Re: Sky Watcher EQ6 R PRO stripdown and rebuild
The machining of the worms at the end of the clutch cylinder was used on the '80s Vixen SP and is still copied to day on the SW EQ-5 and the ES EXOS-2. The general bad machining?of the cylinder to the shaft it rides on makes for very stiff?action when the clutches are released. This makes balancing the payload impossible. A small industry has developed to "tune" these mounts.?
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Re: Relationship between needle bearing wobble and variable worm mesh and backlash
Here are photos of the two versions of G11 worm wheel aka ring gear.? I forgot to add those to the last message.??
One is black and seems smooth anodized aluminum.?
The other is older and appears to be a form of stainless steel.??
The clutch surface of the steel version is rougher than the smooth black aluminum version.
Best, Michael
On Thu, Aug 5, 2021, 11:53 AM Michael Herman via <mherman346= [email protected]> wrote: Nice analysis, Bob.
The G11 ring gear used to be (sometimes during it's production) steel.? It is not black anodized anywhere on its surface...here is a photo.? Later and current production is black anodized.??
If the worklm she'll ( aka ring gear) were steel, I think your idea of using a wider thrust bearing could work.? But for the aluminum variety of G11 worm wheel (I've been calling it a ring gear,...if that's incorrect I apologize) then high clutching force in the center using the steel 1.25 inch shaft could warp it into a cup shape.??
The clutch disk itself also used to grab all through its area from the 1.25 inch diameter center to the 4.25 inch worm wheel OD diameter.? (Not always: the earliest CG11 used a smaller 3.5 inch diameter RA clutch. )?
Nowadays, due to the cutout for the wavy washer, the central area of the clutch top is not contacting the clutch disk except in 3 small radial areas.? Or not at all if there is no wavy washer in place.??
So then you have the new clutch with the central cutout for the wavy washer forces on top at the outside of the worm wheel, and you have the thrust bearing needles radially from the middle from like 3 inch diameter to like 3.7 inch diameter.? Now considering stresses under a string cluch knob force, I can forsee how it could warp the aluminum ring gear... cupping it downward.?? And maybe that could affect how the worm feels the worm wheel teeth if they were quite close.? That is, I'm still trying to understand the report by a few owners that clutch knob force affects the mesh of their worm to worm wheel...what could cause such an effect on the newest mounts.??
The older version steel worm wheel with no wavy washer indent relieves this warpage concern, but the rest of the construction is still mainly aluminum.? Every solid has elastic properties.??
As Dirty Harry once said in a movie, "Man's gotta know his limitations."
Even worms need to know this.
I think it is best to use a high friction clutch pad and keep the axial forces below extreme levels, yet still grip the clutch firmly.??
Have fun imaging!
All the best, Michael
Alan137,
The tilt of the worm wheel (it's not a ring gear) is another issue.? Certainly the worm wheel needs to be elevated above the plate upon which it resides.? There is a large radial bearing and also a thrust bearing, which covers a small portion of the worm wheel diameter, but the shaft clutch disc puts pressure on the entire face of the worm wheel.? If we assume the worm wheel does not flex, then the current bearing arrangement for the worm wheel should be sufficient.? If the worm wheel does show flexure, then perhaps a larger diameter thrust bearing is in order. If meshing of the worm and worm wheel is the concern, then the bearings should be out by the worm wheel teeth for maximum support, not near the center.? In deference to Scott & Losmandy, we are arm chair quarterbacks, the G11 is still a beautiful machine.
The tilt issue still does not change the fact that a tapered bearing for the RA and Dec shafts would minimize shaft tilt, and installation clearances would not be an issue.? Note that tapered bearings use press fit races, both on the outer and inner.? Your wheel hub on your car is an example; to change them the mechanic has to tap them out or use an arbor press.? I could see a fit where a mild tap on the end of the shaft with a dead blow hammer would coax the race off the shaft.?
