Re: Meridian Flips and NINA
On Wed, Jul 21, 2021 at 08:39 AM, <pcboreland@...> wrote:
Paul,
I do not see a files option?
Peter
You need to join the group, first. Files are not visible to unregistered users. /g/Gemini_ASCOM_Driver
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Re: Meridian Flips and NINA
On Wed, Jul 21, 2021 at 08:12 AM, <pcboreland@...> wrote:
Where do I down load the 1.0.82.0 version of the Ascom driver? I can only fine Gemini.Telescope.Net (1.0.75.0).
Version 1.0.82 is not yet officially released, but available for testing here: /g/Gemini_ASCOM_Driver/files/TestRegards, ? ? -Paul
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Re: Meridian Flips and NINA
Where do I down load the 1.0.82.0 version of the Ascom driver? I can only fine Gemini.Telescope.Net (1.0.75.0).
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Re: Runaway slew while using PHD2
On Wed, Jul 21, 2021 at 07:52 AM, alan137 wrote:
Maybe the "stop guiding when slewing" under PHD2 doesn't work because it is "too late" and gemini already got some kind of simultaneous mixed-up command.? I wonder if via ASCOM there is a way for it to tell PHD in advance to stop guiding.? I know that NINA can do it.? But it's still Gemini's fault for not even giving me a STOP button.
There's no way for the ASCOM driver to tell PHD2 to stop guiding, but I can certainly add some checks not to accept guiding command during a slew. While I'm not sure that's what caused the wild slew in your case, such a check might help prevent other unexpected behavior. Regards, ? ? ?-Paul
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Re: Meridian Flips and NINA
I becoming increasingly frustrated trying to execute a successful? meridian flip. Up until this point I thought I had a settings problem, for example setting the western goto limit value correctly. This is not the case. I now realize the flip is executed but the scope stays on the west side and the telescope ends up pointing at the ground. What is happening here and how do I fix this?
To execute a flip I have to set an alarm on my phone to get up, I then park the scope, and then slew back to the target. A lot of time is lost plus this is not good for ones health.
Peter
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Re: Runaway slew while using PHD2
Maybe the "stop guiding when slewing" under PHD2 doesn't work because it is "too late" and gemini already got some kind of simultaneous mixed-up command.? I wonder if via ASCOM there is a way for it to tell PHD in advance to stop guiding.? I know that NINA can do it.? But it's still Gemini's fault for not even giving me a STOP button.
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Re: Need advice selling my Losmandy G11 492 Digital Drive
I've bought and sold on CN , Craigslist Ebay and Facebook Marketplace.. (Not just astro gear)? Ebay seller fees are expensive (10 to 12.5%).? Although you can do a local pickup only sale on Ebay, you need to be sure the buyer gives you a QR code or 6 digit code that you use to confirm that the product was delivered/received, otherwise the buyer can claim he never picked up the product.
Craigslist is strictly cash, as is Facebook Marketplace.? I've never had a problem on CN buying or selling. You do however have to watch out for scams, but it's pretty obvious (zero posts, zero activity, strange transaction requests).?I use Paypal there unless it's local pickup because at least there's some protection.? ?I haven't used A-M because of the fees they charge both buyers and sellers.?
Because of the way most of these places work you don't really know what the final sales price may be.? All you see in these cases is the 'offered' price.? ?That makes using them for getting a feel for pricing a little difficult.
The competition is pretty steep now, and for someone looking for a precision mount, they are likely also wanting? a mount that has most of the modern bells and whistles.? The market is good though so if it doesn't sell it's probably just priced too high.? People are getting a lot more than they have historically for 'popular' used gear because of the demand.?
?
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New G11G with subpar guiding
Hi all,
I've finally gotten around to testing the performance of my G11G and everything wenty great except for some pretty erratic behavior in the RA axis diring guiding. I used all default settings, except for the recommended changes from the guiding assistant, and was able to get around .8" error in the DEC axis but almost 3" error in the RA axis. I'll attach links to the guide/debug log but I'm not sure what to look for when reading them; I was hoping someone here could comment on whether this looks like an issue to be solved in PHD2 settings/PEC training or if this is something going on in the mechanics of the mount.
