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Re: New subscription to Losmandy user group
Thanks all!, |
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Re: What result I can get with the current OPW in my old G11?
When you replace the worms you might want to consider running the worm gear 180 degrees to CWU position, then releasing the clutch and moving your Dec axis back to CWD.? This puts you in the "unworn" side of the worm gear when installing the new precision worm and OPW.? Might as well use the "new side" of the worm gear with the new worm. Over time if you've run motors with the clutch free, there isn't really a completely new worm gear side, but it will still have much less wear.? Similar action can be taken for DEC.? ? |
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Re: Relationship between needle bearing wobble and variable worm mesh and backlash
Under normal operation if the clutch is never released and the relationship between the worm gear and CWD is maintained all the wear on the worm gear occurs on only one side over some portion less than 180 degrees. Over time the condition you report of a 'tight worm' at 180 degrees from CWD? is expected. Normally I would expect no wear on the ring gear anywhere around 180 degrees from what is normally your CWD position. Long period PE and PEC is impacted by absolute ring gear position because of the impact on worm mesh. This is somewhat mitigated by spring loading the worm so it can float in and out to maintain mesh and consistent worm/worm gear pressure.? ?Any shift in the DEC axis relationship to the worm gear by relaxation of the RA clutch will throw off your PEC because the absolute position of the worm gear has changed. Even with spring loading, there will be slight differences. The problem with the clutched design is that there is no index of the DEC axis (CWD) to the RA ring gear absolute position. .? This destroys the 'sync' for guiding, PEC and backlash along with your worm mesh adjustment. So, how can we set a consistent 'start position' for the mount that maintains the relationship??? I suggest the following: Scribe the worm gear along it's top surface where it can be seen with the worm cover off. For some worm gear types where the cover cannot be removed a notched window may need to created to see this mark. The mark needs to be able to be matched to a specific mark on the mount housing at perhaps an existing landmark on he housing (window edge?) .? Creae an index mark to match the DEC axis position to a known orientation to the mount RA housing. You might need to attach and extend a pointer.?? Although less critical for DEC, a similar situation exists because of the relationship between worm mesh and backlash.? A similar solution can be applied. ? |
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Re: Losmandy GM-8: Anomalous wearing of R.A. shaft
It can be that the RA axis shaft has just lapped in to true roundness. I notice that some of this is in the area of the thrust bearing as well. Is it smooth or is it scored?? I'd only be concerned if it feels like there is scoring. Check the thrust bearings Inside diameter surfaces. to make sure they are smooth and the shaft is lubricated where those bearings are.? Some of the tolerances are very tight.? I've noticed some similar discoloration on my G11 RA axis shaft and my mount is a bit newer but still Gemini 1 era.? It's good to to service those bearings as lubricants age and if it hasn't been done in 11 years it's overdue. Since the clutch friction plate was contaminated, obviously there has been lubricant migration.? There are some recent threads on bearing replacement and PE improvement that you might want to review since you are servicing the mount.? Good luck, ? |
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Re: Losmandy GM-8: Anomalous wearing of R.A. shaft
Sandro, No idea exactly what caused your steel shaft discoloration, but it cannot be anodization.? The shaft is steel. It may have been hardened and appears darker color.? It seems simply polished where weight on would have been applied on one side of the top and the torque would have been applied on the opposite side of the bottom.?? The needle bearings are prone to "gumming up" meaning that the roller needles become stuck from oxidation or dried lubrication.? Try soaking the bearings by spraying in a light oil like WD-40. If the needles will roll freely then they are ok.? Yes the plastic clutch disks can slip if they become oily.? Cleaning the clutch surfaces helps get their grip back...for awhile.? It is better to replace the slippery clutch disks with a higher friction? clutch material that will prevent slippage and not allow oils on to the disk surfaces.? I supply those disks domestically to US customers.? David Partridge can supply European owners.? ? Shipping to other destinations is costly and error-prone.?? Best of luck, Michael On Sat, Jul 31, 2021, 8:43 PM <sandro.barbanera@...> wrote:
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Re: Losmandy GM-8: Anomalous wearing of R.A. shaft
Sandro,
It is surprising that anodizing was used on a moving part, as wear would eventually remove the coating over time. In present day mounts, I think these shafts are all stainless steel. The patterns you see can be explained by the way the shaft rides inside the bearings, as Peter has stated, with some slight gap between upper and lower bearings. But if you are not seeing any problems with shaft rotation and you don't have any issues with problematic periodic errors, you are probably OK.? ? The clutch discs can be replaced as the nylon wears down over time. But after cleaning you might try sanding them down with some 220 mesh sandpaper to roughen the surface a little. But after 20 years you may wish to get some new ones. Thoroughly cleaning where the discs ride with some solvent should also help a bit. Best regards, John |
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Losmandy GM-8: Anomalous wearing of R.A. shaft
Hello everybody,
I have a GM-8 that I purchased new in 2000, which I have not used heavily;
so it is still quite new and behaving. Lately I noticed that the clutches
tended to slip, probably due to grease leakage to the nylon discs.?
