In a message dated 4/21/03 4:11:16 PM Eastern Daylight Time, w9sn@comcast.net
writes:
>
> Absolutely nothing to worry about though. (As long as you're within
> the manufacturer's specs.) Just enjoy it.
>
> Cheers,
> Steve K7LXC
>
Risking being unsubscribed, I respectfully disagree.
After looking at the pictures, without knowing material and sizes of tower
members
I see the potential problems:
> Thanks for the several replies. I guess I opened up more than I
> bargained for. Let me put more information here.
> This is a homemade aluminum crank up (made by a toolmaker in a machine
> shop 15 years ago). It is 96 ft to the
> Thrust bearing when erected. I notice what looks to be about 8-12 inch
> sway at the top in about 15mph winds with nothing but the
> bearing, rotor and mast on it.
It might be nicely made by the toolmaker, but it does not demonstrate proper
engineering. The legs that went into concrete, I assume were steel, but they
should have some crossbracing, I saw only straight pieces, one bent?
Crossbracing along the tower in the form of X is not the best especially for
that height. Better way is having full connecting triangles. Difference
between the bottom and top sections 18 - 9" seems to be too small for the
height and design load (which is what?)
Top section between the rotator and thrust bearing has no crossbracing, which
is a major no-no. No way you should have 40m beam on the top!!! This thing
would fold like a parallelogram right at the rotor plate.
> I think I have come to the conclusion
> that I am going to put one set of guys on it 75% of the
> way up.
Was that tower used before and what kind of loads were on it? On the crank
-up tower, even if it is self supporting (how else :-) I would only use guy
wires for backup safety just in case minor gusts came (this tower sure could
use it), but definitely not as something permanent. Having guy wires on the
crank-up is kind of dangerous, cable is taking the vertical stress and it
better be rated for it. I would use that tower nested down during "normal"
weather, crank it up when is nice sunny and no winds, but keep the guy wires
attached to the top of tower without any tension on them, just tight.
> Here is a link to show you the entire installation this week
> showing the tower and all.
> http://www.yorktownhouse.com/crankup.htm This all went up this past
> Tuesday and I cranked it up for the first time yesterday, empty.
> I can leave it cranked partially down but that would put stress on the
> motor drive (brand new) and the manufacturer suggested taking
> The load off of it long term. He said long term with a load should
> cause it to fail. So I installed bracing on the tower for the top
> sections
> To rest on a ? inch piece of steel instead of the motor.
Huh? What bracing?
Winch, motor better be able to take the load "long term" it either is
properly rated or throw it out. The best is to have worm gear drive, it is
self locking at any position. Gears better be rated to take the static and
dynamic loads ALL the TIME.
> There is a 5?
> overlap in the first section, 6? ft overlap in the mid section, and 7?
> overlap
> In the third section. The sections are 27? long each. The whole tower
> weighs about 600 lbs total. My goal here is to install the new 4
> element
> SteppIR yagi with possible force12 two element 40 meter yagi above it.
The way it is, you better forget about anything significant at the top of the
mast.
Maybe some VHF antenna.
> However, being new to this stacking and crank ups, I am a little
> Nervous about doing this so it will stay up. Thank you for all the
> help?..
> _______________________________________________
>
You should be :-(
This is just my opinion based on seeing the pictures and not knowing about
the material and any specs or calculations. I would use it normally at about
60 ft height, with steppIR just above the bearing. If you want to get that
low angle and crank it up to full length, I would use safety guys, just in
case gust came or you forgot to crank it down. You better make sure that
winch can take the load all the time, that and cable is what is holding your
tower.
This is not professional advice, just opinion based on what I saw in the
pictures.
GL and be safe!
Yuri, K3BU
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