Hi,
I have recently picked up an old used G11 with Gemini 1 and the original smooth servo motors. I understand that to upgrade the motors I would also need to upgrade the gearboxes. Is this correct?
whilst I haven¡¯t had much chance to test the mount yet, my main questions are:
1. What are the advantages of the HT motors compared to the original smooth motors?
2. Is it worth upgrading?
I do also have a GM8 with HT motors and Gemini 1. Would these be a straight swap?
Im in the UK so any ordering gets expensive with shipping and taxes so it¡¯s not something that I will definitely do.
thanks
Bryn
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Re: Relationship between needle bearing wobble and variable worm mesh and backlash
Nice work, John.
I can confirm your notes and add a few more insights, as I also took apart two different G11s today.??
One is a very recent G11 production, belonging to Vishal who lives near me.? It has tucked motors and SLW worm blocks.? It has bottom code 219554, and is from this year 2021 production.? That new unit has a black anodized aluminum ring gear.? It has the same cylindrical needle bearing pressed in the ring gear that you have described 6010-ZZC3 EMQ V2. The ring gear has a shallow indent in the top for a wavy washer, but it has no wavy washer installed.?
I also took apart an older G11, that predates tucked motors and SLW. It's marked HGM076064.? I think this means 2007 vintage. It has a nonmagnetic (stainless) steel ring gear.? It also has a bearing pressed into it.? It has no provision for a wavy washer.??
All it means is that the design and materials have changed over the years.
Neither mount shows any looseness of the 1.25 inch steel shafts.? The shaft measures ~1.255 inch OD.? Peter found his shaft was below 1.25 inch OD.? If there is a shaft looseness problem in your mount you must seek the correct fitted shaft from the factory.
I did find that the newest G11 has a slight gap between the ID of the upper thrust bearing and the OD of the centering boss.? It's not much of a gap, about 1/10th inch.? ?
In adjusting Vishal's RA spring loaded worm, we found that the back off bolt must be used.? If that bolt is not engaged, the friction between the spring loaded pivoting worm and the ring gear is quite high, even with the CRC grease in place. The spring is a very heavy one.? As Alan has mentioned, when the worm is backed off the rung gear, the heavy spring has no use at all. It only performs the task your thumb performed when you previously adjusted an OPW worm drive.? It does free up your hand.??
To adjust the SLW worm:
Remove the motor, to free up the gearbox.??
Back out the back off bolt next to the SLW spring until the axis cannot rotate.? If the axis can rotate at all, then your worm blocks have separated and these must be compressed (and I recommend you install an R4 Belleville spring to further keep the bearings under constant compression).? When the SLW spring is in force, there must be zero axis rotation, else this must be remedied first.??
Then use your left hand to turn the worm drive gear, and feel the worm friction. With the SLW spring active the friction will be high.??
Turn the back off bolt inward with an Allen wrench until the friction goes low, yet the axis hysteresis is also negligible.? When done, tighten down the bottom block bolts.? You do not want the SLW assembly to shift laterally after the worm has been set.
Done.??
Best, Michael
The back off adjustment is very sensitive. If the worm is backed off too much you get a lot of RA hysteresis.? If you don't back off enough you have too much worm friction.? So the back off bolt adjustment is very sensitive.??
The SLW worm has only got one mounting 10-32 bolt per block.? In the older OPW it used to have two mounting bolts...one on top and one in front. In the latest SLW only the top bolt is present.? The front mounting bolt was left out to make room for the SLW spring.? The older OPW had tight bolt holes bit the SLW OPW has slots for both blocks.??
So the new SLW OPW having one bolt mounting in slotted holes is more prone to getting whacked out of adjustment during transportation.? That is, if the clutches are tightened down, a torque on the axis can knock the ring gear into the worm.? The worm can then move one of the worm blocks outward and result in worm side to side gap.? ?No matter how hard you lock down the 10-32 single worm bolts, the block can slide in the slotted openings of the OPW.? You are better off leaving the clutches loose to prevent disturbance of the SLW worm assembly during transportation.
