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AWR places great emphasis on the need for very stiff worm supports to
avoid all
flexure. If the bracketry should flex [at all] then it will also unwind
again when the drive load is removed.
Leading to lost motion during acceleration or overshoot during Goto
maneuvers. A perfect recipe for frustration in pointing precisely to the
desired [often all but invisible] object. Once the perfect fit has been achieved the worm brackets must also be firmly fixed with suitably large bolts. Or the drive power available will literally dislodge the worm housings. Meanwhile the worm housings need fine, radial screw adjustment towards and away from the circumference of the wormwheels. There is really only one perfect position for a worm nestled against its matching wormwheel. It must be square to the wheel or the threads and teeth will not allow the necessarily fine adjustment needed.
The pulley to worm, shaft fixing screws must lodge onto small flats or dimples on the worm shaft to avoid them loosening over time. The tiny grub screws provided might be better replaced with stainless steel, hex socket head screws. This would allow more torque to be applied to the screws.
The worm housing bearings must also be prevented from linear movement. The tiny grub screw on top of the bearing housing is hardly adequate except to restrain the bearing from falling out. Over-tightening of this screw can easily lock the bearing solid against rotation! An outboard plate at each end of the housing will prevent bearing shift. The pulley boss will prevent lateral movement towards the worm but may benefit from a thin, low friction thrust disk. PTFE/Teflon might be a good choice but can creep under heavy loads.
Wormwheel
and worm mock-up on oak blocks.The arrows show the positions of the
radial nylon plugs which provide a [barely] slipping clutch against the
axis shaft. Grub screws provide the adjustment of
pressure/friction/slippage. AWR suggested these clutch grub screws be tightened enough to prevent slippage until it just matches the motor stall point. Which sounds to me as if no slippage is desired but the worm/wheel is protected from a total obstruction or hard blow to the OTA.
Which means that hand pushed slews of the OTA would lose the ability to manage further Gotos. The telescope's "aim" would be lost if it was moved independently of the drive system's position sensing. To maintain accuracy after a a hand slew would require shaft rotation sensing and feedback. Rather than reading the stepper motor position relative to the worms/wormwheels. The AWR drive system seems to be treating the wormwheels as if they were solidly connected to the axes for all intents and purposes. The clutch is simply a final safety measure against physical destruction of the wormwheel teeth.
All movement and pointing of the telescope must be done with stepper motor power alone. Which is very different from the usual [and grossly under-powered] synchronous motor drives following a hand slew. The AWR system is much more like how large, modern telescopes would be pointed. The desired position of the field of view is fed into the drive computer. The telescope then sets off by the shortest route to home in [i.e. Goto] that point in the sky. With enough accuracy to place the desired object safely in the field of view. Fine tuning of the object's position is then carried out with the Intelligent Handset's buttons harnessing the stepper motors at very low speed. It is all a matter of scale. A very large telescope, weighing many hundreds of tons, would not even notice a puny human being giving it a firm shove.
Click on any image for an enlargement.
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