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Shallow Braced (non-drilled, hand augered or pounded) Monument Overview

Shallow Braced (non-drilled,hand augered) Monument

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Mount Commonly Used
Stability
Cost
Install Time
Labor
Substrate
Site Impact

SCIGN mount

med

$800

1 d

2-3
U

med

The shallow braced (non-drilled, hand augured or pounnded) monument consists of 4-5 1"-diameter stainless steel legs in a tripod configuration pounded into the substrate up to depths of about 5-6 feet. The legs are welded together at the top. The short braced monument is nearly identical to the shallow drilled braced monument, with the exception that the legs are either pounded into unconsolidated ground  or a hand auger is used to create the holes for the legs.

Rather than epoxied into holes drilled in bedrock. Use the SBM (Short Braced Monument) at locations where there is no bedrock available.

  laugered_monument_final.png
Site P492 of EarthScope's Plate Boundary Observatory (PBO) (left); test site NWOT on Niwot Ridge (middle) and ,Costa Rica   (right).

Pros

  • installable in unconsolidated substrate

  • materials relatively inexpensive

  • drill bits will not get stuck (as in short drilled braced monument)

  • materials and equipment can be flown to remote locations by helicopter

  • can be installed in environmentally sensitive sites

  • relatively quick deployment

  • site permitting potentially easier than for the deep drilled braced monument

Cons

  • labor and tool intensive

  • is probably less stable than the deep drilled braced monument

  • initial cost to purchase required tools potentially expensive

Design and Construction

A heavy duty hammer drill with a special chuck is required for installation.

Documents

Installation Photos

Ed Arnitz of UNAVCO drives the central rod into the ground with a Hilti drill.

The rods can also be pounded into the ground with a sledgehammer.

You first need to make the ends pointed.

sdbm_auger.png

Victor Gonzales (OVSICORI) using the hand auger to dig out the holes for the legs.

 

Approximate Cost

$800

This cost is for the monumentation only; the antenna mount (e.g. SCIGN mount) is not included.

Materials

  • 4 12-foot stainless steel rods (1" diameter) with grooves

  • 3 weld gussets

  • threaded adapter (if using the SCIGN antenna mount; see below)

  • welding rod

  • gas for the generator (if there is no AC hookup)

  • water (for fire safety while welding)

The materials specific to construction of the SBM are available as a kit which can be purchased from:

  • McRoberts Machine, Inc. (Judy or Doug McRoberts)
    402 Martin St
    Longmont, CO 80501
    Phone: (303) - 776 - 2397
    Fax: (303) - 776 - 0704

    When ordering please refer to Part #1090.

Tools

  • AC-powered heavy-duty hammer drill (e.g. Hilti) with bit

  • generator (if there is no AC hookup)

  • chop saw or dry cut saw

  • grinder

  • vertical and angle level(s)

  • leg alignment tool

  • welder

  • file, pick, brush, gloves, helmet, long-sleeved shirt, hat (for welding)

  • compass

Mount Commonly Used

The SCIGN mount is the antenna mount most commonly used with the shallow braced monument, although it is only required when using the SCIGN radome. Otherwise, any other leveling mount, such as the SECO 2072-series antenna mount, is acceptable.

Other Links

Send questions or comments to Support (supportunavco.org).

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Last modified: Monday, 12-May-2014 00:18:29 UTC