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Nico
Tinkerer
Username: Nico
Post Number: 26
Registered: 07-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, September 10, 2010 - 10:11 pm: | 
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Can anyone explain me what is exactly, "dumping grease"? I've seen it was widely recommended around here but can't find a correct translation to Spanish for that product. Is it by chance a synonym of "insulating", "impermeable"?
I don't know, but I need some of that or at least a replacement to use in a focus ring helicoid because it is way too loose.
Thanks you all. |
Scott
Tinkerer
Username: Scott
Post Number: 107
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, September 11, 2010 - 12:24 am: |
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"Damping grease"? Various kinds of grease can be good for damping. Medium viscosity (not too thin, not too thick). I usually use a clear silicon-based grease, which feels about like Vaseline. The main thing, is that you want to choose a grease that will not separate or 'run' if it gets hot, and will stay only where you put it. It has to be thick enough to provide a certain amount of resistance, so that you don't feel any 'play' or friction.
Check in a shop that sells professional-grade tools for electricians. A good auto-parts shop will also have a variety of suitable grease types.
Of course, you will have to completely dismantle the helical to clean away the old grease and add the new grease. |
Glenn
Tinkerer
Username: Glenn
Post Number: 848
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, September 11, 2010 - 03:22 am: |
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A search in the Archive will come up with many suitable types/makes of grease. To answer your question, a 'Damping' grease is one that retains its initial resistance to movement - linear or rotative - even when the grease is being worked, ie subjected to shearing movement. This quality is not always present in greases - they will all provide lubrication, but some will loosen up quite rapidly when subjected for example to the rotative movement in a lens helix. To be frank this property is not important in lenses with a helical diameter of under 2 inches, it only becomes useful in large diameter and heavy lenses, eg the Jena 180mm/2.8 and lenses of similar size. |
Nico
Tinkerer
Username: Nico
Post Number: 27
Registered: 07-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, September 11, 2010 - 07:18 am: |
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Great, now I have a much better idea of what I'm looking for. I'm being too optimistic here but just wonder if I could use something that I've found in my grandfather's mad-doc-lab (he has all kind of technic stuff there). It's a pot labeled "White grease with silicone" which can be way too imprecise. My fear is that it could drain when heated, as Scott said.
Oh and yeah, my half frame camera has a helical of about one inch diameter so...
Anyway, thanks! |
Glenn
Tinkerer
Username: Glenn
Post Number: 849
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, September 11, 2010 - 09:57 am: |
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Nico,
There is a quick way to see if the pot of grease, your grandfather has, is half suitable - I suppose the pot has been sitting, undisturbed, on a shelf for some years subjected to the norms of room temperature? If this is so, remove the lid and see if any oil or 'liquid' has separated out. No signs of separation is a good sign, indicating that the grease is unlikely to separate and thus oil up the iris mechanism etc at normal temperatures. Separation may or may not indicate a grease that is intolerant to high temperatures - some just exhibit a viscosity that is temperature dependent, others will show an irreversible separation of the thickening media. However, one should note that it is the extremes of cold temperatures that usually play havoc with lens and camera lubrication, causing all kinds of malfunction.
I use two greases generally, one for helicals below 2 inches in diameter and another for lenses greater than two inches, both of which function properly in temperatures ranging from the UK's unpredictable to the extremes of a Saharan crossing. I have no idea of the ambient temperatures that you encounter on a day to day basis; however, if a small cone of grease has not spread into a large pool one micron thick, when placed in the sun for a couple of hours, I do not think you will have any problems using said grease! |
Nico
Tinkerer
Username: Nico
Post Number: 28
Registered: 07-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, September 11, 2010 - 05:39 pm: |
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Thanks Glenn, what you said encouraged me to give that thing a chance. There was no separation of liquids, so first I heated it to see if it could spread in extreme conditions (for example a photo safari to the center of the earth, cuz' I left the grease in the oven).
The thing passed the test so it is finally perfectly applied in the helicoid. Now I'm wrestling with the whole thing to put rings back together in the correct position.
Thank you again. Best regards. |
Hai
Tinkerer
Username: Hai
Post Number: 41
Registered: 05-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, October 09, 2010 - 05:31 am: |
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I use Lithium Grease made by Michelin. Bought it few years ago in a fancy bicycles shop and it is great. |
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