Pat I don't think this is entirely correct. If the main pull up cable
were to break the 2nd section would fall bring the 3rd and 4th inner
sections with it. The pull down cable runs from the base of the tower to
the bottom of the 4th or top section and serves to help the tower
retract in conditions where the wind is blowing and may bind the
sections. The pull down cable will not support the weight of the tower.
Not because it's not strong enough but because it's not rigged to do so.
I think I'm right about this can someone else confirm my comments?
Julio, W4HY
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of k0dan
Sent: Sunday, October 02, 2005 10:55 PM
To: Pat Barthelow; towertalk@contesting.com
Subject: Re: [TowerTalk] Lift cable, Galv Steel, vs Stainless
Pat:
I can't address the M.E. issues you bring up, but is the engineer in
question aware that the Tri-Ex LM series uses redundant cables?
That is, there is a pull-up and a pull-down cable, but if one were to
break,
the other one still does hold up the structure, and will raise/lower it
for
emergency purposes? (I know, I have had one cable fail...came off pulley
and
got pinched/broke, and I was still able to safely control the tower.)
Based on my experiences here (west-central Missouri) I would definitely
try
for the S.S. cable, as corrosion and contamination are definitely issues
with galvanized, especially over time.
I have restrung the cables on my LM470D, and while it can be done, it is
a
rather lengthy and tiring process. Anything which will keep the tower
safe,
while extending its maintenance periods, is worth the investment.
GL & 73
Dan
K0DAN
----- Original Message -----
From: "Pat Barthelow" <aa6eg@hotmail.com>
To: <towertalk@contesting.com>
Sent: Sunday, October 02, 2005 4:03 PM
Subject: [TowerTalk] Lift cable, Galv Steel, vs Stainless
>
> I am reviewing the engineering calculations for a Triex LM 354 tower,
a
> paper copy of which is signed and sealed by a Civll Engineer. The 19
page
> doc, gives the uninitiated a small, insight into the calculations,
including
> the mathematical equations used, for all aspects of mechanical
engineering
> of that particular tower. One calcualation, that of loads on, and
thus
> tensile strength requirements of, the lift cable, I am examining for
insight
> to viability of stainless steel lift cable substitute for galvanized
steel
> iin hopes of eliminating worries of deterioration due to corrosion.
> The LIFT CABLE STRESS Calcs:
> (Quote)
> 1/4 x 7 x 19 galv aircraft cable
> Maximum Breaking Strenght = 7000 lbs
> Factor of Safety = 7000/540 = 13.0 >3.0
> (Unquote)
>
> (where 540 is a calculated value of tension on the bottom run of the
cable.)
>
> If I interpret this line correctly, is it saying:
>
> Factor of Safety is 13.0 which is much greater than a minimum factor
of
> safety of 3, therefore easily passes.
>
> Is this an good interpretation of what the Engineer writes?
> If so, then stainless steel lift cable, which according to most wire
tables,
> has only slightly less tensile stregth than similar galvanized steel
cable,
> should also easily meet requirements for lift cable for ham towers..
> Or am I, as an unprofessional observer missing or assuming too much?
> Tnx...
> 73, DX, de Pat Barthelow AA6EG aa6eg@hotmail.com
>
>
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers",
"Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with
any
questions and ask for Sherman, W2FLA.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with
any questions and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
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