re- greasing mount grease

[t1bbbst3r]

Just finished re-greasing the eq5 mount after reading a how to guide from here:

http://www.astronomyboy.com/cg5/

Someone would hopefully find this interesting anyway, couldnt find a review myself to do with this so here goes...

Can confirm that the slow motion controls twist about effortlessly compared to being slightly jerky beforehand (especially the dec.), although there is little or no change to slewing. No doubt this will cut down on the vibration that the slow motion movement causes and will save battery power on tracking systems.

On reflection, as there is no improvement to slewing, although the lithium grease has a lot less friction, just de-greasing then re-greasing the worm + worm gear on each axis leaving the rest of the shafts alone would have the same effect and take half the time.

Is definatly worth doing, especially if, upon inspection, the grease around your worm gears is a viscouse, sticky substance, which will be causing a lot of friction. (Found some Chinese guys hair on my r.a gear, ha)

As long as each seperate part that gets taken off is kept with all the bolts, washers ect. near it in its own area, dismantling/ rebuilding any telescopes mount should be relatively easy, the confidence to do it is more important than a depth of knowledge.

This is my opinion anyway, enjoy!

[E621Keith]

I am afraid you just ruined your mount.

The worm gears needs a load bearing grease and the grease needs to be thick and sticky so they don't get rub off in use. Lithium grease is no good for this. After a short while, the lithium grease will wear thin and rubbed off, then your mount will experience significant increase in wear. The results would be irreversible damage to your worm + worm wheel.

I suggest you immediately remove the lithium grease and replace the grease with something heavier. The grease is thick and sticky for a reason and Vixen ship their original GP mounts with thick sticky grease too. Sky Watcher chose thick grease to match the Vixen original, not because they were cutting cost.

Pete_gamby from Vixen UK posted this in another thread.

In response to John's email, I asked Vixen Japan for their recommendations and received a reply which is helpful to a degree:

“About types of grease, silicon grease of high viscosity (like clear, glutinous malt-sugar) is used for worm gears. Car axle oil mixed with silicon grease (like jelly) is used for RA axis shaft and DEC axis shaft.”

Basically, they have their own “secret sauce” formula for the grease used on the mounts and clearly don’t want to disclose what it is!

HTH

Cheers, Pete

http://stargazerslou...se#entry1670505

edit: Forgot to mention The origianl thick grease is chosen to match the mount's static friction with kinematic friction. A number of people have reported significant increase in periodic error after re-greasing their mount with the wrong grease, and it is believed the friction mismatch is the cause of the increase in PEC.

[t1bbbst3r]

Maybe the tracking errors are from some left behind metal fragments or something after the polishing.... I see what you mean by a difference in friction, but its probably the vibrations of rough edges that could possibly warp some washers or something after a long while, like more than what already happens if your not careful. It does say to re-grease every year i think, unless only using the tiniest amount of grease on the re-coat, ruining the mount is a bit of an overstatement it seems.

I still think that doing the worm + worm gear is extremely worthwhile as basically, it eliminates a lot of friction.

your probrably right where you say about the desighn aspects though, but its not as if the gear to worm surface bears a lot of weight and both of mine were very stiff to what they are now. I cant recommend that bit highly enough, although doing the whole mount myself, I am sure it all will turn out ok for myself anyway....... If that makes any sense!

[E621Keith]

The mount is supposed to be greased for life. If you replace the worm grease it needs to be thick gear grease that has good load bearing property. You can use lithium grease for the bearings and other components, but proper bearing grease is best.

The worm actually experiences a lot of load. First any uneven balance in you mount is magnified by the length of the moment arm (axis to mount saddle vs axis to worm radius), and then all of that off balanced load is concentrated on to the tiny surfaces where the few wheel teeth are in contact with the worm. Light grease will be scraped off in no time. Furthermore, unlike most gear boxes, the worm drive in a EQ mount do not cycle fast enough to redistribute the grease from other part of the wheel, in fact it cycles extremely slowly, so the grease that was applied initially needs to stay there. When the grease wears off, you get metal to metal contact on the polished worm and wheel. If that happens, that'd be the end of your mount.

