[Towertalk] Help: LM-470 Cable problem
Joe Giacobello, K2XX
k2xx@swva.net
Sat, 21 Dec 2002 16:00:02 -0500
Paul, many thanks for your reply.
I checked the cabling on my lowest section and it is different from
yours. In my case, after the cable passes through the bottom two
pulleys it returns to the top of the section and passes through another
pulley and returns to the bottom of the tower, where it is fastened.
I also pushed on the bottom section to see if it was indeed floating.
Usually, I can see it wobble whenever I am raising or lowering the
tower. I t seems atypically rigid to me. Not encouraging. I tried
turning the power rapidly on then off, and there was some upward
movement. It's still too windy to experiment further today. I also
have a friend coming over tomorrow who has more mechanical savvy than I
do. He may be able to make a more competent assessment.
73 and, again, thanks to you (and Roger) for your help.
Joe
Paul Playford wrote:
>DON'T CLIMB IT !!
>
>If you are not satisfied that there is no binding between sections and the
>pull-up cables and pulleys are in good condition then get a bucket truck in
>and inspect things. Maybe even consider a crane to get the antennas off and
>lay it over horizontal for inspection. I had a tower telescope on me once
>(not a Triax) and it was a total loss. I did find I can step out of the
>antenna turning radius in a hurry tho.
>
>I've had my LM-470 up (and down) for 6 years with no problem. I do watch it
>come down if the wind is blowing and I have stopped it (once) when the
>raising cable showed signs of going slack because of the wind.
>
>My LM-470 floats (no binding) between sections and is completely supported
>by the pull-up cables so when you say they seem to have greater tension on
>them that raises a bunch of questions in my mind.
>
> The first question is, do your sections float on the cables?
>
> Second question is what version of LM-470 do you have? On mine, the
>pull-up cable from the drum goes to the top of the bottom section, through a
>pulley, down the outside of the 2nd section to a pulley at the bottom of it,
>across the bottom to another pulley and then back up to the top of the
>bottom section where it is anchored. No binding and the 2nd section floats
>entirely on the cable. And the second section up has two cables (each cable
>on a different side of the section) on it so it floats also. I have seen
>one other LM-470 that has a different cable arrangement for the first
>section. It runs from the drum to the top of the bottom section, comes back
>down to a pulley at the bottom of the second section and then goes back up
>and is anchored at the top of the bottom section, and I can see where there
>might be binding on that tower.
>
> But if you stopped the tower as it was coming down I don't see where
>there could be added tension on the pull-up cables - Hmmm. I do hope they
>didn't go slack and the tower dropped on them.
>
>If I were faced with your problem and I had enough slack in the pull-down
>cable to get it off the drum, that's what I would do.
>And maybe even pull the belt off the driven pulley and ensure that you can
>turn it in each direction by hand and the tower moves up and down. It'll
>turn hard, but that will make you appreciate the electric motor. Then I
>would reinstall the belt and run the tower the rest of the way down while I
>was pulling on the pull-down cable (as I stood clear of any antennas, just
>it case) to keep it from getting tangled up in the tower. Inspect all the
>cables and then run the tower back up, keeping tension on the pull-down
>cable. When the tower was at full heighth then I would attempt to duplicate
>the original tension on the pull-down cable and re-attach it to the drum.
>Then back down with the tower and check/adjust the tension according to the
>tower's manual.
>
>And someplace in there I would be asking myself "How did the cable get off
>the drum and what can I do to ensure it does not happen again?"
>
>And I keep asking myself - "Geeze, what is my exposure here in the event
>something happens?"
>
>
>----- Original Message -----
>From: "Joe Giacobello, K2XX" <k2xx@swva.net>
>To: <towertalk@contesting.com>
>Sent: Saturday, December 21, 2002 5:31 PM
>Subject: [Towertalk] Help: LM-470 Cable problem
>
>
>
>
>>We had a sudden windstorm late last night and I had to lower my LM-470.
>> At about the 45 foot level, I noticed that the positive pull-down cable
>>had started to double wind and then come off the drum. About one to two
>>turns of the pull-down cable wound around the shaft on the right side of
>>the drum that connects to the drive mechanism. Currently, the pull-down
>>cable is very loose and there is no tension on it. Although I have no
>>reason to suspect that the tower is bound up in any way, the tension on
>>the pull-up cable seems greater than usual and I am quite worried about
>>a catastrophic failure if I try to raise or lower the tower any further.
>> I haven't even tried a quick on-off. I wanted to consult with the list
>>first.
>>
>>My questions are:
>>
>>- Has anyone out there experienced this problem before and what did you
>>do about?
>>
>>- Given the current condition, would it be expected that the pull-up
>>cable would have more tension than normal?
>>
>>- I cannot get the section of pull-down cable that came off the drum
>>back on the drum. However, it looks like that I can disconnect the end
>>of the pull-down cable that is attached to the drum (fastened onto drum
>>with bolt), manually wind it back on the drum and then reconnect the
>>end. Assuming the tower is not bound in any way, does rewinding the
>>pull-down cable in this manner and the raising or lowering the tower in
>>the normal manner make sense?
>>
>>Any suggestions would be most appreciated.
>>
>>
>>73 and Happy Holidays!
>>
>>Joe
>>
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>>
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