Re: New (to me) older G11
On Sun, May 18, 2025 at 10:23 AM, George Cushing wrote:
Pretty sure that the worm wheels are anodized after machining. Lapping will remove that hardened surface that results from that process. So not only is lapping unnecessary, it's to be strongly discouraged.
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Scott says that too!? ?
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Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
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Re: New (to me) older G11
Pretty sure that the worm wheels are anodized after machining. Lapping will remove that hardened surface that results from that process. So not only is lapping unnecessary, it's to be strongly discouraged.
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Thank you!
Sent from Chuck's iPhone
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SVM-HT motor (stall) full speed runaway!
Has anyone had SVM-HT servo motors that stalls?
During an imaging session a couple of nights ago SGPro failed to platesolve, went out to check & found Gemini1 hand controller indicating a stall... weirdly the motor was running at excessively fast spinning the scope like a windmill while wrapping the power & USB cables around the mount! reset everything but this just kept happening.?
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I tested the mount next day & all seemed fine, only difference was a higher daytime temperature... next clear night worked fine until a drop in temperature!?
Swapped out the SVM-HT for an original motor I still have & all went well for the rest of the night, think that confirms the SVM-HT has a fault!?
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Any help with this would be appreciated.
Thanks,?
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Peter?
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Forgot to say¡.that stainless stud looks bent. ? Your standoff looks not square in images
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You can replace this stud. ?3/16 x16 tpi I think. ?Not sure length. ? Remove one and measure.?
FWIW
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Brendan
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Hi Charles
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the nylon washer goes on top of gearbox flange (gearbox against mount) and stand-off post screws down on the stainless stud. ? Later models this was changed to a male/female stand-off (no stud). ?Yours has round female/female stand-off with stainless steel stud, like mine.?
Picture tells all?
cheers
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Brendan
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I have a G11 that was bought in 2008, it was upgraded about 10 years ago with new higher torque motors. ? I took it out in the field today to hoist my 100mm Lunt solar Ha scope for public outreach, everything was going OK and then a nine-year-old with no attached parent came bounding through our telescope forest and as luck would have it, the youngster lost footing and ran into my G11 mount. I was standing opposite of the impact point and caught the scope, mount and boy from toppling over.? The boy got off with a scratch above an eye.? My G11 didn¡¯t get off that easy. After I recovered and started again with a power up at CWD the RA was very erratic and making a bit of noise.? And after about five minutes of minor troubleshooting the RA finally refused to move.? I could hear the motor running but nothing moving like it is supposed to.? I packed it up and went home.? I began troubleshooting components by systematically interchanging DEC components into the RA train.? Upon swapping the suspected RA components (motor, transmission, and coupling I could not find a culprit. ? So, I have a question on the order of a couple of parts.? I thought I had a diagram of how they went from when I took it apart years ago to upgrade things, but I can¡¯t find that notebook.? It has to do with the transmission assembly and its fastener order.? The transmission goes in such that the couplers couple and then an internally threaded post screws on a threaded stud and holds the transmission to the worm via the oddly named coupler whose name escapes me right now.? I seem to have two very small nylon (delron) washers that fit over the threaded studs.? My question is does the nylon/delron washer go below the transmission mounting flange or above the transmission mounting flange transmission? ? ? 
In this picture the white object is the nylon/delron washer and is under the transmission mounting flange and the threaded aluminum post tightens directly against the transmission mounting flange. ? Or ? 
In this picture the white object is the nylon/delron washer between the transmission mounting flange and the threaded aluminum post which will tighten against the nylon/delron washer.? This is how I think it should be, but want to make sure.? It has been ten years since I was inside this part of the mount.? AND YES SHAME ON ME for not paying attention when I took it apart today. ? Any help would be appreciated.? Thank You. ? v/r ?
?-??---?Gone... ?-??-??-?
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Looking for GM100 user manual to download: Is there one on this site?
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Re: New (to me) older G11
On Fri, May 16, 2025 at 07:31 AM, Jesse Lichtenberg wrote:
I think I'll be asking John Kmetz to send out some of the MP-50 lubricant he was mentioning. I did tear into the mount a bit last night and it's going to need a very thorough cleaning and regreasing. I didn't see any evidence of galling or anything that gave me pause, but the old stuff in there is pretty gummy in places. I'll replace the needle bearings and skip the temptation to install a third one as it seems it is not really worth it. The main thrust bearings look okay but I'll know more once I get them cleaned up. Lower thrust bearings and wavy washers will be replaced. Worm bearings too, and I'll likely pick up a set of the larger OD clutch spacers from Losmandy.
