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[TowerTalk] Tailtwister failure mechanism

Subject: [TowerTalk] Tailtwister failure mechanism
From: Steve London <>
Date: Wed, 19 Sep 2007 06:46:05 -0600
List-post: <>
I have had 2 Tailtwister failures in the past 3 months with the same T2X, same 
antenna, same tower. What is puzzling is that the failure mechanism has been 
same both times, and I haven't previously seen this kind of failure.

In both cases, the gear shaft has broken. The gears themselves are fine - no 
broken teeth, etc. What I don't understand is how there are any significant 
forces on the gear shaft. The gear shaft is supported by the brake housing on 
one side and the motor bracket on the other side. I just don't see where the 
shear force is coming from.

And, yes, I'm turning a fairly big antenna with it - 5 el 20, 40' boom. The 
rotor is about 2 feet down from the top of the tower. The full weight of the 
antenna is on the rotator (about 90 pounds), with a homebrew thrust bearing to 
limit the lateral forces.

Please, no bashing of CDE, HyGain, MFJ, or my stupidity in trying to use such a 
small rotator to turn such a large beam. Constructive comments only !

Steve, N2IC


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