Thanks in advance,
Vishal
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Re: Needle bearings and axial play, is this a significant performance problem and how difficult is it to fix?
Hi Alan,
Peter is going to list his better replacement parts.? ?(He also has found an 80:1 gearbox that is not marketed by McLennan..it comes from vendor RS Components.? )
To get to the ring gear:
On a G11 or GM8, you? 1. remove the bottom clutch knob and it's flat thrust needle bearing assembly.? (Put those parts in a plastic bag).? 2.? pull out the 1.25 inch shaft as though you were replacing the clutch disk. 3.? To remove the upper ring gear, you must back the worm threads away from the ring gear teeth. (on a GM8 drive you'd have to remove the worm to get the worm sufficiently back from the ring gear.)
4. Lift off the ring gear.? Actually, before you lift it off, you should see if you can lift it up slightly.? If you can lift the ring gear up with the worm still fully engaged, it could mean the worm center is slightly higher than the ring gear center.? If the center of the worm axis and the center of the ring gear heights were absolutely at the same level, (or the ring gear center is higher than the worm center so the worm is riding on the ring gear teeth below center of the ring gear) the ring gear should be trapped by the worm threads.? ?I hope this makes sense!? If the ring gear needs to go higher to be centered, you will need a thicker upper race washer or (as Peter discovered) a new flat needle bearing with slightly larger rollers.? McMaster-Carr sells many different thickness race washers. Peter found that a new needle bearing but same races put his ring gear at the optimal height for his DEC worm.??
5. Under the ring gear will be the flat race washers with the flat needle bearing sandwiched between those flat race washers.?? ? ?a. There will be a thin flat race, and a thicker flat race.? ? ?b. The thin race washer goes underneath (closest to the clutch knob at the other end).??
That's all...from memory.??
Once you take off the upper ring gear you will see the internal cylindrical needle bearings holding the 1.25 inch shaft in place. I was told that the needle bearings can be tapped out to replace them, using a wooden dowel on the G11, but on my GM8 axes, I can't see how to get those bearings out or to put new ones in. If someone knows, please advise how to disassemble the GM8 axis body.?
Best, Michael
How does one get to the thrust bearings?
What's the source and part number for the encoders?
What's the maximum slew rate with the 1024 encoders?
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Re: Needle bearings and axial play, is this a significant performance problem and how difficult is it to fix?
How does one get to the thrust bearings?
What's the source and part number for the encoders?
What's the maximum slew rate with the 1024 encoders?
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Re: Needle bearings and axial play, is this a significant performance problem and how difficult is it to fix?
Nice work, all!
I had a long deep discussion with Peter this afternoon...(he bought a used G11 mount that had belonged to a buddy of mine in San Jose).??
Conclusions:
1. His DEC was a problem but now fixed.? He found as the causes: the DEC thrust bearing would not rotate smoothly or freely, and: the DEC worm blocks put his worm 0.001 inch above his DEC ring gear center.? So the worm center was not at the optimal center location of the ring gear.? ?Peter solved these issues by buying a new upper thrust bearing.? He said his original races were ok but the McMaster-Carr thrust bearing he got was slightly thicker, and rolled much more smoothly, than his original thrust bearing.? The new thrust bearing was slightly higher...raising the ring gear by (he measured) 0.001 inch.? He found the smoothly rotating and now centered DEC ring gear then made his DEC axis problems go away.??
2. Peter noticed that his newly purchased HiTorque motor is different than those of years ago.? Namely: the optical encoder detector is not soldered in, as it was on the older motors.? So it is easy to replace the optical encoder detector and the optical marked disk.? Peter has tried a 1024 tick disk and detector, to replace the stock 256 tick encoder parts.? He says this gives much more accurate motor position, and works better in practice.? The digital setting for the encoder is in Gemini, so you would just change the appropriate settings (motor/gears).