To illustrate how poor choice lithium grease is. Put some lithium, grease on a metal surface and wipe it with a tissue paper. Lithium grease comes straight off, whereas gear grease would stick to the surface and rip the tissue paper.

I'm sure your realised how hard it was to remove the original grease when you degreased the worm and wheel. It's is hard to remove for a very good reason.

You should really re grease your mount with a load bearing grease before it's too late.

[billhinge]

Interesting.

I have an old Fullerscopes mkIII mount I relubricated with lithium grease and found it clogged up after a few weeks.

When I relubricated my CG5 last year I used WS2 grease, actually a suspension of WS2 powder in light oil. Still going strong, the oil flows around the gears and the powder coats the gear surface (google Tungsten disulfide or WS2)

I even lubed my teflon bearings with it, as a result I have my gears much tighter than they were originally and there appears to less backlash and noise

Alternatively, you could get your gears professionally powder coated and run them dry if you like

http://www.ws2.co.uk/engineering-ws2-applications.php (I have no affiliation)

• Withstands loads up to 350,000psi at temperatures between -273oC to 650oC.
  
• Overcomes or reduces mechanical lubrication problems improving performance and extending service life up to
  300-500%.
  
• Maintains the dimensional integrity of the substrate to within 0.5microns withno buildup.
  
• Is inert, inorganic, non-toxic, non-distortive, non-corrosive and resistant to most fuels and solvents.
  
• Resists carbon build-up from burnt deposits due to its extremely low coefficient of friction - less than half that of Moly and Teflon.
  
• Molecularly bonds to all materials and platings.
  

Downside is that it is more expensive that grease and you have to import it from the US

Here is what Celestron recommend http://www.celestron.com/c3/support3/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=2533

[Peter Drew]

I'm in the E621Keith camp on this one. Not any experience of WS2 but the hype reminds me of the Molyslip hype years ago, whatever happened to that?.

[billhinge]

Peter

Fair enough, I'm not asking anyone to try it, just pointing out my own observations and that it works for me

In the end you pays your money and you makes your own choice

[Peter Drew]

So true Billhinge It's just that this issue keeps coming up recently and as a retired astro-engineer who has in the past had to try and repair mounts where the owner had tried unsuitable lubricants, I have some concerns.

[t1bbbst3r]

I think im starting to get the picture. From what I understand through my own practical experiments, because the shafts arent guns or something, they dont have precise, square or even smooth surfaces, so with the thick grease, its a lot better than the thin tft at hiding this fact.

I will have a close inspection after the winter, or if it loosens up and if the grease has worn off then it will be changed for some kind of engine type.

Hmm, seems like ive been walking on egg shells or something. Not being ignorant, its good to know if something youve done is questionable but will leave it for the time being and see just how true everyones evaluations have become after a period of time. Have definately been attributed with some conflicting opinions here, thats for sure!

[cantharis]

I replaced the Chinese glop in my EQ5 as well. The stuff they put in them is so incredibly viscous that it prevents you balancing the mount properly - with my SV102ED in the saddle I could place a balance weight anywhere on the shaft and the RA axis wouldn´t move.

If it prevents the mount from performing its design function it obviously can´t be the right stuff.

A whole lot better now - I can balance the mount properly and so markedly reduce bearing loads. And I can easily turn the worm shafts with my finger tips.

[cantharis]

Here is what Celestron recommend http://www.celestron...barticleid=2533

Mobil Synthetic 1 - which is a lithium grease.

[billhinge]

As I said, I don't use lithium grease. I just mentioned it to give a balanced comment

I agree about the standard grease not allowing proper balance, like you I found the original grease allowed too much latitude in balance to make it accurate

[E621Keith]

I replaced the Chinese glop in my EQ5 as well. The stuff they put in them is so incredibly viscous that it prevents you balancing the mount properly - with my SV102ED in the saddle I could place a balance weight anywhere on the shaft and the RA axis wouldn´t move.

If it prevents the mount from performing its design function it obviously can´t be the right stuff.

A whole lot better now - I can balance the mount properly and so markedly reduce bearing loads. And I can easily turn the worm shafts with my finger tips.

How do you balance your scope?

