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Hi Tim,

A couple of link corrections

For whatever reason John,? the part number got clipped off the links for these two.

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There are long discussions about reduction of PE and improvements in tracking in the archives.

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From what you describe is happening regarding guiding, I doubt that the bearings you're asking about are at the root of it.

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I'd be most suspicious of binding in worm/ring gear interface. If could be just a needed slight adjustment of worm pressure to account for a high spot that's still within ring gear tolerances, a contaminant on the ring gear or similar lubrication issue.? Guide pulses are a much smaller force than average RA tracking forces, so RA tracking could still push through an area that's binding but the guide pulses become ineffective.

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There are a few ways to test this out, but I'd suggest to back off the worm slightly and see if the problem goes away. A lot of guiding issues are caused by too much worm pressure.

Be mindful too that the relationship beteen RA position and ring gear position shifts if the clutch is released or slips. This is why a ring/worm binding issue may not be consistent with RA angle.

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Seeing uneven and wavy wear on the large thrust washers is not what I'd expect.

I agree with John, with that much wear they should be replaced.? The important question though is WHY you're getting this much wear and why it's uneven. An Unbalanced load would tend to pinch the outer edge of the bearing. Heavy over tightening of the clutch would pinch the inner edge. Contamination, incorrect lubrication, or uneven pressure causing a pinched bearing can cause premature wear. If the bearing is pinched it will push lubrication out of the bearing and it can end up contaminating the clutch, causing futher tendency to over tighten in a viscous cycle.

Do you have a wavy washer in your clutch assembly? That, along with too much pressure could explain why the wear is both wavy and uneven.?

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The clutch on the G11 is designed to slip under pressure, not lock up tight.? If you are applying a lot of pressure because the clutch is slipping the most likely reason is load balance or clutch plate contamination. Worn plastic clutch plates can be roughend with sandpaper, but be sure to clean them to remove any trace of abrasive or plastic dust. IME though it's probably lubricant that's migrated into the clutch.?

With excessive pressure, I think Chip has mentioned in past threads there is risk of warping as well, so at this point surface flatness is something to check while you've got things apart. If?

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If you prefer a higher slip resistance clutch, I suggest Michael Herman's high friction replacement clutch disks.

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Since you are cleaning and relubricating,? be aware it is very easy it over lubricate the mount.?

Being fully machined, tolerances are very tight. It's only necessary to just coat the bearings. Just enough is all you want.? Clean away all traces of old lubricants, make sure all solvents dry and there is no residue. Check the bearings dry to be sure they're turning freely and there is no damage before lubrication and assembly. It isn't difficult, but I found it is very easy to get lubricant where it doesn't belong unless you're very very careful what you touch once lubricant gets involved.

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The Jet-lube Artic and Jet-lube MP-50 are aircraft spec lubricants. The big advantage in the Jet-lube Artic is the extended temperature range. If you are in an area where you have very cold temperatures or wide extremes,? stick with it. I've had good success with Superlube as have others,? but I'm in a temperate area. YMMV

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The exception is lubrication for the worm/ring gear interface. This spot is sensitive to lubrication for tracking/guiding performance. I'd take John up on his offer for MP-50. There are a couple of alternatives that you'll find in the discussion threads, such as a brake caliper high temp grease that Michael Herman suggests, but none are? inexpensive, and you'll pay for more than you'll ever use.??

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For full disassembly of the motor drive train you'll want an Allen hex long driver set in SAE English 64ths. I'm not sure about the tucked motors,? but with the untucked ones there is one tight access spot where having a ball end rather than a straight end driver is really called for. I manage somehow but it isn't fun.?

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Hope this long reply helps and you figure out why you're getting this wear.??

On Tue, Feb 25, 2025 at 02:57 PM, <tshelley@...> wrote:

The mount does not seem to stop. The guiding will correct itself in 2-3 pulses after the 30 second phase and the mount continues to make drive noises. As far as did the mount receive a guide pulse, I don't know how to determine that. I know PHD2 produces a guide log that will tell me if it sent a guide pulse but I don't know of a corresponding log for the mount to tell me the mount received the pulse.

