Holman counterbalanced drill rig

Holman counterbalanced drill rig

[′hōl·mən ¦kau̇nt·ər‚bal·ənst ′dril ‚rig]
(mining engineering)
A drill rig consisting of a rail-track carriage with a counterbalanced boom 10 feet (3 meters) long.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.