I balance my system with the clutch disengaged, so what's on the worm wheel have no affect whether the scope is easy to balance or not. The grease in the bearing may be a problem, but the choice of bearing grease is not as critical as worm wheel grease. If you balance you mount with the clutch engaged, then you will be putting on a lot of unnecessary strain on the worm drive.

The fact is non load bearing grease will rub off too easily and will not be suitable for the worm wheel.

[Astro_Baby]

I have been biting my to tongue on this one but feel I should comment........if for no other reason than so many people use my mount rebuild guides.......

Much has been said of lithium grease decaying, if you are using a grease made of dinosaurs then it may well. I have always used a lithium/teflon mix called TF2 and its been fine. After paranoia on here some time ago about grease turning chalky I did a strip of my mount which was greased using TF2 and found that the grease had NOT in fact decayed and neither had it been removed from the worm assembly over time. Anyone who has seen my own mount running has always commented on how quiet and smooth it is.

Much is made of super lubes of various types but the fact is no telescope mount ever runs at ultra low or high temperatures, neither are there high levels lf heating from friction and the loading cant ever be really high in a system that uses a 12v motor. Superlube may well be worth using though if only for its ready availability though it does have a consistency not dissimilar to lithium based greases. Most commonly available lithium grease from bike stores is nearly always a composite of lithium and some other additive.

To my mind the ONLY reason why the mounts are greased at the factory with a super thick lube is firstly to keep the mechanicals quiet and secondly to hide any small deviations in the machining Anyone familiar with the used car trade will be aware of the old trick of filling the engine or gearbox with bananas or STP for the same reason. It hides a multitude of ills in a slack set of machanicals.

My own HEQ5 when supplied from new was so sticky if I released the RA clutch and spun the mount by hand it would be lucky to make one revolution, it would go maybe a quarter of the way round before the lube would stick it. After cleaning and lubing with TF2 the RA is so free that one spin on it will take the RA round three times. Freeer and easier, better balance and a smoother mechanism by far which takes the strain out of the gear train.

Various liths amd superlubes have been used for some time on various mounts across a wide range of forums, mount builders etc, none of them are of the super thick lube variety and none has has ever seen a problem that I am aware of, and I read a lot of mount builld threads.

My HEQ5 and my sisters were both rebuilt by me using TF2 lithium grease, and neither has ever shown excess wear or grease going solid in quite some use. My sisters is obs based and hasnt been touched in three years. On its last inspection about a month ago I took the motor cover off to inspect the grease and all of the motor gears were still well lubed.

The mounts do perform more quietly and with a higher degree of smoothness than when they were lubed with gunk like lubricants. I have also rebuilt mounts for others and no one has ever beaten a path back to my door to say the mount has performed badly or is showing problems.

Another reason why manufacturers probably use ultra heavy lubes is for lifetime greasing, bear in mind the vast majority of these mounts will never be rebuilt, will never be used by afficianados and will most likley be used once or twice before going on ebay as its owner moves on then a thick grease rather than a precision tune makes sense for the factory. Look how many ads appear from people saying "used once, but bored with it/cant understand it/wife wants new shoes etc" appear. The ultra tick grease keeps the mount quiet and a vast majority of owners wont care to tune or wont care period.

Thats my own experience from rebuilding mounts.

[cantharis]

If you balance you mount with the clutch engaged, then you will be putting on a lot of unnecessary strain on the worm drive.

The fact is non load bearing grease will rub off too easily and will not be suitable for the worm wheel.

As far as I am aware it is impossible to balance the mount unless the RA and Dec axes are unlocked!! And mine had so much glop in it with the axes unlocked they were still too immovable to be balanced.

And are you saying lithium grease is not load bearing? Then I can´t imagine why manufacturers put the stuff in the very heavily loaded wheel bearings of our cars.

[Peter Drew]

I think we're talking "apples and pears" here. Ballrace bearing with their high finish, hardened surfaces, will work perfectly with suitable light greases, heavy grease would be inappropriate for high speed running. It is the relatively soft, metal to metal plain bearings found in the lower price bracket mounts that need high load bearing thick clingy grease to avoid pick up scoring or even seizure. I agree that the common thick grease becomes very stiff in cold weather and benefits by being mixed with a little of a lighter type.