The mount does not seem to stop. The guiding will correct itself in 2-3 pulses after the 30 second phase and the mount continues to make drive noises. As far as did the mount receive a guide pulse, I don't know how to determine that. I know PHD2 produces a guide log that will tell me if it sent a guide pulse but I don't know of a corresponding log for the mount to tell me the mount received the pulse.

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Tim

Tim,

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The rebuild and regrease of the thrust washers and bearings is not that difficult. The hardest part is removing the motor to worm assembly and getting the worm tension right when putting it all back? together. Then just spin off the clutch knobs and lift the shaft up and out. Have a nice clean work area laid out for the parts where you can spread everything around for inspection and degreasing. I have found gasoline and brush is the best degreaser, followed by a rinse with JetSpray Gumout Carb Cleaner (handle the solvents with care with much ventilation and place any rags or wash pans outside to dry somewhere safe).

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If your washers have worn by that much, it's time to replace them. But I'm not sure that would cause any 30s delay which may be by something else. Does the mount just stop, or does it cease getting corrective guide pulses?

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John

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Losmandy G11G2 on pier; refurbed Losmandy G11 with OnStep controller; SkyShed design roll-off observatory; ZWO ASI2600MM-P; ZWO ASI071MC; Sky-Watcher Esprit 100 ED with field flattener; Celestron C925 Edge HD with 0.7XFR, William Optics Zenithstar 61 APO; PHD2, NINA, Sequence Generator Pro and PixInsight user

John, thank you for the information. I appreciate it. I will put it to use with caution.

Chip, thank you for all the cautionary statements. I should have provided a more detailed account for why I was asking for this information. The reasons are 2 fold. I'm still having a random tracking issue where the mount doesn't correct guiding for an extended period of time, 30 seconds max. This is not a frequent occurrence but often enough that I feel the need to address it. The second reason is that the wear on the washers of the main axis thrust bearings is uneven. I discovered this when I was cleaning and re-greasing the mount. The last tear down I did was about 2 years ago. Now I did have Losmandy reconfigure the mount last summer to separate the RA and DEC axis for more portability. I asked that they inspect these bearings and replace them if necessary. They responded that the bearings were fine, the mount was essentially new. Admittedly my need for this information is based on my assessment of the bearing's condition, which could be in error. I observed that some portions along the inner radius of the washers were 1/3 to 1/2 of the thickness compared to the outer radius. There was some "waviness" of the inner edge of the washer forming. I do appreciate the need for detail on the bearing configuration. I also understand that dimensional mistakes could render the mount unusable. I really do appreciate the voice of reason reminding me that mistakes can be costly.

I have reduced the weight of my "kit" by about half and reduced the focal length of the main instrument by 40%. I would expect that this would have an impact on this guiding problem.

Apologies for the long winded reply, I know you are both busy.

Tim

Hi Tim,

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Following are the part numbers I have given out to folks in the past, but I have not checked the links in quite a while. There are the Losmandy stock parts (not sure why you can't get them) and others from McMaster and Amazon. I have switched to the heavier duty versions on my mounts which hold more grease and have caged bearings. Personally, I like using the replacement thrust washers mentioned over the stock part as they seem to have a higher hardness and should wear less.? I would also recommend replacing the worm bearings if you are going this far and which are also mentioned. You need the same set of parts for both the RA and Dec drives.

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Here are the upper thrust bearings:

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and one thrust washer:

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You need a one 1/16” or 0.06” thick washer (3 in. ID) and one 1/32” or 0.03” washer for the washer/bearing/washer stack to be the correct height for worm to ring gear alignment.

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And here is the thinner one:

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Some guys like this alternate bearing with caged needles instead:

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Losmandy sells the whole group as a set:

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but you should not need the inner donut which rarely goes bad. Smaller needle type bearings included here.

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3? ?? 5905K29??? ??? Needle-Roller Bearing, Open, for 1-1/4" Shaft Diameter
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1??? 94065K32??? Belleville Disc Springs for Ball Bearing Trade No. R4, 0.406" ID, Packs of 10
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2?????? SR4-ZZC #7 PS2?? BG (.250X.625X.196)
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Then there are the lower thrust bearings and washers as well (1.25” ID).

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or these alternates:

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with upper and lower washers both 1/32”, you need two.