So I decided to disassemble the mount
to perform a complete cleaning and regreasing. I started with the DEC axis
and everything was fine and OK. When I disassembled the R.A. axis I found that
the shaft shows signs of irregular wearing in correspondance of the upper
and lower needle barrels, on opposite sides of the shaft
(see video https://www.youtube.com/watch?v=7wNQLUWngJk). Only the anodization seems to have come off and there are no signs of serious grinding.
Nevertheless, prior to disassembling, the axis rotated quite smoothly and
apparently there was no play whatsoever.
Does anybody have an explanation for what has happened and how to prevent
possible further damages?
Thank you all. Sandro Barbanera |
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Re: Runaway slew while using PHD2
Jim Waters
John, Brian - Wait until release 1.11 goes to beta then test drive the SW again.
Yes - things are being moved around, new stuff added and old stuff tweaked.? Its difficult to keep up at times. ------------------------ Jim W Phoenix, AZ. USA Losmandy GM811G, NINA 1.11, ASI2600MC Pro, Sky-Watcher Scopes |
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Re: Runaway slew while using PHD2
>>>
My eventual goal would be to run a cam on both my Zenithstar 61 and Esprit 100ED at the same time and capture twice the data, maximizing use of sky time. I am wanting to do that too, and here SGP has kind of let us down in leaving out this features in version 4. they claim to be working on it, but its tough to wait. NINA seems promising and continues to evolve. One of the issues I have is that it's continually changing,?and implementations are constantly being updated. For my obs, i can't really deal with that much change on a daily basis. I think when it settles down i'll give it another try. I have it installed on a few other telescope computers, and noodle with it from time to time? On Sat, Jul 31, 2021 at 6:25 PM John Kmetz <jjkmetz54@...> wrote: Hey Jim, --
Brian? Brian Valente portfolio |
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Re: Runaway slew while using PHD2
Hey Jim,
At the time I tried, there was no Framing and Mozaic Wizard, which I really like to use in SGPro. You type in the object name, e.g. NGC 6888, and it brings up a wide field low res image of those sky coordinates, and you can move the tile box around to frame it as you like, or create multiple tiles for a mosaic.? Also, there was no way to edit the sequence as it was running, like adding additional filters, or numbers of frames. You had to stop the sequence entirely to do this. Perhaps these features have been added since then. My eventual goal would be to run a cam on both my Zenithstar 61 and Esprit 100ED at the same time and capture twice the data, maximizing use of sky time. Thanks, John |
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Re: Relationship between needle bearing wobble and variable worm mesh and backlash
Having reset my worm mesh for the least amount of backlash using the Allen wrench method, I would recommended doing it with the scope in the position shown below . One thing to note, if the worm mesh is too tight. the motion of the worm is jerky. This shows up in the PHD2 backlash graph as an initial move, followed by a long period where it does not move as it builds pressure in the gearbox to overcome frictional resistance, only to start moving again.?
