[TowerTalk] Rohn 45 Question

[David Gilbert]

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 at aol.com>
> To: <km1h at jeremy.mv.com>; <towertalk at contesting.com>; <john at 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 at 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
>>
>>
>>
>>
>>
>>
>>
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