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[TowerTalk] CDE AR-22 Rotor

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Subject: [TowerTalk] CDE AR-22 Rotor
From: "John & Peggy" <>
Date: Sun, 26 Dec 2004 13:46:30 -0600
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John's Notes - CDE AR22
FYI - Just some notes I took while trying to get a used AR22 operating
properly.  They come free of charge but you get what you pay for - Hi!
Whether they apply to all versions that were manufactured over the years is
not something I can attest to.  My rotor was an AR-22 XL.  It is a four-wire
system and the controller was very much an electro-mechanical design.
The controller has a 24/ 18V tapped winding transformer.  The primary is
switched on and off via a commutator switch arrangement that is closed
whenever the direction indicator dial is not aligned with the pointer knob.
When the indicator aligns with the pointer, the switch contacts open,
removing power from the transformer.
The secondary winding provides 24vac for the rotor power and 12vac for a
lamp.  The hot side of the 24 vac is applied to the rotor winding via
terminal 1 of the interconnect power strip.  The other side of the winding
is grounded to the controller case.
Ground is applied to a split contact arrangement on the direction indicator
assembly and applies ground to either the CW or CCW winding of the rotor
motor, depending on which side of the pointer knob the direction indicator
dial is on.  These are located on terminals 3 & 4 of the motor and
controller power strip.  There is an AC motor starter capacitor across these
windings to ensure proper phasing.  This capacitor may be located within the
motor housing, external to the motor housing, or in the controller itself -
the latter configuration appearing to be a modification or later revision (I
don't know).
The indicator assembly is a spring-driven clockwork mechanism, that drives
the director indicator dial the appropriate direction towards the direction
pointer knob - when the two are aligned, it hits a stop that ceases further
rotation.  The clockwork mechanism has a split grounding terminal that
grounds the appropriate winding of the rotor so that the rotor is rotating
the same direction of the indicator.  As described above, this mechanism is
strictly spring-driven, the only power involved in the switching mechanism
applying ground to the appropriate CW/ CCW motor winding.
Internal to the rotor housing, there is a cam-driven switch.  As the motor
rotates approximately every 6 degrees, the cam actuates the switch and
through it, power is applied to terminal 2 of the motor and controller
terminal strip.  It appears that this voltage is approximately 18vac.  This
voltage is applied to a solenoid-operated cog mechanism located within the
controller housing that allows the indicator dial to step towards the
pointer knob at a predetermined rate that should be equivalent to the
rotation of the rotor motor.  The other side of the solenoid is grounded, so
as the rotor motor rotates each 6 degrees, it applies power to the position
wire (Terminal 2), activating the solenoid and releasing the cog wheel and
allowing the indicator dial to turn against the spring tension applied to
it.  Each activation of the solenoid will allow one cog position to index,
and this will continue in the desired direction until the indicator dial and
the pointer knob line up, at which time the commutator switch contacts open,
removing power from the controller and motor.
Some simple troubleshooting would include:
If motor doesn't turn
-               Check Starter Capacitor - motor will be weak or inoperative
if it is defective.
-               With motor cable disconnected and no power applied to the
controller, measure the resistance between ground and terminals 3 & 4 - one
or both should be grounded at any given time.
-               Check resistance between Terminals 1 & 3 and 1 & 4 on the
motor - any resistance under 20 ohms, but > 0 ohms would seem to indicate
intact motor windings.
-               Bad commutator switch - check for power to and out of the
Indicator dial not rotating:
-               Defective spring-driven mechanism or binding - check for
free operation.  With power removed and pointer knob moved to one side or
the other of the dial indicator, you should be able to manually index the
pointer by pressing in the solenoid actuator - stepping through it one cog
at a time until the pointer and dial align at the desired setting.
Indicator moving erratically and/or not keeping in sync with rotator
-               Positioning switch contacts in motor housing defective or
need cleaning, adjustment, etc.
A couple of observations regarding the rotor motor:
-               There are two rows of 6 bearings each.  The individual
bearings are set in a cage assembly and sit between the lower motor plate
and the upper rotor housing.
-               The motor and gear train drive a ring gear that interlocks
to the upper rotor housing.
-               My particular rotor did not have the motor start capacitor
internal to the motor housing; it was internal to the controller.
-               The used rotor I picked up was losing sync between the
indicator and actual motor positioning.  The pointer moved erratically and
intermittently jumped several cogs.  I suspect the positioning switch may
need cleaning, which I am in the process of doing but haven't tested it as
of yet.  Anyone else having this same problem and knowing the cause and
solution - I would appreciate any tips!
Hopefully others can fill in some of the holes in my observations, and add
any hints or tricks of the trade.  Please feel free to correct any of my
information - I've tried relay what I saw as I was troubleshooting the used
rotor I picked up, but I suspect there's a lot more to it than I've been
able to state here. I hope the information will help steer you along in the
event your AR-22 needs servicing.  It is a real electro-mechanical wonder.
I would have liked to have had a manual for this rotor but being too cheap
and impatient, I opted to open everything up.  Hopefully it won't remain
that way for long, however.........
John K0JJH




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