Possibly you should reread my posting ...
A plate (positioned between the rotator and the top thrust bearing) with
a hole (but without a thrust bearing mounted on it) positions the mast
laterally just fine when replacing the rotator and leaves no potential
for binding. You don't need a second thrust bearing.
But as I said the first time, that's a separate issue from trying to
avoid damaging the rotator. Carl is saying that having the second
thrust bearing helps prolong rotator life and I don't understand the
supposed mechanism behind that.
Dave AB7E
Ron Todd wrote:
> So why does a rotator want to have that second thrust bearing?
>
> I wanted two because when you take the rotor out and with only one thrust
> bearing you don't have control of the mast horizontally. With two TB you
> always have control.
>
>
>
> ----- Original Message -----
> From: "David Gilbert" <xdavid@cis-broadband.com>
> To: "jeremy-ca" <km1h@jeremy.mv.com>
> Cc: <towertalk@contesting.com>; <K7LXC@aol.com>
> Sent: Saturday, August 25, 2007 3:03 PM
> Subject: Re: [TowerTalk] Rohn 45 Question
>
>
>
>> Carl, you pretty much avoided Steve's question. What rotator failure
>> mode is minimized by having two thrust bearings above the rotator? Can
>> you give any examples of your YCCC buddies that would back up your
>> comments? It would be interesting to hear their experiences first hand.
>>
>> I recently ordered a tower, rotator, and fairly large antenna system ...
>> and both of the tower manufacturers I investigated strongly recommended
>> against using two thrust bearings (at least if both were secured to the
>> mast) for the same reasons Steve mentioned. A single thrust bearing at
>> the top of the tower makes sense, but a simple plate inside the tower
>> with a hole in it facilitates the task of replacing the rotator (which
>> is a separate issue anyway).
>>
>> So why does a rotator want to have that second thrust bearing?
>>
>> Dave AB7E
>>
>>
>>
>> jeremy-ca wrote:
>>
>>> I take it then that you have never experienced the installation of a
>>> large
>>> stacked array without a crane.
>>>
>>> Old wives tales? Hmmm, most of those that I know have at least a Masters
>>> degrees in an engineering discipline.
>>>
>>> Plus NE Yankees are not known for spending money frivolously.
>>>
>>> Cheers Yourself
>>> Carl
>>> KM1H
>>>
>>>
>>>
>>>
>>> ----- Original Message -----
>>> From: <K7LXC@aol.com>
>>> To: <km1h@jeremy.mv.com>; <towertalk@contesting.com>; <john@kk9a.com>
>>> Sent: Saturday, August 25, 2007 1:21 PM
>>> Subject: Re: [TowerTalk] Rohn 45 Question
>>>
>>>
>>>
>>>
>>>> In a message dated 8/25/2007 10:00:45 A.M. Pacific Daylight Time,
>>>> km1h@jeremy.mv.com writes:
>>>>
>>>>
>>>>
>>>>> Thats strange. Numerous YCCC and other serious contesters/DXers with
>>>>> big
>>>>>
>>>>>
>>>> stacked arrays have been using dual bearings for decades with a
>>>> significant
>>>> reduction in rotator failures.
>>>>
>>>> Reduction because of what? Reduction from what to what?
>>>>
>>>> What actual mechanical improvement does the additional mid-bearing
>>>> make?
>>>> More torque reduction? No. More vertical weight reduction? No, the
>>>> weight's
>>>> already on the top bearing. A psychological improvement? Probably. More
>>>> ham
>>>> radio old wive's tales? Probably.
>>>>
>>>> Cheers,
>>>> Steve K7LXC
>>>> TOWER TECH -
>>>> Professional tower services for hams
>>>> Cell: 206-890-4188
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> ************************************** Get a sneak peek of the all-new
>>>> AOL
>>>> at
>>>> http://discover.aol.com/memed/aolcom30tour
>>>> _______________________________________________
>>>>
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>>>>
>>>>
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