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Tonight I will have this G11 out for the first time. I've had a few dry runs in the house just to become familiar with the working parts of the mount and Gemini 2 HC. My question. How tight should the Dec and RA clutches be in GOTO mode and tracking? Partially or more tight? Assuming the scope is well balanced prior to using the GOTO mode of course. Thanks
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Hand tightened is fine. you don¡¯t have to crank them down. ? Also depends on the load. If it¡¯s heavier it¡¯s worth an extra confirming twist ? hth ? Thanks ? Brian ? ? Brian Valente Brianvalentephotography.com ?
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From: Losmandy_users@... [mailto:Losmandy_users@...]
Sent: Wednesday, October 11, 2017 11:04 AM
To: Losmandy_users@...
Subject: [Losmandy_users] Mount Clutch Tensions? ? Tonight I will have this G11 out for the first time. I've had a few dry runs in the house just to become familiar with the working parts of the mount and Gemini 2 HC.
My question. How tight should the Dec and RA clutches be in GOTO mode and tracking? Partially or more tight? Assuming the scope is well balanced prior to using the GOTO mode of course.
Thanks ?
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I just have a push-to GM-8, and a lot of times I'll reach down to loosen the clutch to go to another object and find them already "loose". I don't have to tighten mine much at all with C8's or an AT130. Some people have to really wrench them down. I don't know what the difference is. I suppose if you were going to leave the telescope alone you would want to tighten them down a good bit in case the wind came up.
Bob
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I should clarify that I use it primarily for astrophotography and use computerized go-tos
B
On Wed, Oct 11, 2017 at 11:06 AM, Brian Valente <bvalente@...> wrote: Hand tightened is fine. you don¡¯t have to crank them down. ? Also depends on the load. If it¡¯s heavier it¡¯s worth an extra confirming twist ? hth ? Thanks ? Brian ? ? Brian Valente Brianvalentephotography.com ? ? ? Tonight I will have this G11 out for the first time. I've had a few dry runs in the house just to become familiar with the working parts of the mount and Gemini 2 HC.
My question. How tight should the Dec and RA clutches be in GOTO mode and tracking? Partially or more tight? Assuming the scope is well balanced prior to using the GOTO mode of course.
Thanks ?
-- Brian?
Brian Valente portfolio
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That is my goal as well Brian, but I was just wondering how tight these clutches should be for all of the different modes, GOTO, tracking, etc...
I had them really tight when i was learning this mount, but I realize too if they are too loose the scope will drop...
Rodney
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Never tighten more than the minimum required to prevent slippage. Doing so dramatically increases drag due to (unnecessary) loading of the thrust bearings.
Good Luck !
Jeff
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First, you should shoot for good balance of the load and then introduce a slight eastward bias. Clutch tight enough so that there is no slippage during imaging or slewing.
Tom
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On 10/11/2017 2:20 PM, Brian Valente bvalente@... [Losmandy_users] wrote: I should clarify that I use it primarily for astrophotography and use computerized go-tos
B
On Wed, Oct 11, 2017 at 11:06 AM, Brian Valente <bvalente@... <mailto:bvalente@...>> wrote:
Hand tightened is fine. you don¡¯t have to crank them down. ____
__ __
Also depends on the load. If it¡¯s heavier it¡¯s worth an extra
confirming twist____
__ __
hth____
__ __
Thanks____
__ __
Brian____
__ __
__ __
Brian Valente____
Brianvalentephotography.com____
__ __
*From:*Losmandy_users@...
<mailto:Losmandy_users@...>
[mailto:Losmandy_users@...
<mailto:Losmandy_users@...>]
*Sent:* Wednesday, October 11, 2017 11:04 AM
*To:* Losmandy_users@...
<mailto:Losmandy_users@...>
*Subject:* [Losmandy_users] Mount Clutch Tensions____
__ __
____
Tonight I will have this G11 out for the first time. I've had a few
dry runs in the house just to become familiar with the working parts
of the mount and Gemini 2 HC.
My question. How tight should the Dec and RA clutches be in GOTO
mode and tracking? Partially or more tight? Assuming the scope is
well balanced prior to using the GOTO mode of course.
