It does.? When I disassembled the unit I looked at the thin bearing washer and said, that is not good, but Losmandy has been making quality mounts for a long time so it must be ok. I thought
this arrangement most likely would keep the clutch clean. But I did put the wave washer next to the nut. I am thinking I should make felt packing to help keep the open clutch clean. I still may have a small alignment problem
so if someone knows if the bearing blocks are removable please let me know or a drawing.
Chris
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Re: GM8 Guiding near meridian
Maybe related?
I find that once PHD2 loses its tracking, it doesn't even try to retrack.
I even had the weird situation that it was tracking and seemed fine, then just stopped tracking. It did that several times after I told it to track.? ( I have the "star mass" item turned off...no idea why that even matters. )?
In that last case I cleared the existing calibration, and told it to recalibrate.? That seemed to work... so watch your PHD2 screen for at least one full sub after you turn it on.? Once it loses autoguiding, you can get all kinds of star track zigzags.
Best, Michael?
On Sep 25, 2017 16:05, " cbradshaw1@... [Losmandy_users]" < Losmandy_users@...> wrote:
?
I did check for cable snags, which was my first thought, but everything seemed OK.? Balance seemed good, but I could have had some sliding in the dovetail.? I had to rebalance after I placed a 2" extender to obtain focus.
Thanks,
Charlie
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Re: GM8 Guiding near meridian
I did check for cable snags, which was my first thought, but everything seemed OK.? Balance seemed good, but I could have had some sliding in the dovetail.? I had to rebalance after I placed a 2" extender to obtain focus.
Thanks,
Charlie
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Thanks for the information. Good to hear it should perform at or better than the G11G.?
toggle quoted message
Show quoted text
From: Losmandy_users@... on behalf of chiplouie@... [Losmandy_users]
Sent: Saturday, September 23, 2017 3:39 PM
To: Losmandy_users@...
Subject: [Losmandy_users] Re: GM811G AP Questions
?
?
Hi Bill,
The GM811G is just a G11G bottom with a GM8 top. So the tracking will be just as good if not better than the G11G because the RA axis does all the work once you are on an object and the G11G base is more than capable of carrying a 60lb. payload and in
this application Losmandy has underrated the drive to fit a spot in the new mount lineup.?
Chip?
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Re: GM8 Guiding near meridian
Hi Charlie,
First, I am glad you said that your guiding up to the meridian was excellent.? That says all of your hardware and software and electronics are working perfectly. ?
As for the problem itself, I think your counterweight or dovetail balance may have not been exactly on the mark.
When you are pointing at the meridian, the scope is on its maximum lateral extent and the counterweight is at the other end.? If there is a weight imbalance between them, the RA motor and clutch must exert the highest force at that position.? When you are at CWD, there is essentially no force on the RA axis or DEC axis, as these forces are taken up by the mechanics of the bearings. ?
Secondly, check your cabling, etc for any snags...those are common issues in the dark, as the scope is moving things can snag up. ?
Third, check your clutch holding ability.? If you bump your scope does the RA or DEC axis move?? If so I'd be wary of the small 3 inch OD 1.25 inch ID clutch disks of the GM8. ? I have made far better holding clutch disks; if interested contact me.
All the best, Michael
On Mon, Sep 25, 2017 at 2:27 PM, cbradshaw1@... [Losmandy_users] <Losmandy_users@...> wrote:
?
Saturday night I started imaging, guiding with PHD2 (the guide log image has been uploaded).? For the first hour, guiding was perfect.? I then had some severe jumps, but it settled down.? Then, as it approached the meridian, I had sever swings and overshoots.? I changed exposure, aggressiveness and min motion without success.
I'm thinking my GM8 backlash is bad.? Any other suggestions?
Regards,
Charlie
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GM8 Guiding near meridian
Saturday night I started imaging, guiding with PHD2 (the guide log image has been uploaded).? For the first hour, guiding was perfect.? I then had some severe jumps, but it settled down.? Then, as it approached the meridian, I had sever swings and overshoots.? I changed exposure, aggressiveness and min motion without success.
I'm thinking my GM8 backlash is bad.? Any other suggestions?
