I think they had an arrangement like this on some of the EZ-Way towers
. I seem to remember doing some research on an EZ Way tower and saw an
optional rotor cage that fitted to the top of the tower
Phil
N9LAH
On 6/8/2012 6:29 PM, K8RI wrote:
> On 6/8/2012 5:55 PM, Steve Jones wrote:
>> Rick-
>>
>> I think you're asking for trouble if you don't have a thrust bearing above
>> the rotor. The wind will either crack the rotor housing or break the bolts
>> holding it to the plate. This sounds like a pre-fab cellular tower. A
>> friend of mine built a sturdy open-sided metal box to put on the top of his
>> tower. The box enclosed the rotor at the bottom and a thrust bearing on
>> the top. This assembly protects the rotor and the mast. You might want to
>> consider such an accessory.
> Some time in the last year of two we had a discussion on here about this
> and some one posted links to a cage that had been built to go on top of
> tubular towers. It held the rotator and provided support for a sleeve,
> or thrust bearing above the rotator. I haven't looked for it, but it's
> likely to be in the archives.
> It just forms a 3 or 4 sided box with the bottom and top tapered like
> the top of a 25 or 45G tapered top. It had (in this case) the top of the
> mast extending into the cage with the rotator mounted on that. They
> could have easily made a rotator, or accessory shelf to which they could
> bolt the rotator.
>
> 73
>
> Roger (K8RI)
>
>
>> Vy 73,
>>
>> Steve Jones
>> N6SJ
>>
>> ----- Original Message -----
>> From: "Rick Kiessig"<kiessig@gmail.com>
>> To:<towertalk@contesting.com>
>> Sent: Thursday, June 07, 2012 11:20 PM
>> Subject: [TowerTalk] Tower advice
>>
>>
>>> After a multi-year battle with the city, I am finally in the process of
>>> drawing up plans for a tower that have a decent chance of being approved.
>>>
>>>
>>>
>>> The tower height will be about 9m above immediate ground level (but I'm
>>> near
>>> the top of a 100m-high hill, so I have some hope of getting a decent
>>> signal). The tower will be octagonal galvanized steel, 290mm diameter at
>>> the
>>> base, 140mm at the top, in 4 sections. I'm planning to use a PST-61
>>> rotator
>>> with either an Ultrabeam UB50 or a SteppIR UB-18 (the rotator is
>>> intentionally oversized, since I'm hoping to increase the size of both the
>>> tower and the antenna in a few years when the city's rules are changed to
>>> reflect a recent court decision in favor of hams). The tower was not
>>> originally designed for use as an antenna mast, but the manufacturer is
>>> willing to do a little customization to make it work, such as adding a
>>> plate
>>> at the top of the tower with bolt holes to match the mounting plate on the
>>> PST-61.
>>>
>>>
>>>
>>> Would it be OK to run RF and control cabling on the inside of the tower
>>> without supports for strain relief other than one at the top? (coax will
>>> probably be LMR-400 UF in conduit, not direct burial; the total length is
>>> pretty short (roughly 20m) so the expense and hassle of using LMR-600 or
>>> Heliax may not be worth it).
>>>
>>>
>>>
>>> The manufacturer has suggested three 20mm grommeted exit holes close to
>>> the
>>> top of the tower, one for each of the three cables that will be needed
>>> (slightly below the mounting plate for the rotator). Sound OK?
>>>
>>>
>>>
>>> The tower will have an access plate at the base, which I can use to tie
>>> the
>>> coax shield to a ground rod that would be present in that space. The base
>>> of
>>> the tower would also be tied to ground rods. Is there anything else I
>>> should
>>> allow for in or near the base?
>>>
>>>
>>>
>>> I was thinking of running one conduit for the RF coax and a separate one
>>> for
>>> the antenna and rotator control cables. Is that overkill?
>>>
>>>
>>>
>>> This design would not have a thrust bearing or an interior shelf for the
>>> rotator. The rotator would need to carry the full load of the antenna (5.8
>>> x
>>> 6.6m, 44kg, 10.1 sq ft wind load). Am I asking for trouble, even with the
>>> oversized PST-61?
>>>
>>>
>>>
>>> What's a reasonable maximum length for the mast, going from the rotator to
>>> the antenna? I'm thinking of using 50mm galvanized water pipe. A longer
>>> mast
>>> would mean a slightly shorter tower and a little more flexibility with
>>> total
>>> height (very tightly restricted here), but would also present a larger
>>> load
>>> on the rotator, right?
>>>
>>>
>>>
>>> 73, Rick ZL2HAM
>>>
>>>
>>>
>>> _______________________________________________
>>>
>>>
>>>
>>> _______________________________________________
>>> TowerTalk mailing list
>>> TowerTalk@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/towertalk
>>>
>> _______________________________________________
>>
>>
>>
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>> TowerTalk@contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
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