NN4ZZ Tilt Plate Project

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NN4ZZ Tilt Plate Project

• June 2007 -- V7

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Goals

• Free standing, tilt-over tower
• Gain antenna for 20-10M
• Antenna height 70-80 feet
• Convenient operation
• Antenna maintenance from
• the ground, no ladders or climbing

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Tower and Antennaselection

• U.S. Towers MA-850
• Steppir 4 el yagi
• The next few slides show the tower construction
  and steppir specs

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U S Tower MA 850
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MA-850 foundation

• 7 x 7 x 7 -- 13.5 yrds
• 4,000 psi fiberglass

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Tiltover base

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Motorized winches
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Steppir 4 element

• Monobander on 20-10
• Control from the shack
• Tracks transceiver

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Steppir Specifications
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Problem / Solution / Strategy

• Problem - How to lower an antenna with a 32 foot
  boom and 36 ft elements to ground level.
• Solution - Develop a method to tilt the antenna
  so it can be lowered to ground level for all
  maintenance
• Strategy - Keep it simple, make it sturdy
• Over engineer the design. If its worth doing,
  its worth over-doing

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Tiltplate 1 2 - Two versions

• The first design (tiltplate1) has been in service
  since April 2004.
• I decided to build another one for my second
  tower. A new design (tiltplate2) was created
  with direct rotator mounting.
• The power point is divided into sections to
  highlight both designs
• Both versions work equally well

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Tiltplate 1 2 - Common Components

• Steppir 4 element 20-10 meter yagi,
• U S Tower MA 850, 85 foot tubular crankup tower
  with motorized winches.
• Same bearings, shaft, etc used for both designs.
  
• Aluminum plate material is the same, just cut
  differently

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Tiltplate 1Mast mounted plate design.Major
Components

• Yaesu G-2800 DXA rotor
• Aluminum plates hinged on an aluminum shaft. Use
  of pillow bearings to provide tilting capability

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G-2800 DXA
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Tiltplate diagram

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Design Notes

• Uses gravity to hold boom plate in place. Boom
  plate is held about 5 degrees off vertical. The
  boom is rotated to compensate for the offset and
  to keep antenna elements parallel to the ground
• No latch - allows boom plate to tilt in high wind
• Supports a dynamic loads of 3,000 pounds on
  bearings, shaft.
• Boom plate is kept close to the rotor to minimize
  offset load

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Tiltplate Materials

• Stainless steel clamps, McMaster Carr part
  29535T11 (for 1 diam shaft) pg 1446
• ½ inch aluminum plate 18 x 12, McMaster Carr
  89155 k29
• Severe duty pillow block bearings, McMaster Carr
  6494K14
• 1 inch diameter aluminum shaft, McMaster Carr
  5911k36

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Aluminum Shaft
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Bearings
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U bolts for shaft
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Tiltplate
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Building the Steppir
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Fully Assembled(Tower tilts to the left and
toward viewer. Elements are parallel to the
tower)
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Closeup of Tiltplate

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Tiltplate 2Rotator direct mounting
design.Major Components

• Same basic concept. Same materials used for
  construction.
• Also using a Yaesu G-2800 DXA rotor
• Mast plate directly mounted to the rotor instead
  of using a mast
• Fewer parts (no mast or mast clamps)

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G-2800 DXA
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TiltPlate 2
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Tiltplate 2

• Direct mount to rotator
• Eliminates the possibility of mast slippage
• Same basic tiltplate design
• Fewer parts (no mast or mast clamps)
• Cleaner look

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Tiltplate 2 installed
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Tiltplate 2 - view from below
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Tiltplate 2 tower at 70 degrees
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The Wind

• Most frequent question is does it bang around in
  the wind? Answer No does not move at all
  expect in high winds over 30 MPH
• Wind from the ends has no effect
• Wind from the boom plate adds to down force
• Wind from mast plate is mostly blocked
• Designed to gently lift in very heavy wind

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Tiltplate performance

• No surprises
• Highest wind gust so far, 52 MPH on July 4, 2004
• Smooth tilting operation, no problems in over 3
  years of operation
• Costs about 400, most expensive item is the
  aluminum plate.

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Completed project

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For More Information

• Web page www.nn4zz.com
• Email al_at_nn4zzk.com
• Opening slide, the wave Page, AZ
• Dish Antennas, the Very Large Array in Socorro,
  NM