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I have always had decreasing mount performance (guiding that is) as the temps dropped, so I thought I'd try an experiment.
I put a brand new gearbox in the freezer - and guess what - the grease turns to sludge and the gearbox is hard to turn.
Now - the motors probably have enough torque to overcome this, but I wanted to throw this out there to see if anyone else has done this.
A ton of talk on these forums about grease for the worm gears - perhaps it's time to discuss the grease used in the gearboxes.
I might be way off base, but try it - - put a gearbox in the freezer for a couple of hours and let me know what you think.
Dave Fenstermacher
Woodbridge, VA
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I placed a damaged gear box in the freezer (-5F) for about 40 minutes and the grease got real stiff.? I don't think it would cause issues.? The servo's have enough torque.
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On Wed, Feb 24, 2021 at 05:43 PM, davidfenster@... wrote:
I have always had decreasing mount performance (guiding that is) as the temps dropped, so I thought I'd try an experiment.
I put a brand new gearbox in the freezer - and guess what - the grease turns to sludge and the gearbox is hard to turn.
Now - the motors probably have enough torque to overcome this, but I wanted to throw this out there to see if anyone else has done this.
A ton of talk on these forums about grease for the worm gears - perhaps it's time to discuss the grease used in the gearboxes.
I might be way off base, but try it - - put a gearbox in the freezer for a couple of hours and let me know what you think.
Dave Fenstermacher
Woodbridge, VA
Dave,? The gearbox is not the problem if you have a straight 2+piece worm block. The problem is material shrinkage when cold which reduces backlash even causes stalls. The solution I have been preaching is to set backlash on a cold acclimated mount. This make the backlash in a warm condition excessive but personally I don't image in the daylight.? -- Chip Louie Chief Daydreamer Imagination Hardware?
? ?Astropheric Weather Forecast - South Pasadena, CA?
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Here's the thing - I get all the worm backlash stuff, but for Dec, the stiff grease could cause issues with the reversals (Stiction is a term that comes to mind :)).
By the way - I see the decreased performance in Dec. with decreasing temps.
Here's what I'm gonna try when I get a chance.? Flush all the grease out of the Dec gearbox and put in a light oil.?
There is not much need for grease in these gearboxes (low load when guiding - arguably high when slewing) as the teeth are (I think) involute (I only eyeballed them once) which have a rolling contact.
A bit of grease will help with backlash, but it it gunks up under low temps, then - well - it kinda has the reverse effect.
I tend to write in fractured - hyphenated - parenthetical - sentences - so sorry in advance.
Thoughts on gearbox grease?
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So how do you replace the grease without destroying the gearbox??
I think stiction is minimal.?
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Hi David
Have you used your mount at these temps or is it the freezer experiment?? ??
One of the best things you can do is increase the voltage towards the higher end, 15-18v. you can also reduce your slew speed (btw, these are the same recommendations as astro physics).?
We have many losmandy mounts in the wild operating at cold temps. We get inquiries on the Gemini, the hand controller, power sources, battery life, etc. but i have yet to hear of an issue regarding the gearbox or motor performance?
Brian
Here's the thing - I get all the worm backlash stuff, but for Dec, the stiff grease could cause issues with the reversals (Stiction is a term that comes to mind :)).
By the way - I see the decreased performance in Dec. with decreasing temps.
Here's what I'm gonna try when I get a chance.? Flush all the grease out of the Dec gearbox and put in a light oil.?
There is not much need for grease in these gearboxes (low load when guiding - arguably high when slewing) as the teeth are (I think) involute (I only eyeballed them once) which have a rolling contact.
A bit of grease will help with backlash, but it it gunks up under low temps, then - well - it kinda has the reverse effect.
I tend to write in fractured - hyphenated - parenthetical - sentences - so sorry in advance.
Thoughts on gearbox grease?
-- Brian?
Brian Valente portfolio
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I have imaged at ~25F without any major issues but I am running at 15.2 volts.
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David,
Kudos for you doing this engineering experiment.
A friend is bringing over his Celestron AVX next week because it became unmovable in our last cold spell here in Northern Illinois.
I'm expecting to find frozen grease along with overtightened bearings and gears - he bought it used and I'm betting the prior owner overdid the backlash adjustment. That or the factory did in response to persistent complaints about backlash by customers who don't know how to work with less than perfect stuff. I've seen multiple mounts which had the RA and DEC bearing thrust pre-load nuts way too tight. I suspect the assemblers read the automotive spec for the bearings and used that pre-load.
