Keith,
I don't think the problem is a design flaw with the 2800, I believe it not
rated for very large 3 element 40 meter full sized Yagis (including
the SteppIR MonstIR) in strong winds.
Orion 2800 rotators failed catastrophically in three different installations in
my local area when used with very large antennas
(full size 3 element 40M Yagis and SteppIR MonstIRs). In each case it
was a result of 40-50 MPH winds typical for this area. Each failure
occured soon after installation of the rotator.
"Square feet" is an inadequate rating for rotator capacity. Very large
antennas distribute wind loads over a large structure, and considerable
energy is stored in the flexing of very long elements in the wind. This
stored energy creates heavy torque loads that overload all but the strongest
rotators.
The Orion 2800 doesn't have a problem handling large "shorty forty" and
long boom Yagis for the higher bands. I use an Orion 2800 to turn a
5 element 20M Yagi on a 48 foot boom at 200 ft, and its been trouble
free for nearly ten years. But I wouldn't consider putting an Orion
on my full size 3 element 40M Yagi at 200 ft, that's a job for a
prop pitch rotator, such a those that are readily available from K7NV.
73!
Frank
W3LPL
---- Original message ----
>Date: Sun, 22 Apr 2007 21:10:44 -0500
>From: "Keith Dutson" <kdutson@sbcglobal.net>
>Subject: Re: [TowerTalk] Mast slipping
>To: <towertalk@contesting.com>
>
>Frank,
>
>Are you saying the Orion has a basic design flaw that no amount of
>strengthening or improvement will correct? If so, please elaborate.
>Thanks.
>
>73, Keith NM5G
>
>-----Original Message-----
>From: towertalk-bounces@contesting.com
>[mailto:towertalk-bounces@contesting.com] On Behalf Of
>donovanf@starpower.net
>Sent: Sunday, April 22, 2007 5:32 PM
>To: towertalk@contesting.com
>Subject: Re: [TowerTalk] Mast slipping
>
>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
>>
>>
>>
>>
>>
>>
>>
>>************************************** See what's free at
>>http://www.aol.com.
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