[TowerTalk] Max antenna weight

[John Langdon]

I used HDR300s for years, setup with a 2:1 gears to turn rotating towers,
including the add on limit switches.  In this application antenna weight and
balance did not matter.  Inertia and holding torque did. 

The bad news was they broke often, so I ended up keeping a complete spare
unit that could be swapped out while I fixed the broken one. Luckily the
rotors were mounted at ground level.  

The good news was they were fairly easy to work on, and parts and support
were readily available from HyGain.  When the company was sold, the status
and support for that particular rotor became pretty uncertain, and I
hopefully switched to something else.

I have since tried several 'husky' rotors with impressive torque specs, and
had lots of problems.  Like the HDR300, I spent more time on repairs than I
did actually operating the station.

In retrospect, given the many hours of troubleshooting and repair, and even
at my low hourly labor rate, it would have been cheaper in the long run to
just bite the bullet and get a prop pitch. I am a lot happier now, and I get
on the air a lot more. 

73 John N5CQ


-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Roger
(K8RI) on TT
Sent: Tuesday, November 10, 2015 3:20 AM
To: towertalk at contesting.com
Subject: Re: [TowerTalk] Max antenna weight

My experience with the HDR rotators was not good. They depend on limit
switches for rotation stops.
2 HDRs in just a couple of months.  One was used, but worked fine. OTOH
Several of us could not remove the mast clamp. I eventually had to cut it
off.  As it was heavy cast, that put it beyond a cutting torch.  It was
before I had the plasma torch.  I gave both away.

Then again, I have little faith in rotators that use wedge brakes and tiny
little motors with a huge gear ratio.
I did not have the big array torque balanced.  I released the brake and the
wind took it past the stops before I could stop it with the motor.  
It tore up 5 rotator loops.  Once the wind was turning the array, I could
not stop it with the motor.
Having said that, I do have a Ham IV for a modest sized C19XR.

I'd not use one except for torque balanced antennas, or relatively small
arrays that are difficult to balance.
Put a wrench on most of these rotators, release the brake and you can easily
turn the rotator.  Many can be done with your bare hands sans 
wrench.   Be careful if you try this.  A screw-up can cost you broken 
fingers, or worse, particularly if there is a mistake in the wiring, or the
limit switches fail.

Just my opinion based on one set of antennas.
As for units, most of us relate to ft lbs rather than inches, although for
some the metric system is easier.
As Jim pointed out, converting that big number based on inches to ft lbs,
can be rather revealing.

73

Roger (K8RI)

On 11/9/2015 8:47 AM, Jim Thomson wrote:
> Date: Sun, 1 Nov 2015 19:47:00 -0500 (EST)
> From: "jcjacobsen at q.com" <jcjacobsen at q.com>
> To: w8qwdave at casair.net
> Cc: towertalk at contesting.com
> Subject: Re: [TowerTalk] Max antenna weight
>
>
> Dave,
>
>
> Google and the MFJ/Hy-Gain site are your friends. Hy-Gain recommends the
HDR-300, T2X, or the Ham IV for this antenna.
>
>
> >From the T2X manual: Max Effective moment is 3400. You get this from the
sum of turning radius and weight, so 22' times 88 lbs equals 1936, so that's
in limits. Antenna weight is 88 lbs, so that shouldn't be a problem, given
the triple bearing race of the T2X. T2X rated at 20 sq ft of area.......
>
>
> In closing, I am neither an antenna Guru or an engineer, so you should
only consider what is in print, the MANUFACTURES print as in the
manuals.............. other wise, YMMV. OR you could spend the bucks and get
a REAL engineer to run the numbers.
>




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