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The potentiometer is mounted in an adapter that sits down into the bearing bore of the azimuth
gearbox. Since the torque required to turn a potentiometer is minimal, the mounting adapter is held in
place by a setscrew. The potentiometer is protected with an aluminum cover from the weather and the
use of the elevation handcrank.
The azimuth potentiometer is slotted and driven with a cross pin in the output of the worm gear box.
The potentiometer is mechanically set at the one-half travel position when the azimuth cable
termination block is directly across from it. This is accomplished by loosening the setscrew (1/8 allen
wrench) and rotating the adapter. The potentiometer may also be electrically zeroed by the controller.
See section 4.1 of Controller manual.
3.6 AZIMUTH STOW AND LIMIT SWITCHE S.
The Controller uses the azimuth potentiometer voltage to determine limits. Therefore, the positioner is
equipped with only an azimuth stow position switch. Limit switch mounting holes are provided if
needed for other brand controllers.
The azimuth stow and limit switches are mounted under the azimuth platform accessible through the
12 inch diameter access hole on the base. The switches are fixed to reference ground (the truck) and
are actuated by falling into a concave notch in the azimuth bearing clamp ring. The azimuth stow
switch holes are slotted for + / - 2° adjustment.
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Figure 3.4
3.0 AZIMUTH POSITIONING SYSTEM
3.1 AZIMUTH BEARING
The azimuth bearing is a precision ground Slim Line ball bearing with a dynamic and static moment
capacity of over four times the worst-case wind load specification. It is press / shrink fit into a special
aluminum bearing ring consisting of main internal and external rings with clamping rings. Both sides of
the bearing are sealed against contaminants with Teflon O-rings. The bearing is packed with Mobil 1
synthetic grease at assembly.
Because of the excess capacity, low rpm, and low number of cycles compared to the bearings B10
design life, no wear is expected. No maintenance should be required over the life of the positioner. A
grease fitting is furnished for the azimuth bearing to flush out contaminants if the positioner is operated
in extreme environments.
Over time, some of the oil in the grease will separate from the binder. Since this oil is very thin, it may
seep past the 0-rings. It will be red in color. If this occurs it is considered quite normal and should not
be considered a problem unless it is excessive. If so, use a standard grease gun with Mobil 1 synthetic
grease to repack bearings. Pump in grease very slowly as the unit rotates in azimuth. Look for grease
to begin to seep past O-ring seal between az platform and az bearing ring.
3.2 AZIMUTH GEAR BOX
The azimuth gearbox is a patented low backlash worm gear box. The worm gear drive isolates any
backlash in the motor drive from the system. Also, since it is a 40:1 ratio it will not backdrive
eliminating any need for a brake on the drive train. (Figure 3.1)
The motor drives the input worm via a quill / female hole and square key. The worm shaft is extended
with a hex shape for the handcrank. The azimuth capstan is secured to the output shaft with a square
key and zero backlash hub.
Figure 3.1
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