Bob Beckley, Project Leader
Trail crews and others working on backcountry maintenance and construction projects have to move heavy objects. Often, the work has to be done in areas without large trees that could be rigged with cables to support the operation. Portable steel tripod towers can help in such situations. When these towers are used with steel cable and a Griphoist winch (figure 1), heavy loads can be moved (figure 2).
Figure 1--The portable tripod was used to move rocks downhill
in this skyline operation with the load suspended from a cable.
The operator used a Griphoist winch to control the cable tension.
The tarp protects the cable from being damaged by the rocks.
During 1999, the Bitterroot National Forest's Steve Bull watched trail crews in Rocky Mountain National Park use a portable tripod. The tripod was designed to move relatively small rocks above timberline. That tripod was designed by Lester Kenway of Trail Services, Inc., Bangor, ME. The design used legs similar to those of the portable tripod, but did not have a top plate assembly. Instead, a bent length of "allthread" rod and nuts were used to bind the legs together and hang the snatch block.
In 2003, the Bitterroot National Forest trails program needed a portable tripod to install bridge stringers weighing more than 1,000 pounds that were being packed by stock to a remote location. Steve Bull created a conceptual design for a tripod head with the assistance of Charlie Mabbott and the leadership of Nick Hazelbaker. Sam Allsop of California State Parks had a top plate assembly design of his own. Bull created a modified design based on Allsop's design.
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