Best regards, Michael
[Edited Message Follows]
Please see pics from my RA rebuild done in November 2020, after about 3 years use. The RA shaft has the scoring Peter has mentioned, heavier on one side than the other. Also note RA assembly with RA shaft removed. In a perfectly machined mount, the ring gear spindle, and the seats for the two needle bearings seen down inside would all need to be all concentric and axially aligned with high precision. When the RA shaft is inserted, the weight will change the way the axle rides in the bearings and also the tilt of the ring gear. So two axis centered should be centered and parallel, the RA shaft axis and the ring gear axis. But when we lock down the clutch we are essentially not perfectly aligning them but are locking in whatever cone error between them found at CWD. Even as RA rotates, the end of the RA shaft will swing in a slight cone pattern, always rubbing one side of the shaft against the needle bearings, Tighter fits between needle bearing and shaft can help, but? a tighter ring gear bearing also may be a factor.
Noting the back side of the ring bearing, I see it is labeled 6010ZZ C3, a 50 mm bearing. The price of these is pretty low and I don't know if any higher grade replacement might help the cause. They seem to be pressed into the main ring gearing inside a serrated brass sleeve,? and how to knock out and press in a new one would have to be explored. And how parallel the inner bearing race to the axis rotational is unknown.??
So if both needle bearings and ring bearing are all replaced what improvement might we expect, we would have to try and see.
Please note scoring of the flat washer where the thrust washer rides, which is also asymmetric, noting a slight tilt to the thrust bearing over the base plate it rides on,? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
John
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Re: 76sec error on new OPW-11
John,
Your points well taken. It's probably too big a step to make that recommendation unless there's evidence that there is eccentricity in gear. As you point out, there can be a lot of variation in how the mount is used from fixed installation to setup for each session. From what I'm learning there are ring gears made of different materials. In my case, it's black, so probably anodized aluminum. The original worm was steel and now there's a OPW with brass.? Steel worm on an anodized ring gear? I'm not sure what the thinking was.
I would not suggest rotation of the RA ring gear as a matter of course... Any eccentricity or variation can change the PE . The recommendation for indexing is to get repeatability.? There is also an issue with slew limits which requires that the relationship between DEC axis and RA position be maintained. It's a matter of procedure to maintain CWD. If you want to use stored PEC then you need to maintain the relationship between CWD, worm gear and DEC axis orientation across the clutch.?
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Re: Relationship between needle bearing wobble and variable worm mesh and backlash
Please see pics from my RA rebuild done in November 2020, after about 3 years use. The RA shaft has the scoring Peter has mentioned, heavier on one side than the other. Also note RA assembly with RA shaft removed. In a perfectly machined mount, the ring gear spindle, and the seats for the two needle bearings seen down inside would all need to be all concentric and axially aligned with high precision. When the RA shaft is inserted, the weight will change the way the axle rides in the bearings and also the tilt of the ring gear. So two axis centered should be centered and parallel, the RA shaft axis and the ring gear axis. But when we lock down the clutch we are essentially not perfectly aligning them but are locking in whatever cone error between them found at CWD. Even as RA rotates, the end of the RA shaft will swing in a slight cone pattern, always rubbing one side of the shaft against the needle bearings, Tighter fits between needle bearing and shaft can help, but? a tighter ring gear bearing also may be a factor.
Noting the back side of the ring bearing, I see it is labeled 6010ZZ C3, a 50 mm bearing. The price of these is pretty low and I don't know if any higher grade replacement might help the cause. They seem to be pressed into the main ring gearing inside a serrated brass sleeve,? and how to knock out and press in a new one would have to be explored. And how parallel the inner bearing race to the axis rotational is unknown.??
So if both needle bearings and ring bearing are all replaced what improvement might we expect, we would have to try and see.
Please note scoring of the flat washer where the thrust washer rides, which is also asymmetric, noting a slight tilt to the thrust bearing over the base plate it rides on,? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
John
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Sky Watcher EQ6 R PRO stripdown and rebuild
Just came across this new video posted to YouTube:
The author shows how to completely tear down, clean and upgrade the SkyWatcher mount, for those who are interested and mechanically inclined or curious. The main idea in the rebuild was to change out all the bearings used by the manufacturer with upgraded replacements (sounds familiar). One item to note is that the ring gear is not exactly a gear, but is a hollow brass cylinder with a ring gear machined into the end. I suppose this design may keep the ring teeth positioned very closely perpendicular to the rotational axis, and also not allow any deviation away from the worm gear.?
