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Locked
Re: GM811G dec backlash
Jim Waters
"Jim i seem to recall our conversations, and that we did think there was something up with the axis, but you did not want to send it in (? I don't know if i recall that correctly). At any rate I know you mentioned you were pleased with the G11 Dec upgrade."
I am happy with my G11G.? I can set the NINA 'Dither' value to 4 and have a DEC backlash around 2".? Sometimes its 3".? I don't recall if TVC was set to 15 for that value or 0.? When I completely disassembled my GM811G DEC I found that the outer worm bearing would wiggle in the worm bearing block.? Everything is packed away and I suspect I will have to rebuild the DEC at some point. IMHO - Grub screws are a weak link.? If anybody has backlash or even guiding issues they should check all grub screws first.? I tried Blue?Loctite on some of the DEC grub screws and that was a disaster.? The grub screws are so small it almost welds them into place.? The Loctite tends to wick to other areas.? I tried Loctite on a spur gear grub screw and it wicked to the output shaft of the servo motor gearbox.? It took forever to get that gear off. ------------------------ Jim W Phoenix, AZ. USA Losmandy G11G, NINA 2.0 Beta / ASTAP, ASI2600MC Pro, Sky-Watcher Scopes |
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Re: Understanding a titan
Thanks for all the comments:
Few questions:
2. I'm also not sure about the bearings as they are sort of 'rumbly' - video attached here: Are these sounding okay? I'm not keen to disassemble to mount further or how to replace them, but just want to check. 3. Is using SuperLube okay as a replacement for grease. It was recommended for the HEQ5 but this may be a different beast. I need something I can from the limited selection in New Zealand |
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Re: Understanding a titan
Just to assist a little....
e either axes balance, a tight worm mesh or motor settings.?? See link.?? Also a search show this pops up quite a bit.? Mostly balance worm mesh and occasional motor settings (I've noted a few Maxon users having to up their servos settings in the servos page to get better results...aka less warnings? like you are seeing).? There is nothing wrong with the Maxons...they are excellent. ?? If you do try adjustments try do one at a time to see how it goes.?? I suspect its more balance, mechanical or mesh (and or motor settings) I did note your PCB had an early mod capacitor across gnd to H bridge pin 16 (servo enable) ...but I believe this was an early mod to help Maxon motors stay still on switch on as they tended to "jump". Since it was working ok I left it.? I think Rene' said to me it superfluous as they originally (early G2s) had different servo firmware for the Maxon motors, but, nowdays they don't, the firmware is all the same for all motors. Do get back.....interested to see how it goes.?? The previous "runaway issues" were constant and caused by cables and DIN socket pins (amongst many other issues) .?? But I have a vested interest in ensuring that it (the system I repaired) works ok for you and to specs.?? If I remember you were looking to find someone who knows these mounts and could assist...sadly I know no one in Wellington.?? Driving the worm by hand (or with a tool) you can feel for tight spots or increased resistance.?? Also search for balance and Tr heavy messages in the forums and worm meshing procedures.? Lost to absorb for you.?? If you have the worm bearings out then yes, re-mesh and worm alignment with the gearbox and main gear is very important and precise.? Sadly I'm not the best mechanically inclined on these mounts as I just don't mechanically fiddle with them much....mainly just electronics. Search the "help menu" for "titan tips by bob allevo"...its a pdf.?? There are other titian assy pdfs? and also a "how to balance your mount" in the same "help menu" Do get back.....the forum is a great place for help cheers -- Brendan |
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Locked
Re: GM811G dec backlash
On 7/20/2022 6:48 PM, Brian Valente wrote:
I don't know if you want to debate this here and I'll "back off" if you prefer. But I have to respond to this one..... In a spring design, the backoff screw doesn't limit how far the worm meshes, it attenuates how hard the spring pushes.Sorry, but I have to disagree. The backoff screw does not change the spring tension at all. It merely limits how far the spring can push the worm assembly towards the ring gear. If the worm is lightly in contact with the ring gear, part of the spring tension is carried by the screw and part of it is carried by the worm against the ring gear. But that is a VERY delicate and temperature sensitive balanced condition. The backoff screw allows you to position the worm so that it either does not touch the ring gear or just BARELY touches it. In this condition, the backlash is minimal and this seems to be the way the