[amsat-bb] Counterbalance weight on antenna rotator?

[Leffke, Zachary]

I use 1 inch perforated square tube (https://www.lowes.com/pd/Steelworks-L-x-1-in-W-x-1-in-H-Plated-Steel-Perforated-Square-Tube/3049421).  On the crossboom, I use a mast adapter bracket with holes drilled to mate to the perforated square tube and U-bolts with a saddle clamp to mate the bracket to the crossboom.  On the other end I use a Walmart Barbell handle chopped in half with an angle grinder (https://www.walmart.com/ip/CAP-Barbell-Standard-14-Dumbbell-Handle-w-Collars-Single/45014178).  The non-threaded sided is welded to the other end of the perforated steel tube and is horizontally aligned with the threaded end facing away from the tower (to avoid hitting anything when pointed at zenith).  I then use their standard barbell weights to get the right counter-balance (https://www.walmart.com/ip/CAP-Barbell-Black-Olympic-Grip-Plate-Single-2-5-45-lb/47917559), held in place by the threaded collar of the barbell handle.  The weights are about 2.5-3ft 'behind' the rotator, so mileage may vary for the amount of weight needed for the counterbalance.  I use two of these, one on either side of the crossboom.  Spray painted everything (including the weights) with an appropriate paint to avoid rust over time.

Using the u-bolts on the crossboom for this setup is a double-edge sword.  The pro is you can slide them left/right to get balance for azimuth, and then adjust the amount of weight for the elevation balance.  The con is that if the U-bolts aren't a solid mechanical connection with lots of surface area contact, and if the rotator is jittery at all, the brackets can slip sometimes....not really an issue if the saddle clamp and u-bolt are sized right for the crossboom and have lots of surface area contact.  You could also pin the bracket to the rotator if you wanted to avoid this, but then it's a bit less modular and you'd have to pay attention to hole alignment, drill the crossboom, etc.


Overall, pretty cheap solution that works at VT on a few different antenna setups......but it does require the use of an angle grinder and welder the way we did it.

-Zach, KJ4QLP

-- 
Research Associate
Aerospace & Ocean Systems Lab
Ted & Karyn Hume Center for National Security & Technology
Virginia Polytechnic Institute & State University
Work Phone: 540-231-4174
Cell Phone: 540-808-6305


-----Original Message-----
From: AMSAT-BB <amsat-bb-bounces at amsat.org> On Behalf Of Scott via AMSAT-BB
Sent: Friday, October 4, 2019 11:19 AM
To: amsat-bb at amsat.org
Subject: Re: [amsat-bb] Counterbalance weight on antenna rotator?

Hi Bob!

I don't have any additional weight as a specific counterbalance, but I did 
mount my two X-Quads at their balance points.

So, while I was only as scientific as the "balance the antenna on your 
finger until it doesn't dip in either direction" method to find the center 
point, I feel like I am putting minimal stress on the elevation rotor.

Since my S-Band Wimo helical could not be mounted at just any point along 
its length, I did add a few inches of PVC to the bottom of the boom. 
Epoxied inside the PVC are a few fishing weights to cause the obvious 
mounting point on that antenna to also be the balance point.

-Scott,  K4KDR

=======================================================

-----Original Message----- 
From: Bob Hammond via AMSAT-BB
Sent: Friday, October 04, 2019 10:56 AM
To: amsat-bb at amsat.org
Subject: [amsat-bb] Counterbalance weight on antenna rotator?

Do a lot of you, or all, use a counterbalance weight on your elevation
rotor?  If so, how did you implement it?

I have 3 antennas (2M, 70cm, 23cm) on my cross boom and want to reduce the
load on the Yaesu rotor so it lasts longer.

73s,

Bob
W7OTJ 

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