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Re: [TowerTalk] Mast slipping

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Mast slipping
From: <donovanf@starpower.net>
Date: Sun, 22 Apr 2007 18:32:04 -0400 (EDT)
List-post: <mailto:towertalk@contesting.com>
Keith,

I know this isn't a popular message; however...

The actual experience of three different PVRCers who tried to turn full size 3 
element 40M Yagis and SteppIR MonstIR Yagis with Orion 2800 rotators is that 
the rotator was quickly destroyed by normal heavy
winds.

You don't want your new antenna project keeping you awake at night
during heavy winds!  That's no fun.  

My recommendation is that you sell that 2800 and purchase a rebuilt
prop pitch from K7NV.  You will sleep well and it will not de destroyed by any 
wind.

I'm not down on 2800 rotators, I have four of them and they are great
for anything smaller than a full size 3 element 40M Yagi or a SteppIR
MonstIR.

73!
Frank
W3LPL

---- Original message ----
>Date: Sun, 22 Apr 2007 17:21:11 -0500
>From: "Keith Dutson" <kdutson@sbcglobal.net>  
>Subject: Re: [TowerTalk] Mast slipping  
>To: <K7LXC@aol.com>, <towertalk@contesting.com>, <alwilliams@olywa.net>
>
>Ya'll have me wondering about my 40M tower plan.  Last fall I took delivery
>of two M2 40M4LLDD Yagis.  This antenna has 4 elements on a 42 foot boom,
>but a surprisingly sparse 13 square feet windload rating.  They will be
>mounted at 100 and 200 feet on a 190 foot Rohn 55G tower.  The top antenna
>will be rotated by an Orion 2800 that was purchased at the same time.  The
>lower will be rotated by a TIC Ring.
>
>This tower was supposed to be going up this spring but unexpected surgery
>has delayed the project for a year.
>
>After hearing about all of the mast slipping problems I decided to take the
>Orion out of its box and have a look.  According to the instructions, the
>"positioner" has been recently improved and strengthened.  Since I do not
>have an older unit, I have no way of knowing what is improved or how much
>stronger it is.  Here are some specs:
>
>wind area              35 sq ft
>start torque   4200 in lb
>rotating torque        3200 in lb
>braking torque 17000 in lbs
>vert load cap  1800 lbs
>
>I took a photo of the mast clamp halves (see below).  Interestingly, there
>is a hole in each that is sized to take a 1/4 inch bolt.  This could
>certainly be used to pin the mast but leaves doubt about the strength to
>hold it.
>
>http://www.dutson.net/Transfer/HamRadio/Orion2800Clampds.JPG
>
>73, Keith NM5G
>
>-----Original Message-----
>From: towertalk-bounces@contesting.com
>[mailto:towertalk-bounces@contesting.com] On Behalf Of K7LXC@aol.com
>Sent: Sunday, April 22, 2007 12:04 PM
>To: towertalk@contesting.com; alwilliams@olywa.net
>Subject: Re: [TowerTalk] Mast slipping
>
> 
>In a message dated 4/22/2007 8:43:23 A.M. Pacific Daylight Time,
>towertalk-request@contesting.com writes:
>
>>  About a year ago I had a conversation with the m2 people  about their
>rotator
>clamp slipping on my Monstr's mast.  What follows  is my memory of the
>conversation:
>
>>  1. It is better to  have the clamp slip than to harm the rotator.  (Note:
>
>the
>wind  banging repeatedly on the gearing can weaken the gears?)
>
>>  2.  The specified braking torque has not been measured (or  calculated?).
>
>>  3. Pinning voids the warranty.  I would  assume that using a 
>> different
>mfrs
>clamp would also void the  warranty.
>
>>  4. They recommended a clamp bolt tightening  sequence that should be
>followed.  Unfortunately I wasn't able to get  a firm answer on what torque
>to tighten the nuts to.  The sequence to  follow is:
>
>>  a) bolt the rotator to the mounting plate but  leave the bolt/nuts 
>> not
>tightened
>b) with the bolts to holding  the rotator to the mounting plate loose,
>tighten the bolt/nut pair of the  clamp that is nearest the bottom.
>c) tighten the next (middle)  bolt/nut pair of the clamp
>d) tighten the top bolt/nut pair of the  clamp
>e) repeat steps b,c,d several times
>f) now lastly,  tighten the bolt/nuts of step a
>
>>  I did get an answer of 40  ft/lbs from the m2 person but I think that 
>> was
>just pulled out of the  air.
> 
>    Very interesting but not useful. It doesn't do  anything about the
>significant design flaws of the Orion mast clamp that ARE  the problems.
>None of the above will keep the mast from slipping. 
> 
>Cheers,
>Steve      K7LXC
>TOWER TECH 
>
>
>
> 
>
>
>
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>http://www.aol.com.
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