Regards,
Charlie
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Hi Chris,
The wavy spring washer should not be located where it is constrained by its OD! As delivered Losmandy mounts place the wavy spring washers directly working on the outer bearing race. Many people, myself included, see this as an odd assembly order as this placement localizes wavy washer spring pressure on the relatively thin thrust bearing race which should never happen in this sort of assembly.? ? So the common wisdom assembly order used by many mechanically inclined folks is as follows, on the RA axis starting from the outside and moving in toward the mount: polar scope cap-clutch knob-spring washer-thick black anodized aluminum RA spacer-outer thrust bearing race-caged needle bearing-thrust bearing race-mount seat for race. The Dec axis is the same sans the polar scope cap.? ? Some thing to be aware of, I have cleaned and re-lubricated several Losmandy G11 and GM8 mounts owned by many different people from many different generations of Losmandy production. I have seen only these two variations in the assembly order and sometimes an additional thicker bearing race washer on RA and/or Dec axes. I don't know why this is or even if Losmandy supplied the mounts in this condition. I only noted the differences and assembly order and put them back as I found them with the wavy spring washer in the outer position, they seem to work fine once reassembled and tested. ? I hope this helps!
Chip
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? For those who care. My major problem with high torque was the wave-washer. It had an OD of 51.01 mm and the bore of housing is 50.80 mm. An interference that when assembled restricting
shaft rotation. This was depicted by large scrapes on the shaft. The strange thing is the scrapes were only on one side, which would indicate I may also have some of the same problems Eric had. This could not be confirmed
because a dial indicator read less than 0.0005 inches run out, which is the limit of accuracy of my setup. I ground down the OD of the washer, but, the easiest thing is just put it next to the knob. I would like to have
an assembly drawing but can¡¯t find one. Also, do the blocks that hold the shaft bearings come off? I posted an image, look in photostream or Chris Strang.Eric, thanks for the thought.
Chris
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Hi Chris,?
Hope your wife has a speedy recovery.
Eric
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Thanks Eric for the follow-up note. I will look at it when I can, my wife is very ill in the hospital and my astronomy is on the back burner. I have the precision tools and
skill to make the repairs if I can find the problem. I started this ¡°topic¡± by asking if the clutch should influence the worm torque, and the answer is no. As I remember, there was no indicators of rubbing and the worm turn
the shaft nicely with low clutch loading, but I will recheck as to your suggestion.
Chris
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Re: Does anyone know what would cause a Zig-Zag star trail in photos?
Best not to cross post between losmandy/Gemini yahoo forums. especially since the photos are on the other group forum.?? Obviously there is some worm zig zag but I'm not the best at actual operational adjustments to comment, others will...probably best on other forum.
Also best to use a signature or name at end of post for others to address you when replying, it just good etiquette.? Don't fret your not the first or last ever to do this..
regards
Brendan
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Re: Does anyone know what would cause a Zig-Zag star trail in photos?
Dragging cable?
Regards,
Charlie
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Does anyone know what would cause a Zig-Zag star trail in photos?
See photo section for 2? posted 3 min exposures, one guided using PHD and one un-guided
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Hi Chris,?
Clutch loading is the same problem I had. ?My DEC axis became stiff when the clutch was tightened. My top bearing housing was not installed straight (you can see evidence of this on my DEC Shaft).?
http://www.ericchesak.com/Galleries/Astro-Images/GM8-4/i-KD9QSXB/A
If you're still having issues, I'd encourage you to try this:
-Remove the motor and worm/bearings - the axis should rotate freely -Tighten the clutch - if the axis stiffens you likely have an alignment problem (provided the bearings are good and all surfaces are properly greased). - Also check the shaft for wear or bearing marks
I believe this to be a fairly common problem. ?Mine was out only about 4-5 thousands of an inch and it caused serious problems with a stiff axis, as the clutch was tightened. This distance is not readily visible (a couple sheets of paper thick) but can significantly affect the performance. With the housings properly aligned, it's smooth as glass.