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A lot of mounts came from the factory with Jet-Lube MP-50 applied to the upper thrust bearings and washers, and more importantly the ring to worm contact. The Jet-Lube Artic grease was applied elsewhere. Please let me know if you want some MP-50 as it is expensive and only comes in larger containers. I can send a small tin at cost with enough for a rebuild if you are in the USA.

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Please get back if you have any questions.

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Good luck,

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John

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Losmandy G11G2 on pier; refurbed Losmandy G11 with OnStep controller; SkyShed design roll-off observatory; ZWO ASI2600MM-P; ZWO ASI071MC; Sky-Watcher Esprit 100 ED with field flattener; Celestron C925 Edge HD with 0.7XFR, William Optics Zenithstar 61 APO; PHD2, NINA, Sequence Generator Pro and PixInsight user

On Mon, Feb 24, 2025 at 01:49 PM, <tshelley@...> wrote:

Hi, Chip, Losmandy has not had these for months. Losmandy refuses to respond to requests for information about these parts. Otherwise I'd be happy to be able to get them from Losmandy.

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Is there something wrong with your main thrust bearings?? These almost never god bad unless the mount has been misused,.assembled incorrectly , had the wrong lubricant used or the mount has has long exposure to grit and moisture.??

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It is very important to use the correct parts with the correct bearing stack height or you risk ruining other more expensive parts.? As I posted I've seen the results of people's DIY repairs and it often turns out badly.??

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If Losmandy doesn't have them in stock there is probably just no reliable.soirce for them at the moment. Be careful of fake name.brand bearings and / or inferior bearings.??

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Hi, Chip, Losmandy has not had these for months. Losmandy refuses to respond to requests for information about these parts. Otherwise I'd be happy to be able to get them from Losmandy.

On Sun, Feb 23, 2025 at 02:34 PM, <tshelley@...> wrote:

Does anyone have a handle on the specs or a source for the RA and DEC main thrust bearings? I'm not looking for the smaller thrust bearings used in the clutches.

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Thanks in advance, Tim.

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Why, do you need replacement thrust bearings?? Why not just call Losmandy and order them, they have the correct factory spec parts in stock sitting on the shelf.? There is a bit more to it than just buying some bearings, you will need bearings and hardened and ground thrust bearing races that are not only the correct O.D. and I.D. but also the correct thickness so the stack height is within the designed stack range.?

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I'm not saying you couldn't find something close that might work if you had a good bearing supplier but they are not going to be something you can buy at your local Ace hardware or DIY center.? I've actually purchased, repaired and sold a couple of mounts that had incorrect spec thrust bearings the owners purchased at a local tractor supply.? Seriously, I bought them for almost nothing because the owners couldn't get the mount to work correctly after they had "repaired" them.??

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Does anyone have a handle on the specs or a source for the RA and DEC main thrust bearings? I'm not looking for the smaller thrust bearings used in the clutches.

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Thanks in advance, Tim.

On Fri, Feb 21, 2025 at 04:10 PM, Russell Milton wrote:

Michael has repaired my Gemini-1 and it's on its way back to me. Problem was moisture got inside and accumulated in the lower end of the enclosure. This corroded the fuse holder and a capacitor. Michael recommended bringing the Gemini-1 back indoors when not being use. Also some sort of cover over its exposed surfaces will discourage dew from accumulating while in use. I'm considering drilling some holes in the bottom end of the metal enclosure to allow for any moisture that might find its way there to escape.

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Russ

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That said make your life easier, take the Gemini and other electronics inside.? At least protect them with a low-Watt heating element under the mount.??

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sadly I’ve seen this before more than once. ?Sadly I’ve even seen ?corroded CPU sockets. ? The environment must be extremely onerous and or moisture by the buckets.?

Luckily Michael repaired it, excellent!. ?But it’s a good warning to all Gemini users not just G1s. ? G2s can get this as well?

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cheers

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Brendan

Michael has repaired my Gemini-1 and it's on its way back to me. Problem was moisture got inside and accumulated in the lower end of the enclosure. This corroded the fuse holder and a capacitor. Michael recommended bringing the Gemini-1 back indoors when not being use. Also some sort of cover over its exposed surfaces will discourage dew from accumulating while in use. I'm considering drilling some holes in the bottom end of the metal enclosure to allow for any moisture that might find its way there to escape.