The problem is rampant: Unsuitable grease installed by Sun Bathers in America and China. Same mentality that puts electronic parts only spec'ed to 0 deg C in telescope mounts, as Meade has done in the past.
A decade or so ago a friend of mine had to install heaters on the bearing housings of an early production Paramount because of grease and bearings seizing in the cold. It was installed (as it should be) in an unheated dome in western Michigan. I once installed a small 12V heater pad on a 120V synchronous motor such as we used in the old days pre-servo and stepper.
Things like this bring to mind the Eastern Front in the winter of 1941. Maybe the companies should hire a few engineers from Novosibirsk?
To me I'd worry about excessive wear on the first few gears, even if the mount functions as others have said.
But perhaps there is nothing to be done about it aside from keeping an eye on it.
Again, Kudos.
Mark Christensen
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Hi Mark,
Good points.? Some thoughts...?a long email.??
Until now I have ignored the gearbox as an area that could "freeze up".? I just bought 2 new gearboxes at the factory this week. These are my first two brand new gearboxes.? I do live these days in a very benign climate that never freezes.? Denver is calling to me, however...
?In turning the output shaft of the new gearboxes by hand, at 78F temperature (a nice warm February day in Burbank!!!) the rotation was notably slow and viscous.? The new units have a cellophane type tape over the motor pinion gear entry port to prevent particles from entering, and prevent lube from flowing out on a hot day in storage.? My old gearboxes spin very loosely and freely by comparison.??
If you were in a freezing climate, could you clean that viscous lube out and put in Superlube, say??
Maybe a soak in alcohol or WD40 would dilute the internal grease, and you could easily pack in lighter Superlube.? The parts are plastic (ABS maybe?) Maybe brass and stainless?steel inside?? Can't use a harsh solvent like Berryman B-12 "Chemtool" as it might soften the plastic.? Can't insert anything in the gearbox that might leave a fiber or particle.??
My old gearboxes, all on used mounts,? had essentially zero lube left in them.? The gears spun freely and loosely.? I never got a new gearbox til now to tell they are intended to have lube packed inside.? I'd try the Superlube that is advertised, and astronomy tested, to go to very low temperature.??
The stock gearbox does not disassemble...it is sealed by rivets.? The McLennan gearboxes from Element14 do disassemble with 4 tiny flat head screws.? But not the McLennan gearboxes from RS components...those have a sealing paint over the assembly screws.? If you can disassemble the gearbox it helps in replacing the greases of course.?
____
Always experiments to try...some other notes...
____
On the possible overloading the worm bearings Mark raised:
On my G11 and GM8 worm bearings I use a single R4 Belleville spring washer (in each axis) to preload the axis (under the far worm bearing that I polish down til it will slide).? Fully compressed by hand (not crushed!) a single spring provides up to 7 pounds of axial force on both worm bearings and keeps the worm in position at the gearbox end bearing, at all temperatures.? ?But that's my mod...not the factory recommended component.??
If the worm blocks were compressed (say really super tight by using a C-clamp !) at daytime temperature, then bolted down hard,... then cooled down at night the aluminum contraction on the brass worm could really tighten down on the little R4ZZ bearings as you mention.? Aluminum expands and contracts slightly faster than brass... so the OPW or mounting flange would compress the worm bearings most at low temperature.
On the G11T, I asked at the factory how much to torque down the far 4-hole end screw that preloads the big Titan worm bearings (30 mm OD diameter bearings).? Mr Losmandy said..."just touch".? That is, screw in the endcap until? the cap just touches the bearing end.? I think that means put no torque on the screw cap.? That is for the Titan and G11T worm RA drives.? (See picture of that part.? In that photo I have a simple spanner wrench to tighten down the end cap....before getting the recommendation this week. ). I'll try that looser approach this coming week when I get home.??
Lots of factors to consider on the slippery road to perfection.? Every idea must get tested out to see how it improves or worsens PE.? What is the level you need for your imaging work?? Getting good tracking with autoguiding and maybe PEC too? Keep shooting!??