Maybe using the shaft as one of the bearing surfaces of the needle bearing was a mistake, or more likely a compromise.? ?If you want no slop, you have to captivate the bearing somewhere, you can't just put it together and hope for the best.? Getting better quality bearings is only a partial solution, the design has to be there as well.
Looking at the design, the Teflon pad is doing double duty, it slips and it grips.? It has to provide a stiction free surface to easily nudge the scope, yet in the next moment, we apply tremendous pressure and expect it to NOT slip.? As was mentioned, this is a large range of preload on those thrust bearings.? Instead the Teflon pad being called upon to grip, use a ring in place of the setting circle ring.? Use a full circumference belt that would grip the worm wheel, and then that belt would be attached to the RA axis disc (the disc holding the Teflon pad).? A throw of a lever would apply full grip, or no grip (like a large diameter hose clamp, but with a lever instead of a lead screw).? This would separate the preloading of the bearings from the Telfon clutch performance. You could even use the degree ring itself, cut it in one place, and attach a lever to reduce the circumference.? Then attach it to the RA or Dec axis disc just above it.? Yet, I still see problems with this approach, tightening the ring might put radial pressure on the worm wheel.? Not finished with my coffee yet.
Bob
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Re: Relationship between needle bearing wobble and variable worm mesh and backlash
Nice analysis, Bob.
The G11 ring gear used to be (sometimes during it's production) steel.? It is not black anodized anywhere on its surface...here is a photo.? Later and current production is black anodized.??
If the worklm she'll ( aka ring gear) were steel, I think your idea of using a wider thrust bearing could work.? But for the aluminum variety of G11 worm wheel (I've been calling it a ring gear,...if that's incorrect I apologize) then high clutching force in the center using the steel 1.25 inch shaft could warp it into a cup shape.??
The clutch disk itself also used to grab all through its area from the 1.25 inch diameter center to the 4.25 inch worm wheel OD diameter.? (Not always: the earliest CG11 used a smaller 3.5 inch diameter RA clutch. )?
Nowadays, due to the cutout for the wavy washer, the central area of the clutch top is not contacting the clutch disk except in 3 small radial areas.? Or not at all if there is no wavy washer in place.??
So then you have the new clutch with the central cutout for the wavy washer forces on top at the outside of the worm wheel, and you have the thrust bearing needles radially from the middle from like 3 inch diameter to like 3.7 inch diameter.? Now considering stresses under a string cluch knob force, I can forsee how it could warp the aluminum ring gear... cupping it downward.?? And maybe that could affect how the worm feels the worm wheel teeth if they were quite close.? That is, I'm still trying to understand the report by a few owners that clutch knob force affects the mesh of their worm to worm wheel...what could cause such an effect on the newest mounts.??
The older version steel worm wheel with no wavy washer indent relieves this warpage concern, but the rest of the construction is still mainly aluminum.? Every solid has elastic properties.??
As Dirty Harry once said in a movie, "Man's gotta know his limitations."
Even worms need to know this.
I think it is best to use a high friction clutch pad and keep the axial forces below extreme levels, yet still grip the clutch firmly.??
Have fun imaging!
All the best, Michael
Alan137,
The tilt of the worm wheel (it's not a ring gear) is another issue.? Certainly the worm wheel needs to be elevated above the plate upon which it resides.? There is a large radial bearing and also a thrust bearing, which covers a small portion of the worm wheel diameter, but the shaft clutch disc puts pressure on the entire face of the worm wheel.? If we assume the worm wheel does not flex, then the current bearing arrangement for the worm wheel should be sufficient.? If the worm wheel does show flexure, then perhaps a larger diameter thrust bearing is in order. If meshing of the worm and worm wheel is the concern, then the bearings should be out by the worm wheel teeth for maximum support, not near the center.? In deference to Scott & Losmandy, we are arm chair quarterbacks, the G11 is still a beautiful machine.
