Jeff Liebermann wrote in message
...
On Wed, 10 Aug 2011 08:17:53 +0100, "N_Cook"
wrote:

I don't know if its relevant with these encoders but a few times I've
found
with preset size pots that appear in audio mixers. The grease hardens and
then lifts the very feeble wipers of the pots. No track wear at all as
the
wiper action is so slight , so why the grease ?

Good question. You might need a microscope to see the groves.

My guess(tm) would be to prevent oxidation and prevent the small
amounts of the resistance material from landing across contacts. I
also recall reading that it reduces pot noise improves the "feel" by
adding some drag, but that's mostly on the shaft, not the wiper.

This explains much:
http://www.nyelubricants.com/lubenotes/Lubenote_Potentiometers.pdf

Looks like they have different greases for different problems:
http://www.nyelubricants.com/applications/sensor_potentiometer.shtml
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Of course being a seller of lubricants there is no tabling of the long-term
performance as far as immunity to hardening. That "velvet feel" becoming
gumming up the works . And pot track lubrication being insufficient to cause
"aquaplaning" and then with aging/ chemical reaction, hardening and forming
a wedging under the wiper and so loosing contact for all or most of the
track run.

A job for tomorrow is to take some measurements of one of those tiny preset
size pots.
The wiper arcs are something like 3 off 10mm long , and section .2x.4mm IIRC
but I will try and measure the contact force , I'm guessing at this stage of
order 10 gm. Once one wiper lifts I imagine its not long before all 3 lift
at some part of their travel.