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The polar scope is almost certainly original with a dated reticle (which is not illuminated). I'll either leave it in place or make a cap to replace it. For small stuff like that I usually just 3D print threaded caps out of polycarbonate filament.
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At the moment I am planning to tuck the motors and use a pulley/belt system. It is tempting to consider a direct drive system with 400 step motors given the 360 tooth system on the G11, but I've not quite decided yet. I can move discussion concerning that to the other Losmandy Groups.io forum if need be.?
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The rule with bearings here is if the wear is just normal polishing and the shafts are not damaged like galling or wide deep scratches and there is not lip being formed on the shafts there is no reason to replace them.? Clean with solvent, blow dry with shop air and relubricate them.? Scott Losmandy will tell you the same thing for all bearings, this is his advice regarding his mounts.? I would take his advice unless you want to spend money for not good reason or increase the likelihood of bunging up your mount. Regarding the clutch adjustment knob side thrust bearings, again if there is no wear or damage to the rollers or races just clean, dry, relubricate and reinstall them.?
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Worm bearings are a no brainer as they are cheap to replace and as stated almost impossible to get clean enough once contaminated.? You might want to spend some of the money you just saved by not replacing the needle and thrust bearings on slightly higher precision bearings for the worms bearings.? The standard R4 bearings may contribute to some worm noise.? Pass on expensive ceramics, just buy higher precision stainless steel bearings but don't get too carried away with the tolerance level, they will need to run smoothly in extreme temperature shifts.?
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Just leave the drive system conversation here.? I think you'll have an audience.? I always find it entertaining to see what people think even if it is often based on conspiracy theories. LOL. ? ? ??
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Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
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Re: Dec backlash adjustment
On 5/16/2025 5:34 PM, Oberon510 via groups.io wrote: With regard to TVC I had mine set to 5 and then set it back to 0 for the last PEC training session. I will test different TVC settings and disable backlash compensation in PHD2. I would suggest that you leave PHD2's backlash compensation enabled.? It is a good way to judge the current residual backlash after any TVC compensation is applied.? Just make sure it never auto adjusts itself to near zero.? If so, reduce TVC. As I recall, I had TVC set to about 10 on level 5.? In level 6, I think I have it set to around 40 (each increment of TVC compensation in level 6 with 4X encoder resolution is 1/4 what it is in level 5). Paul -- Paul Goelz Rochester Hills, MI USA pgoelz@... www.pgoelz.com
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Re: Dec backlash adjustment
Thanks all for the suggestions. I have completed all the cleaning and greasing plus readjusted the Dec worm gear. With hand testing it appears to have removed some of the backlash but the test will come when I can do more measuring with PemPro and PHD2.
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With regard to TVC I had mine set to 5 and then set it back to 0 for the last PEC training session. I will test different TVC settings and disable backlash compensation in PHD2.
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For now I will limit any more changes until I fully retest everything but all good suggestions.
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Thanks,
Ken
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Re: Dec backlash adjustment
On 5/16/2025 11:39 AM, Mark Christensen wrote: I'd bet, given your efforts, that the motor gearbox is the culprit. Short of replacing it, while hoping for a better gearbox, your best bet is to try Paul's suggestion. If the motor gearbox is the culprit, you are in luck.? The gearbox and transfer gears present a constant amount of backlash and can be easily compensated for with TVC.? Just never let the compensation in PHD2 approach zero or the system can oscillate.? If the PHD2 compensation approaches zero, decrease the TVC value slightly until the PHD2 backlash rises again. Because TVC compensation is 10X faster than compensation using guide corrections it is too bad that Gemini and PHD2 can't communicate and dynamically adjust the value for TVC like PHD2 does for its own compensation. Paul -- Paul Goelz Rochester Hills, MI USA pgoelz@... www.pgoelz.com
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Re: Dec backlash adjustment
The worm/worm wheel interface (which is what your efforts have addressed) isn't the whole game: There is the motor gearbox, for example, along with any transfer gears between the
gearbox output and the worm shaft (if applicable).
