[TowerTalk] Rotator at bottom of tower

Sat Jan 21 00:07:26 EST 2006

----- Original Message ----- 
From: "K8RI on Tower talk" <k8ri-tower at charter.net>
To: <TOWERTALK at contesting.com>
Sent: Friday, January 20, 2006 11:35 PM
Subject: Re: [TowerTalk] Rotator at bottom of tower

> <snip>
>>
>> Given that the mast would have to be large, I would use schedule 40
>> aluminum
>> pipe about 4 inches in OD but will probably not do it unless I run into a
>> scrap deal on the pipe.  Regarding the welding process, I am sure that a
>> plate, perhaps about 3/8" thick, 6 inches wide and 2 foot long at each
>> joint
>> with a few heavy duty muffler clamps would hold it.  You could even pin 
>> it
>> for extra insurance.  Painting a perfectly straight line on the entire
>> length of the pipe would give visual confirmation as to whether it had
>> ever
>> slipped.
>>
> I have the rotator mounted down in the tower. There is about 44 feet (two
> standard lengths) of 1 1/2 structural steel tubing with 1/2" wall.  The

Whoa!  I can't trust this keyboard.  That's supposed to be 1/4" wall

Roger(K8RI)

> center of this is reinforced with 22' of 2" steel tubing with a 1/4" wall
> which leaves about 10 to 11 feet of 1 1/2" above and below the 2".  The 2"
> is now pinned in 4 places. With 2 5/16" bolts one sheared off so it now 
> has
> two 3/8 bolts on each side of center.  Even with all the stuff I have up
> there I get very little rotational movement.
>
>> 3.5 inch schedule 40 aluminum pipe would be 63 pounds per 20 foot length.
>> If I had a large enough hold in the top of the tower, I don't think I
>> would
>> have a problem dropping them through the top.
>
> If you have a top plate you would have enough room to weld flanges on the
> pipe and lower those down through the top.  It takes one whale of a good
> pole to hole 20' of pipe though.  They generally come in an odd length of 
> 21
> or 22 feet.  Aluminum may come in standard 20' lengths.
>
> Roger Halstead (K8RI and ARRL 40 year Life Member)
> N833R - World's oldest Debonair CD-2
> www.rogerhalstead.com
>>
>> Mounting the rotator independent of the tower would take the torque off
>> the
>> tower and if a thrust bearing could also be independent of the tower 
>> there
>> would be no weight on the tower itself from the mast and antenna.
>>
>> Sounds like a lot of work and perhaps I will not do it but still
>> considering
>> the possibility.
>>
>> Stan, K5GO
>>
>>
>> ----- Original Message ----- 
>> From: "Wolfert, William R." <WWolfert at columbuspolice.org>
>> To: <stan at aqity.org>
>> Sent: Friday, January 20, 2006 7:40 AM
>> Subject: RE: [TowerTalk] Rotator at bottom of tower
>>
>>
>>> Stan
>>> I'm not an engineer but I agree with the other TT'ers that indicate the
>>> 1.5"
>>> pipe is too flimsy to handle the torque to which it will be exposed. You
>>> didn't say what type of tower you have, but did you consider how you
>>> would
>>> get long sections of pipe into the center of the tower, unless you plan
>>> to
>>> use a crane. I have AB-105 tower, which bolts together and I had
>>> considered
>>> inserting a piece of 3" about 21' long to use as a drive pipe (from a
>>> prop
>>> pitch) to turn 3 separate antennas on side mounts. I pictured unbolting
>>> enough side braces to slip the pipe inside. OK that would work. THEN... 
>>> I
>>> pictured myself on the tower trying to get the pipe into the hole I made
>>> (I
>>> do all my antenna/tower work by myself- as do many TT'ers I've come to
>>> learn- great encouragement!) and realized this would be a mechanically
>>> difficult venture. And that's with tower that I could make a much larger
>>> "hole" in by unbolting the braces. Even if you have help, really picture
>>> you
>>> doing the task, maneuvering a (very) heavy piece of pipe from one end 
>>> and
>>> putting it into a very small space with lots of little hands to grab it
>>> (tower bracing). And that is just one piece. You mentioned you need 
>>> 105'!
>>> Once the pieces are inside the tower, they then need to be connected
>>> (welded) together! I think this is not a small task at all. Good luck
>>> with
>>> whatever you decide and if you go for it, be safe my friend.
>>>
>>> 73's Bill  WR8K
>>>
>>> -----Original Message-----
>>> From: Stan Stockton [mailto:k5go at cox.net]
>>> Sent: Wednesday, January 18, 2006 7:55 PM
>>> To: towertalk at contesting.com
>>> Subject: [TowerTalk] Rotator at bottom of tower
>>>
>>> I am "considering" the possibility of running 105 feet of pipe extending
>>> the
>>> existing mast to near ground level and mounting the rotator at that
>>> location.  The antenna is 20M5L48.  I have to take the rotator down
>>> because
>>> of a maintenance issue anyway and thought that in the long run it might
>>> be
>>> nice to have the rotator low to the ground.
>>>
>>> The plan would be to use 1.5" Schedule 40 pipe (1.90" OD), leave the two
>>> thrust bearings that are located at the top of the tower and down about 
>>> 6
>>> foot, add another thrust bearing about 10 feet above the rotator and 
>>> have
>>> about 3 or 4 other brackets with UV inhibited PVC bearings to center the
>>> mast from about 20 feet to about 110 feet.
>>>
>>> If any of you have done something similar, I would appreciate knowing 
>>> the
>>> pros and cons of such a plan.
>>>
>>> Thanks...Stan, K5GO
>>>
>>> _______________________________________________
>>>
>>>
>>>
>>> _______________________________________________
>>> TowerTalk mailing list
>>> TowerTalk at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/towertalk
>>>
>>
>>
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