[billhinge]

Peter

Hmm, now getting confused, the conversation was about worm gears a minute ago, mine just has a couple of small ball races in which the worm sits , nothing else (I replaced mine with ceramics) and I coat the worm and gear with WS2

The other large ball races are inside the main Dec and RA housing (also regreased) , are you saying just the worm and gear needs heavy grease or the actual ball races holding the worm?

[Photosbykev]

I'm slightly surprised by all of the talk of the bearings being heavily loaded. Imo they will be working well inside their design spec and certainly well below typical rpm levels that the bearing life is based on. Assuming the factory installed bearings are the cheapest available then the actual bearing rating will be lower than expected but even so we are talking orders of magnitude between the rated loadings and actual loadings. The worm, wheel and gears are another kettle of fish as they won't be high precision even if they are quoted as such and I would expect the material specification and tolerancing to be very optimistic

[Peter Drew]

In a nutshell, I would be happy with a lithium type grease to be applied to ballrace bearings but I would want to grease unhardened metal to metal surfaces with a sticky high load bearing alternative. Vixen Polaris mounts and their clones have metal to metal aluminium bearings and need the latter.

[earth titan]

Knew I'd seen something in an engineering trade mag, but couldn't remember where. Over the holiday, I found it:

http://www.machinerylubrication.com/Read/1080/worm-gears

IMHO, based on experience as an engineer building printing presses, you need different lubes for different areas. What is right for worm gears, where sliding friction is required, is different for spur gears, is different for bearings. In most cases, where gearboxes contain different types of gears, a compromise is settled on.

Also be aware of the contents of the grease and oils. If they contain sulphur (used an additive to chemically bond the lubricant to the surfaces), then they may react with yellow metals such as brass and cause pitting.

Lubrication is a science in itself. We used to employ a lubricant 'expert' who really wasn't someone you wanted to set next to at a dinner party......

[billhinge]

Yes the science is called tribology, one of my final year university projects many years ago was measuring the coefficient of friction of frozen alcohols e.g., methanol, ethanol etc

[cantharis]

Pretty good load of conflicting ideas here.

May I say - there are, certainly in engineering terms, NO high load bearing surfaces in any EQ or Alt-Az mount - there are LOW loads when the mount is slewing and EXTREMELY low loads when it is tracking. Which is why the manufacturers are very happy to use soft - and cheap and easily machineable materials - like brass and Al and even PLASTIC gears. Lubricants like Lithium greases are MORE than capable of managing such LOW loads.

[Peter Drew]

Hmm, there certainly are some conflicting ideas on this subject. My take on this is that manufacturers can get away with using soft, cheap and easily machineable materials precisely because they use these sticky heavy load bearing greases.

[billhinge]

Amazing how this thread rumbles on, must be boredom or cloudy nights

My take is that it is budget driven choice of materials that are used in manufacture, surely if science played a part in the selection of the grease then the same logic would be applied to the other materials, ie better alloy casting than the actual monkey metal used in basic mounts

By pure chance I was googling something else this evening and came across this article on the William Herschel telescope 2010-2012 http://www.ing.iac.es/conferences/wht201020/abstracts2.html , at the bottom is a paragraph and sentence "An innovative jukebox-like exchanging mechanism inside the cryostat based on rolling hybrid bearings technology with tungsten disulfide as solid lubricant has been chosen to hold the movements inside the cryostat.", no mention of superlube though

[Astro_Baby]

Well a few months ago I was rebuilding an EQ6 and I had to reassamble the DEC with no grease at all while working out the shim sizes and trying to fix an annoying problem with its movement. With no grease at all the mount was amazingly ligh and easy to turn.

My eldest son, sometime ago when we were rebuilding another mount, asked why I never went for a super fine grease, something of the viscosity of WD40 and I confessed that I sisnt know, just that lithium and superlube are whats generally recognised as the best.

It would certainl though be tempting to rebuold my own mount with somw super light grease, obviously WD40 would be no use as it tends to evaporate over time and its way too thin as well. Same for gun oil or similar. But if ai ever come across a super thin grease with good ahesion proprties I will for sure give it a go.