The Robbins H-100 was a high-production blast-hole drill employed by a number of surface-coal-mining companies in the Illinois Basin during the 1960s and 1970s. Starting with development work in 1960 as a joint project of Peabody Coal and the Robbins Drill Division of Joy Manufacturing, the huge drill was able to simultaneously punch two horizontal holes up to 10-5/8-inch diameter into the overburden. Rather than operate in the conventional manner from the top of the bench and drill vertical holes, this machine worked from the base of the high wall in the previously mined-out cut and drilled horizontal holes directly into hard overburden requiring blasting. In the right geological conditions, the H-100 horizontal drill offered several advantages including reduced explosives usage and greatly reduced drilling footage, translating into lower costs when compared to the vertical method.
The Robbins H-100 had an operating weight of 185 tons and was available with diesel-electric or straight electric drive. The drill unit with independent twin masts could drill one or two holes simultaneously for a depth of 150 feet into the high wall. Pressure on each bit was 90,000 pounds provided by horizontal hydraulic cylinders. Each was equipped with its own Joy rotary screw air compressor, water system, and 100-hp reversible electric motor providing rotation through a 2-speed transmission. Each drill mast could be raised or lowered to operate up to 10 degrees above or 12 degrees below the horizontal.
The upper works carrying the twin masts was mounted on a 2-crawler undercarriage fitted with 42-inch shoes. Each crawler assembly was independently driven by a reversible hydraulic motor. The operator controlled all functions from his state-of-the-art cab fitted with indicator lights showing the status of the various drill functions including hole depth, drill pressure and rotation speed.
The drilled holes were loaded with a special machine called a hole tamper. Designed by Robbins, the machine was mounted on a crawler tractor such as a Caterpillar D6. It consisted of a table supporting a series of square-section wooden poles hinged together in concertina fashion. A rubber-tire friction drive drove the poles horizontally into the hole pushing the detonator and explosives into position.
Robbins Drill Co. began producing rotary blast-hole drills in 1952. Davis Robbins was heavily involved in the repair of heavy stripping equipment for an operating coal company. He experienced high costs of drilling and blasting overburden up to 135 feet deep with existing machines, and called for new technology. When no one would build the drill he required, Robbins started his own drill-manufacturing company using his creative ability and industry knowledge. Throughout the 1950s and 1960s, Robbins developed a full line of crawler and truck drills including diesel hydraulic, diesel electric and all-electric models. Because Robbins provided excellent field support, distributor backup, and parts availability, his machines became popular, not only in coal-producing regions, but also in rock quarries, iron-ore mines and construction.
You can read more about historical surface-mining equipment in Keith Haddock's illustrated book "Extreme Mining Machines" available in most bookstores. Also, consider a membership in the Historical Construction Equipment Association, www.hcea.net.