[TowerTalk] Mast slipping

[TexasRF at aol.com]

First hand feedback: a full sized 80m 3-el yagi (1200 #) will windmill a  
large prop pitch with about 45 mph wind. This is for a very well balanced design  
with equal element spacing.
 
You can't imagine how disconcerting it is to be belted off  next to one of 
those big drives and hear it screaming as the antenna rotates 90  degrees in 
about five seconds!
 
I had to scrounge up an original disc brake for the prop pitch motor to  hold 
that load in the gusty Texas winds.
 
Wonder how one calculates twisting torque when the load is balanced? There  
seems to be a missing bit of information needed to do such a calculation;  
variation in wind speed over an area of say 100ft in width.
 
73,
Gerald K5GW
 
 
 
In a message dated 4/25/2007 11:12:26 A.M. Central Daylight Time,  
kdutson at sbcglobal.net writes:

I don't  think the drive can be back-driven.  It's just that you would  need
about 30,000 in-lbs of torque to break anything.

73, Keith  NM5G

-----Original Message-----
From:  towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com]  On Behalf Of Jim Lux
Sent: Wednesday, April 25, 2007 12:21 AM
To: Kurt  Andress; TOWERTALK at contesting.com
Subject: Re: [TowerTalk] Mast  slipping

At 06:14 PM 4/24/2007, Kurt Andress wrote:
>Pinning the  mast to the clamp doesn't void the warranty, because the 
>prop pitch  gear train (at least like I build them) can't be broken.


I assume  that's mostly because the gear train is a back-drivable spur or
planetary  set as opposed to a worm/pinion? If you overload it, it just turns
the  motor?

Jim,  W6RMK


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