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My "new" used Losmandy G11 mount needs help

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#1 rcole_sooner

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Posted 31 October 2012 - 07:44 PM

**********

Edit: I should change the title to "owner needs help". :o I think I got this sorted out, but feel free to read. I was expecting 16x sidereal rate to be quicker than it is. I think.

**********

Well, I thought I'd save some money and get a use one, but it is not looking good.

The "drives" do not seem to be working.

The motors are turning the worm gears, but the worm gears are turning the ra/dec gears. It looks like worms are just spinning and not touching the target gears.

There does not seem to be any adjustment, but I figure this is the place to get help.

Any ideas, before I call it a dud, and try to get my money back.

#2 mikemxyzzy

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Posted 31 October 2012 - 08:08 PM

The worms are held by a block at each end that can be adjusted in and out. The Yahoo Group Losmandy_Users has many documents on worm adjustment.

There are some web sites as well:

http://www.astro.uni...11_tuning.ht...

as well as some websites that show complete teardowns:

http://www.astromast...1maintenance...

#3 rcole_sooner

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Posted 31 October 2012 - 09:32 PM

Yeah, I found those and some other sites.

They don't show any adjustments for make the worm tighter against the gear.

It is odd that both worms are acting the same, which makes me think I just don't understand something.

All I know is the worms are spinning, but the gears are not moving.

Nothing looks stripped or damaged.

I am very confused.

#4 wasyoungonce

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Posted 31 October 2012 - 09:54 PM

Check your clutches (knobs) are done up.

If the worms are turning then it's almost impossible to not drive the axes unless the clutches are loose.

#5 rcole_sooner

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Posted 31 October 2012 - 10:02 PM

My first thought, but the gears are not even moving. I've tried tightening the clutches and loosening them. If the gears are not turning, then I don't think the clutches matter.

I got a video uploading, it should be here shortly.

#6 rcole_sooner

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Posted 31 October 2012 - 10:17 PM

Here we go, a video. It is out of focus, the best my phone could do. You can still see the worm turn (LOL!), and the RA gear not move (thanks to some grease as a place marker).

http://www.youtube.c...h?v=nsnOhRspatc

I'm not sure how to insert a video, on this forum.

Oh, man, I can see it move in that video.

Does that seem slow, for 16x?

I need to go make one of the dec drive, that is where I first thought I had the problem.

#7 Steven

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Posted 31 October 2012 - 10:24 PM

You need to adjust the meshing between the worm and wheel. Search the web for instructions.

#8 rcole_sooner

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Posted 31 October 2012 - 10:31 PM

Okay, the DEC is turning too, just impeceptively slow.

I figured at 16x, it would practically be slewing.

I'll check for articles with the word "meshing" in them.

#9 wasyoungonce

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Posted 31 October 2012 - 10:34 PM

Ok looked at the video...looks like the main gear was not turning.

Can you see if the worm and gear are meshed? If not ...as others have stated they need adjustment.

The mount gears may have been deliberately de-meshed prior to sending it to you to protect the worm & main gear.

#10 rcole_sooner

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Posted 31 October 2012 - 10:40 PM

I cannot figure out how to mesh the gears.

There does not seem to be any adjustment for that.

The blocks on either side of the worm, just tighten onto the base.

There is no adjustment towards or away from the gear, as far as I can tell.

#11 Ranger Tim

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Posted 31 October 2012 - 10:47 PM

Loosen the two large pocket (allen) bolts that attach the worm blocks to the mount and push the blocks into the RA gear. Use a straight edge (I use the worm cover) to align the two worm blocks and also keep them pushed together and tight to the motor shaft. How much free play the worm has to wiggle (esp. side-to-side) will contribute to how much backlash you will have. Tighten and try the movement again. Some folks also insert a thin metal spacer under the worm blocks to force the worm farther into the ring gear - I would use a sacrificial feeler gauge for this if you find this necessary.

Adjusting the worm is a seasonal affair for me. Wide temperature swings will cause the backlash to become excessive or the worm to become too tight. I like it to be "just right."

Whatever you do, clean that sucker up. There is a ton of unnecessary grease on that worm, which will eventually trap lots of grit and dust. I can't even see the ring gear to tell if the worm is just skipping due to insufficient contact or if you have some abraided/broken teeth on the gear. BTW, all these parts are available from Losmandy, and they are reasonably priced.

