Initial Equipment Demonstration
After conducting numerous phone interviews and an extensive literature and market search, MTDC arranged a field demonstration of the JAWZ attachment April 23 and 24, 2007, at the Cimarron National Grassland in Elkhart, KS. Cimarron National Grassland participants were Joe Hartman (district ranger), Andy Chappell (wildlife biologist), Nancy Brewer (rangeland management specialist), and Tim Higgins (heavy equipment operator). Dan Garcia de la Cadena, wildlife staff officer for the Kiowa and Rita Blanca National Grasslands, also attended the demonstration. Those participating from Starhill were John Lyddon (president) and Stuart Cave (employee). MTDC project leader Keith Windell was also present. The objectives of the equipment demonstration were to determine how much force is needed to pull clumps of tamarisk plants from the ground and to determine whether the JAWZ (figure 1) attachment could perform the task.
Figure 1—The Star Hill JAWZ attachment was
used to
pull tamarisk plants from the ground.
Figure 2—A Dillon 20,000-pound dynamometer used to
determine how much force was needed to pull tamarisk.
To determine how much force was required to pull the tamarisk, a Dillon dynamometer (figure 2, serial No. AP505) was placed between a chain wrapped around the base of the tamarisk clump and a large, surplus military forklift designed for rough terrain (figures 3a and 3b). The largest tamarisk clumps the forklift could drive to were chosen for the test. The results apply to tamarisk growing in sandy soils. Results will vary for other species of tamarisk or other soils. Other species of tamarisk found throughout the West are larger than the tamarisk pulled during this study. The sandy soil also made it easier to pull the tree clumps than if the soil was heavy clay or if the soil was frozen. Although the chain tended to slip, the forklift operator pulled 15 tamarisks (table 1).
Figure 3a—A surplus military forklift designed
for rough terrain was used to pull out tamarisk.
Figure 3b—Collecting pull data.
After the soil dried out later that summer, the forklift (which can pull with 12,000 pounds of force) could not pull out the tamarisk. Pull tamarisk in the spring when soils are moist!
Some of the clumps were larger around than the JAWZ could open (34 inches maximum). In these cases, the JAWZ grabbed a portion of the tamarisk stems at or slightly below the ground line.
| Clump No. | Force (pounds) | Comments |
|---|---|---|
| 1 | 8500 | |
| 2 | 5400 | |
| 3 | 5400 | |
| 4 | 9400 | |
| 5 | 8400 | |
| 6 | 7200 | |
| 7 | 3000 | (The reset button on the dial's face may have been brushed) |
| 8 | 3100 | |
| 9 | 4800 | |
| 10 | 3600 | |
| 11 | 5300 | |
| 12 | 7400 | |
| 13 | 3800 | |
| 14 | 5400 | |
| 15 | 10000 | (Extra large clump) |
The JAWZ attachment was tested on two different wheeled skid steer loaders: the Cimarron National Grassland's Bobcat S160 rubber-tired skid steer (figure 4) and a John Deere 260 skid steer (figure 5) borrowed from the Kiowa and Rita Blanca National Grasslands.
Figure 4—The Bobcat S160 skid steer loader.
Tamarisk bundles were easier to pull out when they were rocked from side to side. The Bobcat S160 rubber-tired skid steer, which was lighter and had better flotation than the John Deere 260 skid steer, was less likely to get stuck in the sandy soils. The Bobcat S160 has an operating capacity of 1,600 pounds, a boom breakout force of 3,000 pounds, and a tipping load of 3,200 pounds. It has 56 net horsepower and an operating weight of 5,752 pounds. The Bobcat S160 had a more difficult time pulling tamarisk than the John Deere 260.
Figure 5—Tamarisk pulled up by the John Deere 260 skid steer loader.
Note the size of the tamarisk's root.
The John Deere 260 has an operating capacity of 2,400 pounds, a boom breakout force of 4,800 pounds, and a tipping load of 5,000 pounds. It has 69 net horsepower and an operating weight of 8,250 pounds.
After two afternoons of pulling trees, the general consensus among those participating in the demonstration was that the Bobcat S160 was too small. Although the John Deere S260 was more capable, its weight made it more susceptible to getting stuck in the sandy soils. Rubber-tracked loaders or skid steers with over-the-wheel rubber or steel tracks would have better flotation than wheeled vehicles.
Holes were left after the tamarisk was pulled (figure 6). The Cimarron National Grassland employees felt that these holes would probably fill in naturally.
Figure 6—The hole left after a tamarisk has been
pulled from sandy soil at the Cimarron National Grassland.
The JAWZ arms were not always perfectly synchronized. Sometimes there was a delay when the arms opened. Starhill representatives said the arms become unsynchronized when one arm pushes against a firm object and the other closes. This causes the arms to be out of synch when they open. Starhill representatives said it is a simple matter for the operator to reset the JAWZ arms. Resetting the arms to the wide-open position before using the attachment to grab the next clump of tamarisk stems worked, but took time.
Sometimes the JAWZ arms slipped on the tamarisk stems, a problem that Starhill representatives attributed to operator error and inexperience. After the operator first closes the JAWZ around the tamarisk, the operator needs to hit the toggle to make sure the hydraulic grip remains tight while the tree is being pulled. This technique is not so important when the JAWZ attachment is used to pull metal stakes, but the technique is essential when the JAWZ attachment is used to pull a softer object, such as a clump of tamarisk.
Participants at the demonstration felt it might be worthwhile to try mounting the JAWZ attachment on a compact excavator. An excavator would be able to work farther away from the tamarisk stems, could reach over obstacles, would not have to drive to every single tamarisk clump, and would be able to pile the tamarisk more efficiently for burning. Cimarron National Grassland employees were concerned that a larger excavator might cause resource damage, especially excessive soil disturbance.
After the demonstration, MTDC asked Starhill representatives to search for a commercial adapter plate so the JAWZ could be mounted on a compact excavator, investigate the hydraulic arm timing issue with the manufacturer (Paladin Brands) of the JAWZ attachment, and look into the possibility of developing an optional commercial brush bar for the JAWZ attachment. A brush bar would reduce the risk of damaging the skid steer. MTDC agreed to purchase the JAWZ attachment and compact excavator adapter plate for the Cimarron National Grassland in exchange for Cimarron National Grassland employees conducting a study comparing the use of the JAWZ attachment to pull tamarisk to the use of a brush saw to cut off the tamarisk.
