Losmandy telescope mount modifications

Re: belt drive with gemini2

mherman346@... (Michael Herman) — Mon, 03 Jun 2024 23:42:55 -0700

Hi Aaron,

Funny you should ask this.

When I ordered my G11T Titan belt drive parts, I ordered 2 of each pulley
part and 3 of the belt itself. Another owner living near Las Vegas asked
me to buy my spare parts... and off they went. He said his RA's PE went
down to about half before that belt modification.

In making my parts, I only needed to modify one pulley...for the Titan 10mm
worm shaft.

I had a local machine shop drill out the larger hub pulleys for the RA
Titan worm shaft to 10mm.

I ordered 4mm hub pulleys for the McLennan gearbox shaft. The stock
Losmandy gearboxes have a larger 3/16th inch shaft, and if I went with the
stock gearbox I'd have needed to drill that pulley too.

My pulleys teeth counts were 1:2 from the gearbox:worm. Thus, my 25:1
McLennan gearbox appears to Gemini units as a 50:1 gear reduction. This is
exactky what Losmandy did in making the "Titan-50" ... they used 2
different gears for the gearbox to the worm to reduce stress on the plastic
gearbox gears. In the older "Titan" and the newer "G11T Titan RA" they used
1:1 gearing.

But you must understand this: the native flaw that sometimes is discovered
in the stock gearbox is a "1/7.5" oscillation of the sidereal period...and
non integer ratios like that cannot be removed by standard PEC (but the
"double Period PEC in PemPro is intended to make that 1/7.5 look like a
1/15 oscillation that can be PEC corrected. )

On a G11 this results in an RA PE of 32 seconds. That's hard to
autoguide out. On a Titan (with 25:1 gearing) you get a 42 second
oscillation. But on a Titan-50 you get a 21 second oscillation! So if you
are going to do my form of "Titan-50 belt drive" you really need to also
replace the RA gearbox with a McLennan 25:1 gearbox. The McLennan gearbox
design uses only integer gear ratios so can always be improved by standard
PEC.

So the kit I could offer becomes complicated. It would in my mind include
the McLennan 25:1 gearbox that's about $45 these days, and a 1:2 pulley
system, and it would work very nicely as mine does. Or perhaps use a
stock gearbox (25:1) and 1:1 pulley as Allen Ruckle did (and he claimed
excellent results on his G11T). It's an owners decision how deeply to try
and get the last bit of improvement from the G11T RA.

I think it's just as easy (and instructive) for an owner to dive into the
belt drive upgrade.

Stay well and have fun,
Michael

On Mon, Jun 3, 2024, 11:02 PM Aaron Lovett via groups.io <mrlovt=
[email protected]> wrote:

Michael, have you ever thought of building and selling an aftermarket
upgrade kit with the parts already prepared?

Re: belt drive with gemini2

mrlovt@... (Aaron Lovett) — Mon, 03 Jun 2024 23:02:12 -0700

Michael, have you ever thought of building and selling an aftermarket upgrade kit with the parts already prepared?

Re: Ra Extension Block with through mount cabling option.

mrlovt@... (Aaron Lovett) — Mon, 03 Jun 2024 23:01:51 -0700

Interesting - I'd love to see a working example. I'm also game to test a prototype on one of my G11Gs.

Re: Problem G11T AR

davidrico13@... — Mon, 27 May 2024 01:55:26 -0700

Hello everyone, I'm posting an image I took recently of M51, 50 minutes of integration, canon 400D and cls sv bony filter. stacked with pixinsight. With the tracking of the mount itself, the G11T is a great machine ❤️

Re: Ra Extension Block with through mount cabling option.

malanick@... (David Malanick) — Thu, 29 Feb 2024 07:17:23 -0800

Did you ever make these? I'm down to 2 cables, power and Ethernet. Looking to experiment partial through the mount cabling options.

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Re: Problem G11T AR

davidrico13@... — Tue, 17 Oct 2023 10:09:28 -0700

Hi Chip, I want it slow so I can move around the lunar surface visually, appreciating the details, and if a Sky Watcher mount can do it, a Losmandy should do it without a problem.

Re: Problem G11T AR

chiplouie@... (Chip Louie) — Tue, 17 Oct 2023 07:48:30 -0700

On Tue, Oct 17, 2023 at 02:06 AM, <davidrico13@...> wrote:

Yes, the vibration only appears at a very slow centering speed, in the normal
value there is no vibration, with the change of bearings the sandy noise has
disappeared but the vibration is still present, so I use a higher centering
speed, but I will continue looking adjustments until it no longer vibrates at
a very slow speed in centering.

But my question was what is the reason you are trying to use such a slow centering speed?

--
Cheers/Chip

Re: Problem G11T AR

davidrico13@... — Tue, 17 Oct 2023 02:06:12 -0700

Yes, the vibration only appears at a very slow centering speed, in the normal value there is no vibration, with the change of bearings the sandy noise has disappeared but the vibration is still present, so I use a higher centering speed, but I will continue looking adjustments until it no longer vibrates at a very slow speed in centering.

Re: Problem G11T AR

chiplouie@... (Chip Louie) — Mon, 16 Oct 2023 19:15:01 -0700

So the standard speed for centering which is the slowest speed before guiding is 90? Assuming that 90 is the standard value why were you trying to go half the standard speed for the mount? Was it too fast at the eyepiece?

So is this "issue" is only an issue if you set the centering speed to a very slow, less than half the standard speed? I just wanted to get clarification here so I understand what we were all banging our head over.

Is the chatter only present at these ultra slow centering speeds? It doesn't happen at the normal centering speeds?