Peter |
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Re: Losmandy GM-8: Anomalous wearing of R.A. shaft
I explain the reason for this here:?/g/Losmandy_users/topic/relationship_between_needle/84580649?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,84580649
Peter |
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Re: Relationship between needle bearing wobble and variable worm mesh and backlash
1. I've previously pointed out the loose fit of the Dec and Ra shafts in relation to the the needle bearings. It's has been pointed out that this looseness if needed in order to get the shaft through the needle bearings and when the clutch is tightened this looseness should not matter.? However, this looseness results in the shaft having just two points of contact per the drawing, and means it's rotation is ever so slightly off axis. This was determined by inserting the shaft into freshly greased needle bearings and removing it without rotation.?
? 2. I have previously pointed out how sensitive setting the worm mesh pressure is. +/- 0.0005 to 0.001 makes a big difference in the ability to finger rotate the worm in order to move the ring gear. The closeness of the mesh has a direct relationship to backlash. 3. I and Michael Herman have found that changing out the thrust bearings from the stock Losmandy to ones sourced from McMaster can have a significant effect of ease of rotation resulting from a better worm ring gear mesh. I have also found that a large PHD2 error in the 2600s or higher range is most likely due to the thrust bearings. It should be noted that the stock Losmandy and McMaster thrust bearings have been measured to be the same thickness, but they do differ in their construction. The stock Losmandy bearings have a crimped edge which is not even in diameter the case of those I have. This implies that the rollers are not pointing to the exact center of the bearing, resulting in an off axis force as a function of rotation. I greatly reduce this error with the McMaster thrust bearings. 4. The ring gear rotates on a bushing (in the case of the G11 this is brass). With the clutch off off I have found that the ring bearings rotates easily through 360 degrees.? 5. With the clutch tightened I have found that the if the worm is meshed at the CWD position there is a tight spot when the axis is rotated 180 degrees. This tightness can result is a stall at the 180 degree position, but regardless represents a variation in the backlash as the axis rotates.? This is the Dec axis. CWD position where the worm mesh was set. Even distribution of grease. Grease distribution at 180 degrees of ration. In my case I had a stall at this point.? So what causes this to occur. I believe that the clutch plate being off axis by virtue of the needle-shaft loose fit, produced off center pressure? on the ring gear, which has some degree of movement by virtue of riding on the brass bushing, that forces the ring gear into the worm as it rotates. Hence the worm mesh and backlash changes as a function of rotation Peter |
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Losmandy GM-8: Anomalous wearing of R.A. shaft
Hello everybody,
I have a GM-8 that I purchased new in 2000, which I have not used heavily;
so it is still quite new and behaving. Lately I noticed that the clutches
tended to slip, probably due to grease leakage to the nylon discs.?
So I decided to disassemble the mount
to perform a complete cleaning and regreasing. I started with the DEC axis
and everything was fine and OK. When I disassembled the R.A. axis I found that
the shaft shows signs of irregular wearing in correspondance of the upper
and lower needle barrels, on opposite sides of the shaft (see video). Only the
anodization seems to have come off and there are no signs of serious grinding.
Nevertheless, prior to disassembling, the axis rotated quite smoothly and
apparently there was no play whatsoever.
Does anybody have an explanation for what has happened and how to prevent
possible further damages?
Thank you all. Sandro Barbanera |
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Re: What result I can get with the current OPW in my old G11?
Andre,
The bearings I used during my last rebuild were from Boca Bearings and were SR4-ZZC #7 PS2 BG (.250x.625x.196), which I believe Michael H. had recommended. They were about $10-12 at the time. They are the same dimensions as those that Losmandy uses, but there may be sources in Brazil that are equivalent. Yes, they are all probably made in the Southeast Asia, regardless. McMaster-Carr also offers some sealed and permanently lubricated bearings that can go close to $30 each, but if there is an advantage to these, I have not heard the report as of yet. But to answer your question, if Losmandy sent you the new bearings as part of your order, yes they are perfectly fine to use. Many of us just order the worm by itself, to replace a damaged one or to seek better performance. Then we can use the Losmandy bearings, or some of the ones from the other suppliers as a matter of choice, to explore potentially better guiding behavior. Sorry if I wasn't clear earlier. Good luck with your rebuild. John |
Michael Herman