Just wondering, does the axis turn when the clutches are loose? Is there lubrication down in the needle bearings? This mount is not difficult to disassemble, so tear it down, clean the clutch pads and bearings, then relube the bearings with an appropriate amount of Superlube. A little goes a long way. Check for corrosion. Don't get grease on the plastic clutch pads when you reinstall.

My "new but used" Losmandy turned out to be problematic as well, but it just needed some TLC. Now, the mount is very predictable and performs like a fine watch. The electronics (Gemini) can be another animal entirely. Don't give up on her, chances are it can be fixed easily. Many of us have been in your situation. Persevere for a bit longer and it will become obvious what is wrong. Good luck with it and continue to post your progress.

#12 Ranger Tim

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Posted 31 October 2012 - 10:53 PM

If you are using the Digital Drive (non-Gemini go-to) controls, be aware they do not "slew." The motion will seem glacial even at 16x if you attempt to move the mount from one object to the next. Simply move the mount by hand to the area of interest and then use the motors to center the object. You must have go-to in order to slew the mount with the motors.

#13 rcole_sooner

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Posted 31 October 2012 - 11:03 PM

Yes, I am using the Digital Drive (non-Gemini go-to). I am beginning to think that is. I was expecting 16x to be slow, but ... well not that slow.

Yes, the clutches grab and release, and the mount is easy to turn and smooth, when they are loose. And completely tight, when they are tight.

I need to get it out under some stars and test it. I was just trying to do a quick test inside.

I think it may be working, and I just was expecting something different.

Thanks, for everyone's help and advice.

#14 Ranger Tim

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Posted 31 October 2012 - 11:13 PM

Take heart, you will learn to love the digital drive for its predictable behavior. But then you will also begin to covet the Gemini system for the go-to slews. There will continue to be folks that are divesting themselves of the Gemini 1 systems to upgrade to Gemini 2, and that is when you will strike for a good deal on a used package. For now, nail all the bright objects that are winging into view this winter. They are easy to find and center in the camera. The digital drive is a capable system.

Get a phone jack splitter to provide a location to plug in a guide camera. Plug it into the jack for the hand control.

#15 rcole_sooner

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Posted 31 October 2012 - 11:39 PM

Yep, I've got a lot of practicing with some easier targets, before I go for the dim hard to find ones.

I also have a GPUSB, that I think may work for guiding.

I've got to actually get some Losmandy dovetail plates, for my scopes. They all still have vixen style bars.

Then I have to decide how to do my DLSR. Side-by-side with my C80ED, or piggyback on my C9.25.

It is going to be a new adventure going from my LX200 to this G11 setup. It has been something I've wanted to do, for quite a while.

#16 Cliff Hipsher

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Posted 01 November 2012 - 11:09 AM

**********

Edit: I should change the title to "owner needs help". :o I think I got this sorted out, but feel free to read. I was expecting 16x sidereal rate to be quicker than it is. I think.

**********

Well, I thought I'd save some money and get a use one, but it is not looking good.

The "drives" do not seem to be working.

The motors are turning the worm gears, but the worm gears are turning the ra/dec gears. It looks like worms are just spinning and not touching the target gears.

There does not seem to be any adjustment, but I figure this is the place to get help.

Any ideas, before I call it a dud, and try to get my money back.


Google Losmandy BACKLASH.

We poor LXD-75 owners have a similar problem.... ;)

#17 Ant78

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Posted 01 November 2012 - 11:21 AM

there's a digital manual that exists on the losmandy site, you can download that and print it out, useful to have.

#18 Ranger Tim

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Posted 01 November 2012 - 01:18 PM

You may want to consider the dual saddle by Losmandy or ADM. It will accommodate either style of dovetail.

#19 nebultick

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Posted 01 November 2012 - 06:18 PM

16x is so slow you will barely be able to see the mount move at 16x it would take an hour and a half for the mount to do a complete revolution.

#20 rcole_sooner

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Posted 01 November 2012 - 07:36 PM

Thanks, again everyone. So much to learn.

I went and checked what sidereal rates my LX200 had, and it went up to 128x. I just punched numbers in the dark, and didn't really pay much attention to the readout. I never knew I was going that high.

Big difference between 128x and 16x.

Still I stared at the cogs on the gear and never saw a cog move into the worm, but it was a trick of the mind. Once I saw it moving by jumping the video time around, I went back and watched closer. I did see cogs move into the worm, but very, very, very slowly.

As fast as that little cog is moving, I did not think it was possible for the gear to move that slow.

I was wrong.






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