Before the charge is placed in the cleaned hole, the BMS Micro-Blaster should be cocked and its safety clip attached. The tube of the BMS Micro-Blaster should be slipped into the hole to see whether it fits properly. If the hole is sized and aligned properly, place the cartridge into the hole with the brass cap pointing up. The brass cap is the primer. If the cartridge is inserted upside down, the BMS Micro-Blaster will misfire. Once the cartridge is in place, the BMS Micro-Blaster actuator tube is slipped into the hole on top of the charge.
|The BMS Micro-Blaster should always be cocked before it is slipped into the hole, especially when there is a live charge in the hole. If you cock the BMS Micro-Blaster while the tip of the actuator tube is touching the cartridge, the cartridge may fire, seriously injuring you.|
A small slot on the side of the BMS Micro-Blaster will display a green stripe on the actuator tube when the BMS Micro-Blaster has been cocked. Lock the safety mechanism in place to prevent an accidental firing. Once you are comfortable that the system is cocked and the area is secure, unlock the safety mechanism. The BMS Micro-Blaster is fired (figure 5) by pulling the 25-foot lanyard from its end. An alternative CO2-powered firing mechanism (BMS Micro-Blaster II) was not reviewed.Transparent office tape can be used when placing the charge in the hole. After the hole has been drilled, cock the BMS Micro-Blaster and lock the safety mechanism in place. Attach the primer end of the cartridge to the end of the actuator tube with a piece of tape. Place both of them into the hole.
This method may reduce the need to thoroughly clean the hole and reduce the potential for misfires. Under damp conditions when the drilling dust has become wet and difficult to remove, this method of placing the charge may be more dependable than other methods. The tight clearance between the actuator tube and the hole allow just a thin piece of tape to be used. If the tape is dislodged and drilling dust or the tape works its way between the cartridge and the firing pin, the BMS Micro-Blaster may misfire.All BMS Micro-Blaster kits come with detailed instructions and are simple to operate.
When the charge is fired, expanding gases fracture the rock (figure 6). The rock's size, structure, and type will determine the number of holes and charges needed to break the rock into manageable pieces. During field tests conducted by MTDC, one charge was enough to break rocks weighing 100 to 250 pounds. Larger rocks required several holes and charges. Crews field testing the BMS Micro-Blaster in Alaska broke rocks that weighed up to 1,000 pounds by using multiple charges.Harder rocks break or fracture more easily than soft rocks. The softer the rock, the more likely the rock is to absorb the energy of the blast rather than to be broken by it.
In Alaska, field crews were able to use the BMS Micro-Blaster to shape lips and ledges on embedded rock. Forest Service crews in Colorado were less successful. Breaking embedded rock is more difficult than breaking loose rock, because the ground may absorb the shock wave. When shaping embedded rock, it is best to break the rock to a free edge. This means starting near an edge and breaking away sections of rock. You may use the BMS Micro-Blaster in a horizontal position to remove protruding surfaces.
The detonation produced little flying debris. A rubber doormat (figure 7), or a piece of carpet, could be used as a blast mat. A mat also helps hold the BMS Micro-Blaster in place during detonation and minimizes noise. Despite the advantages of a blast mat, the BMS Micro-Blaster can be used without one.
The actuator tube in earlier versions of the BMS Micro-Blaster tended to shift, causing misfires. BMS made several design changes that improved performance and corrected those problems. Anyone who has earlier versions of the BMS Micro-Blaster may wish to contact the company to have the actuator tube modified.
BMS has developed a new model called the BMS Micro-Blaster II. According to BMS, the BMS Micro-Blaster II can be configured to fire three cartridges using a manifold-valve assembly powered by a portable air tank. BMS says that this system has broken rocks that weighed as much as 2 tons, splitting the rock along a fairly straight line. MTDC has not evaluated this product.
The BMS Micro-Blaster (figure 8) works in the vertical and horizontal positions and appears to be a good tool for shaping rock walls and steps. It also works well when building trail segments and when splitting rocks (figure 9) to a size that can be handled more easily. The BMS Micro-Blaster is small and light, making it portable.
Suggested retail price of the BMS Micro-Blaster at the time of this printing was $375. A package of 10 loads was $15.
The SDS bit holders for hand drilling can be found at mountaineering stores. One source is Pika Mountain: http://www.pikamtn.com/
Doug Blanc, Tongass National Forest
Nick Hazelbaker, Bitterroot National Forest
David E. Michael, Tahoe National Forest
Jeff Leisy, Pike and San Isabel National Forests
Ralph Swain, Rocky Mountain Region Recreation, Heritage, and Wilderness