If this is all correct then the whole you must use only MoS2 grease or you will have chattering thing appears to be fictional?

You also had a sandy sort of white noise coming from the bearings. I imagine, now that you are telling us what that you were trying to set your centering speed to a very slow speed, that the bearings had no significant impact on the chattering but might contribute to a high frequency noise in PE error if measured.

This sounds like how the often strange nonsensical Losmandy mythology is born.

--
Cheers/Chip

Re: Problem G11T AR

jjkmetz54@... (John Kmetz) — Mon, 16 Oct 2023 03:25:58 -0700

Glad your efforts were successful, David. Clear skies!

John

Re: Problem G11T AR

mherman346@... (Michael Herman) — Sun, 15 Oct 2023 13:39:56 -0700

Nice work !

Looks like the mount, withnthe updated RA worm bearings, is behaving better
than your seeing conditions. You must have excellent polar alignment too
to image 9 minutes without autoguiding.

Have fun in the world of imaging!

Michael

Re: Problem G11T AR

davidrico13@... — Sun, 15 Oct 2023 13:23:13 -0700

Hello, yesterday I made this exposure of about nine minutes and there are no jumps in the image, they are stretched because I do not do self-tracking, it is the tracking of the mount itself, the other image is the lyra with three minutes of exposure, punctual stars.

Re: Problem G11T AR

davidrico13@... — Sat, 14 Oct 2023 08:14:34 -0700

I think the standard speed for centering is 90, there are no vibrations there, I think I will stick to 50 as it works smoothly, a servomotor also arrived with problems, it took four months to resolve due to lack of stock, luck is with me. Fortunately it was resolved well and I am happy.

Re: Problem G11T AR

chiplouie@... (Chip Louie) — Sat, 14 Oct 2023 07:50:11 -0700

Hi David,

Wow, there was also a bad servo motor? You have not had much luck fall on the good luck side of chance.

So has the mechanical chatter been resolved or does the chatter still happen when the speen is below 50? I have no idea what the standard default speed for centering is on a G11T but try a step or to slower or faster then the default. Maybe there is an interference oscillation interaction between the mount's mechanical frequency and the servo motor electronics that can't be dampened by grease but could be tuned out electronically?

What version firmware is your Gemini-2 on? Have you considered updating to L6? I don't think you should move to L6 if you want to use PEC but if if you like many people do not use PEC when imaging relying on PHD2 then it won't matter and L6 will be a nice upgrade.

--
Cheers/Chip

Re: Problem G11T AR

davidrico13@... — Sat, 14 Oct 2023 00:26:46 -0700

Yes Jhon, the ball bearings are installed with your fingers, they arrived like this from the factory with those knocks, the mount also had other failures, the poorly manufactured AR gear plate and a servomotor that jerked in DEC, everything has been solved now, The distributor in Spain fixed the gear plate and a replacement servomotor for me.

Re: Problem G11T AR

davidrico13@... — Sat, 14 Oct 2023 00:20:44 -0700

Hello people, yesterday I received the Hachi bearings, I installed them and everything is very smooth, but with a value below 40 in the centering speed the image in the telescope continues to vibrate, when the value is above 50 the image is stable, You may have to search for a different setting until you can find it.

Re: Problem G11T AR

jjkmetz54@... (John Kmetz) — Mon, 09 Oct 2023 19:08:52 -0700

On Mon, Oct 9, 2023 at 04:05 AM, <davidrico13@...> wrote:

Yes John, when I dismantle the worm I take care of it as if it were a small
bird, I leave it away from the workplace, a bearing has several dents in the
shield, it arrived like this from losmandy, I'll post a picture.

( /g/Losmandy-Hackers/attachment/1223/0/0.jpeg )

That does not look healthy David. If the ball bearings are under those dents, they are probably not rolling properly. But I can't say what the interior of that bearing looks like to diagnose. Whenever I install the G11 worm bearings I just use finger pressure, no hammering. However, the needle bearings around the main shafts take some coaxing with a rubber mallet to get into final position inside the mount body.

John

Re: Problem G11T AR

davidrico13@... — Mon, 09 Oct 2023 01:05:41 -0700

Yes John, when I dismantle the worm I take care of it as if it were a small bird, I leave it away from the workplace, a bearing has several dents in the shield, it arrived like this from losmandy, I'll post a picture.

Re: Problem G11T AR

jjkmetz54@... (John Kmetz) — Sun, 08 Oct 2023 20:18:15 -0700

On Sun, Oct 8, 2023 at 06:32 AM, <davidrico13@...> wrote:

Today I received liquidmoly from Amazon and I dismantled the worm block and
the crown, cleaned the old grease and put in the new one, I also checked the
worm under a magnifying glass and found a possible defect, I will send a photo
to Losmandy so they can verify the worm. I attach images. The sandy noise was
solved a lot and with the worm block out of place I turned it and verified
that part of that sound comes from the bearings, next week with the
installation of the Nachi it should be improved.

Hi David,

When you have things taken apart, use caution as to not bump or nick the brass worm. The yellow metal is fairly soft and can be ruined by dropping or just putting in a box with metal items. I wrecked my best worm with the lowest periodic error by mixing it in with other parts and tools and it developed a 30 arc-sec jump every 240s, the worm period for the G11. Now I wrap the worms in bubble wrap whenever they are out of the mount.

Also, if you are now replacing the bearings, try to work some grease into the interior to coat the ball bearings. If this was the source of your problems, it sounds like the bearings were dry and friction destroyed the balls and races inside. If you don't see any visible opening, a drop or two of heavy oil, like motor oil, into the seam could more easily penetrate to help with lubrication.

John