assembly is adjusted at the factory. Trouble is that neither gear is perfect so you have high and low spots, not to mention thermal effects. In the Losmandy design, the spring is so strong that the screw is always in contact. Any irregularities in the gearing cause either no contact (more backlash) or too much contact.... without moving the assembly at all. If those irregularities are sufficient to actually move the worm assembly outward (ie., lifting the backoff screw away from the baseplate), the full spring tension is now carried by the worm against the ring gear, which can cause motor stalls and / or windup. On my mount, those irregularities are detectable in the tone of the motors but not sufficient to move the backoff screw away from the baseplate. Backlash is under control unless the temperature changes radically. But again, the worm never moves and the backoff screw is always motionless against the baseplate. >>>At least on my GM811, unless the worm is very carefully adjusted I canWhat I am saying is that if I am well polar aligned, there will be no long term DEC corrections needed. BUT, lets say the seeing is causing random 2" perturbations in the guide star position, sufficient to cause PHD2 to issue DEC corrections. And lets say (for example) that I have significant backlash. Now, lets imagine that on guide frame #n the star has moved 2" from its starting point due to seeing. PHD2 issues a correction..... but due to backlash, the scope never actually moves. Now, in guide frame #n+1, seeing has moved the star back to its starting position. PHD2 thinks its correction from frame #n successfully moved the star and reports zero backlash but in fact there was a lot of backlash and the scope never moved. My guess is that this can cause PHD2 to report inconsistent backlash numbers, and very likely under report the actual backlash if perfectly polar aligned. If not perfectly aligned, backlash is irrelevant. I'm suggesting that this phenomenon with a well polar aligned scope can mask significant backlash and cloud the issue. Perhaps we agree on the bottom line though..... unless you are actually trying to chase seeing, DEC backlash is probably less important than one might think? But it is there in some amount and not well controlled in the current SLW design. Paul -- Paul Goelz Rochester Hills, MI USA pgoelz@... www.pgoelz.com |
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Locked
Re: GM811G dec backlash
>>>
I have had my share of DEC / SLW problems with my GM811G and in several instances the backlash was greater than 60 seconds.? This occurred while Dithering.? Most of these problems were caused by grub screws coming loose, bad gear-to-worm coupler and other areas.??? Jim i seem to recall our conversations, and that we did think there was something up with the axis, but you did not want to send it in (? I don't know if i recall that correctly). At any rate I know you mentioned you were pleased with the G11 Dec upgrade. Brian On Wed, Jul 20, 2022 at 4:06 PM Jim Waters <jimwaters@...> wrote:
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Brian? Brian Valente astro portfolio? portfolio astrobin? |
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Locked
Re: GM811G dec backlash
I have had my share of DEC / SLW problems with my GM811G and in several instances the backlash was greater than 60 seconds.? This occurred while Dithering.? Most of these problems were caused by grub screws coming loose, bad gear-to-worm coupler and other areas.? Once these problems were resolved my DEC backlash was never under 3 seconds.? For me I found that locking down the DEC assemble produced better, more consistent results. I ended up upgrading my DEC so now I have a G11G (SLW on DEC only).? My DEC backlash is better with more consistent results but my backlash is still around 2 seconds.FYI EDIT - With the SLW you can't rely on PHD2 to give you an accurate backlash number. Jim ------------------------ Jim W Phoenix, AZ. USA Losmandy G11G, NINA 2.0 Beta / ASTAP, ASI2600MC Pro, Sky-Watcher Scopes |
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Re: GM811G dec backlash
Paul >>>How in the world can the "spring loaded worm assembly" accommodate gearing imperfections (ie., ride the highs and lows) if the stop screwis always in contact with the base plate? In a traditional non-spring design, it would not. This is how the older Losmandy worm mechanisms work with the backoff screw In a spring design, the backoff screw doesn't limit how far the worm meshes, it attenuates how hard the spring pushes.? >>>At least on my GM811, unless the worm is very carefully adjusted I can have significant DEC backlash.... like several seconds.? When it getsthat bad, I think the only reason it does not always show up in my guiding is that I am well polar aligned and most DEC corrections are generally just chasing random seeing artifacts, which average out to zero required correction.? And if I am NOT well polar aligned, the DEC corrections are unidirectional, masking any backlash.? Either case I think will fool PHD2 into thinking I have less DEC backlash than I really do. I don't really follow you here Paul. Looking at a guidelog would be more helpful, Unidirectional guiding won't show any backlash because there's no reversal, spring loaded or not If you are doing 'well polar aligned' guiding, and your Dec is having corrections that include reversals, it will show the backlash. I don't know how a mechanism could have backlash but not show it in guiding (fool PHD2 into thinking you have less backlash)? I guess that's where I'm not understanding.? On Wed, Jul 20, 2022 at 2:02 PM Paul Goelz <pgoelz@...> wrote: On 7/20/2022 11:17 AM, Brian Valente wrote: --