I just confirmed the motor construction is easier, by taking the back off my own recently purchased HiTorqie motor.? As Peter said, the optical encoder detector is inserted into a socket.? So it is easy to remove the back detector and then a tiny set screw removes the optical marked wheel.??
All the best, Michael
Here's a pic gearbox side.
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Re: Needle bearings and axial play, is this a significant performance problem and how difficult is it to fix?
Here's a pic gearbox side.
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Re: Needle bearings and axial play, is this a significant performance problem and how difficult is it to fix?
On Mon, Jul 19, 2021 at 03:11 PM, <pcboreland@...> wrote:
The whole reason why I am testing with a rigid coupler is to ensure that the worm and motor shaft are axially aligned as much as possible. But, as you say, there is a potential problem here. If the worm and motor are not axially aligned by even a small amount something has to give, and it will be the motor. It will bob up and down relying on the spring action of the McLennan motor plate. This is a bad situation, so once the worm is set I loosen off the motor screws to make sure things are self aligned before retightening.?
I experimented with some success with rigid aluminium couplers on an original OPW design. I bored both ends and precision fitted for my DEC paying particular attention to concentricity and tolerances. So it wasn't exactly 4mm on the McLennan shaft and 1/4" on the worm shaft side. I also kept as much material and turned the OD of the coupler accordingly as to keep it as close to the worm bearing and the gearbox brass bush. I have 4x M3 SS grub screws at 90 degrees standard arrangement to secure both ends. When fitting it they're is enough play in the plate holding the gearbox on the side of the OPW and on the gearbox eyelets to secure everything aligned. so you first secure the worm then the worm shaft, the gearbox shaft, the gearbox and the gearbox plate last. Rotating by hand you can feel any hard spot. If there is one you release any pressure by losening the coupler grub screws on the same end then retighten. The McLennan has a few mm of longitudinal play so that takes care of any shaft runout. Took me a few iterations of turning alu stock to get it right as dimensions and concentricity are critical but I got one right in the end. I imaged one night with TVC set to 0 and an old version of ?PHD with DEC guiding set to auto to make sure I got N/S corrections imaging at the zenith scope pointing straight?up with camera weight hanging down. it did the job. Most importantly when the mount got very cold it was still fine. No change in behaviour.
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Re: Needle bearings and axial play, is this a significant performance problem and how difficult is it to fix?
I think if you can get to the bottom of your puzzle it will help others
know what issue to look for.??
***
Seriously??
Even an idiot like me knows the answer to this.. And even your text based
drawing shows this.. And you told me this.. in person.. three years ago.. ¡°You
can¡¯t adjust the worms without the clutches tightened¡±..
?
If
you adjust the worm to ring gear, and *then* tighten the clutches, you pull the
ring gear down.. However slight, this then moves it away from the ¡°perfect¡±
mesh you just set.. Tighten the clutches to how you would use them, then adjust
the worm..
?
Derek
?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Michael Herman
Sent: Saturday, July 17, 2021 9:09
PM
To: [email protected]
Subject: Re: [Losmandy_users_io]
Needle bearings and axial play, is this a significant performance problem and
how difficult is it to fix?
?
Peter,
Glad to read your last posting, not your "hit by lightning" obituary!?
?What a story!
You may need a lightning rod near your observatory.??
On to the question: why does your clutch force affect your worm to ring
gear spacing?? Ideally, it should have no effect, but you are not the
first to report that it does have an effect. I always wondered what's causing
this effect, as it is not observed on my systems.
So let's think it through.? Something on your system is
getting distorted by the tightening of your clutch knob. The distortion is
changing the worm to ring gear mesh.? What piece is distorting causing the
worm to tighten or loosen on the ring gear teeth???
In worm drive systems, one critical setting is the center of the worm
gear axis (center of the worm long axis) to the center of the ring gear teeth
(center plane of the ring gear.)
Like this:.? --- ((((o ---- with the (((( being the ring gear and
the o being the worm seen end on.? The center of these is supposed to be
equal height on the center level I indicated with?
Looking from the top down, the axes are composed of:
Upper part of axis ...dovetail if DEC say
Bottom of upper clutch surface
Ring gear ((((( upper surface?
