[TowerTalk] Ham IV

Dick Green WC1M wc1m at msn.com
Mon Feb 12 11:18:11 EST 2007

Nothing new about that feature. The Hy-Gain DCU-1 controller has it, as does
the Idiom Press upgrade for the stock Hy-Gain controller. It's not really a
rocking motion. Whenever you move to a preset, the controller attempts to
turn the rotor a few degrees in the opposite direction, then proceeds with
moving to the selected target.

Hy-Gain (before MFJ bought the company) was well aware of the sticking
problem, but was unable to fix it. I think part of the problem is that
there's more than one failure mode. One is definitely temperature-related.
We here in the frigid Northeast often experience a "stuck" Tailtwister or
Ham IV when the temperature gets below freezing. It can happen anywhere the
rotor happens to be parked. The other mode seems to be independent of
temperature and happens when the rotor is run against a stop. Rocking back
and forth can free the rotor in both cases.

I don't know much about the second failure mode -- it's never happened on
the two Tailtwisters and two Ham IVs I have in my system. Then again, I
don't run the rotors against the stops very often. 

I experienced the low-temperature problem frequently on a Tailtwister that I
no longer have, and have sometimes seen it on my two Ham IVs. It's never
happened on the two Tailtwisters I have now (knock on wood.) When I had the
bad Tailtwister, it would get stuck virtually every time the temperature
dropped below 32 degrees. Most of the time, rocking back and forth freed the
rotor, but not always.

Hy-Gain was well aware of the temperature problem. They told me some rotors
had it and some did not, and they had so far been unable to determine the
cause of the problem. They, and many hams, have tried repacking the bearings
with low temperature grease, but there have been mixed results. Hy-Gain felt
that the brake wedge was getting stuck, and that this was caused by the
shape and spacing of the teeth, and was also influenced by the size of the
load. They had a new design for the brake wedge, but didn't have a test
setup in which they could conveniently test the rotor under load at low
temperature. Since my Tailtwister was mounted at the bottom of a rotating
tubular tower, and we frequently have cold temperatures, I offered to help
them. They sent me a brand new Tailtwister with the old brake wedge, and I
sent mine to them. They fitted my Tailtwister with the new brake wedge and
sent it back. Unfortunately, the new brake wedge did not fix the problem at
all -- the symptoms remained exactly the same.

But while Hy-Gain was "upgrading" my rotor, I discovered that the
Tailtwister they sent me did *not* have the problem. When the new wedge test
failed, Hy-Gain agreed to let me keep that rotor and I sent the bad one back
to them. I think that was at least 7 years ago, and the Tailtwister has not
frozen up even once since then (knock on wood.) Sometimes the Ham IVs are
reluctant to start when the temperature is well below zero, but a few pushes
of the preset button (i.e., rocking back and forth) has always freed them.
Since the cable runs are very long to those two rotors, I doubled the gauge
of the brake and ground leads to reduce the voltage drop. This seems to have
reduced the frequency. I bought a refurbished Tailtwister from Norm's Rotor
Service about 3 years ago and it has never frozen (again, knock on wood!)

After the revised brake wedge failed, Hy-Gain speculated that the problem
might have something to do with the "clutch". I'm not familiar with the
insides of these rotors, but apparently there's a pair of friction plates
and one of them has a surface made of cork. As I recall, Hy-Gain thought
moisture on the cork might freeze at low temperature and prevent the plates
from pulling apart. Never looked into this possibility.

Hy-Gain rotors are OK, but I'm not wild about the brake wedge design. If
either of my Tailtwisters ever develops chronic freezing problems, I'll
replace them with a worm-gear rotor -- probably the big Yaesu. 

That's probably more than you all want to know about this...

73, Dick WC1M  

> -----Original Message-----
> From: W2RU - Bud Hippisley [mailto:W2RU at frontiernet.net] 
> Sent: Sunday, February 11, 2007 10:29 PM
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] Ham IV
> Bill Parry wrote:
> >Usually just rocking the rotator back and forth does the 
> trick.  I have 
> >had the problem on my Ham-M rotators many times and this 
> trick always 
> >works for me....I haven't ever seen a rotator of this variety that 
> >didn't do this to some extent. Very common.
> >  
> >
> The Green Heron controller has a special Tailtwister "mode" 
> with this rocking motion automatically built in for just such 
> situations.  In fact, one of *my* Tailtwisters was the 
> inspiration for the mode -- it has suffered from wedge 
> lock-up for years and years.  
> Bud, W2RU

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