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jcferguson
02-21-2007, 12:05 PM
Hi, does anyone know what is in potentiometers that gives them that smooth friction? Is it some kind of grease that I could add to bearings to make them roll with some fluid friction?


Carlos Ferguson

stamptrol
02-21-2007, 09:14 PM
Carlos,

There are a couple of mechanical reasons why most pots work smoothly:
1. the shaft bearing is relatively large for the load and any lubricant tends to stay where it belongs.
2. the typical resistance element is carbon based and has quite a hard surface compared to the copper/brass/silver sliding contact so that friction is inherently quite low. Some use a small amount of lubricant which also helps.

As for bearings, a well chosen bearing (load, speed, type) will give exceptional smoothness and life. Most bearing guys will tell you that the cause of most bearing failure is mis-application and over-lubrication. Have a look at a bearing manufacturer's website for more insight. ( Try Timken, SKF, NTN, etc)

Cheers,

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Tom Sisk

http://www.siskconsult.com
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jcferguson
02-21-2007, 10:11 PM
I had one of those experiences with google last night where it take a while to figure out what to call the thing that you are searching for... I don't think I described it in my post very well. I think what I am looking for is called "damping grease". What I want is actually more friction, a controlled kind of friction, like in a stereo volume knob. The only stuff I could find is in a 90$ kit though... the stuff is like gold!

http://easyweb.abtnet.com/inetisscripts/abtinetis.exe/ecproductlist@public?tn=1059_grease.tem#


Carlos

Loopy Byteloose
02-21-2007, 11:18 PM
Ideally wire-wound potentiometers are the smoothest available, but they can be quite large and have limited values.

I have a spray can of stuff· {Kontact}·to clean up and quiet down rough pots, but it only does so much. That works for a while.· At times, it is easier to change a rough pot with a better quality new one, preferable well sealed and audiophile quality.

Sadly, that cannot always be done.· For instance, my computer speakers have a very rough set of minature pots that are too small and too oddball to replace.· And the spray can only do so much.

In this case, I will try to find new speakers with a more servicible chassis set up and be carefully to listen to them before I buy.

The worst are slide potentiometers [on mixing boards]·because they usually face upwards.· Thus, the slot has a whole world of dust and junk falling into it and creating conductivity problems.

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"If you want more fiber, eat the package.· Not enough?· Eat the manual."········


···················· Tropical regards,····· G. Herzog [·黃鶴 ]·in Taiwan

kjennejohn
02-22-2007, 02:30 PM
A google search using "high viscosity silicone oil" produced this:

http://www.airsoftarms.com/viewproductdetail.php?ProdID=8137

$7.99·per small bottle. Looks like it's for air guns. Special order, they claim it takes 4 - 6 weeks to get it.

It produced other hits. I just stopped on this one because it sounded right.

Later!

kenjj

Loopy Byteloose
02-22-2007, 07:21 PM
Expensive oil! Maybe a sewing machine shop could do better.
Mineral oil from a drug store [without scent or additives] is another
Lithium grease would be much cheaper and stay in place. Try an automotive supply. More stable than vasoline.

The Kontact spray both lubes the shaft and eliminates metal corrosion on electrical contacts.
Aside from using it on pots, I used it on the starter and turn signal buttons of my motorscooter as weather gets into them.
It works on relay contacts and damp ignition points too.

The simple fact is that at room temperature, there are a lot of oils and greases that would work. But they do not conduct electricity.
You have to be frugal and neat.

Also, oils do come in the kind that stay liquid and others that do dry hard as a coating [linseed oil, poppy oil, tung oil, soy, etc.] We make paint with the latter.

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"If you want more fiber, eat the package.· Not enough?· Eat the manual."········


···················· Tropical regards,····· G. Herzog [·黃鶴 ]·in Taiwan