[TowerTalk] positive pull down for Tri-ex towers

[Bob Maser]

Most towers that were designed not to have positive pull down cannot be 
EASILY modified to have the pull down feature.  It all comes down to the 
fact that the pull up cable has to wind in at the same rate that the pull 
down cable is letting out and vica-versa.  If you make a miniature model 
you'll see what I mean.  Case in point, I have a non-pull down Tri-Ex 
LM354HD.  It has the 6" diameter cylinder that is used to spool in the cable 
as the tower is raised.  A wire attached to the bottom of the top section 
does not spool onto the cylinder at the same rate.  It could be made to sync 
with the pull up cable but that would involve adding more pulleys, tough to 
do.  Best thing to do is to crank the tower down only when you can watch the 
cable.  Slack is a big no-no.

Bob W6TR
----- Original Message ----- 
From: "David Jordan" <wa3gin at comcast.net>
To: "'Craig Clark'" <jcclark at wildblue.net>; <towertalk at contesting.com>
Sent: Thursday, July 10, 2008 4:34 PM
Subject: Re: [TowerTalk] positive pull down for Tri-ex towers


> Some of the Tri-ex towers, esp the older ones had all the pull cables on 
> the
> same section face. In the case of the CT-100 all the section above the
> bottom section support all the sections above and there is a pull to the
> same side on all the sections which may not be noticed on a shorter 
> crank-up
> but can be seen on the taller crank-ups. In the newer models the pull 
> cables
> are rotated to a different face each proceeding section which helps 
> diminish
> the effect. There is actually significant wiggle room between the tower
> sections and the pull cables will take out the wiggle room to the side 
> where
> the pulley are welded. Think about 1/4 to 1/2" times eight sections and 
> you
> have 4" to one side.
>
> The good news is the antenna doesn't care ;-)
>
> 73,
> Dave
> Wa3gin
>
>>
>>Craig Clark wrote:
>> > All installations are different. I attributed mine to the top section
>> > "tilting" a bit when extended even thought the installation was plumb.
>> >  73, Craig Clark, K1QX
>>
>
>
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