User guide

92
Pedestal
7: Azimuth Positioning System
Azimuth Bearing
The azimuth platform sits on top of a ball bearing platform with a dynamic and static moment capacity of over four times the
worst-case wind-load specification. The assembly is surrounded by a double seal to protect the bearing platform, which is
permanently lubricated. This rests on the azimuth drum and the azimuth cables wrap around the drum and capstan.
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.
Azimuth Gearbox
The azimuth gearbox is a low backlash worm gearbox. The worm gear drive isolates any backlash in the motor drive from
the system. In addition, since it is a 15:1 ratio, it will not back drive, thus eliminating any need for a brake on the drive train.
The motor drives the input worm via a quill/female hole and square key. The azimuth capstan is secured to the bore of the
output shaft with a square key. The gearbox contains synthetic oil. Because of the design capacity of the gearbox, low rpm
and comparative limited cycles experienced by the system, no wear or maintenance is expected.
Azimuth Motor
The azimuth drive motor is a servo quality 24DC motor with an integral 19.7:1 spur gear train. The motor armature rotates at
up to 4000 rpm causing a high-frequency noise that will vary, depending on the loading condition of the motor. An optical
encoder is mounted to the other end of the motor output shaft to provide real-time positional information to the TracStar
controller. The maximum gearbox output speed is 253 rpm. The output shaft is "D" shaped with a special adapter with a slot
for a square key. Since the low backlash worm gear drive isolates the backlash from the motor, any backlash between the
shaft adapter, square key, or motor gear train will never be seen by the reflector boresight. Any backlash at any of these
points is of no consequence to the system performance. No maintenance or wear of the elevation motor is expected.
Azimuth Roto-Lok Cable Drive
The patented azimuth Roto-Lok drive produces a drive system with zero backlash, high stiffness, no wear, no lubrication,
and maximum reliability. The system consists of three 1/16 9x17 stainless steel aircraft control cables, reverse-wrapped
twice around the capstan with solid connections on one end and high force, Belleville springs on the other end occurring at
the azimuth spring block. One cable has the capacity to withstand an 80 mph wind load. The additional cables are used to
provide increased stiffness and drive redundancy. If a cable becomes damaged during usage, merely cut off the cable
and continue to use the positioner. You can replace the cable at your maintenance facility whenever time permits.