The tilt issue still does not change the fact that a tapered bearing for the RA and Dec shafts would minimize shaft tilt, and installation clearances would not be an issue.? Note that tapered bearings use press fit races, both on the outer and inner.? Your wheel hub on your car is an example; to change them the mechanic has to tap them out or use an arbor press.? I could see a fit where a mild tap on the end of the shaft with a dead blow hammer would coax the race off the shaft.?
Maybe using the shaft as one of the bearing surfaces of the needle bearing was a mistake, or more likely a compromise.? ?If you want no slop, you have to captivate the bearing somewhere, you can't just put it together and hope for the best.? Getting better quality bearings is only a partial solution, the design has to be there as well.
Looking at the design, the Teflon pad is doing double duty, it slips and it grips.? It has to provide a stiction free surface to easily nudge the scope, yet in the next moment, we apply tremendous pressure and expect it to NOT slip.? As was mentioned, this is a large range of preload on those thrust bearings.? Instead the Teflon pad being called upon to grip, use a ring in place of the setting circle ring.? Use a full circumference belt that would grip the worm wheel, and then that belt would be attached to the RA axis disc (the disc holding the Teflon pad).? A throw of a lever would apply full grip, or no grip (like a large diameter hose clamp, but with a lever instead of a lead screw).? This would separate the preloading of the bearings from the Telfon clutch performance. You could even use the degree ring itself, cut it in one place, and attach a lever to reduce the circumference.? Then attach it to the RA or Dec axis disc just above it.? Yet, I still see problems with this approach, tightening the ring might put radial pressure on the worm wheel.? Not finished with my coffee yet.
Bob
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Re: Relationship between needle bearing wobble and variable worm mesh and backlash
Just a small detail - the clutch pads are not Teflon!? They¡¯d be useless for a clutch if they were. ? Not sure exactly what plastic they are but you can be sure they¡¯re not Teflon. ? David ?
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From: [email protected] <[email protected]> On Behalf Of Robert Benward via groups.io
Sent: 05 August 2021 19:08
To: [email protected]
Subject: Re: [Losmandy_users_io] Relationship between needle bearing wobble and variable worm mesh and backlash? Alan137,
The tilt of the worm wheel (it's not a ring gear) is another issue.? Certainly the worm wheel needs to be elevated above the plate upon which it resides.? There is a large radial bearing and also a thrust bearing, which covers a small portion of the worm wheel diameter, but the shaft clutch disc puts pressure on the entire face of the worm wheel.? If we assume the worm wheel does not flex, then the current bearing arrangement for the worm wheel should be sufficient.? If the worm wheel does show flexure, then perhaps a larger diameter thrust bearing is in order. If meshing of the worm and worm wheel is the concern, then the bearings should be out by the worm wheel teeth for maximum support, not near the center.? In deference to Scott & Losmandy, we are arm chair quarterbacks, the G11 is still a beautiful machine.
The tilt issue still does not change the fact that a tapered bearing for the RA and Dec shafts would minimize shaft tilt, and installation clearances would not be an issue.? Note that tapered bearings use press fit races, both on the outer and inner.? Your wheel hub on your car is an example; to change them the mechanic has to tap them out or use an arbor press.? I could see a fit where a mild tap on the end of the shaft with a dead blow hammer would coax the race off the shaft.?
Maybe using the shaft as one of the bearing surfaces of the needle bearing was a mistake, or more likely a compromise.? ?If you want no slop, you have to captivate the bearing somewhere, you can't just put it together and hope for the best.? Getting better quality bearings is only a partial solution, the design has to be there as well.