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Russ

I just want to second George’s reply, as I too have a perfect balance on my G11T. Granted, it’s sporting a RASA 11 v1 at the moment, but I’ve seen (and have the screenshots!) total RMS as low as 0.12” without pec (still haven’t got that right) on good nights. Typical garbage guiding is around 0.3” up to 0.5” if guiding with thin clouds passing through.

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I’ve actually seen PHD2 charts of over a minute without a single correction (0.5” exposures).?

Guide cam is a ASI178mm, 4x Bin (I refuse to lose stars).

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I use PHD2’s PEC RA algo and started using Limit Switch for Dec after seeing a video by the legend himself, Brian V.

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My trick is minimal maintenance. Must be the crushed exoskeletons smoothing out the tracking.

I think so. Weather isnt cooperating but at least the mount is going the right way during some test slews.

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Keep us posted on your progress!

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also, i collect most of my images for dso with a 110mm WO refractor, or a 61mm WO refractor. the 12"SCT just happens to be the biggest scope i have, and i mainly use it for planetary, which is unguided. but i figured what the heck, lets try some?

Perfect, ive picked it up, and if we ever get a clear night, ill get to start testing this things limits, thanks again to Jim! great seller.

On Sun, Feb 16, 2025 at 10:53 AM, Paul Goelz wrote:

On 2/16/2025 10:47 AM, Chip Louie via groups.io wrote:

The issue of grease migration is caused by using the wrong grease.?
The grease must be able to maintain its viscosity hot or cold to work
but it cannot melt or separate.

Hmmmm..... when I disassembled my GM811 about a year after I bought it
new, I found the clutch area (including the clutch disks) was totally
saturated with grease.? I suspect Losmandy did not use "the wrong
grease".? More likely a side effect of the clutch design. When
assembled, the clutch disk touches the ring gear and bearing. Any grease
in the bearing will slowly flow out onto the clutch disk.? And did.?
Thinking that was a bad thing I cleaned it and re-assembled.? Only to
find the clutches once again covered in grease the next time I
disassembled.

While the clutch was disassembled, I discovered another small issue that
I corrected.? The clutch disk center hole was slightly under sized,
causing the disk to buckle slightly when forced over the shaft.? This
could require excessive clutch tension just to overcome the buckle and
force full clutch engagement.

I continue to wonder why people are so focused on getting a "solid"
clutch lockup.? IT IS NOT NECESSARY.? The only forces I can see that
would cause slippage while tracking would be rotational friction,
imbalance or wind.? Note that rotational friction INCREASES with clutch
pressure (as does erratic tracking) due to the inherent friction in the
cylindrical roller thrust bearings.? I run my clutches very loose.? I
can easily push my scope around even when very cold and it NEVER slips
while tracking.? I have even had a couple sessions where I inadvertently
left the clutches totally loose and it tracked just fine.? I only
discovered it after the fact.? The tighter you run your clutches, the
more you run the risk of introducing other issues like premature thrust
bearing wear and erratic RA tracking.

Paul

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Paul Goelz
Rochester Hills, MI USA
pgoelz@...
www.pgoelz.com

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Paul what color was the grease??

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IME working with telescope mounts for quite some time now the right amount of grease for a well (read this as frequently), maintained mount is just to wet the rollers and/or balls and races with no overflow.? If there is anything more than this too much grease was applied.? It's? pretty simple, if you use the right lubricant and apply it correctly it cannot migrate.??

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Like I have posted before, I have been using a light touch on the clutches for quite some time for imaging and it works perfectly.? For visual use I run them almost fully free with just the lightest contact so the drive will still track. Of course the payload in the saddle must be well balanced on 3 axes but that is no hardship IME.?

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IME people that need to have a hard clutch lock up usually have a heavy or long payload that is out of balance and/or contaminated clutches.? This has been my experience other than a few people who had cranked down on the clutches so hard that the clutch plate on the axle was distorted preventing clutches from working due to the much reduced surface area and had to be cut and ground back to flat by Losmandy.? No surprise once flat again the clutches held just fine.??

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