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I'd bet, given your efforts, that the motor gearbox is the culprit. Short of replacing it, while hoping for a better gearbox, your best bet is to try Paul's suggestion.
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The way I get around it, not having a newer mount with the spring loaded worms, is to very slightly miss-align the polar axis and then slightly miss-balance the DEC axis.
That way the DEC guiding motion never reverses. Same idea as biasing the RA balance eastward since the RA never reverses when guiding.
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That way both worms are always in contact?with the worm wheels and are moving in one direction when guiding.
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Mark Christensen
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Re: New (to me) older G11
I think I'll be asking John Kmetz to send out some of the MP-50 lubricant he was mentioning. I did tear into the mount a bit last night and it's going to need a very thorough cleaning and regreasing. I didn't see any evidence of galling or anything that gave me pause, but the old stuff in there is pretty gummy in places. I'll replace the needle bearings and skip the temptation to install a third one as it seems it is not really worth it. The main thrust bearings look okay but I'll know more once I get them cleaned up. Lower thrust bearings and wavy washers will be replaced. Worm bearings too, and I'll likely pick up a set of the larger OD clutch spacers from Losmandy.
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The polar scope is almost certainly original with a dated reticle (which is not illuminated). I'll either leave it in place or make a cap to replace it. For small stuff like that I usually just 3D print threaded caps out of polycarbonate filament.
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At the moment I am planning to tuck the motors and use a pulley/belt system. It is tempting to consider a direct drive system with 400 step motors given the 360 tooth system on the G11, but I've not quite decided yet. I can move discussion concerning that to the other Losmandy Groups.io forum if need be.?
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Re: Dec backlash adjustment
On 5/16/2025 12:32 AM, Oberon510 via groups.io wrote: Hi,
I have been getting some complaints from PHD2 that my Dec backlash is high and I used this video to adjust the spring loaded worm gear ".
It didn't make much difference and now I am about to clean and regrease the worm gear but hoping for some more advice/pointers on other things to look for or do as part of the process.
Any guidance appreciated.
Thanks,
Ken Hi Ken, In my experience with my GM811, I was never able to get my raw (uncompensated) DEC backlash below about 2000mS (two seconds) by merely adjusting / tweeking / re-greasing.? And that was after carefully doing the worm bearing squeeze and setting a value for TVC.? Sometimes it was better.... and sometimes it was much much worse.? Pointing location and balance had major impact on the amount of backlash. You can adjust the value of the TVC parameter in Gemini2, which will compensate for a fixed amount of backlash.? TVC is actually my preferred backlash compensation because it runs at about 10X the guide speed (unlike PHD2's compensation which runs in real time) so (for example) 2000mS of backlash compensation occurs in about 200mS using TVC.? But there's a BIG catch..... if your uncompensated backlash changes over time and ever drops below the amount of TVC compensation, the system will oscillate.? In my experience, the total system backlash was variable enough that even with a carefully chosen value for TVC, PHD2's backlash compensation (which was in the area of 2000mS give or take a lot) would occasionally fall to near zero and DEC would oscillate.? Reduce TVC and try again and you eventually end up with a very low value for TVC.... So in desperation I did a deep dive into the system and identified several suspect areas, most of which were inherent design choices or machining limitations. I made several mechanical changes to the DEC (and RA) drives (some simple and some not so simple), run my clutches very loose, and my backlash is now very consistent.? I also made and installed a 3rd axis counterweight to compensate for the fact that my filter wheel shifts the center of mass of the scope off the DEC axis slightly. After all this, and with a carefully chosen value for TVC, PHD2's backlash compensation CONSISTENTLY runs between about 200mS and 800mS.? If it ever rises above 800mS I know it is time to re-adjust the "spring loaded worm" pressure, which is typically required twice a year due to seasonal temperature changes. If there is any interest (and if it is allowed here) I can go into more detail.? All but one of my modifications are non-destructive, fully reversible and of varying difficulty.? But the bottom line is the combination of bearing choices and machining tolerances in the GM811 added up to quite a bit of backlash (and significant 74 second periodic error too).? After my modifications.... "it just works" and I get very good tracking and guiding.? A bad night for me is anything above 0.6" RMS.? On very stable nights (Detroit metro area) I have seen it in the high 0.3" RMS range.? My 240 second periodic error is almost un-measurable.? But more importantly, it does that night after night regardless of where I am pointed. Maybe a longer answer than you were looking for, but it is a complicated subject. Paul -- Paul Goelz Rochester Hills, MI USA pgoelz@... www.pgoelz.com
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Hi,
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I have been getting some complaints from PHD2 that my Dec backlash is high and I used this video to adjust the spring loaded worm gear "https://www.youtube.com/watch?v=LGmj3bEDVNM".
