GEM Mount re-lubing query; lithium grease – brown vs. white?

[Dennis]

Hello,

I’ve just stripped down my Vixen GPDX mount, as the turning torque was far too great – the (10 yr old) grease had almost solidified and continued usage would strain the motors. I've cleaned the old gunk off the worms, wheels, housings, bushes etc. using mineral turpentine and everything looks new and shiny once more.

Browsing around the web, it appears that most mount re-lubers seem to prefer White Lithium Grease. However, I have a tub of Castrol LM (http://www.oomco.com/castrol/castrol_commercial_greases.asp)grea se, which is a brown lithium grease, and was wondering if there is much of a difference for the intended application? I don’t have any white lithium grease and wouldn’t know where to obtain it?

The affected Vixen GPDX mount components appear to be made of Stainless Steel, Aluminium and Bronze.

Thanks!

Dennis

Castrol LM data:

Castrol LM multi-purpose, Lithium base greases start with specially selected mineral oils of outstanding oxidation and corrosion properties and are manufactured to close control of drop points, penetration numbers, alkalinity and ash content to offer high stability, long life, excellent resistance to changes in consistency and good water-proof quality.
Castrol LM - a premium quality grease primarily designed for wheel bearing lubrication. It is outstanding as a general chassis lubricant and is suitable for most automotive applications.

[[1ponders]]

Dennis, I contacted Bintel quite some time ago and they use a white grease called "Super Lube - Synthetic Grease". I got mine from Wagner Electronic Services 138 liverpool RD Ashfield 2131 ph 02 9798 9233
http://www.wagner.net.au/

[bloodhound31]

Can you use white petroleum jelly? (Vaseline)

Baz.

[GeoffW1]

Hi Dennis,

Either would do. White lithium grease is preferred wherever water or moisture might be present as it has a higher resistance to that. So, if the parts are directly subject to dew, it would be good.

However if all is internal and sealed then the LM grease is fine. If you do want to get the white grease, it is even available in a spray form, brand CRC or WD40, from auto parts stores.

Cheers

[timelord]

Baz lovers lube is no good--on a warm summers day it will melt and run like water--besides its not really a lubricant that is suited to gear or bearing loads.
Alex.

[Dennis]

Hey Guys

Many thanks for your help with my query – it’s great to be able to get advice and answers to these kind of specialist questions.

I will follow Geoff’s advice re White Lithium Grease. A Google search indicated that I should be able to pick up some “3-IN-ONE Professional White Lithium Grease” from one of the following places, all local to me:

HW stores: Bunnings or Mitre 10.
Auto stores: Autobarn, Repco or Supercheap Auto.

I have also since discovered that Vixen allegedly uses a 100% silicone grease on the worm gear and a synthetic grease on the bearings, so I’ll pick up some silicone grease too, just for the worm.

Cheers

Dennis

[wasyoungonce]

super lube:

http://cgi.ebay.ca/Super-Lube-21030-Synthetic-Grease-with-PTFE-3-oz-tube_W0QQitemZ230044305101QQihZ013Q QcategoryZ1267QQrdZ1QQssPageNameZWD 1VQQcmdZViewItem

Although if you have phosphor bronze bushes, they should be soaked in oil as they absorb the oil and this leaches out during operation..aka self lubricating.

All the rage appears to be going to the silicon synthetic greases although low viscosity mineral greases should suffice. The grease holds the oils in suspension and releases it in operation. Since the mechanicals are at low speed synthetic grease should do ok as advised by timken:

http://www.timken.com/lubrication/faq.asp


http://www.bearings.machinedesign.com/guiEdits/Content/BDE_6_4/bdemech6_44.aspx

[h0ughy]

Thanks for asking the questions Dennis, i was wondering which one was used?

[Dennis]

Hi Guys

Job now done! RA and DEC axes both re-greased with all the old gunk removed. The mount moves so much more freely now, and the slews sound so much less strained. Need to take it out and test GoTo accuracy and tracking accuracy to make sure I haven’t disturbed anything.

In the end, I used 3-IN-ONE Professional White Lithium Grease obtained for $10 from Autobarn, for packing the shafts and bushes, and Silicon Grease for the Worm.

Here is some more information I found along the way:

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http://tech.groups.yahoo.com/group/ss2k/message/6549

Teflon greases and lubricants shouldn't be used in telescope mounts. Any lubricant containing suspended particulates will harm worm accuracy.

http://physics.beloit.edu/observatory/user/manual.html

"Greases containing suspended particles (e.g., moly or graphite) should never be used in precision bearings or screws, as these particles will seriously interfere with tight tolerances."

White lithium grease is an excellent mount lubricant for all climates and temperatures.
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SS2K Yahoo Groups:
“Vixen uses two types a 100% silicone grease on the worm gear and a synthetic grease on the bearings”.

“I have a Mountain Instruments MI-250 and Larry Meyers recommends white lithium grease for the gears”.

+++++++++++++++++++++++++++++++++++ ++++++++++++++++++++
http://tech.groups.yahoo.com/group/ss2k/message/6559
I am aware that most Teflon particulate lubricants have particulate sizes of about 100 microns on average and most of the particulates are not spherical but more like irregular shaped pancakes that stack up, pack up, break up and redistribute themselves under normal operation. They are also very compressible.

There are some where the particulates are ground to sub-micron size for specialized high-speed, high temperature applications.

In all cases the lubricating film thickness is unpredictable and highly variable in operation. Certainly not conducive to telescope mount accuracy.

Here is the only sub-micron Teflon lubricant I could find on-line:

http://www.worldklass.com/pro_drytef.html

Much better to use a lubricant that is much more compatible with scope mounts like white lithium grease.

+++++++++++++++++++++++++++++++++++ ++++++++++++++++++++

I also read a couple of instances where use of petroleum based greases may contribute to some adverse reactions between stainless steel and aluminium.

I am repeating the above stuff like a parrot, as I have little knowledge in the domain of lubricants and so cannot attest to its accuracy and/or relevance.

The quintessential CG5 mount website:

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

Cheers

Dennis

[Dennis]

Today, I saw exactly the same product in Bunnings.....for $6.40...:shrug:

Cheers

Dennis

[bird]

This is also what I use when I service my G11, it's waay better than anything else you're going to find. My small tube of the stuff (bought from Farnell) will last me approximately 10 lifetimes at the rate I'm using it :-)

cheers, Bird