I'm very happy with my existing G11 and GM8 and GM811 mounts.? They have gotten down to about 1 to 1.5 arcsec RMS PE...with no PEC used.? That could go lower with PEC, and Brian urges the use of PEMpro to generate the PEC curve.? He reports excellent results on his mounts, and he goes a lot of imaging.??
But at present I'm working on a difficult case with a G11T mount, carrying a massive C14HD f/11 focal length like 3900 mm and piggyback 80 mm guide scope/finder scope on top.? (even with 0.7 FL reducer, the long FL and mass of scope and heavy counterweights is a tough challenge).? I'm getting good suggestions from the factory and other G11T and Atlas owners.? Some owners got very good PE results and I'll be happy to replicate their achievements.? ?When I get "there"...I'll let you know what worked in my case.?
Best,
Michael
On Thu, Feb 25, 2021, 7:46 AM Mark Christensen < mjcw500@...> wrote: David,
Kudos for you doing this engineering experiment.
A friend is bringing over his Celestron AVX next week because it became unmovable in our last cold spell here in Northern Illinois.
I'm expecting to find frozen grease along with overtightened bearings and gears - he bought it used and I'm betting the prior owner overdid the backlash adjustment. That or the factory did in response to persistent complaints about backlash by customers who don't know how to work with less than perfect stuff. I've seen multiple mounts which had the RA and DEC bearing thrust pre-load nuts way too tight. I suspect the assemblers read the automotive spec for the bearings and used that pre-load.
The problem is rampant: Unsuitable grease installed by Sun Bathers in America and China. Same mentality that puts electronic parts only spec'ed to 0 deg C in telescope mounts, as Meade has done in the past.
A decade or so ago a friend of mine had to install heaters on the bearing housings of an early production Paramount because of grease and bearings seizing in the cold. It was installed (as it should be) in an unheated dome in western Michigan. I once installed a small 12V heater pad on a 120V synchronous motor such as we used in the old days pre-servo and stepper.
Things like this bring to mind the Eastern Front in the winter of 1941. Maybe the companies should hire a few engineers from Novosibirsk?
To me I'd worry about excessive wear on the first few gears, even if the mount functions as others have said.
But perhaps there is nothing to be done about it aside from keeping an eye on it.
Again, Kudos.
Mark Christensen
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Well, no, I haven't done this.
Where I live our winter is usually 1-3 days when it?might get down to freezing, 32¡ã F. I believe is was 2 days this year, first week in January.
So I know my house freezer, and especially the garage chest freezer gets sub-zero.
So not realistic for me to even attempt.
I do question your method, as it seems rather crude as tests and evaluations go.
I have had much experience in Industrial accident analysis and evaluations. Mostly equipment failures, but also some human errors.
All lubricants have Data sheets on them, and state the temperature range they operate in. So that needs to be considered.
In the Freezer, is very ambiguous. Granted it is probably what you have available. But not exactly scientific evaluation.
Turns to sludge is not so. is the deposit after many hours of lubricant failure and deposit on parts. (In this case in point)
Realistically, I'm pretty sure Losmandy states a range of temperature the equipment is designed to operate in, and I do remember it was not Sub-zero.
(For reason unbeknownst to me I think I recall zero F was the cold side.)
Also, realistically "Hard to turn" is far from a repeatable measure. If you were to want something repeatable, operation of the drive motor and a record of the amperage as different temperatures would be a good start.
At least others could have some idea, beyond using a 12 inch monkey wrench.
Truth be known, I bet you have varying performance from your car between summer and winter. ;^)
How did your gearbox perform after you brought it to a more normal range? Or did you forget to note that?
If you want to clean and relube your drives, I believe is the "Soup de Jour" everybody is recommending.
It's even food grade. But I don't like the taste of it myself.
--
SonnyE
(I suggest viewed in full screen)
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Michael
>>>In turning the output shaft of the new gearboxes by hand, at 78F temperature (a nice warm February day in Burbank!!!) the rotation was notably slow and viscous.?
new gearboxes are packed with grease, You just need to exercise it a bit, simplest way is to grab the shaft in your fingers and whirl it around like a new year's clacker (that's a thing right?) and you will find after a few minutes it loosens up significantly?
On Thu, Feb 25, 2021 at 10:52 AM Michael Herman < mherman346@...> wrote: Hi Mark,
Good points.? Some thoughts...?a long email.??
