> >From what Ive heard over the past 25 or so years is that many load the
> Tailtwister with roughly 1/2 the weight of the array when dealing with a
> large stacked array and dual bearings. Hy-Gain doesnt specify maximum dead
> weight.
>
I realize "large stacked array" is a relative term, but from experience, I
don't consider the Tailtwister type of rotator any where near adequate for
what would be called "large stacked arrays". That is moving into the area of
double worm gear drives and not spur gears.
> Since very few would bother actually measuring the weight the rule of
> thumb
> has been to place the full weight on it and then jack up a "hair" and then
> simultaneously tightening the clamp and bearing. Naturally this requires 2
> bodies on the tower.
>
> Far from scientific but it should even keep some old wives happy.
>
> The proof is when rotator failures are reduced from what they were or
> preferably eliminated.
>
> With just a single bearing on the top plate and the rotator located 7-10'
> down in the tower a decent wind will flex the rotator plate quite
> noticably.
>From my calculations this is far too close to the top. To keep the side
forces down the rottor should be at least as far down in the tower as the
top antenna is above the top of the tower for anything but small antennas.
> That bearing has way too much slop to my liking. Ive also seen a few
> installations that use an industrial bearing block in place of the TB-3.
>
> My Orion is the original 2300 with a few upgrades. I remember Loren (who
> was
> the Create distributor for the USA and so aggravated with them he designed
> his own) telling me to put the full weight on it. When I told him it was a
> KLM 4M40 plus a 40' boom 20M and a 38' 6M on a 27' mast he sort of
> hesitated. After it broke the 2nd time the 2800 upgrade came about and no
> more problems.
>
> Carl
> KM1H
>
>
>
>
> ----- Original Message -----
> From: <K7LXC@aol.com>
> To: <towertalk@contesting.com>; <K8RI-on-TowerTalk@tm.net>
> Sent: Sunday, August 26, 2007 12:14 PM
> Subject: Re: [TowerTalk] Fw: Rohn 45 Question
>
>
>>
>> In a message dated 8/25/2007 9:04:15 P.M. Pacific Daylight Time,
>> towertalk-request@contesting.com writes:
>>
>>> Most of the rotators I've seen (and I'm a long way from seeing them
>>> all)
>> really need a load in the vertical plane for their bearings to work the
>> properly.
>>
>> Roger, thank you for cutting to the chase. You are entirely correct
>> but
>> hardly anyone is aware of this and only the Orion even mentions it in
>> their
>> owner's manual. While I haven't seen any catastrophic failure trends
>> with
>> "floating" rotators, they are all designed to have some preload to seat
>> the
>> bearings in their races.
>>
>> Cheers,
>> Steve K7LXC
>> TOWER TECH -
>> Professional tower services for hams
>>
>>
>>
>>
>>
>>
>>
>> ************************************** Get a sneak peek of the all-new
>> AOL
>> at
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>> _______________________________________________
>>
>>
>>
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>
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>
>
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