Brian? Brian Valente astro portfolio? portfolio astrobin? |
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Locked
Re: GM811G dec backlash
On 7/20/2022 11:17 AM, Brian Valente wrote:
we seem to be going around on this - the whole point of a spring-loaded worm is that it recognizes there are high and low points in the gear, and it will *fully mesh* riding those highs and lows. You may be referring to something more like "full force of the spring"?OK, I have held my tongue but I can resist no longer. I hesitate to post this but I'm curious....... How in the world can the "spring loaded worm assembly" accommodate gearing imperfections (ie., ride the highs and lows) if the stop screw is always in contact with the base plate? I seriously doubt that the stop screw EVER lifts off the base plate..... and if it ever does, the inward spring tension with the stock design and settings is sufficient to either stall the motor or cause serious stiction and wind up. Both will cause significant tracking and backlash issues. If the stop screw does not lift away from the base plate, the worm carriage does not move at all.... aside from any bearing slop. The only benefit that I can see from the SLW design as it stands right now is that it allows easy field adjustment of worm mesh. And that is actually a good thing. I can adjust it easily by ear while slewing and tweeking the stop screw. Now, IF the spring tension was much lower AND IF the worm pivot and slide were slop free (they are not) AND if the worm bearings had adjustable preload..... then the SLW might actually do what it is expected to do. At least on my GM811, unless the worm is very carefully adjusted I can have significant DEC backlash.... like several seconds. When it gets that bad, I think the only reason it does not always show up in my guiding is that I am well polar aligned and most DEC corrections are generally just chasing random seeing artifacts, which average out to zero required correction. And if I am NOT well polar aligned, the DEC corrections are unidirectional, masking any backlash. Either case I think will fool PHD2 into thinking I have less DEC backlash than I really do. Paul -- Paul Goelz Rochester Hills, MI USA pgoelz@... www.pgoelz.com |
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Re: Backspace
Problem resolved; FINALLY!? My imaging train of the SW 0.77FR - spacers - Filter Wheel - ZWO2600MC was fixed by removing one of the spacers (I believe 30mm) that came with the SW/FR and then attaching the rest of the imaging train but I added spacers after the FR to get the whole train at the required 92mm (I believe that what is required).? Took 3: 5 minute test subs last night (yes I know there are a few sat trails) but I just wanted to combine images and see how the corners looked.? Can still do some fine-tuning but happy with the results.
REALLY APPRECIATE all the help with this problem.? Looking forward to doing some more mosaics now!!! |
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Re: 492 digital drive not turn on
The problem is the aged?design of the PCB. Today today vias are integral with the traces. The 492's design uses vias that were pressed like rivets.? In time actuating the switch breaks the connection between the via's flange and the trace and develops an intermittent open circuit. I just scrape the green epoxy off the trace and resolder.? |
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Re: There's something weird about PEC in my mount
Thank you for your answer. I thought that PEMPro syncs automatically with Gemini at the beginning of data acquisition. Do you mean that I have to press the sync with worm button before data acquisition or before programming the mount?? Note that there is a problem as when I program the mount the PE is reduced but If I repeat the data acquisition with "PEC on" the next day then the PE is even greater or the same in Pk-Pk value than with "PEC off". In other words, the PEC is effective only the same night that it is acquired. And the only events from the end of a session and the beginning of the next session are that the mount is parked in CWD, Gemini is switched off, the next day switched on and cold started, and the RA clutch released to rotate the axis in the PA routine of Sharpcap.
