FHWA RTP Contact

Christopher Douwes
Trails and Enhancements Program Manager
Federal Highway Administration
FHWA HEPH-10 Rm E74-474
1200 New Jersey Ave SE
Washington DC 20590-0001
Phone: 202-366-5013
Fax: 202-366-3409

State RTP Contacts

Contact your State RTP Administrator to ask about policies and funding in your State.

Portable Backcountry Rigging Tripod

United States Department of Agriculture Forest Service Technology & Development Program

November 2005

2300

0523-2341-MTDC

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).

Photo of a worker standing in a rock field where the portable backcountry rigging tripod has been used to move rocks downhill. The Griphoist winch, used to control cable tension, is labeled in the photo.
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.

Photo of the portable backcountry rigging tripod set up and ready for use. The tether line, snatch block, cable, and load are labeled in the photo.
Figure 2--It is easy to move and place a heavy load when the
portable tripod is used for rigging. Tether lines are used to
control the load's descent and to place the load.

Highlights... Rigging can be used to move heavy loads in the backcountry. Sometimes trees are not available to serve as anchors when setting up rigging. Portable tripods can be used when trees are not available. A welder could use MTDC Drawing No. 1035 to fabricate portable tripods that can be packed on a horse or mule. Operators must follow all OSHA guidelines for rigging operations.

Highlights...

Rigging can be used to move heavy loads in the backcountry.
Sometimes trees are not available to serve as anchors when setting up rigging.
Portable tripods can be used when trees are not available.
A welder could use MTDC Drawing No. 1035 to fabricate portable tripods that can be packed on a horse or mule.
Operators must follow all OSHA guidelines for rigging operations.

Development of the Portable Tripod

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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