All food for thought.
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Re: Relationship between needle bearing wobble and variable worm mesh and backlash
The bottom one would be from before June 1998 when the 323 area code was created.?
BTW, if you wanted a G-11 for Christmas in 1998, it was $3400, with a tripod and digital drive controller; no Gemini available. Given inflation and the various enhancements, today¡¯s prices are pretty darn good.?
toggle quoted message
Show quoted text
On Aug 4, 2021, at 1:41 AM, Michael Herman <mherman346@...> wrote:
? There is a serial number at the bottom of the RA axis.? ?? The company must have a way of deciphering that into the mfg date.??I think the first 2 digits after the initials HGM indicate the year of manufacture.??
The bottom photo shows label HGM9602012 so likely it is from 1996 .? ?That is my oldest version badged Celestron G11 ("CG11").??
The middle picture shows a "Losmandy G11"? RA labelled HGM138135 must be from 2013.
The bottom image is a GM8 RA labelled HGM076064 so I think it's from 2007.
Best, Michael
P0? I may be able to call in to get the date of manufacture of my G11 but it has a black ring gear and is a gem-1 with the last version of the hardware. Standard un-tucked motors.
I'll confirm the worm gear and bearing arrangement tomorrow. It does NOT have space for a wavy washer between the clutch plates.
Does that put it in the 2005 time frame.??
<PXL_20210312_183511508.jpg> <20190129_161132~2.jpg>
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Re: G11 Performance Enhancement Criteria - Design Improvements and Ideas to overcome Performance Limitations
The issue of "indexing" is a red herring, especially for these newer mounts.
I have scales on both my axes, so I always know the absolute position.
I think the current ring gear is hard anodized aluminum, which is harder than brass, and so won't wear out.
Even if it did, wear and tear is a part of everyday precision instruments.? This reminds me of the story of the machinst who is worried that their mill table is going to wear out in the center because that range is used all the time.? So he makes sure to spend 1/3 his time working on the left side of the table, and another third working on the right side, in the hopes that the saddle will wear in evenly.
If you really hated uneven wear, you'd slip the clutch 1/4 turn each session.
Despite the fake news propaganda that came out along with the "spring-loaded worms" (they're not), the RA axis should still be operated in a barely loose to somewhat loose condition and east bias so that only one side of the worm gear's teeth push the axis along.? This is for lowest friction.
For the DEC axis, I make sure to adjust / check the worm mesh before any long imaging session.? Assuming that the friction in the axis is low (mine is), then it will work fine for all worm meshes from barely tight to "obviously loose and rattly" given that the axis is also purposely unbalanced so that one side of the worm teeth do most of the work.? This will give the lowest backlash.
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Re: Relationship between needle bearing wobble and variable worm mesh and backlash
Tapered roller bearings don't constrain the ring gear mechanism in tilt, which is important for worm mesh alignment.
I think needle roller thrust bearing is the right one to use because it is the stiffest axially (and in tilt) and thus should change in height the least under different clutch preloads.
Thus I think the only "improvement" needed here is a tighter clearance on either the axial roller bearing for the ring mechanism, or maybe a regular radial bearing instead.
BTW, I don't have any significant problems on my new G11 DEC axis.
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Re: 76sec error on new OPW-11
On Wed, Aug 4, 2021 at 03:05 AM, Michael Ben-Yehuda wrote:
Put an index mark on the worm gear and worm so you can visualize the rotation. You may notice that the worm gear may show some smoothing or wear on some section. Since this is a new worm, you may want to rotate the worm gear so the 'used' side is away from the worm. This will give your 2 fresh unworn surfaces to work with and avoids any uneven wear on the worm gear from the stainless steel worm.?