?
Best regards,
Daniel |
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Re: There's something weird about PEC in my mount
Thank you very much for your answer. It seems that you may be right!? Last night I performed some tests and, without releasing the clutches, the PEC curves are aligned and synced. However, to be sure I will perform some other tests tonight. This time I'm gonna try to obtain 2 PEC curves in sequence without releasing the clutches and 2 more realising the clutches in between.? If the first pair of curves are aligned and the second misaligned then we will have some evidence about the cause of this issue.
I will post the results. Best regards, Daniel |
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Re: How Much Space is needed?
On Wed, Jul 20, 2022 at 03:33 AM, Chip Louie wrote:
concrete is not so easy to change the height of the pier as using a steel pier in the height of your choiceAgree with this as part of my pier is permanent and can't be changed. If I had to do again, I would have sunk some "L" bolts into a concrete base at ground level in a square pattern. That way you can change or modify your pier as needed, or alter type and height as needs progress. But the bolt spacing has to match your pier or an adapter plate that fits to a pier. ? -- _____________________________________________________________________________________________________________________________________________________________________________ Losmandy G11G2 on pier; SkyShed design roll-off observatory; ZWO ASI2600MM-P; ZWO ASI071MC; Sky-Watcher Esprit 100 ED; Celestron C925 Edge HD with 0.7XFR, William Optics Zenithstar 61 APO; PHD2, Sequence Generator Pro and PixInsight user |
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Locked
Re: GM811G dec backlash
As a followup to this discussion - and for those interested in a bit of reading - Roland at Astro-Physics did a nice writeup on spring-loaded worms and some explanation of what it means (spring-loaded worms are also on all modern AP mounts): ? On Wed, Jul 20, 2022 at 8:17 AM Brian Valente via <bvalente=[email protected]> wrote:
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Brian? Brian Valente astro portfolio? portfolio astrobin? |
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Locked
Re: GM811G dec backlash
? ? >>>?I mentioned to him that I suspected that the ring gear was not perfectly round to the extent that it could cause the problems.? He acknowledged that that was indeed a possiblity because of manufacturing imperfections. that is always the case with gears - there are always small imperfections which is why there is periodic error, etc. we seem to be going around on this - the whole point of a spring-loaded worm is that it recognizes there are high and low points in the gear, and it will *fully mesh* riding those highs and lows. You may be referring to something more like "full force of the spring"? >>
Please don't say such things, it is baseless and disrespectful. henk? I apologize if it came across that way, I wasn't?referring to your comments :)? I was only saying the behavior shown in initial PHD 'backlash measurements' are more indicative of stiction on a new spring-loaded mount, not backlash. That is all. If it were true backlash, you would see that amount in the entire guiding run ? On Tue, Jul 19, 2022 at 9:01 PM HenkSB <haling@...> wrote: On Tue, Jul 19, 2022 at 03:41 AM, Brian Valente wrote: --
Brian? Brian Valente astro portfolio? portfolio astrobin? |
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Re: How Much Space is needed?
