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Wanted to share a fantastic thank you to the staff of Losmandy for expediting my tripod extension for arrival this past Saturday.? I had a crew here working on my observatory on Saturday and when I talked to Losmandy earlier last week, we realized the extension for the scope I ordered would not make it to my site on Saturday (they were shipping it the day I called), Losmandy changed the shipping priority on their own so the extension would arrive on Saturday, which it did.

We modified the observatory and the mount setup and had everything up and running for dusk on Sat Night and spent the next few hours imaging!!!!? I ordered the extension because my scope and camera system was able to strike the pier plate (even with safety limits in place) and I was too worried about that.? The 12" extension now allows enough clearance for the scope/cameras to point straight up with no issues.

Thanks again Losmandy!!!!!!!!!!!!!!!!!!!!!!!

Russ

Michael,
I assume that wrapping on the OTA is for insulation to minimize expansion and dewing??

Tom

My opinion is that you need just enough clearance to allow the bearing to tilt inside the block by a tiny bit.? Maybe about 0.001 - 0.002" clearance

Thanks for the comments, Michael.
I expect the G11 axis to have half the error and half the time lag because the motor / gearbox / worm have to spin twice as fast.
I think an over-tight worm mesh makes extra friction, which exacerbates any flexure earlier in the system, such as gearbox or Oldham coupler torsional flex.
By the way, don't you have a whole bunch of gearboxes laying around?? Can you test how much flex or play there is by locking the output shaft and trying to turn the input shaft?? And also with the McLennon boxes.
For the laser I used a binder clip to clip it onto the upper spur (big silver) gear.? The point was to check backlash before it got to the worm.? I also tried attaching it to the dovetail but it just moves too slow.? In another thread, some guy suggested mounting an actual telescope with high power eyepiece.
I came up with the idea of the lever because it became too hard to track changes in the screw tightness when the movements are "try to turn it as little as possible", or maybe 1/57th of a radian.? Who knows how much that is anyway??? I figured I could put a scale or markers underneath it to track changes, and then in the future I would have specific settings for this DEC value or summer vs winter weather.? Haha, that's so smart and clever, but alas, real life is not that easy and the adjustments were not very repeatable.? As they say, "the best laid schemes of mice and men, could not put Humpty Dumpty back together again".
I think the clutch force does pull the main axis body (plus ring gear) down by a little bit, but I will need to prove it by using a set of feeler gauges.
And now that you mention it,? my RA drive does seem to have some kind of low level high frequency noise.? It's not really bad, but it seems like the RA guide trace is always a little more noisy than DEC.? Not sure how either axis can have any "noise" given that it has a yuuuuge moment of inertia.

On Sat, Apr 3, 2021 at 11:28 AM, Michael Herman wrote:

Stuart Hutchins, a very experienced and knowledgeable group member, has been explaining the details of bearing seals, concerns about polishing dist entry, and precision belt drives to me. He just suggested that you could mount the R4 bearing between a pair of R4 Belleville spring washers to compress and hold the bearing on a 1/4 inch precise mandrill, then use like a drill to precisely spin the bearing...and some fine sandpaper to buff down the bearing OD more consistently.? I have not tried this nice idea yet.? He was concerned that the polished bearing OD needed to be precisely round, but since the OD of the bearing merely needs to slide, not rotate, I don't feel that level of roundness perfection is necessary.? The inner races must be precisely round as they must roll without "rumble" which is why I prefer the highest ABEC quality...but even so I get extra bearings and feel them for smoothness.

Hi Michael,

After reading through your info, I was considering how to build a rig to get a circular polish on a bearing. I came up with the following using a 1/4" bolt. It consists of a nut, washer (non-Bellville), rubber washer, Boca bearing, rubber washer, washer, and a second nut. By tightening the nuts toward each other, you can seal the bearing between the two rubber washers to prevent any sanding debris from entering. Then when done polishing you can wash with some solvent without having any residue get in between the races. I tried to spin it in a drill tonight and it seems decently centered with little wobble. Now I could hit the outer race with a Jeweler's file or a small strip of sandpaper while rotating.

I measured a new bearing and a new bearing block and their OD and IDs, respectively were both 0.625". Now I am wondering how much tolerance to apply for a proper sliding motion of bearing inside block. You mentioned the blocks will contract with cold, so thinking what the final polished bearing OD should be. Take off 0.005"? What do you think?

John