Thanks____
__ __
____
--
Brian
Brian Valente
portfolio brianvalentephotography.com <>
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Hi Rodney,
Ideally you want to snug the clutch knobs up just enough to hold and no more but it really makes about zero difference to the servomotors. Obviously there will be a very small additional load placed on the thrust bearings if you really crank the knobs down but in reality this presents minimal additional load on the servomotors because for the most part the thrust bearings are already fully loaded by gravity working on the load presented by the mount and any payload in the saddle. You can easily verify this if you have a Gemini 2 by monitoring the lag data on the Servo page of the Gemini. You can have the clutch fully loose and fully tight and will see no change in lag or duty cycle.?
Chip
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I read the balance instructions for this Losmandy scope Mount. I have to balance the RA and the Dec axis's before hand. To ensure a minimal load on the servo motors during the scope movement. I played with this in the room here and saw what too loose of a clutch can do. Scope will flip-flop around. Have to be careful not to damage the scope and hold it with your hand while doing the balancing.
So I sort have a mediocre tension on those. From a 1-10 scale probably a 4 or 5...
Thanks for your input!
Rodney
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Hi Rodney, Bob, and gang,
Bob raised the question about how some folks have to really wrench down the clutch knobs to get the gear to stay put...other don't seem to. It does not make sense to new users of the system... so here goes a quick explanation of the design, what goes wrong, and a simple solution...
The mount was originally designed (G11, GM8) to be a push-to, with its very nicely accurate RA and DEC markings.?? Only later when the astrophotography field really developed, did everyone find these mounts to be superior due to their high stability and low PE. The Gemini system provided complete GoTo, and its easy computer interface makes it a delight to find deep sky targets for imaging.??
But... the clutches... are the same as originally designed for push/slip operation.? The clutches lead to trouble for AP work with heavy mass systems.? ?There are reports all over the web about how these slip.. a subtle bump in the dark and ... much wasted time re-synching or re-aligning while the precious imaging target slides across the sky.? ? ? The 3-handled clutch knobs are a benefit, and extra cost, but the system still slips for high scope weights.??
? Losmandy supplies a plastic disk, which they now say they have a higher friction plastic, but they did not have them in stock for my GM8 or my older CG11.
The biggest problem is not really the friction, it is inevitable oily contamination. ? ? I found was diffusion of oils from the lubricated needle bearings, and the tight surfaces allow that to move into the clutch surface by capillary action.?? ? ? Over time, the clutch disk will get an entire surface coated in oil and that of course can never by held firmly by the clutch mechanism.
The nice website has written that cardboard is a better clutch material... but of course cardboard can get moist...and does not resist oils.
I have found a much better material for this purpose - oil and water proof and higher friction.?? ? ? I use mine on the GM8 and CG11, and have a heavy Meade LX200R 12 inch SCT on the CG11.? It does not budge during imaging.?? ? ? You don't need much clutch knob force to hold the scope system quite firmly.?? ? ? ? ?This saves possibly distorting the flat metal surfaces.?? ? ? The RA and DEC will still budge if strongly pushed, but not with a casual bump in the night.?? ? ? If one sets mount limits, particularly for unattended astrophotography, there is no issue, but even if the system RA were to run into the mount, these clutch disks will slip to prevent serious damage.??
Let me know in an email to mherman346@... if you want a set of these improved clutch disks for astrophotography work.? ? ? ?I have? G11 (2 of 4.25 inch OD), GM8 (2 of 3.0 inch OD), and also for my own CG11 (one each 4.25 and 3.5 inch OD).? Let me know if you need a different OD for Titan etc.? They mail in a flat envelope that should ship at low cost.?
Very best, Michael
On Wed, Oct 11, 2017 at 11:33 AM, tom loeblt@... [Losmandy_users] <Losmandy_users@...> wrote:
?
First, you should shoot for good balance of the load and then introduce
a slight eastward bias. Clutch tight enough so that there is no slippage
during imaging or slewing.
