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Quite sticky mount... and some ideas to balance loads...
Very nice set of emails. Everyone has different mount versions, even if nominally the same model ("G11"). The idea to put in a spring, to separate the upper and lower metal faces of the clutch, is a newer version.? Losmandy never included that in earlier decades of the G11, and it needs a special groove cut in one of the metal clutch drive disks...it is absent on earlier G11 mounts like mine.? I am not aware of it being on any other mount models, but Losmandy does innovate.? I don't think you need it... CWD is the position you want to park at, but it has the disadvantage that all weight forces +scope and counterweights) are on the 1.25 inch RA shaft and it's bearings.? So any imbalance is hard to detect at that position. A better approach is to rotate the RA by 90 degrees, then balance the DEC and then the RA. For the DEC axis balance, you simply rotate the RA axis until the DEC axis is parallel to the ground...then fasten down the RA axis. Then loosen the DEC clutch knob, and balance...usually adjusting the DEC dovetail is sufficient. However, the RA axis, set at your polar elevation, is more tricky. On my system, I don't want to mess with my elevation knob, because my mount is usually close to polar aligned already, and I don't want to mess that up. So, once the DEC is balanced as above, I stay at the RA position where the DEC axis is horizontal.? Then the scope and camera load must be balanced by the counterweights.? A slight shove of the counterweights or the scope around the RA axis, in both CW and CCW directions, is sufficient to overcome static friction, and you can see if the load is close to perfect balance.? Both directions should "decay" to a stop at about the same travel angle.?? The mount is quite strong and a slight imbalance is normally no worry.? Many people in the past have intentionally unbalanced their axes to assure one side of the worm drives the ring gear.?? The final issue to watch out for, related to clutch behavior, is oily contamination of the plastic clutch disk, or it's mating metal surfaces.? If that occurs, you will find the axis slipping...it can be a high viscosity oil so the slippage can be very gradual and temperature dependent.? A cleaning of the surfaces with a solvent like isopropyl alcohol usually suffices. Have fun with your system and clear fall skies, Michael On Sun, Sep 29, 2019, 9:04 AM fbasti62 <franco.basti@...> wrote: Thx all |
¿ªÔÆÌåÓýJust wanted to add some data to the discussion.? I purchased a new G-11 about 3 years ago and experienced the issue with the sticky RA balancing (I¡¯m at 40 degrees North latitude), so I ordered the wavy clutch washer from Losmandy and that made it significantly easier to balance.? I then measured the force needed to slowly move the RA using a cheap spring balance at the end of the counterweight shaft when the counterweight shaft was horizontal -- it required about 350 to 400 gm (measured perpendicular to the RA axis.) ?Subsequently, I passed that G11 on to my son and this past June I bought a new G11 with the tucked-in motors and SLWs.? Again, the balancing was somewhat problematic, now requiring 900 to 1000gms to get the RA to move.? I had assumed that the new model would come with the wavy clutch washer, but apparently that¡¯s not the case, although I have not taken it apart to look. ? I would also note that compared to a Celestron AVX, the G11 is still fairly sticky, even with the wavy washer installed. ? Joe? ? ? From: [email protected] <[email protected]> On Behalf Of Michael Herman ? Very nice set of emails. Everyone has different mount versions, even if nominally the same model ("G11"). ? The idea to put in a spring, to separate the upper and lower metal faces of the clutch, is a newer version.? Losmandy never included that in earlier decades of the G11, and it needs a special groove cut in one of the metal clutch drive disks...it is absent on earlier G11 mounts like mine.? I am not aware of it being on any other mount models, but Losmandy does innovate.? I don't think you need it... ? CWD is the position you want to park at, but it has the disadvantage that all weight forces +scope and counterweights) are on the 1.25 inch RA shaft and it's bearings.? So any imbalance is hard to detect at that position. ? A better approach is to rotate the RA by 90 degrees, then balance the DEC and then the RA. ? For the DEC axis balance, you simply rotate the RA axis until the DEC axis is parallel to the ground...then fasten down the RA axis. Then loosen the DEC clutch knob, and balance...usually adjusting the DEC dovetail is sufficient. ? However, the RA axis, set at your polar elevation, is more tricky. On my system, I don't want to mess with my elevation knob, because my mount is usually close to polar aligned already, and I don't want to mess that up. ? So, once the DEC is balanced as above, I stay at the RA position where the DEC axis is horizontal.? Then the scope and camera load must be balanced by the counterweights.? A slight shove of the counterweights or the scope around the RA axis, in both CW and CCW directions, is sufficient to overcome static friction, and you can see if the load is close to perfect balance.? Both directions should "decay" to a stop at about the same travel angle.?? ? The mount is quite strong and a slight imbalance is normally no worry.? Many people in the past have intentionally unbalanced their axes to assure one side of the worm drives the ring gear.?? ? The final issue to watch out for, related to clutch behavior, is oily contamination of the plastic clutch disk, or it's mating metal surfaces.? If that occurs, you will find the axis slipping...it can be a high viscosity oil so the slippage can be very gradual and temperature dependent.? A cleaning of the surfaces with a solvent like isopropyl alcohol usually suffices. ? Have fun with your system and clear fall skies, ? Michael ? On Sun, Sep 29, 2019, 9:04 AM fbasti62 <franco.basti@...> wrote:
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