[TowerTalk] HyGain considerations

[Dick Green]

> Some have had problems with the T2X and winter-sticking.  Any consensus
> on how much to worry about this?  Other than this one problem, the T2X
> is at the top of my list right now, but this is Indiana, and I can't
> have it STUCK all winter!  Tnx

The archives probably have a lot of info from when I asked for help on this.
Try searching in the December 1997 - February 1998 range.

My personal experience and surveys on the reflector indicate that:

1. Some T2X rotors do it and some don't. I had one that refused to start on
the first try every time the temperature dropped below 32F. I have two
friends in the local area with T2X rotors that sieze up in a similar
fashion. We all have TH-7s. My two friends also have shorty-fortys on the
same mast. I have a U.S. Tower 70' rotating tubular that weighs over 1000
lbs. I guess you could say that we all have a fair amount of start-up
torque, but well within specs for the T2X. We all have rotor cable runs
between 200-450 feet.

2. The problem typically does not cause a permanent sieze-up. It can be
overcome by "rocking" the rotor back and forth using the standard controller
or by repeatedly hitting Start on the DCU-1 controller (which is programmed
to briefly reverses the motor before proceeding in the desired direction --
evidently to overcome the sticking problem.) In my case, once the rotor was
free, it worked fine until it had sat idle in the cold for some period of
time. The time was related to how cold it was -- the colder it was, the less
time it took to stick again. It ranged from overnight to a couple of hours
(32F to -20F.)

3. No one has been able to pinpoint the exact cause. Some speculate that
it's the grease and swear that changing to low-temp grease fixes the
problem. However, Hy-Gain switched to a low-temp grease and newer models
still stick. Others think it's the rotor cable length. I tried moving my
starting cap to the rotor, doubling up the wires on the brake and the motor,
but all to no avail. Still others speculate that it's the brake wedge
getting stuck. But most people acknowledge that they can hear the "clang" of
the solenoid retracting when the T2X sticks.

A tech at Hy-Gain proved that with sufficient friction on the wedge, the
oval-shaped hole in the wedge would allow the solenoid shaft to retract
without bringing the wedge back with it. He thought that the narrow spacing
between the splines in the housing might, under certain load conditions, put
enough friction on the wedge to cause this. He had Engineering design a new
wedge that replaced the oval hole with an opening that would not allow the
shaft to retract without the wedge. Since my rotor is bottom-mounted, I
volunteered to work with Hy-Gain last winter to test that theory. They sent
me a new rotor to use while they modified my old rotor with the new brake
wedge. One surprise was that the new rotor worked fine at all temperatures.
The other surprise was that the modification had absolutely no effect on the
old rotor -- it stuck below 32F just like it always has. I shipped the old
rotor back and kept the new one (the old one was still under warranty.) It
worked fine, although it was near the end of the winter and didn't get
deadly cold. It'll get a more definitive test this winter.

BTW, the tech did not think that the sticking was so much correlated with
temperature as with load -- i.e., the wind blowing a certain way. That
clearly wasn't true in my case -- the sticking and re-sticking time were
100% correlated with temperature. The fact that it always began to stick at
32F implicates the freezing temperature of water, and the time it took to
stick again implicates the time it takes water to freeze at a particular
sub-freezing temperature. My theory is that, over time, water vapor creeps
into the mechanism (it's not vaportight) and freezes on some critical part.
Rocking back and forth breaks the ice or, more likely, melts it through
friction or sublimation. After a while, the moisture re-freezes. Once I
convinced the tech that temperature plays a definite role, he said that ther
e are two small cork disks inside the motor itself that come together, sort
of like a brake, to stop the motor when voltage is removed. I think it's
possible that the cork absorbs water from vapor in the air. When the temp
drops, the wet disks freeze together and keep the motor from starting. After
repeated rocking, the grinding of the disks against each other melts the
ice, freeing the disks to move apart, which allows the motor to run. After
the rotor has been idle for a while, the still-wet disks freeze together
again. The time it takes is related to the temperature.

Now, with all that said, there's one more thing to keep in mind -- multiple
causality. I've heard enough variations on the sticking problem to believe
that there may well be multiple design problems with the T2X that can cause
sticking: perhaps grease, perhaps the oval hole in the brake wedge, perhaps
low motor or solenoid voltage, perhaps frozen motor disks. Hard to say.

Even with the sticking problem, I think the T2X is a great rotor for the
money. There aren't a lot of comparable alternatives. One of my friends with
a sticky T2X replaced it with the big Yaesu (G2800 is the number, I think.)
He loves it and there's no sticking. But from what I've heard, the
less-expensive Yaesus do not use the same design and are not as reliable.
But if you're going up to that price range, there are some other good rotors
to consider as well. If you need to stay in the T2X price range, it's still
a good bet. The sticking problem isn't fatal, and you might get lucky and
get one that doesn't do it. Or, you might be successful in making MFJ
finally fix the problem. (Did I really say that?)

73, Dick WC1M



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