Michael Ben-Yahuda, Respectfully, I now believe your assertions that we only use 50% of RA ring gear is not correct. This would only be the case if we never ever loosened the clutch to change the scope position. For instance if you were at zenith the ring would be about 90 degrees off CWD. And then if you had one of the cross-app communications errors, or some kind of power failure, you might have to break the clutch and rotate the telescope 90 degrees back to CWD, but the ring gear stays where it was. If you do a Cold Start (necessary if you have lost orientation) from CWD, the ring is still 90 degrees from the old CWD, but the Gemini now is starting from the new ring CWD rotation. If this happens twice in a row, the ring is now 180 degrees from the original CWD gear position. Or in other words once you break the clutch and do a CWD Cold Start you could be at any random point on the ring gear. There can be no good unworn side, or bad worn-down side, to switch back and forth from. Making this recommendation as a means to better guiding may be misleading. Regards, John K.
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Re: Relationship between needle bearing wobble and variable worm mesh and backlash
I am not sure why they used needle bearings in the RA and DEC axes.? Tapered roller bears are really the bearing of choice in this application.? The taper roller bearings combine the function of the thrust bearing and the needle bearing in one, simplifying the design. Pre-loading of the bearings will center both ends of the shaft and take on tremendous axial and radial loads.? Two bearings and you are done.? They are on your car axles and take thousands of pounds of live load and hundreds of RPM.? ?You also don't need a lot of preload.? Even axially capable bearings would be a good alternate (they look like regular ball bearings but the races are purposefully machined to accept a large axial load, again combining a thrust and radial bearing).? Unfortunately, they are all more expensive.??
Regarding the clutches, I agree, putting more pressure on the clutch bearing surfaces invariably puts more pressure on the roller bearings.? Not that the pressure scares me, I just think the necessary slop between the shaft and the needle bearings, and combined functions, makes it difficult to fine tune the mount to the next level.??
I own a G11, well over 20 years old.? Some of my best guiding is around 1" RMS using a 400mm guide scope and a ZWO120.? The graph is ugly (up to 4" peaks) compared to others that have been posted.? I am not sure where to start to fix this.? Currently I am performing the Onstep conversion and I will be rotating the drive to the top to clear the altitude adj knob and I am also spring loading the worm.
Bob
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Re: 76sec error on new OPW-11
Peter,
That's the right side journal that moves to adjust the backlash.
I thought it was funny that it wouldn't be anodized but the cut is definitely not right.
I purchased the OPW as a standalone.
I already purchased the brass worm.
This is on a 2006 (?) G-11 with straight in motors.
I was in the machinist trade over 30 years and this looks like it overlooked somehow during QA.
If I don't hear back from Brian I'll email Tanya tomorrow and show her the picture.
Jim P
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Re: 76sec error on new OPW-11
Jim,
That's not right. It looks all chewed up. They are smooth and black on the bottom. The left hand one has no movement in it's hole. The right hand one can move a little in it's hole. They ought to replace these, or better yet take a look at the entire worm assembly, as there could be other manufacturing issues. What about the hole in the plate?
Peter
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Re: 76sec error on new OPW-11
Brian,
Here's the logs from the other night.
Last night something happened with my NINA sequence and it's all screwed up.
There's also a picture of one of the bearing blocks that came with the OPW from your shop.
It looks like something shifted during the cut and there is a step on the journal that rides in the base plate.
In your opinion, do you think this could lead to problems?
The way it is now, only about half of the journal is in contact with the base at any one time.
Jim P
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Re: 76sec error on new OPW-11
On Wed, Aug 4, 2021 at 09:41 AM, Keith wrote:
Peter:
- The left arrangement in the photo does nothing as it follows the shape of the bearing itself and there is no spring force at all (I noticed this when I first tried the washer as well)
- I really don't think your 80s error is bearing related, and is probably from the McLennan gearbox.? When I used to have the bearing error, it was clearly 76s and not 80s.
