Underground safety is a high priority for today’s miners. Recently introduced personnel carriers – “man trips” in mining parlance – from Wallace Auto Parts & Service Inc., Raleigh, Ill., will make the daily commute far safer for many miners. Man trips are used to transport the miners and their equipment into and out of the mine in which they work. A typical ride to work might include driving down an incline to a level of 200 ft or more under the surface to the beginning of the mine shaft. From there they might travel four miles or more to the work face — in narrow, pitch black tunnels lit only by the lights from the man trip and helmet lamps.

Wallace builds diesel powered mining equipment, agricultural machinery and attachments, plus tilt utility trailers. A typical diesel utility vehicle (DUV) is only 8 to 9 ft wide to allow enough side clearance for driving in the 18 foot wide main and side corridors of the grid layout used in modern mining. That width doesn’t allow much margin for error when going around corners, so a shorter wheelbase vehicle provides a major advantage for mine navigation.

In the past, seat space in a man trip offered the same type of problems encountered while flying economy class on a sold out airplane. Couple closely placed seats with miners wearing safety belts, a cap lamp battery, self-rescue breathing apparatus for use in emergency, and a tool pouch with several specialized tools, and the result is extremely tight quarters at best.

Rugged individual seats were used in previous designs from Wallace, so miners had to keep themselves and their gear inside the allotted space. However, their legs, arms, heads, or tool pouches often extended outside the safety envelope as they attempted to gain more elbow room, which could cause injury from being hit by protruding objects if the vehicle veers too close.

Peabody Energy, St. Louis, the world’s largest private-sector coal company, approached Wallace to design a man trip that would provide a higher degree of safety for their employees. This safety initiative was driven by Peabody Energy’s Willow Lake Mine, which is close to Wallace’s plant. Wallace has long been known for innovation within the field — they supplied the first DUV approved for use by West Virginia. Today, the use of DUVs, including man trips from several manufacturers, is common throughout the coal mining industry. Thus, Wallace was a logical choice to take on the challenge.

The challenge posed to Wallace resulted in the Hydra-Drive man trip. Wallace’s Diesel/Mining Div. designed the Hydra-Drive family of man trips from the ground up with a view to improve both the safety and the comfort for the miners. The Hydra- Drive provides ample space for each miner and a much safer ride than previous machines. Hydraulics was chosen to run both propulsion and steering systems because it is more compact than other power transmission options, thereby allowing more space for miners.

Establishing goals

The Hydra-Drive man trip had to be designed from scratch because Peabody’s requirements were too extensive to permit modifying an existing machine. Peabody’s goals included:

  • Reduce the weight of the vehicle to permit a shorter wheel base.
  • Increase the average seating width per passenger inside the safety envelope.
  • Limit the vehicle’s speed on grades to allow safe descent to the mine shaft.
  • Create a smooth and consistent vehicle drive comparable to that of an automobile.
  • Provide better visibility for the vehicle’s driver.

The first goal was accomplished by choosing a hydrostatic transmission (HST) (HST) and moving the engine to the rear. The drive shaft tunnel had occupied 8 in. of valuable seating space down the center of the car from the front-mounted engine to the rear axle. Weight saved by this change, along with others, allowed the wheelbase to be reduced from 148 in. to 107.

In addition to eliminating the drive shaft and drive shaft tunnel, designers also made the frame 10 in. wider. Older designs provide only 21 in. of seating width per miner, whereas the Hydra- Drive allows 25 in. on average.