Until now I have ignored the gearbox as an area that could "freeze up".? I just bought 2 new gearboxes at the factory this week. These are my first two brand new gearboxes.? I do live these days in a very benign climate that never freezes.? Denver is calling to me, however...
?In turning the output shaft of the new gearboxes by hand, at 78F temperature (a nice warm February day in Burbank!!!) the rotation was notably slow and viscous.? The new units have a cellophane type tape over the motor pinion gear entry port to prevent particles from entering, and prevent lube from flowing out on a hot day in storage.? My old gearboxes spin very loosely and freely by comparison.??
If you were in a freezing climate, could you clean that viscous lube out and put in Superlube, say??
Maybe a soak in alcohol or WD40 would dilute the internal grease, and you could easily pack in lighter Superlube.? The parts are plastic (ABS maybe?) Maybe brass and stainless?steel inside?? Can't use a harsh solvent like Berryman B-12 "Chemtool" as it might soften the plastic.? Can't insert anything in the gearbox that might leave a fiber or particle.??
My old gearboxes, all on used mounts,? had essentially zero lube left in them.? The gears spun freely and loosely.? I never got a new gearbox til now to tell they are intended to have lube packed inside.? I'd try the Superlube that is advertised, and astronomy tested, to go to very low temperature.??
The stock gearbox does not disassemble...it is sealed by rivets.? The McLennan gearboxes from Element14 do disassemble with 4 tiny flat head screws.? But not the McLennan gearboxes from RS components...those have a sealing paint over the assembly screws.? If you can disassemble the gearbox it helps in replacing the greases of course.?
____
Always experiments to try...some other notes...
____
On the possible overloading the worm bearings Mark raised:
On my G11 and GM8 worm bearings I use a single R4 Belleville spring washer (in each axis) to preload the axis (under the far worm bearing that I polish down til it will slide).? Fully compressed by hand (not crushed!) a single spring provides up to 7 pounds of axial force on both worm bearings and keeps the worm in position at the gearbox end bearing, at all temperatures.? ?But that's my mod...not the factory recommended component.??
If the worm blocks were compressed (say really super tight by using a C-clamp !) at daytime temperature, then bolted down hard,... then cooled down at night the aluminum contraction on the brass worm could really tighten down on the little R4ZZ bearings as you mention.? Aluminum expands and contracts slightly faster than brass... so the OPW or mounting flange would compress the worm bearings most at low temperature.
On the G11T, I asked at the factory how much to torque down the far 4-hole end screw that preloads the big Titan worm bearings (30 mm OD diameter bearings).? Mr Losmandy said..."just touch".? That is, screw in the endcap until? the cap just touches the bearing end.? I think that means put no torque on the screw cap.? That is for the Titan and G11T worm RA drives.? (See picture of that part.? In that photo I have a simple spanner wrench to tighten down the end cap....before getting the recommendation this week. ). I'll try that looser approach this coming week when I get home.??
Lots of factors to consider on the slippery road to perfection.? Every idea must get tested out to see how it improves or worsens PE.? What is the level you need for your imaging work?? Getting good tracking with autoguiding and maybe PEC too? Keep shooting!??
I'm very happy with my existing G11 and GM8 and GM811 mounts.? They have gotten down to about 1 to 1.5 arcsec RMS PE...with no PEC used.? That could go lower with PEC, and Brian urges the use of PEMpro to generate the PEC curve.? He reports excellent results on his mounts, and he goes a lot of imaging.??
But at present I'm working on a difficult case with a G11T mount, carrying a massive C14HD f/11 focal length like 3900 mm and piggyback 80 mm guide scope/finder scope on top.? (even with 0.7 FL reducer, the long FL and mass of scope and heavy counterweights is a tough challenge).? I'm getting good suggestions from the factory and other G11T and Atlas owners.? Some owners got very good PE results and I'll be happy to replicate their achievements.? ?When I get "there"...I'll let you know what worked in my case.?
Best,
Michael
On Thu, Feb 25, 2021, 7:46 AM Mark Christensen < mjcw500@...> wrote: David,
Kudos for you doing this engineering experiment.
A friend is bringing over his Celestron AVX next week because it became unmovable in our last cold spell here in Northern Illinois.