? ?is the top of the lower clutch surface
Top race of the thrust bearing (thicker plate)
Rotating center of the thrust bearing
Bottom race of the thrust bearing (thin plate)
Thick mounting plate, holding the worm gear bearing blocks.
Mount axis body (thick aluminum cylinder)
From that construction it seems impossible to shift the ring gear to
worm gear height just from axial compression.?
But the ring gear is a metal disk and is being pulled from the
center.?
?Can that ring gear disk curve down in the center from the high
force, and curve up at the outer edge?? That must mean the upper flat
surface is distorting also.? Seems unlikely....but all those arts are
aluminum.? If the worm gear gets tight all the way around 360 degrees
rotation this may be what's going on.
Or else something else must be shifting.??
?I think you found you have a slight gap between the
1.25 inch shaft and the needle bearings.? If that were present, consider
another possible movement:?
We now know there can be a gap between the 1.25 inch steel shaft and
the tubular needle bearings inside the mount axis body.? It is therefore
possible that the axial force causes the ring gear to shift or?
"tilt" in the axis body.? The ring gear could tilt toward or
away from the worm.? That is, the axial force causes the 1.25 inch shaft
to go slightly non perpendicular.? As you rotate the axis around 360
degrees you would find one side would go "tight" and the area 180
degrees would go loose.? That would be the test for that effect.
If the latter is the problem, I'd ask Losmandy to replace the 1.25 inch
shaft with a larger OD shaft.? That should eliminate the gap and the
potential for tilt during clutch force changes.??
It is also a benefit to reduce clutch force as much as possible yet
maintain the grip.? I recommend you try my high friction clutch disk to
reduce clutch pressure, and reduce distortion of the mount
materials.??
Anyway, I feel that somehow your undersized 1.25 inch shaft is the root
cause of your worm to ring gear difficulties.? I think that can be
addressed by the factory.? I know you are trying to solve this by needle
bearings, but I think the alternative answer could be the shaft
replacement.??
I think if you can get to the bottom of your puzzle it will help others
know what issue to look for.??
?
I think I may have discovered something interesting regarding why it is
so difficult to both reduce and get a consistent backlash value for Dec.
First, while out in the field disassembling my mount for the umpteen time, I
had a very close call. Focused on the work at hand, I did not notice a
thunderstorm moving in over head. Once I became aware of the suituation, I
closed the observatory roof and started heading back to the house, when I felt
a strange sensation, followed by a crackly noise, and I immediately hit the
group. Almost instantaneously I heard and felt the crack of lightning. Several
minutes later fire engines arrive at my neighbors house less than 800 feet from
where I was standing. I never thought of this as a dangerous hobby?
After changing out the needle bearings, and adding a third, I noticed how stiff
the worm gear was to turn after I had tightened the clutch. When I later
measured my backlash I had actually gone from 2500ms to close to 4000ms, even
though a visual inspection of the mesh seemed good. Actually, I set the mesh
with the clutch undone, using finger feel to sense if the alignment was good
(no high-low spots) and little to no blacklash. The loading placed on thrust
bearings seem to be were the problem resides. I ordered new clutch plates and
just received new thrust bearings from McMaster- Carr. I'm concerned by the
stiffness and I think this means considerable pressure has to build up before
there is any rotational movement in the worm. This pressure (force) has the
created in the gearbox and coupler. This is both bad for the gearbox and means
a large backlash.?
I will post my findings with the new parts next week.
Peter
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Re: Price check for CG11 with Gemini 2
Thanks for the feedback and advice. I'm in no hurry - perk of being an astronomy professor is that I just get to have three setups for class instead of two until it sells. Shipping for both (this is my second G11, just the older one) was only about $200 - once from AZ to IL and the second from FL to IL. so slightly scary, but I hoped I mitigated that with the offer to meet in-person.?
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Re: Price check for CG11 with Gemini 2
Seems
good to me.. Either be patient (and edit the ad to keep it near the top), or
drop the price to a ¡°priced to move now¡± price, would be my suggestion.. .ie it
depends on how fast you ¡°need¡± to sell it..