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It didn't make much difference and now I am about to clean and regrease the worm gear but hoping for some more advice/pointers on other things to look for or do as part of the process.
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Any guidance appreciated.
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Thanks,
Ken
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Re: New (to me) older G11
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Are you planning to "tuck-in" the steppers and use belt drive reduction to transmit stepper motion to the worms or are you going classic Losmandy style straight line with the stepper coupled directly to the worm?? Lots of options here.?
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Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
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Re: New (to me) older G11
I
had a very dusty dirt road about 20 feet from my G11.. For me, as ¡°closed¡± as
possible was preferable.. Landlord wanted to pave it, but I threw a fit about
that.. Didn¡¯t want a heat retaining piece of tarmac due west and close to my
scope.. Dust was preferable to bad seeing!
??? Ancient
history now.. City dweller and 3/4¡¯s blind..
Derek
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From: [email protected] [mailto:[email protected]] On Behalf Of John Kmetz via groups.io
Sent: Thursday, May 15, 2025 12:12
AM
To: [email protected]
Subject: Re: [Losmandy_users_io]
New (to me) older G11
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On Wed, May 14, 2025 at 01:11 PM, Derek C Breit wrote:
I much prefer thrust washer, thrust bearing, thrust washer,
anodized donut, spring washer, and finally the clutch knob.
This allows the ¡°anodized donut¡± to help keep dust and dirt out of
the thrust bearings and provides an even load on the thrust washer..
Pretty sure this was the ¡°preferred¡± method from Winslow
astronomy.. Someone knows.. or can say I am crazy..
Derek
It will probably work that way as well, Derek, maybe even better I'm
just going by how it comes from the factory. User's choice.
_____________________________________________________________________________________________________________________________________________________________________________
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: New (to me) older G11
On Wed, May 14, 2025 at 07:51 PM, Jesse Lichtenberg wrote:
<<< SNIPPED >>>
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I'm glad to hear that nothing is missing in the photos and that the spacer rings are just undersized. I may pick up a set from Losmandy or perhaps just make something myself (or be fine with what I've got). Yes the polar scope was out at the time I took that photo - it is now back in place. I will likely remove it again and make a cap for it as I don't often use polar scopes anymore. I actually replaced the lens in the polar scope of my EQ6 with something a bit more suitable and made an adapter to mount a small mono sensor. Something like a Polemaster, I suppose, just for polar alignments. I may do the same with the G11.
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Lots of good info here shared for the worm adjustments. I spoke a bit with Losmandy and while they didn't comment on the age of the mount it does seem a safe bet that it's of an older vintage. They did recommend a cleaning and relubrication. I have SuperLube on hand but will make sure it's the right stuff before I tear into things. I have to move about 800 miles away first. Hoping to start working on it in June.?
<<< SNIPPED? >>>
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If you are going to be using a computer with your mount you will have no need for a polar scope.? So you can recoup a little money by selling it especially if it is in good condition and has the small silver illuminator and current reticle.? This will more than pay for replacement polar cap and regular sized thrust bearing spacers.??
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The replacement polar scope cap is an all machined threaded alloy cap that is black anodized to match the mount.? You will not save anything by making your own and for what they charge for the right part.?
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The SuperLube multi-purpose NLG1/2 with Syncolon (Teflon) should be the synthetic oil based grease, NOT the silicone based version!??
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Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
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Re: New (to me) older G11
Lots more good information here - thank you again! I was turned to the bellows coupler as an option after reading the OnStep forums regarding other G11 installations. What I've purchased is pretty much exactly what they recommended, but I've no problem deviating from that if the system calls for it. More reading and research on my part is needed, and I'm grateful for the information and sources shared here!
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Chip Louie
charles jagow
plinthley
