Hi gang,
Yes ..thank you for the detailed parts list.
That is very helpful.
Peter and I have been discussing his experience and some good?ideas came out of those discussions.? Among them... (Peter is going to try these out).
1. Peter has a problem with his G11 unit that I thought was very rare.? Chip said he knew of one other such unit too.? The problem is that the 1.25 inch shafts are slightly too small diameter and the 1.25 inch needle bearings are not tight enough.? Chip said the person who had this problem sent his mount back to have larger OD shafts installed. Peter feels the shipping will be prohibitively expensive from the East coast.??
I don't feel any wiggle between my 1.25 inch steel shafts and their 1.25 inch needle bearings.? But....
... there must always be some gap, else you could not assemble the 1.25 inch shaft into the mount.? You must always be able to get the 1.25 inch shaft inserted down the two needle bearings.? So some gap is required for this desihlgn.??
So let's say because of the necessary gap, there must always be some small variation of the RA axis to the pole, even after a very good polar alignment.? And depending on where you are pointing, there will be some small angle off unless the Gemini pointing model calculated it as some kind of cone angle error.??
Is this a real problem?? Not for my imaging.? What's going on with Peter's system?
Peter says he is getting outstanding PHD2 tracking, like 0.6 arcsec, from his piggyback guide scope and it's autoguide camera.? But he is perplexed by getting oblong stars in his main camera when he is pointing South like to Sagittarius.? When he points to zenith he gets excellent tracking and excellent images.
I suggested to Peter that his polar alignment is getting shifted somehow in error when the weight distribution of his mount changes.? Thus, his autoguiding is really tracking the guide star very precisely, but his main scope and camera are not at the same exact center.? So any polar misalignment leads to an image rotation of the main image.? The solution is to use an off axis guider (OAG) so you actually autoguide off the main telescope starlight.? Peter is going to do this (he has an OAG but was not yet using it).
2. The second topic was: does the R4 Belleville spring (if you install one of course)? always center the outer part of the far R4ZZ worm bearing that it is forcing?? Peter put the spring in and thinks his 76 sec error got larger (known to be RA worm bearing ball pinch).? ?What could cause that?
The answer is: the R4 Belleville spring will try to center the outer part of the bearing on to ride in the bearing center part only if:
??a) the outer part has enough room to tilt in the bearing block cylinder (needs to have enough undersize to tilt in the cylinder wall diameter)
??b) the worm is not pushing the bearing against the ("flat") cylinder wall.? Remember the OD of the bearing is a straight cylinder and that bearing cylinder can get pressed flat against the cylinder wall (like the piston in a car engine).?
It's like the bearing on the spring under it is like a person resting on a mattress.? If there is enough room away from the wall, the person can shift to get most comfortable position.? But if the person is pushed up against the wall, he may not be able to completely accommodate his best resting position.??
The moral of this fable is that you must not push the worm very hard into the ring gear and expect the Belleville spring to eliminate that bearing ball pinch...(.if there is a ball pinch 76 sec oscillation present in your PE test data.)
Now the important part if you have an SLW? (spring loaded worm):
If you?don't use the SLW back off bolt, then the extreme pressure of the very strong spring will push the worm so hard on the worm wheel that the far bearing will be pushed to it's wall, and it cannot "rest" on the bearing center.??
And so, if you have a ball pinch oscillation (76 to 80 sec has been reported) then you won't get rid of that even with a Belleville spring and undersizing the far worm bearing.??
You must also release the pressure of the worm on the bearing against the cylinder wall.
I see the solutions as these options:
??A. Keep the SLW mechanism with very lightly loosened bottom worm block bolts, so the worm OPW assembly can pivot.? Then: you must use the SLW back off bolt to very very very slightly back the worm away from the worm wheel.? As soon as the worm is "loose" from the high friction of touching the worm wheel, stop.??
??B. Remove the SLW spring and adjust the worm to worm wheel spacing as in earlier times (aka the good 'ol days) using slight thumb pressure.? Then lock down the bottom worm block mounting bolts.? You can use spark plug feeler gauges to measure the OPW to mount distance and make the spacing that way, as in earlier days.
Anyways, ...those were our discussion points.? Peter is going to try the OAG approach and he may find imaging success that way.? I sure hope so!
Photos:?
Top is the SLW spring assembly, removed from the mount. The spring is quite strong.
Middle is the SLW front view with the spring removed and the "back off bolt" still in place.? Note that the single 10-32 BOL holding the right bearing block to the OPW assembly has not yet been reinstalled.??
Note that these bearing blocks now have an adjustment slot in the OPW where the holding bolt goes in. (The drilled hole to the right of the back off bolt is where the SLW spring goes in.)
?Earlier OPWs had single drilled bolt holes, and no slot, and the earliest OPWs had a bolt on the top and the front that held each bearing block in two locations.? Today's OPW only has a single 10-32 bolt holding the bearing block to the OPW.??
Bottom is the left side of the drive showing the two transfer gears.??
Best to all,?
Michael
