All great ideas.
"Over time the condition you report of a 'tight worm' at 180 degrees from CWD is expected "
I assume you are making this statement because you expect wear to occur.? Lets assume wear is negligible for a moment. The fact that the Dec shaft can not sit perfectly centered on it's axis because of the needle bearing slop due exacerbated by the weight of the scope. When the clutch is tightened and you rotate the full 180 degrees it is unable to adjust it's position, hence pressure is placed on the ring gear that forces it into the worm at the 180 degree position. Of coarse as one rotates from CDW position this force steadily increases with the degree of rotation. If there was no movement between the shaft and the needle bearings then this problem would not exist.?
Actually, my thinking is that most of the slop in the RA shaft is taken up when the thrust bearings are loaded as the clutch is tightened, at least in theory.? I agree that the wear should be occurring on the brass worm, not the gear. However I do think that some smoothing and wear of the gear does occur. The 'tight worm' occurs when when during maintenance the worm mesh is readjusted on the smoothed side of the worm gear with very tight tolerance to minimize backlash. In your case, enough variance to eliminate the gap for lubricant as your pictures clearly document and even cause a motor stall.? In my case, the original owner had a steel worm, and only much later upgraded to precision brass and a OPW assembly. I expect more variation between the 'worn in' and 'unused' sides of the gear.? I agree that the problem wouldn't exist if there were no movement between the shaft and needle bearings and also a press fit worm gear on precision bearings rather than a bushing. Solutions to those problems are really fundamental changes in the design.?
The indexing issue I raise is a matter of repeatability.? We have a software correction system that we can't keep in sync with the hardware and a hardware system that we can easily throw out of sync with itself.??
I've been following several threads and the work being done to reduce guiding error and corrections.? The results have been amazing.??
Having put in that much effort and money it's important to understand what will cause performance improvements to be lost. Any hope of using stored PEC? depends on indexing
to be maintained.? My suggestions were to establish a consistent 'zero starting point' reference orientation.? Establish a 'Home' starting position for the worm gear and for the orientation of the DEC housing to the worm gear by indexing the across the clutch. If you are going to disturb the worm mesh or motor drive train, index the components so their relative positions can be restored.
It's the only way to create reproducible and repeatable results.?
I see enough design issues that I am going to start a separate topic for them.? Many of the suggestions, ideas and solutions go beyond process, procedure or part replacement with matching higher spec equivalents. We should recognize the difference for the sake of the larger user community who should not equate suggestions to use specific skills and techniques to optimize results as product shortcomings. Yes, in some cases shortcomings are avoided. This is true for any complex high precision equipment.? Technique and mindful process only becomes more important as the precision goes up.
I can't think of a recent better example than Peter' improvement on guiding and tracking accuracy.? A casual reader of the topic might think at the top
"that the G11 has poor performance and isn't very precise". However pretty quickly if you're paying attention you see that Peter is already getting repeatable arc-sec accuracy at the start of this effort. MOST people don't have the kind of gear or sufficient skill to achieve where Peter starts.? He reduces his RMS guide error down to 0.56 arc-sec and then down to 0.14 arc-sec, the limit being his motors smallest single step. Perhaps it's even a little better and he should slow the guide rate? I think at this level further effort has diminishing returns. Clearly his success is due to his skill and knowledge which he generously shares.
I learn a lot reading here.?
Especially - Don't set my goals too low
