On Tue, Feb 23, 2021 at 09:31 AM, Sebastian Kotulski wrote:
Hello.
Help me to diagnose an issue with a RA axis drive. I have never heard such tapping noise before. Is it a gearbox or motor failure. The mount slews as usual but when it stops I can hear this weird knocking noise.?
Please, watch the movie in the link below, and help me to diagnose the problem.
Sebastian
That sounds awful, adjust your servo motor to gearbox they are too tight. You should adjust the servo motor to gearbox backlash, you do this by loosening the cap screws on the servo motor and moving the motor to minimize the noise you hear. then recheck for that knocking.
If you still have the knocking check the Oldham coupler grub screws, there are 4 of them and if there are flats on your gearbox and worm one of the grub screws should to be on the flat. The grub screws should be snug not gorilla tight and the plastic part of the coupler should be fully compressed, no gaps visible. Also verify that the worm has no movement between the bearings and cannot move back and forth on the worm shaft axis, check this by moving the RA back and forth checking for worm movement, this must be ZERO! If you still hear the noise you may have a dirty sticking worm bearing, most likely the worm bearings given the sound and location, the bearings are consumable parts, do not try to save them by cleaning it is a waste of time and the bearings are cheap. Replace them all at once with high quality stainless steel ABEC5 or better precision bearings - R4ZZ is the size. McMaster Carr sells them at a reasonable price and they are excellent quality.?
I have also heard this sound under two other conditions. Very over tightened clutches causing too much drag on thrust bearings, you get a slip stick effect which is bad for smooth movement. The Porter Slip clutches are reliable when the plastic clutch discs are fresh and clean. But over time due to use of the wrong lube and or too much lube the clutch discs get oiled and they slip causing people to over tighten them and you get the creaking noises when the RA is driven at tracking speeds. This happens on the DEC axis too but because the DEC is never driven at tracking speeds you never hear it. Has the mount been disassembled for cleaning and lubrication using SuperLube with Teflon? If not or you have no idea what I'm talking about get someone in you club to help you who knows the Losmandy mounts. Short of that look for YouTube videos on how to do this. Using the wrong lubricant and/or too much of even the right lubricant is not a good thing. You cannot reliably diagnose this issue by loosening the clutches and rechecking, sometimes the bearings are dirty and causing this slip-stick issue but sometimes it can give you an indication you need to have a look at the bearing and lube condition.?
I have also heard this when I under tightened the clutch with Michael Herman's high friction clutch discs. I tend to use minimal clutch tightness with the high grip discs because they are so good. But if the load is not well balanced and there is any slippage the clutch discs will creak if there is any slipping movement at all of the RA and DEC. If you don't have M.H. clutch discs this is not your issue.??
I doubt the problem is in the servo motor, the knocking is too slow speed, not like in the other guy's video which is fast and related to the input speed of the servo motor which indicates the gearbox has an issue.
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Chip Louie Chief Daydreamer Imagination Hardware?
? ?Astropheric Weather Forecast - South Pasadena, CA?
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Chip Louie