conveyor line. During this test, the chipper could produce more chips than the hopper and belt could carry. Chips bounced out of the hopper and overflowed its sides. As chips moved up the line from the hopper, they were lost at gaps in the side extensions (figure 3). Most of the chips remained on the belt and were successfully transported into the truck.

Slash Productivity—This test was conducted twice. Initially, the 1,500-pound slash pile was close to the loading point. During the second test, the pile was about 20 feet from the loading point. The initial test took a total of 62.7 minutes with only 7.5 minutes of productive loading time (working time without delays). The delays were caused by slash falling off the conveyor, slash getting caught in the side extensions, or conveyor sections separating from one another.

The belt had problems moving certain types of slash, including long pieces, curved pieces, forked pieces, and lightweight pieces. Some of the problems occurred at the overlaps between sections. Other losses occurred when the conveyor sections were at an angle to one another rather than straight. The net manual loading productivity with three workers averaged 6 green tons per productive hour.

For the second test, the conveyor line was reconfigured with the sections butted straight, end-to-end. The slash pile was 20 feet from the loading point. The realignment significantly reduced delays, with a total test time of 14.3 minutes and productive loading time of 12.0 minutes (3.8 green tons per productive hour). Productivity was lower because the pile was farther from the belt. Even in this configuration, however, workers needed to stand along the belt to reload pieces of slash that fell off.

Figure 3—Chips fell from gaps in the conveyor's side extensions.

The conveyor sections were deployed into the unit, blocked, and connected with a 1-foot overlap between sections (figure 4). The piling crew moved material from the piles (figure 5) to the belt. The operation ran for a total of 111.4 minutes with 72.7 minutes of productive time. Most of the unproductive time was spent replacing the side extensions after they were knocked loose by pieces of slash. As in the slash test in the gravel pit, there were problems conveying many types of slash. Additional personnel were required to keep material on the belt. After all the piles were removed and chipped, the volume of the chip pile was 761 cubic feet. Based on two measurements of chip density averaging 10.5 pounds per cubic foot, the chip pile weighed about 4 green tons. This averages to a production rate of 3.3 green tons per productive hour.

Figure 4—Even though the conveyor sections were overlapped and side
extensions were installed, slash was difficult to keep on the conveyor.

Figure 5—Piled slash was removed during some of the tests of
the portable conveyor.