[TowerTalk] Tri-Ex LM470 cables (was Lift cable, Galva Steel, vs. Stainless)

Fri Oct 7 02:21:20 EDT 2005

Julio, thanks for your comments, much appreciated.

My original post was not clear or accurate enough.

I'm looking at a drawing from the manual (page 46) and if memory serves me
right, what happened was a problem with the raising cable (which you
correctly state only runs from the winch to a pulley on top of the bottom
section, and then around the pulley to the bottom of the second lowest
section. That cable developed some slack, slipped off the pulley at the top
of the lower section, and eventually got pinched and broke.

Lucikly I noticed the breakage right when it happened, and the tower
sections did not telescope downward...they were still held in place by the
pulldown cable. I was able to cautiously retract the tower sections, release
all tension on the cables, and replace the broken cable.

So in my fortunate case, there was some redundancy, however as you and
others have stated, the entire structure is not fully redundant, and a
failure of some of the other cables could have catastrophic results.

I have received other comments that my current slack problem (pulldown cable
develops several inches of slack when tower is apporx 75%-100% extended)
could be the result of the drum being compressed from heavy loading of the
tower and/or different size wire being used for the pullup and pulldown
cables. I need to do further analysis of these comments. I suspect the cable
sizes may be slightly different...I replaced the broke cable with a NOS
cable I had on hand from Tri-Ex, and while they look the same, I haven't
measured them and it could be they don;'t match.

I need to get some free time to get out there and inspect, analyze, replace,
repair.

Thanks again for your comments.

73,

Dan
K0DAN

----- Original Message -----
From: "Julio Peralta" <jperalta at tampabay.rr.com>
To: "'k0dan'" <k0dan at comcast.net>
Sent: Tuesday, October 04, 2005 6:16 PM
Subject: RE: [TowerTalk] Lift cable, Galva Steel, vs. Stainless

> On my tower the MAIN pull up cable is only connected between the 1st and
> 2nd sections. If that cable breaks the second section will return to the
> ground quickly. Sections 2, 3, and 4 have no direct connection to the
> MAIN pull up cable. Since some the higher sections have 2 short cables
> connected between their adjacent sections I guess it's possible if one
> of the cables broke that section would still be supported by the other
> cable. BTW the pull down cable is connected directly from the bottom of
> the 1st section to the bottom of the 4th or highest section. If this
> cable were to break the tower would not fall immediately unless the
> tower were in a bind and the breaking strength of the pull up cable was
> exceeded.
>
> What I took exception to was your statement that if either the pull up
> cable or the pull down cable broke the tower would not come down which
> is not the case.
>
> I'm not sure what the cables between sections 2 & 3 and 3 & 4 are called
> but they are not the MAIN pull up or pull down cables.
>
> Julio, W4HY
>
> -----Original Message-----
> From: towertalk-bounces at contesting.com
> [mailto:towertalk-bounces at contesting.com] On Behalf Of k0dan
> Sent: Monday, October 03, 2005 11:36 PM
> To: paul at w8aef.com; Pat Barthelow; towertalk at contesting.com
> Subject: Re: [TowerTalk] Lift cable, Galv Steel, vs Stainless
>
> Hi Paul...
>
> Help me understand here (I knew my statement would somehow get me in
> touble)...
>
> There's one wire which comes off the winch wound clockwise, another
> would
> counterclockwise. Obviously they work reciprocally.
>
> I had an event a few years ago, where, due to excess slack on one of the
> cables, it slipped off the pulley on the upper section and got bound
> between
> the "axle" of the pulley and the pulley mounting hardware on the top
> section. It stretched and broke. The tower remained standing. Luckily I
> was
> aware that some failure had occured and by inspection from the ground
> was
> able to determine what had happened. Slowly, carefully, I was able to to
> lower the tower without further incident.
>
> The cables were repaired and replaced (I am using heavier duty EHS
> cable),
> and all seems well again, altho I still have troubles keeping a good
> balance
> between the winch cables "too tight" or "too much slack". The
> spring/turnbuckle assembly does not seem to have the range of adjustment
> to
> avoid one side of the winch from getting too much slack.
>
> So my question...what happened in my case which gives me the impression
> of
> redundancy?
>
> And the bonus question, do you have a suggestion as to how to pull in
> the
> slack off the winch? (The manual's narrative is not adequate. I talked
> to
> one of the guys at Tash who suggested putting a cbale grip + come-along
> on
> the slack cable and pulling and extra loop onto the winch, but I have
> never
> figured out where to connect the come-along or how to make my cable grip
> hold onto the cable...what with the thimble and other hardware covering
> the
> end of the cable).
>
> Appreciate your comments.
>
> 73
>
> Dan
> K0DAN
>
> PS Mine's an LM470D
>
>
>
> ----- Original Message -----
> From: <paul at w8aef.com>
> To: "k0dan" <k0dan at comcast.net>; "Pat Barthelow" <aa6eg at hotmail.com>;
> <towertalk at contesting.com>
> Sent: Monday, October 03, 2005 12:40 AM
> Subject: Re: [TowerTalk] Lift cable, Galv Steel, vs Stainless
>
>
> >
> > ----- Original Message -----
> > From: "k0dan" <k0dan at comcast.net>
> > To: "Pat Barthelow" <aa6eg at hotmail.com>; <towertalk at contesting.com>
> > Sent: Monday, October 03, 2005 2:54 AM
> > 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.)
> >
> > Not true my LM470.  There are two pull UP cables on each side of the
> upper
> > sections.  Only one pull up cable for the 2nd section from the bottom.
> The
> > upper cables are not redundant but are arranged such that the sections
> float
> > on them, that is they do not push against one or the other side of the
> tower
> > as would be the case if there were only one cable.
> >
> > Further, the upper cables are only 3/16" diameter.
> >
> > And I would never trust just one cable to pull up my tower.  If I did
> have
> a
> > cable break the plug would be pulled on the up/down motor until all of
> the
> > cables were replaced.
> >
> > And the pull-down cable is just that, for pulling down.
> >
> > de Paul, W8AEF
> >
> >
>
>
> _______________________________________________
>
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