- FWIW, I asked someone at Boca Bearings if they thought ceramic bearings would be any better for this application, and they didn't really think so (but of course one can always try)
Keith
Keith, Thanks for this input. You could be entirely right about the 80s error. I too have speculated about this and the McLennan gearboxes. Although its pretty constant in magnitude between the 25:1 and 125:1 models. There are reports of the 76s error moving to 80s with the OPW drive, but there are? reports of people a new mount and OPW with a sizable 76s error. Interestingly I do not have this error. I'm moving in an entirely different direction going with onstep and using servos with high resolution optical encoders to direct drive the worm. No more gears. Of coarse when this is built I will know one way or the other where this 80s error originates. Peter
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Re: 76sec error on new OPW-11
Peter:
- The left arrangement in the photo does nothing as it follows the shape of the bearing itself and there is no spring force at all (I noticed this when I first tried the washer as well)
- I really don't think your 80s error is bearing related, and is probably from the McLennan gearbox.? When I used to have the bearing error, it was clearly 76s and not 80s.
- FWIW, I asked someone at Boca Bearings if they thought ceramic bearings would be any better for this application, and they didn't really think so (but of course one can always try)
Keith
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Re: 76sec error on new OPW-11
Chip,
Just to be clear, the arrangement on the left places pressure directly on the ball race as shown in the drawing, while the arrangement on the right place pressure on the outer shell? You are correct I did follow Michaels drawing detail on this.?
Peter
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Re: G11 Performance Enhancement Criteria - Design Improvements and Ideas to overcome Performance Limitations
Michael B-Y has tallied quite a list of design concerns.??
Comments and known solutions:
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Clutch slippage:
The slippery clutch problem (losing index position relative to motor tick position, and slippage caused by oil contamination of the disk surface) can be solved easily by replacing the slippery disks with a high friction seal type.? ( I do make high friction clutch disks for these mounts. )?
There is a wavy heavy washer in the back of the axis, under the clutch knob, that "preloads" the thrust bearings and the clutch disk.?? ? ?a) on RA this is a static force (from the wavy spring and the entire weight of the scope and counterweights x sine of the polar elevation angle) preloading the axis ? ?b) on DEC this is a variable force, because the weight goes from 100% to 0% as the RA and DEC angles change.? Pointing to zenith gives 100% weight on the clutch and if the CW bar is horizontal the weight is 0%.? If your scope is weightless (say a short 80mm doublet) it won't matter.? If your scope is heavy (12 inch Newtonian) the effect is dramatic. This is why the wide variety of our amateur users have a wide variety of issues...or no issues at all.?
_____
The needle bearing problems that have been listed affect some mounts and not others.? It was recently reported by Mark Crossley here in email, but not on his website, for his mount of decades ago.? On my own 5 RA and 4 DEC axes, I cannot feel this problem. All shafts are snug in the needle bearings.? My mounts span the production years 1996 to 2016.? It was not felt this week in Vishal's mount of 2021.? But it was also discovered by Peter in his mount... predates tucked motors.??
So this problem is rare but has occurred. This is a production control/ quality control issue and the solution is to have the factory fix it.? The shafts must fit snugly into the cylindrical needle bearings.? If the factory undercut the 1.25 inch shafts, or the bearings have slightly smaller needle rollers, or the outer enclosure race sleeve is larger, then the axis will have excessive play.? That's why the mounts have to be hand fitted at the factory.?
Peter planned to solve his axial play by getting needle bearings with larger roller needles, but this is then a problem for getting the bearing into the mount body, and getting the shaft into the bearing.? Peter did find his cylindrical needle bearings could be popped out on his mount with finger force, but I could not remove my bearings even with hammer blows and a wood dowel.? ?So these needle bearings certainly vary as does everything else mechanical. Peter also is thinking about plating the shafts to increase their OD.? This is more work and then you must ensure perfect plating adhesion.??
I feel that the only viable and correct solution is at the factory. The shafts have to be fitted by the factory and re-worked with the proper diameter shaft.? Or different bearings ... every mechanical thing that is made has an allowed tolerance.? The burden of fitting the parts together properly falls on the mount maker.? They need a quality control checklist and staff to follow it.? ?Chip has told me that the rare cases he has heard of this problem were fixed at the factory, which is nice as he lives near that location.? But these problems should not ever have left the factory in the first place.??
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Worm to ring gear spacing
This is a research paper of its own, but the solutions are: ? 1. Get better quality RA worm bearings. ? ? ? ? Factory bearings are usually nice and smooth rotation.? Unknown quality rating (ABEC bearing quality rating system exists...and there are cheaters everywhere on earth.) ? ? ? ?Owners can buy ABEC-7 quality rated for about $11 each from several suppliers.?? ? ? ? Hugo Garnica extolls these:
G11 Ceramic Bearings for better PE
From Hugo Garnica in Tehachapi California:
??
