Correction. 36' BOOM. Not mast as I originally wrote.
73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie
-----Original Message-----
From: Jeff AC0C
Sent: Thursday, July 21, 2016 8:39 AM
To: towertalk ; Steve Maki
Subject: Re: [TowerTalk] Biggest rotor that will fit in a Rohn 25G
Thanks for the guys who have replied so far.
The top section is a flat top with a bearing. The rotor would sit down at
the junction of the first and second section point.
The antenna under consideration is probably something like a Tennadyne T12
covering 10-30m, 36 foot mast, 53' max element and about 150 lbs. 16 sq ft
if I remember right. I may stick a small 6m beam up above the T12 but that
would not offer much in the way of wind loading compared to the LPDA, other
than the contribution to torque felt by the top mast bearing.
73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie
-----Original Message-----
From: Steve Maki
Sent: Thursday, July 21, 2016 5:34 AM
To: towertalk
Subject: Re: [TowerTalk] Biggest rotor that will fit in a Rohn 25G
On 7/20/2016 17:26 PM, Bill Tippett wrote:
K8RI: > A heavy duty rotator with a large antenna should be mounted well
down into the tower. Mounted at the top, in the tapered section would
likely put very high stress at that point.
I mounted my rotator at the same point in 45G and had no problems for >10
years with the antennas/wind speeds in Colorado described previously. If
still concerned, you could mount a straight 25G section above a straight
25AG4 and install the rotator in the 16" window. Of course this would
require a long mast (~15'). I don't know which LPDA Jeff is considering
but I doubt it's >32 sq. ft.
And besides, the rotational torque will be resisted by z-braced sections
below the rotator.
The only concern with the normal R25 rotator mounting position is
lateral loads encountered with tall masts. I've seen pointy top sections
fold over in that scenario.
-Steve K8LX
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