Eric
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Thanks Eric for the note. My problem appears to be different from yours. It is/was totally related to clutch loading. With low clutch pressure they could be easily rotated
by hand, very low torque and extremely smooth. In my second post I explained my repair (luck) of the RA drive, but not the dec. With this new knowledge I will disassemble the dec. drive one more time for an interference or
incorrect assembly. By the way Paul, after the RA reassembly the RA high torque problems are gone and no¡°high load¡±reports displayed for any RA position (vertical or horizontal) or movement.
Chris
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Hi Chris,?
This sounds precisely like the problem I had with my GM8. ?It's possible one of the bearing housings is misaligned with the main bore. ?When this is the case, as the clutch is tightened, the system is pulled further out of alignment creating binding. ?I outlined some procedures to check the alignment by using feeler gauges. ?
If you pull the worm, check for binding with and without the clutch tightened. ?This is a fairly definitive test. ?I'd be happy to answer questions as you look into it.
Best,?
Eric
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Hi Bill,
The GM811G is just a G11G bottom with a GM8 top. So the tracking will be just as good if not better than the G11G because the RA axis does all the work once you are on an object and the G11G base is more than capable of carrying a 60lb. payload and in this application Losmandy has underrated the drive to fit a spot in the new mount lineup.?
Chip?
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Hello all,
Brand new to the group, and I am looking for some data on the GM811G mount. Specifically, I am looking for information on how it has been working for Astrophotography. How is the Periodic Error? How has guiding/tracking been? Any quirks I should know of,
in terms of balancing, etc? Currently I use an AP1100 GTO mount, but was looking for a lighter weight companion. The GM811G with the LW Tripod (already own the HD Tripod; my AP1100 rides on that beast) fit the bill in terms of weight, and also has a fantastic
50 lb rated AP capacity. Also helps that it is made here in the USA. :)
Any info would be great.
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Hi Chris,
I think your report makes some sense...
In the case of the high load weights, the weight of these (x sine and x cosine of the downward angle) ?are acting the same as having the DEC and RA clutches tightened.? In a way, the load is pre-loading the clutch disk.? So a high weight would cause the same behavior as tightening your clutch knobs (at least in CWD position... moving the scope around in RA and DEC would change those angles and the sine and cosine values).
Also, if the low scope+counterweight load and low clutch knob force somehow allowed the Ring Gear to ride up and therefore engage the worm off center-to-center, it would have looked (to the worm) like you had pushed the worm-to-ring gear space too close so you'd get "Lags" or "Stalled" issues. ?
Again,... I don't know what mechanically could cause the Ring gear to go off its lowest position and suggest you call Losmandy to find out why. ?
All the best and good luck,
Michael
On Sat, Sep 23, 2017 at 11:34 AM, christystrang@... [Losmandy_users] <Losmandy_users@...> wrote:
?
Thanks Michael & Paul. The mystery goes on. Last night I was trying to evaluate a homemade ¡°on-axis-guider" I made from a Meade flip mirror. With clutch pressure set
as low as I could I kept getting ¡°high drive load¡± reports (system well balanced in all three planes). I tell myself never work on a mount in the dark but I did, not because of the reports but I had conservatively set
the backlash too loose for auto guiding. I removed the motors and began adjusting RA backlash. To my SURPRISE after adjusting backlash and the clutch, the worm torque was well within limits. The only thing different from
the many previous tries is that there was a full load ( 20# scope/camera + 19# weights) on the RA axis. I had NO SUCH LUCK with dec. The RA reports were gone.
Chris
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Thanks Michael & Paul. The mystery goes on. Last night I was trying to evaluate a homemade ¡°on-axis-guider" I made from a Meade flip mirror. With clutch pressure set
as low as I could I kept getting ¡°high drive load¡± reports (system well balanced in all three planes). I tell myself never work on a mount in the dark but I did, not because of the reports but I had conservatively set
the backlash too loose for auto guiding. I removed the motors and began adjusting RA backlash. To my SURPRISE after adjusting backlash and the clutch, the worm torque was well within limits. The only thing different from
the many previous tries is that there was a full load ( 20# scope/camera + 19# weights) on the RA axis. I had NO SUCH LUCK with dec. The RA reports were gone.
Chris
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Michael Herman
Eric Chesak
John