[TowerTalk] Mast slipping

Dubovsky, George George.Dubovsky at andrew.com
Thu Apr 26 08:11:21 EDT 2007


The small p-p gearboxes are closer to 10k:1, and I presume the large are
about the same. I would not have thought you could ever back-drive a
p-p, but I believe Gerald. That motor must have been LOUD!

73,

geo - n4ua

> -----Original Message-----
> From: towertalk-bounces at contesting.com [mailto:towertalk-
> bounces at contesting.com] On Behalf Of Keith Dutson
> Sent: Wednesday, April 25, 2007 8:01 PM
> To: TOWERTALK at contesting.com
> Subject: Re: [TowerTalk] Mast slipping
> 
> Let's see...
> 
> 90 degrees in 5 seconds extrapolates to 360 degrees (1 rev) in 20
seconds,
> or 3 rpm.  I understand most of those prop pitch motors have about
1000 to
> 1
> gear reduction, so the motor must have rotated at about 3000 rpm.
Yep,
> that's screaming!
> 
> 73, Keith NM5G
> 
> 
>   _____
> 
> From: TexasRF at aol.com [mailto:TexasRF at aol.com]
> Sent: Wednesday, April 25, 2007 11:32 AM
> To: kdutson at sbcglobal.net; TOWERTALK at contesting.com
> Subject: Re: [TowerTalk] Mast slipping
> 
> 
> 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
> _______________________________________________
> 
> 
> 
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> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
> 


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