Looking at the design, the Teflon pad is doing double duty, it slips and it grips.? It has to provide a stiction free surface to easily nudge the scope, yet in the next moment, we apply tremendous pressure and expect it to NOT slip.? As was mentioned, this is a large range of preload on those thrust bearings.? Instead the Teflon pad being called upon to grip, use a ring in place of the setting circle ring.? Use a full circumference belt that would grip the worm wheel, and then that belt would be attached to the RA axis disc (the disc holding the Teflon pad).? A throw of a lever would apply full grip, or no grip (like a large diameter hose clamp, but with a lever instead of a lead screw).? This would separate the preloading of the bearings from the Telfon clutch performance. You could even use the degree ring itself, cut it in one place, and attach a lever to reduce the circumference.? Then attach it to the RA or Dec axis disc just above it.? Yet, I still see problems with this approach, tightening the ring might put radial pressure on the worm wheel.? Not finished with my coffee yet.
Bob
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Re: Relationship between needle bearing wobble and variable worm mesh and backlash
Alan137,
The tilt of the worm wheel (it's not a ring gear) is another issue.? Certainly the worm wheel needs to be elevated above the plate upon which it resides.? There is a large radial bearing and also a thrust bearing, which covers a small portion of the worm wheel diameter, but the shaft clutch disc puts pressure on the entire face of the worm wheel.? If we assume the worm wheel does not flex, then the current bearing arrangement for the worm wheel should be sufficient.? If the worm wheel does show flexure, then perhaps a larger diameter thrust bearing is in order. If meshing of the worm and worm wheel is the concern, then the bearings should be out by the worm wheel teeth for maximum support, not near the center.? In deference to Scott & Losmandy, we are arm chair quarterbacks, the G11 is still a beautiful machine.
The tilt issue still does not change the fact that a tapered bearing for the RA and Dec shafts would minimize shaft tilt, and installation clearances would not be an issue.? Note that tapered bearings use press fit races, both on the outer and inner.? Your wheel hub on your car is an example; to change them the mechanic has to tap them out or use an arbor press.? I could see a fit where a mild tap on the end of the shaft with a dead blow hammer would coax the race off the shaft.?
Maybe using the shaft as one of the bearing surfaces of the needle bearing was a mistake, or more likely a compromise.? ?If you want no slop, you have to captivate the bearing somewhere, you can't just put it together and hope for the best.? Getting better quality bearings is only a partial solution, the design has to be there as well.
Looking at the design, the Teflon pad is doing double duty, it slips and it grips.? It has to provide a stiction free surface to easily nudge the scope, yet in the next moment, we apply tremendous pressure and expect it to NOT slip.? As was mentioned, this is a large range of preload on those thrust bearings.? Instead the Teflon pad being called upon to grip, use a ring in place of the setting circle ring.? Use a full circumference belt that would grip the worm wheel, and then that belt would be attached to the RA axis disc (the disc holding the Teflon pad).? A throw of a lever would apply full grip, or no grip (like a large diameter hose clamp, but with a lever instead of a lead screw).? This would separate the preloading of the bearings from the Telfon clutch performance. You could even use the degree ring itself, cut it in one place, and attach a lever to reduce the circumference.? Then attach it to the RA or Dec axis disc just above it.? Yet, I still see problems with this approach, tightening the ring might put radial pressure on the worm wheel.? Not finished with my coffee yet.
Bob
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No need to change the gearbox for either the Maxxon or HT motors. ? I¡¯ll leave others to comment on whether it¡¯s worth upgrading as I¡¯m still using the ¡°original¡± motors. ? David ?
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From: [email protected] <[email protected]> On Behalf Of Bryn Evans via groups.io
Sent: 05 August 2021 11:43
To: [email protected]
Subject: [Losmandy_users_io] Worthu to HT motors? ? [Edited Message Follows] 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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Sorry?
yes ok to swap. Put a HT on each RA only
Winning.?
--
Brendan
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Bryn
you don¡¯t need to change the gearboxes. ?The newer motors just produce more torque at same current the older motors draw. ?Thus are more efficient ?and ?less axes stalls?
Might be nice to get one for your RA as this does the most work. ?Motors fo last for a long time but the old versions are getting long in the tooth
if you have Maxon motors ¡.stay with the maxon. ? They are brilliant?
--
Brendan
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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.?
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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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Michael Herman
David C. Partridge