I'm expecting to find frozen grease along with overtightened bearings and gears - he bought it used and I'm betting the prior owner overdid the backlash adjustment. That or the factory did in response to persistent complaints about backlash by customers who don't know how to work with less than perfect stuff. I've seen multiple mounts which had the RA and DEC bearing thrust pre-load nuts way too tight. I suspect the assemblers read the automotive spec for the bearings and used that pre-load.
The problem is rampant: Unsuitable grease installed by Sun Bathers in America and China. Same mentality that puts electronic parts only spec'ed to 0 deg C in telescope mounts, as Meade has done in the past.
A decade or so ago a friend of mine had to install heaters on the bearing housings of an early production Paramount because of grease and bearings seizing in the cold. It was installed (as it should be) in an unheated dome in western Michigan. I once installed a small 12V heater pad on a 120V synchronous motor such as we used in the old days pre-servo and stepper.
Things like this bring to mind the Eastern Front in the winter of 1941. Maybe the companies should hire a few engineers from Novosibirsk?
To me I'd worry about excessive wear on the first few gears, even if the mount functions as others have said.
But perhaps there is nothing to be done about it aside from keeping an eye on it.
Again, Kudos.
Mark Christensen
-- Brian?
Brian Valente portfolio
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I'm pretty sure Superlube tastes - like - well - grease :)? I laughed for a few after reading that!
I never intended this to be some super engineering paper where I put a gearbox on a shaker table, cool it with nitrogen,instrument the thing, throw salt at it, and measure torque.
(I have a background in T&E with aerospace systems)
My freezer is at about -10F which isn't that far from some folks operating environment.
All I really wanted to do is throw this out there.
We are always trying to get that last 1% from these awesome mounts and I think we ignore the gearboxes in the flow of power from the motor to the camera/eyepiece.
Just try it - - - I'll tell you all right now that if you simply throw a gearbox in the freezer, you will really be surprised at the increased torque to rotate the gearbox.? My MARK ONE fingers and eyeballs put it at close to an order of magnitude above room temperature.
Isn't Losmandy in Burbank CA?? Doesn't really get cold there - does it.... (I wish I was in Burbank, CA)
Clear skies and may your camera never have bad columns.
Dave
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Hey Brian - Ain't ragging on the mount.? I love mine.? I have always used slow slew speeds as I think everything is happier that way.? I also use a higher voltage power supply.
All I'm sayin' is try it.? Throw a gearbox in the freezer and then report back (Pretty sure you all have a few lying around).
All the best,
Dave
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>>>Throw a gearbox in the freezer and then report back (Pretty sure you all have a few lying around).
that's the first thing I did when i read your post :)?
then I emailed scott :) :)?
then i checked the support logs :)?
Hey Brian - Ain't ragging on the mount.? I love mine.? I have always used slow slew speeds as I think everything is happier that way.? I also use a higher voltage power supply.
All I'm sayin' is try it.? Throw a gearbox in the freezer and then report back (Pretty sure you all have a few lying around).
All the best,
Dave
-- Brian?
Brian Valente portfolio
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I'm guessing alcohol.? any solvent that won't eat the plastic case/gear.? There is a plastic gear so be aware of that (no idea what won't eat that)
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On 2/25/2021 6:49 PM, davidfenster@... via groups.io wrote: Hey Brian - Ain't ragging on the mount.? I love mine.? I have always used slow slew speeds as I think everything is happier that way.? I also use a higher voltage power supply.
All I'm sayin' is try it.? Throw a gearbox in the freezer and then report back (Pretty sure you all have a few lying around).
All the best,
Dave Just FWIW, I have a newer GM811 running on 12V on the same 5A supply that runs my mini-PC and cameras and have zero issues here in metro Detroit at temperatures as low as 10F. I do not limit the slew rate. The motors sound exactly like they did last fall when it first arrived and it was warm outside. Paul -- Paul Goelz Rochester Hills, MI USA pgoelz@... www.pgoelz.com
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I have a newer G11G, up here in Michigan and was getting a lot of DEC stall warnings as the temperature got down in the single digits. I was able to stop them that night by increasing the stall limits. The next day I took off the worm cover and cleaned off the worm and lubricated with some Mobil 1 0W-20 while driving the DEC axis. Seems better.?
Sometimes if I haven't run the mount for a while I also use a program I wrote to exercise both axis.
Rick?
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Chip Louie
Michael Herman