?
There
might be some apprehension on if COVID is gonna shut things down and evaporate
peoples disposable cash.. Shipping costs might be scary, as I was able to drive
20 miles and do the transaction in person..
?
Derek
?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of gsnarayan@...
Sent: Monday, July 19, 2021 7:47
AM
To: [email protected]
Subject: [Losmandy_users_io] Price
check for CG11 with Gemini 2
?
I'd advertised an older CG11 with the Gemini 2 upgrade on and despite lots of views, there haven't been
any bites. I was wondering if this is just because of the lack of the OPWBs and
brass worms, or my price was off for some other reason.
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Re: Needle bearings and axial play, is this a significant performance problem and how difficult is it to fix?
Peter,?
Glad you were able to make a solid connection between motor and worm. McMaster is a super supplier and you can find a whole lot of specialty bearings connectors, gears, etc. I have used them many times before. I looked at those flex couplers before but couldn't find the right size to fit into the standard arrangement with the tucked motors like I have. I was a bit concerned about the low torque ratings on this type of spiral cut aluminum, and also whether they hold up at temperatures below freezing.?
I did buy a few flex couplers like these months ago:??which are similar to the Oldham couplers Losmandy uses, but haven't had the chance to test them out yet. They are supposed to be very low backlash and you can buy separate halves for the different shaft diameters.? The one draw back is that the center disc readily pulls away from the shaft caps unless the shafts are rigidly held in place, nothing to hold the assembly together other than locked position.?
Replacing the Oldham coupler must result in lowering the overall backlash of the gearing, and lessen the total guiding error as well all seek :).
JK
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Re: At some point, I may begin commenting on the G11 DEC axis...
On Sun, Jul 18, 2021 at 08:58 AM, <pcboreland@...> wrote:
You can set the step size on he brain/algorithm form. Default is 500ms.
I set the step size smaller, but it uses 500ms anyway. For TVC, I used 10, which is what I derived from the G8 axis.? I didn't change it when I upgraded to the G11, but from the backlash test, at large excursions there is almost no hysteresis lag, so this value is about right.
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Re: Needle bearings and axial play, is this a significant performance problem and how difficult is it to fix?
What I meant was that our methods determined a TVC value for the gear backlash only.? This part is generally fixed and doesn't depend of sky location, gravity, temperature, etc.? I don't have an opinion on using extra TVC to take out worm backlash too.? I encourage you to keep increasing the value until "something bad happens".
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Re: Needle bearings and axial play, is this a significant performance problem and how difficult is it to fix?
On Mon, Jul 19, 2021 at 02:19 PM, alan137 wrote:
Both our methods (laser or allen wrench)? use TVC to remove all the gear backlash BEFORE it gets to the worm.? There is additional backlash between the worm and ring gear (including ring gear eccentricity), and this is the part that varies due to all those factors mentioned.
?
Allen, I have to quibble with you here. TVC does not just remove the gear backlash (I assume you mean gearbox), it removes all the backlash including the worm "mesh" backlash. Did I understand correctly what you said? For others reading this thread, ring gear eccentricity is a valid point. I hand rotated my ring gear 360 degrees by hand winding the worm and found one small spot where I felt I had a different level of rotational resistance. I made sure this area was not within the operating area of the Dec axis. Previous to my open worm setup, I could? feel high/low pressure situation for each worm rotation. This I took as periodic-error/alignment problem. When I strapped the 1/4" aluminum bar between the bearing blocks it went away. Now this is the old worm design and the OPW does not suffer from this problem as far as I can tell. Also, if you have the old worm you may have the bearing blocks that are silver underneath. These are a different specification the the new blocks. Specifically, the round insert portion on the left hand block is under 3/8" and wobbles in the hole. This is obviously going to lead to big problems. Further, the new block are a little larger and do not fir into the old cover plate, hence why I had no choice in going to an open worm design, which prove fortuitous as I learned a lot from having access to the entire assembly while in operation. Peter
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Paul Kanevsky
Michael Herman