aughtago,
Not sure I know what you mean but the Losmandy MA is about 4.5" tall from the base to the top of the MA so it doesn't add much height.? When I was describing the pier foundation advice I did not include the foundation diameter. I had an engineer look at what is needed for a mount that could carry 100 pound payload, the EQ mount and the counterweights needed for that 100 pound payload. I used 300 pounds on top of the pier and said it needs to be bombproof up to 48" tall using a steel pier with a welded round steel base resting directly on the concrete pier not elevated on the j-bolt anchors, this is important to minimize vibration. Therefore, I wanted the pier foundation top to be well finished flat and level. This pier foundation can support a pier up to 14" diameter and mount up to an AP1600 fully loaded and last at least 20 years.? ? The engineer thought a metric ton of concrete with plenty of rebar 4' deep would do the trick. So what he came up with was a 36" diameter 48" deep hole filled with a 36"x12" cylinder of concrete with another 18"x42' cylinder of concrete on top finishing 6" above grade. This is basically about a metric ton of concrete and overkill for my 300 pound top of the pier requirement. You could also reduce the diameter at ground level to the working diameter, 8"-10" but I would not go all the way up as concrete is not so easy to change the height of the pier as using a steel pier in the height of your choice.?? -- Chip Louie Chief Daydreamer Imagination Hardware? ? ?Astropheric Weather Forecast - South Pasadena, CA? |
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Re: There's something weird about PEC in my mount
Daniel,
Your curves match well enough, so I would just say offhand these curves are not synched. On the PEMPro Setup page, try using the Synch Worm Cycle button, and double check the worm period is set for your mount, e.g. 239.34 for a G11. I don't think breaking the clutch changes this curve, it has to do with the worm rotation and encoder read. I think there is a Losmandy video or instruction sheet on best practices of using PEMPro with Losmandy mounts, but I am not positive where the webpages are located at the moment. John -- _____________________________________________________________________________________________________________________________________________________________________________ Losmandy G11G2 on pier; SkyShed design roll-off observatory; ZWO ASI2600MM-P; ZWO ASI071MC; Sky-Watcher Esprit 100 ED; Celestron C925 Edge HD with 0.7XFR, William Optics Zenithstar 61 APO; PHD2, Sequence Generator Pro and PixInsight user |
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Locked
Re: GM811G dec backlash
On Tue, Jul 19, 2022 at 03:41 AM, Brian Valente wrote:
It can only be fully meshed everywhere if there are no high and low points for any OTA position.? If there are low points there will be radial play between the ring gear and the worm.? I conclude that from Scott's video.? In fact I think you explained the same. I once called with Scott about the problems that I had with my G11S.? I mentioned to him that I suspected that the ring gear was not perfectly round to the extent that it could cause the problems.? He acknowledged that that was indeed a possiblity because of manufacturing imperfections.? The riding high and low of the ring gear could easily be felt when manually turning the worm in different OTA positions.? Please don't say such things, it is baseless and disrespectful.
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Re: Understanding a titan
ok now i re-read the posts above properly...sigh!
The ARM was replaced as the HC was not communicating....this fixed that.?? The Runaways were cable issues and bad solder joints at the PCB...users know the original G2 type sockets with their cracking their "Cup pin" thru to the PCB.? I fixed the long cable and also made another longer cable ...re-soldered new pins in all socket cups, all these were tested .? Also had to mod the Ethernet for LAN jitter issues.? Andrew has maxon motors i remember holding them lovingly though one felt smother....i think i stated this and suggested this be the Ra motor...but I cannot be sure. ? They both worked ok but one was more noisy than the other.? It appears the system is moving to position (there will always be pointing errors at the start due to how users position CWD).?? I suspect there is a mechanical issue at play here,? but do adjust the motor Ra tracking Lag and Power percentage upwards a little.?? Don't go mad with these the most I've ever adjusted it around 42-48.?? Michael and others are best for this on mechanical but i'd suggest take off the motor and gearbox and turn the worm by hand.?? Some users make a tool to do this as its difficult to do so with fingers Id also suggest trying something simple first maybe just point at a star, centre it and see if it tracks!?? Maybe use Gemini ASCOM.??? I did check the ST4 port as part of testing regime and sidereal rate? was tested to be accurate within .01 of a second over 1000 motor revolutions (using an opto chopper disc on motor) .? I do these things because I've seen them fail or are slightly wrong I'm sorry to hear its giving issues...but we are here to help? Keep us posted?? That bearing sounds dodgy the heavy duty Tr is probably a balance issue -- Brendan |
Chip Louie
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