Tom
On 10/11/2017 2:20 PM, Brian Valente bvalente@... [Losmandy_users]
wrote:
>
>
> I should clarify that I use it primarily for astrophotography and use
> computerized go-tos
>
>
> B
>
> On Wed, Oct 11, 2017 at 11:06 AM, Brian Valente <bvalente@...
> bvalente@...>> wrote:
>
> Hand tightened is fine. you don¡¯t have to crank them down. ____
>
> __ __
>
> Also depends on the load. If it¡¯s heavier it¡¯s worth an extra
> confirming twist____
>
> __ __
>
> hth____
>
> __ __
>
> Thanks____
>
> __ __
>
> Brian____
>
> __ __
>
> __ __
>
> Brian Valente____
>
> Brianvalentephotography.com____
>
> __ __
>
> *From:*Losmandy_users@yahoogroups.com
> Losmandy_users@yahoogroups.com>
> [mailto:Losmandy_users@yahoogroups.com
> Losmandy_users@yahoogroups.com>]
> *Sent:* Wednesday, October 11, 2017 11:04 AM
> *To:* Losmandy_users@...
> Losmandy_users@yahoogroups.com>
> *Subject:* [Losmandy_users] Mount Clutch Tensions____
>
> __ __
>
> ____
>
> Tonight I will have this G11 out for the first time. I've had a few
> dry runs in the house just to become familiar with the working parts
> of the mount and Gemini 2 HC.
>
> My question. How tight should the Dec and RA clutches be in GOTO
> mode and tracking? Partially or more tight? Assuming the scope is
> well balanced prior to using the GOTO mode of course.
>
> Thanks____
>
> __ __
>
> ____
>
>
>
>
> --
> Brian
>
>
>
> Brian Valente
> portfolio <>
>
>
>
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Remember to balance the Dec (The
Telescope) and then the RA (The Counterweight).. As I just read the G11
instructions.. yet again.. I know they list this backwards..
?
See..
?
Derek
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From: Losmandy_users@...
[mailto:Losmandy_users@...]
Sent: Wednesday, October 11, 2017
2:45 PM
To: Losmandy_users@...
Subject: RE: [Losmandy_users]
Mount Clutch Tensions
?
?
I read
the balance instructions for this Losmandy scope Mount. I have to balance the
RA and the Dec axis's before hand. To ensure a minimal load on the servo motors
during the scope movement. I played with this in the room here and saw what too
loose of a clutch can do. Scope will flip-flop around. Have to be careful not
to damage the scope and hold it with your hand while doing the balancing.
So I sort have a mediocre tension on those. From a 1-10 scale probably a 4 or
5...
Thanks for your input!
Rodney
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Chip, does one hundred percent of the load applied by the clutch knobs not go through the thrust bearings?
With no scope mounted and clutch loose, so the axis rotates as freely as is possible, does the amount of force needed to rotate not increase by several hundred percent when high tension is applied to the clutch knobs? In my world it does, I guess it's just me.
Jeff
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Hi Jeff,
Yes of course, as you apply pressure on the clutch discs the load on the thrust bearings naturally is increased. The thing is there are two thrust bearings and as you increase the total load the lower thrust bearing reduces the load on the upper bearing. I have not run the calculator to check the forces involved but the bearings are good for at least 4,900lbs per bearing and up to 6,000RPM so a few extra pounds shared between the two bearings would seem to represent a fairly low load. Also consider that the servomotor output is reduced 25:1 before the worm gear reduction which is something like an additional 360:1 reduction so the additional load should not represent a big change in load.?
As I said above, if you have a Gemini 2 you can monitor the servo feedback data using the Gemini's web server. Or you can try this, easy demonstration: remove the worm block from the DEC axis and loosen the clutch knob and feel the force needed to rotate the DEC axis. Now tighten the DEC axis clutch knob and rotate the DEC axis, it will still rotate freely, if you can feel an increase in force it will not be much and the DEC shaft will still rotate freely. This is what bearings do, they reduce friction and the force necessary to rotate the axes even while loaded up.?
Chip
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Hey Chip, regarding your first comment... ?"The thing is there are two thrust bearings and as you increase the total load the lower thrust bearing reduces the load on the upper bearing."?
