[TowerTalk] Star guys vs rotating tower ?

[StellarCAT]

I had a 143' R45 rotating tower (RTS with rotor at 40') .... and now have a 
147' R55 rotating tower (K0XG w/ rotor at base) ... I can't say I've ever 
seen it 'twist' ... the whole thing turns and pulls on the slack on the 
chain but I've not seen it twist per se. I too like the idea that it is 
allowed to do so. This of course means the rotor has to be more robust - but 
the K0XG, and it turns out the RTS are quite so.

I had 20' of tower above the top guy on the R45 system with antennas just 
above that guy, 10' above it and 18' above it ... it "curved" with really 
high winds ... now with the R55 system I have 25' of tower above that top 
guy with bigger antennas - at 1' above it, 13' and 22' .... but it is rock 
solid - that stated it hasn't been in the presence of winds like I saw in 
AZ, yet.

Gary
K9RX



-----Original Message----- 
From: Richard Thorne
Sent: Monday, October 16, 2017 10:17 AM
To: towertalk at contesting.com
Subject: Re: [TowerTalk] Star guys vs rotating tower ?

Jim,

I have a 140' rotating tower.

We get regular high winds here in Amarillo.  The last big wind storm was
back in June when we had 80mph straight line winds.  Both my
towers/antennas survived nicely, but my fence on the north side was
blown over and it had steel posts.

My rotating tower will twist in the wind.  If the winds are high enough
it will end up moving the prop pitch rotor in one direction or the
other.  If I have a wind event that moves the tower I'll walk out with
my iphone, bring up the compass app and take the new reading.  Then I go
back to the shack and enter the new heading in my Green Heron rotor
controller.

I think it's a good thing that the tower rotates within the rings when
it gets windy as it takes the stress off of the system.  Since the prop
pitch doesn't have mechanical stops it's very easy to re-calibrate.

My 2nd tower is 80' of 45g.  It's on a pier pin for the same reasons,
wind.  The tower can at least twist a bit to relieve the stress on the
tower.  It has a normal set of guys vs star guys.  I want the tower to
twist freely if needed.

The only problem I have on the 45g tower is the Orion rotor.  The stock
mast clamp is terrible.  I have to climb the tower several times a year
to re-position the antenna stack.  One of these day's I'll order a K7NV
or Champion after market mast clamp.  Then again, it may not be a bad
thing for the antenna system to slip a bit vs tearing something up like
the rotor itself.

Rich - N5ZC



On 10/16/2017 8:06 AM, Jim Thomson wrote:
> Ok, heres something I dont get.    Star guy setups....  with 6 guy wires. 
> The idea is to reduce tower twist.    I can readily see that  vs a 
> standard 3 guy wire ...per level setup.
> Then we have folks with a rotating tower assy, whose guy wires essentially 
> allow  for unlimited  tower twist.   The only thing I can see limiting the 
> twist is  either the rotor at the bottom of the rotating tower,
> and / or the  bearings at each rotating guy ring assy.   The folks with 
> rotating towers typ load em up with yagis  from top to bottom.   All yagis 
> are mounted to the same tower face, so you now have a TQ offset from
> boom to exact center of tower... which just  makes any TQ issues worse.
>
> It appears that a  rotating tower assy  is one giant,  100-200 ft tall 
> driveshaft.   How much twist do you rotating tower owners see in a 40-75 
> mph windstorm ?  (and tower sitting there, not being rotated at the time).
> Ok, what if no wind at all, nice sunny day, and you rotate  tower say 300 
> degs.   Do you see any twist when rotor initially engaged ?     IE: base 
> of tower is turning, but very top of tower has not started to rotate..yet.
>
> What am I missing here ?   Rotating towers  vs  star guys is from one 
> extreme to the other.   One would think with a 100 ft rotating tower...and 
> esp with a 200 ft  rotating tower,  it would twist like a pretzel ?
> When I worked for the telco, the odd site would have star guys, if a guyed 
> tower was used, and large diameter microwave dishes used.  Same deal, 6 
> guy wires used, with star guy assy just below the dish.
> In some cases,  a square tower was used, with 8 guys,  2 for each of the 4 
> x faces...and  4 x guy anchors  on the ground,  90 deg apart.    I can 
> understand the telco application, the dishes had their side built up, and
> they have an extremely narrow  main lobe.  With the sides of the dish 
> built up, there is no side lobes.   For amateur HF,  its not an issue. 
> But tower twist is an issue.  Or is it a non issue ?   Obviously 65G will 
> twist less than
> 25 G.   For this discussion, lets use  45 or  55G as  tower used in a typ 
> rotating  setup.
>
> Jim   VE7RF
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