Hi Alex,

If I understand,?
1: You have 2 mounts with Gemini-1 Controllers, 1 is "GM8", another is ??. ("Other")
2: Only the GM8 mount, with it's original Gemini-1 control box, has the motor stall symptom.
3: When you temporarily install the "Other" control box on the "GM8", the "GM8" works with no stalls.
4: After returning the Gemini-1 controllers to their original configuration, the "GM8" STILL works.
5: It's only upon the next night of operation or testing (the 'GM8's (mount), controllers, and it's motors, etc. have had time to cool back to ambient temp.) that the problem resurfaces.

Q1: How long does it take for the stall to occur ? Right away at startup? or after a little while??

Q2: When you take the original GM8's Gemini-1 controller and put it on the "Other" mount (cold), does it have motor stalls also ? (even if it has different motors, etc)?
(is it possible to perform this test, or are there other limiting factors?)

Presumably the cabling is the same during both tests, and the only thing that changes is the controller board, what else could be different?

Assuming the cabling, supply power, and mount motor load requirements are similar, isn't the only physical thing that is effectively changing, is the motors have been on (maybe for awhile),
compared to them being cold after a day of non-use.

Curious,
Astronut Tim

On startup, either cold or warm, my GM8 Gemini 1 has a motor stall.?

I swap in a different control box (from my other Gemini 1 mount) and there is no motor stall.?

Then, I swap in the first control box, and the mount operates fine.?

Next night I come back and that same control box has a stall on startup.?

IN other words, something on startup stalls the motor with one box, but not the other. And, once I use the second box, the first box will work properly.

Any ideas?

Alex

Here's an extreme example of the problem. This is a worm block commonly found in up market Celestron Nexstar mounts made in the first decade of the 2000s, like the Nexstar GPS Alt/Az and CGE mounts.?

While playing with on of these I notice there was a lot of play in the worm. Tightening the adjustment screw until the play disappeared produced a horrid notchiness like a out of round tire.?



Digging into the design of the block, this what I discovered. The block is one piece. In order to assemble it one end was bored to let the worm and the adjustment en bearing pass through it. The outer diameter of the worm is larger than the bearing fitted to it. Thus the bearing is left to float around in its seat.?

Yes; the first suggestion was about the pierside-setting and the second?suggestion was to implement a pause before the meridian

i played around and testes it again last night, but the mount is not moving!!!

So i went back to SGP and everything works fine :-)

Hi Tom,

The reason the Belleville discs improve PE is that they force the bearings to rotate in a predictable way with the motion of the worm. Left to their own devices the ball bearings tend to stall then start again in unpredictable ways likely when the clearances are taken up by misalignment in the worm and bearings. Placing a light load on bearings is a well documented mechanical engineering practice for precision mechanisms and many bearing manufacturers have engineering notes on the practice. That is how I found out about this many years ago when I applied the idea to my HEQ5-Pro/Sirius and EQ6/Atlas mounts 6-7 years ago back in my EQMOD says.?

Another good idea I had but didn't try due to updating to OPWs was to fix the worm blocks to the worm cover to in essence make the cover a rigid bridge between the blocks to make backlash easier to do. The way to do this would be to use a pin on the top and cut a slight recess under the existing grub screws on the cover to set the blocks in the cover well aligned with the outer bearing which is being preloaded by the Bellevue disc. By bridging the blocks they would move as one making backlash easier to set well. The other thing to try to achieve is to locate the gearbox output shaft as closely on axis as possible with the worm shaft.??

--

Chip Louie - Chief Daydreamer Imagination Hardware

Did you get an answer from NINA Discord?

EDIT - I just found the Discord reply's.

Hi Thomas.? Here's what I do with the two-bearing-block configuration:

1. Remove the cover plate, and screw in the two set screws so that they are inset a little bit (will be using the cover in a later step).
2. Loosen the Oldham coupler set screws (4).
3. Tighten the 2 bearing block screws underneath until they are barely snug (but still able to rotate a bit).
4. Put a feeler gauge behind the right block.
5. Use one of the cover plate flat sides to simultaneously push both bearing blocks toward the mount (the cover is meant to keep the blocks colinear) while simultaneously pushing the right block toward the gearbox (either pushing the right block directly, and/or rotating the DEC axis to move the worm gear toward the gearbox; I believe Scott shows this in one of his Youtube videos).
6. Tighten up the bearing block screws underneath (not too tight).
7. Tighten the worm-side Oldham set screws, and use this to rotate the worm by hand through a large range (ideally 360deg).? If there is any binding, use a thicker feeler gauge and repeat (or thinner if you want a tighter mesh).
8. If there is any side-to-side movement of the worm, try again and eliminate.
9. Loosen the Oldham set screws.
10. Loosen the gearbox screws and adjust/rotate the gearbox (typically the 'ears' are a bit larger than the screw diameter, or even drill these larger if need be) until the gearbox shaft is colinear to the worm gear as best as you can, then tighten the gearbox screws.
11. Move the two ends of the Oldham coupler toward each other to minimize any gaps, then tighten the Oldham set screws (one of them on the gearbox side should be set to the flat part of the gearbox shaft).
12. Power up the mount and try to slew. Observe the runout of the Oldham coupler and adjust the gearbox if it doesn't seem in line (nylon coupling disc offset from either of the hubs).
13. If the DEC assembly strains/stalls when slewing, back off the worm mesh (thicker feeler gauge) and repeat.? If you experience excessive backlash while imaging, try to tighten the mesh (thinner feeler gauge) and/or double-check that there isn't any lateral (side to side) movement of the worm in the bearing blocks.

That's the gist of it anyway.? Losmandy uses JetLube MP-50 grease, many here recommend Superlube synthetic grease with syncolon.

Keith

Thanks? Keith.

开云体育

Sonny,

Since I live in a democracy, I stay away from King rate.
I think it is Imperialistic...

But, I could be wrong. ;^)

--
SonnyE


(I suggest viewed in full screen)

Yes it will.

Keith

--

I think ,? Ovision worm block is no more available.

(Now that I ordered it), can someone confirm the HPW will fit early G11 mounts?

Thanks,
Tom

Congrats Sebastian! Glad your efforts have paid off with improved imaging.?