Huh? My logic suggests load applied to a nut at one end would be evenly distributed between the two thrust washers that are being loaded together. As for the loads being within the capacity of the motors and drive train, I am not arguing that, But, not having the calculator out either, I'm gonna assume that 50 in lbs is easily done by hand on a 1 1/4 inch well lubricated nut and I'm gonna also guess that puts a couple hundred pounds load on Mr. and Mrs, thrust bearing. Within its capacity? Absolutely. Does it add drag? As I said only a couple hundred percent increase. Does it hinder smoothness? You better believe it does. Big time. I have one apart on my bench right now, (with perfect, very low hour bearings) ?I have personally?applied 10,000 + pound loads to the same bearings (in larger sizes) in structural testing applications (it's what I do) and know just how the feel changes as load is slowly applied. BTW, these bearings were well within? their advertised limits and lived to see another day but at? max load, it tool probably a 200?Ft. Lbs. to turn the loading nut ! That's what bearings do, they reduce friction, they do not eliminate it ! Remember, we are dealing with two wimpy little bearings with stamped steel races, not sweet high end tapered roller bearings. (unfortunately)
Back to my original statement, doing all we do to achieve the best tracking possible ($), I would consider it foolish to have any load on any bearing in any direction that was not absolutely necessary. Even if the gains seem trivial, it's free! But that's just me. All good.?May your clutches remain grease free -
Jeff ?
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Jeff,
My comment was with the clutch loose, the lower bearing carries zero load. once you start to apply clutch pressure the lower thrust bearing starts to carry some of the load. As clutch pressure is increased the load on both bearings is increased until you reach the point where both bearings are each carrying about 1/2 of the total on axis load. That point is where can be no additional movement on the thrust axis, no more compression of the clutch material can be made and all bearing surfaces are in full contact, this not a small load in terms of PSI but the axle will still turn freely. You can disagree all you want to, the fact remains that you can easily turn the RA or DEC axles with the clutches fully locked up. Try it or alternately, as mentioned previously monitor the Gemini's power and encoder feedback from the servomotors.?
Yes but 50 in/lb is much less than is needed to lock up the clutches fully. The average adult barehanded can achieve approximately 7-13 ft/lb of torque and the winged clutch knobs increases this at least double, possibly three times.. Here is a quick bearing force calculator you can use. ? have fun.
Chip ??
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" the fact remains that you can easily turn the RA or DEC axles with the clutches fully locked up"
And you can keep twisting the knobs far past that point Chip. That's my whole point.
People speak of using tools on the knob. I have read it here and seen them grossly over tighten in the field myself. Over tightening is what I was addressing.
Jeff
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Hi Jeff,
Well we can't help it if people don't know what "tight enough" means. For those people Michael Herman has some trick clutch pads which are much grippier than the slick hard plastic discs used by Losmandy. I think he sells them for a bit more than the Losmandy clutch discs but this material will do the trick.?
I know there have been some G11 and GM8 mounts which people cannot lock their slip-clutch on no matter how much they torque the clutch knobs down. I suspect there is another issue which nobody has addressed which is unique to a slip-clutch mount. The clutch surfaces must be nearly perfectly perpendicular to the RA or DEC axis and parallel to one another for the hard plastic clutch discs to clamp effectively. The more surface you have for a given friction coefficient clutch disc material the higher the grip and better the lock up. If the plates are not parallel the surface area is significantly reduced and the working clutch surface area will become too small to hold the load. If there is no mechanical interference limiting free movement of the clutch plates and the clutch does not hold with a reasonable amount of torque on the clutch knobs the only possible problem can be the clutch plates are not parallel enough to allow the clutch pad material for supply enough friction for lock up. It doesn't take much for this to become an issue given that the clutch disc material is a hard plastic material and Michael Herman's solution is two fold, the clutch disc material has a higher friction coefficient and the material is slightly more compressible. This material solves the friction issue by having more friction and addresses the lack of perfectly parallel surfaces with the compressibility of the disc material. The combined characteristics of this material should resolve these issues without having to resort to sending the mount to Losmandy for resurfacing. Of course at some point if the clutch plates are out of spec excessively even an large increase in friction coefficient will not allow the clutches to lock up fully.?
