I have not counted the TIC gearing, but I imagine that the fastest spinning
part is the motor. The German windshield wiper gear motor that is in my
units has a no load RPM of 33. This seems really slow for a pulse
indicator, although I am sure that there are ways to incorporate a faster
spinning shaft just for the indicator. However this would not be an easy
retrofit. There are many other styles of TIC motors and I have no idea how
they are constructed. I am not sure how you are calculating pulses, my
medium prop pitch rotator has one magnet and gives 7063 pulses per antenna
revolution and my small PP rotator also has one magnet and gives 9576
pulses.
John KK9A
From: Scott [mailto:scottb@radios-online.com]
Sent: Thursday, April 03, 2014 7:12 PM
To: john@kk9a.com; towertalk@contesting.com
Subject: Re: [TowerTalk] TIC Potentiomenter
I haven't looked to close at this yet but will stick my neck out and say yes
I believe it will work just fine. At 9000 rpm on a pp with a T bar and 2
magnets your resolution would be 300% better than what the gear slop alone
could give you. I haven't counted the gearing but let's say it's 50:1, even
a 30 rpm shaft with 2 magnets on a T bar will give you better than 1/4
degree resolution. You only need 1 degree.... Jeff in conversation
calculated out my new retrofit for the pst motor at 1/10 of a degree or
something like that. Suffice to say it's got plenty of pulses :) (15,500
per antenna revolution I think was the number, you can do the math)
Several have sent pics of motors, will look at this when I get some time.
Don't see it as being a problem though and you would increase the
reliability of the unit by a gazillion % with a hermetically sealed switch.
Obviously must have the rt20/21 controllers for flexibility of setting up
but this seems to be the new standard for making all this stuff work.
Scott
N1CX
At 07:22 AM 4/3/2014, john@kk9a.com wrote:
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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