I have three TIC rings built circa 2006. I've had only one pot failure,
which occurred at least four years ago. I have a box of spare pots -- two
Bourns that I believe came from TIC and seven Vishay that I obtained on my
own. I'm going to guess that there were originally eight Vishay pots and
that that the eighth is the one I used to replace the bad pot. Given that
somewhat sketchy info, I'm of the opinion that the Vishay pot should work
and that it's no less vulnerable to water incursion than the Bourns version.
That said, I can see some sort of grease at the base of the shaft of the
Bourns pots that doesn't look like it would make the pot waterproof but
perhaps makes it more water resistant than the Vishay pots, which don't have
grease or an o-ring or any other sealant.
I have a friend who has an older version of the smaller TIC ring, probably
built in the early to mid 90s. He has had a lot of problems with pot
failures over the years and has tried both Bourns and Vishay pots. It was
virtually guaranteed that the pot would fail during the winter. Most of the
time the pot would still fail when the weather warmed up, necessitating a
replacement, but sometimes it would be just fine. I think the reason is that
the pot wiper would freeze in place and if the rotor was turned while it was
frozen it would break off. This could happen because that version of the TIC
controller allowed the motor to turn even when the pot didn't. My friend
later replaced the controller with an aftermarket controller that won't let
the motor move when the pot doesn't move, and that appears to have
drastically reduced the frequency of having to replace pots.
I've not had anywhere near that much trouble with the pots in my TIC rings,
but I've had a different problem: frozen grease. As John points out, the
biggest design flaw of the TIC motor is that the shaft points up. On my
motors, there's a rubber grommet at the base of the shaft that's glued in
place with 3M Super Weatherstrip adhesive. This is supposed keep the water
out, but after a short time the adhesive fails and the grommet rides up the
shaft, exposing a large gap between the housing and shaft through which
water can enter the gear box. Once that happens, the grease gets
contaminated and can freeze at low temperature. The result is a motor that
won't move until the temperature warms above freezing or some direct
sunlight to fall on the motor. This seems to happen more often with my
middle TIC ring, which is at 64', than it does with the rings at 34' and
95', despite replacing the middle ring's motor a couple of times, swapping
it with the other motors, etc. Perhaps the ring is a little more
out-of-round and pushes against the motor shaft more, causing the grommet
adhesive to flex.
Anyway, none of this would be a problem if the motor was mounted upside
down!
73, Dick WC1M
> -----Original Message-----
> From: john@kk9a.com [mailto:john@kk9a.com]
> Sent: Thursday, April 03, 2014 7:22 AM
> To: towertalk@contesting.com
> Cc: cc-6569@comcast.net
> Subject: Re: [TowerTalk] TIC Potentiomenter
>
> A reed switch works great on a prop pitch motor, where the motor is
spinning
> 7000-9000 RPM. The shaft that the TIC pot is connected to turns much
slower
> so I am not sure how accurate the indicator would be. TIC used to use
Bourns
> potentiometers which were somewhat sealed. They were not perfect, but I
have
> had good results with these. I do not know if the Vishay unit has any
shaft seal.
> One big problem with the TIC motors is that water can leak around the gear
> shaft and into the pot, which has the shaft pointing up. It would be nice
if the
> motor were installed upside down. While in Illinois I had many pot
failures when
> it got below freezing and any moisture inside froze. I installed motor
heaters
> which helped a lot. A pot that is highly moisture resistant would be an
easy
> solution, if such a thing exists. I spent an hour or so yesterday
searching for
> replacement potentiomers and so far I have not found a better solution.
>
> John KK9A
>
>
> To: towertalk@contesting.com
> Subject: Re: [TowerTalk] TIC Potentiomenter
> From: Fred Sanborn <cc-6569@comcast.net>
> Date: Wed, 02 Apr 2014 18:59:10 -0500
>
> John,
> I agree the Vishay 10T pot does not seem to be a good solution. I "worked"
> the pot back and forth more today and it never came back enough to be able
to
> use the RT-21 without the "no motion" error message again. We did have a
> sever winter here in N. IL with a good amount of precipitation. However, I
just
> did a pot replacement and put the rotor back in service September so I am
very
> disappointed.
>
> I am serious when I put the question out there to the TowerTalk community.
> Has anyone considered or implemented a redesign of the TIC ring rotor
direction
> indication method to get away from the dreaded unreliable pot?
>
> TNX es 73, Fred KG9X
>
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