Chip?
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I think we are all under too much pressure!
We must stop beating ourselves up... there is certainly a design issue with the plastic clutch disks.? They slip for a variety of reasons:? ??
? ?1. the plastic is slippery or worse, has an oily surface (plastics have an oily plasticizer anyway, but oils from the bearings creep up too)
? ?2. the clutch metal faces may not be flat or if flat, not parallel.? ? ? ? ? ?It is an open question as to whether torquing down too hard on the clutch knobs can distort the aluminum plates.??
? ?3. the clutch knob has a coarse thread.? It takes more torque to get a hard grip on the (plastic) clutch disk.
? ?4. some people report the clutch knob cannot get to "bottom" and even Mark Crossley says he had to put on two plastic spacers? ? ? ? ? (see his site:? ? ? ? ) ? ? ? ?this means there are or were at one time clearly some mechanical aspects that were not held in spec.? A few washers of the right size and voila... perfect.??
? ?5. some people overload their G11, like me... and still expect miraculous performance....and we still get it.? Company7 wrote that the G11 holds C14s fine...maybe not for AP...
? ?6. wonder why these sell for $125 if they are not needed?? ?
If you look at Mark Crossley's site, , he notes that the clutch disks he uses are cardboard.? He mentions that many other owners use strap wrenches to tighten down the clutches for AP work.? I was once one of those folks.? ?I am settled on a better material now and think this is it.? Now if my skies would only stay clear and I could get back home to play...
All the best and happy imaging...!
- Michael
On Fri, Oct 13, 2017 at 3:38 PM, chiplouie@... [Losmandy_users] <Losmandy_users@...> wrote:
?
Hi Jeff,
Well we can't help it if people don't know what "tight enough" means. For those people Michael Herman has some trick clutch pads which are much grippier than the slick hard plastic discs used by Losmandy. I think he sells them for a bit more than the Losmandy clutch discs but this material will do the trick.?
I know there have been some G11 and GM8 mounts which people cannot lock their slip-clutch on no matter how much they torque the clutch knobs down. I suspect there is another issue which nobody has addressed which is unique to a slip-clutch mount. The clutch surfaces must be nearly perfectly perpendicular to the RA or DEC axis and parallel to one another for the hard plastic clutch discs to clamp effectively. The more surface you have for a given friction coefficient clutch disc material the higher the grip and better the lock up. If the plates are not parallel the surface area is significantly reduced and the working clutch surface area will become too small to hold the load. If there is no mechanical interference limiting free movement of the clutch plates and the clutch does not hold with a reasonable amount of torque on the clutch knobs the only possible problem can be the clutch plates are not parallel enough to allow the clutch pad material for supply enough friction for lock up. It doesn't take much for this to become an issue given that the clutch disc material is a hard plastic material and Michael Herman's solution is two fold, the clutch disc material has a higher friction coefficient and the material is slightly more compressible. This material solves the friction issue by having more friction and addresses the lack of perfectly parallel surfaces with the compressibility of the disc material. The combined characteristics of this material should resolve these issues without having to resort to sending the mount to Losmandy for resurfacing. Of course at some point if the clutch plates are out of spec excessively even an large increase in friction coefficient will not allow the clutches to lock up fully.?
Chip?
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With that I agree Chip, and I may look into a set of those pads just out of curiosity as my own out of square issue persists despite my best efforts.?
Jeff
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I'm getting the feeling (maybe a little late- hehe) that there are a whole lot of Losmandy mounts with potential axis to thrust bearing face alignment issues. (meaning thrust bearing face to axis squareness)?
Obviously grease covered clutches account for many of the reported slippage vs tightening problems reported but, having my GM-8 apart and seeing my RA axis with >.003" out of parallel remaining (across <2" Dia, despite some serious mallet action and the best efforts of a #3 arbor press - no gaps ever detectable) I can only guess that is the machining consistency we get at this price point. (Grrrr) The fact that I have also encountered metal on metal contact adjacent to the altitude scale which explained why the Alt knob was so hard to turn when I traveled north for totality also reinforces this conclusion.
FWIW? ? -Jeff
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photon_trap
Michael Herman