Re: Specs for the main axis thrust bearings.
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
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Re: Specs for the main axis thrust bearings.
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
? ?? ??
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
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Re: Specs for the main axis thrust bearings.
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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Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
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Re: Specs for the main axis thrust bearings.
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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Re: Specs for the main axis thrust bearings.
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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Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
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Specs for the main axis thrust bearings.
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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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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Michael Herman is a great friend and resource to the Losmandy community.? I can't imagine the Losmandy world without his contributions.?
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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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Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
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Problem was moisture got inside and accumulated in the lower end of the enclosure. This corroded the fuse holder and a capacitor
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
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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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Re: East-Heavy Guiding With G11T?
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.
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Re: Did my Gemeni 2 firmware become corrupt?
I think so. Weather isnt cooperating but at least the mount is going the right way during some test slews.
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Re: G11G Imaging Weight Capacity for Imaging?
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Keep us posted on your progress!
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Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
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Re: G11G Imaging Weight Capacity for Imaging?
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?
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Re: G11G Imaging Weight Capacity for Imaging?
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.
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Re: Unable to fully lock RA axis on G11
On 2/17/2025 1:22 PM, Chip Louie via groups.io wrote: Paul what color was the grease?
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. I honestly can't say for sure what color it was.? It was the factory applied grease, whatever they used in 2019 when I bought it.? By 2020 or thereabouts when I disassembled it, it had migrated copiously over all surfaces.? I cleaned everything and a year later it had again migrated.? I decided to just ignore it since the clutches seem to work adequately in spite of the greasy surfaces. Paul -- Paul Goelz Rochester Hills, MI USA pgoelz@... www.pgoelz.com
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Re: Unable to fully lock RA axis on G11
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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Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
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Re: Unable to fully lock RA axis on G11
On Sun, Feb 16, 2025 at 03:19 PM, Paul Goelz wrote:
more to this story
Most likely regarding the clutches.? The topic begins with the characteristics of a Celestron Losmandy G11, something available before they offered the G11 themselves.? Updates and materials, such as to the clutches, have changed over time, and it is uncertain how many service updates occurred.
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And that which works, suffices for using the mount.? I use a current G11G with SLW in stock configuration, and I engage the clutch using the clutch-knob-set securely (high).? A level at which friction breaks above 10 ft-lbs at the axis, with significant force vectors along the clutch shaft.? With this setting, targets also track within the 0.8 to 0.2 range, depending on the guide star, field, and environmental conditions.? Usually, below 0.5, but in the higher range as wind gets into the 12-knot wind buffet range.
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Unfortunately, on clutch engagement the available documentation just says: disengaged and engaged.? I am fairly certain from the design there must exist a minimum clutch tension.? One that loads the counterweights on to the lower housing and removes the clutch rod load off the clutch idle pin bearings.? This makes sense as the load carried and the counterweight mass must figure into any minimum level.? And use with the current G11G indicates that just setting the clutches tight also works as expected when tracking.
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Doug
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Re: Unable to fully lock RA axis on G11
On 2/16/2025 2:00 PM, Thomas Kallenbach via groups.io wrote: Is this the kind of RA tracking that might be caused by clutches being too tight?
It is really hard to say for sure. There are multiple possibilities including atmospheric causes.? But yes, it is possible.? Do the experiment..... loosen your clutches on the same night in the same location in the sky and see if it smooths out.? I typically tighten until I feel contact and then go 1/8 to 1/4 turn more.? Less is more. I spent a great deal of time a year or two ago trying to track down the cause of inconsistent tracking and excessive DEC backlash.? In the process I disassembled and re-assembled, measured, re-greased, tried different greases and made several physical modifications. The end result is that I went from being extremely frustrated with a MINIMUM of 2.5 seconds of DEC backlash to now being extremely happy with the performance.? No RA jumps EVER, and DEC backlash that is consistently between 100 and 800 mS.? Typical tracking is maybe 0.6" RMS on a crummy night and I have seen it as low as 0.3" RMS on a good night. There is more to this story but A) I don't mean to hijack the clutch discussion and B) no one seems to be particularly interested when I bring it up ;) Paul -- Paul Goelz Rochester Hills, MI USA pgoelz@... www.pgoelz.com
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Re: Unable to fully lock RA axis on G11
Is this the kind of RA tracking that might be caused by clutches being too tight? 
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Re: Unable to fully lock RA axis on G11
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 -- Paul Goelz Rochester Hills, MI USA pgoelz@... www.pgoelz.com
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Chip Louie
Russell Milton
Chris Potter