These are (expensive?) all ceramic bearings and he says they got rid of all his bearing PE problems.? Not cheap and I don't know how they would fit in all bearing blocks, or be able to preload them.? You'd have to likely enlarge the bearing block cylinder.? Anyway I have not yet tried these out.
2. Get rid of the worm axial shift issue. This is only done by preloading the wirm with a spring.? Industry makes precise springs for each bearing type.? The G11 and GM8 use an R4 size Belleville spring.??
3. Align the entire bearing to the worm axis.? This requires a perfect cylinder hole inside the worm block.? Some slight automatic realignment of the bearing can be obtained by polishing down the bearing OD (if it's a metal bearing, not ceramic!) and using a Belleville spring.? The reduced bearing OD can then slightly adjust it's OD axis to follow the worm 1/4 inch shaft.??
But that can only work well if the worm is not pressed firmly into the ring gear.? Why?? If the worm is pressed tightly into the ring gear, the outward force must push the bearing into the wall of the bearing block.? If the bearing block hole is not perfectly aligned with the wirm axis, the bearing must follow the block axus, not the worm axis.? This is why the worm must maintain a slight gap to the ring gear..unless you have perfect worm blocks and an OPW to hold the blocks outer surfaces parallel.
Solution:? Leave a slight worm gap, and hang a weighted cord (a few pounds is usually adequate) around the RA axis with the weight hanging (always) to the East.? This gently preloads the ring gear to the worm gear.? Hanging to the East eliminates a possible "chatter" of the ring gear as friction from the worm gear can vibrate the ring gear.? And use a low friction high pressure capable grease there between the worm and ring gear.??
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Other stuff:
I find the AZ and Elevation locking knobs go too slack when loosened to adjust polar alignment.? So I preload those bolts with 3/8 Belleville spring washers.? Then you get an easily adjustable pressure on these locking points.? Be sure your AZ and Elevation don't wiggle when you are trying to image.
____
I'll not go further...here.
I hope I've made helpful comments.? The argument for buying a domestic mount has been that the factory has always supported it's customers with solutions if they discover a manufacturing error. They must continue this tradition. On a new mount the answers must come from the factory, or else replace it.???I think the answers must come from the factory for severe mechanical problems like the 1.25 inch needle bearings fit.? They have the parts to make them fit.??
Have fun and happy imaging!
Michael Herman
I have a hard time believing that there is a 43 minute periodic error
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Re: Wanted High Torque Motor and Gemini 1 or 2 controller.
Hi Rodd,
I do have a Gemini 1 that I believe is in good condition.? I upgraded my Titan to Gemini 2 last year.? No idea of fair value or shipping costs from USA.
Michael
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What are expected RMS arc second guiding numbers? new G11G users are getting?? -and at what focal lengths.
This is for the new G11G with the spring loaded worm.
Thanks for the input everyone!
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Re: 76sec error on new OPW-11
On Wed, Aug 4, 2021 at 08:15 AM, Chip Louie wrote:
This drawing has an error probably because you saw Michael Herman's drawing and don't understand how this is supposed to work.?
The bearing's outer shell is the part that is pressed by the spring disc NOT the inner race which carries the worm!
By orienting the spring disc to contact the inner bearing shell or possibly worse the bearing dist cover you are creating pressure and drag where it should not be and potentially leaving the problem of unloaded bearing balls in the bearing unchanged.?
This drawing needs to be replaced with the correct orientation not just an edited text.?
Chip, OK, since I have gotten several push backs on this, and since I have quite a few guide logs that show a consistence error, I will reverse the washer and report back. I truly hope you guys are right! Peter
Please believe me on this point as was adding Belleville spring discs to HEQ5 and EQ6 mounts before the GOTO computers were standard to solve this issue and the impact of thermal changes. Bearing induced PE is not unique to Losmandy mounts but it is more obvious because there is no threaded cap to retain the bearings which can e used to preload the worm bearings.?
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Michael Herman