I guess his wall bracket wasn't very tough. Mine has five 6 foot long 5/8
threaded rods tied into the ceiling joists in the attic.........as well as 2
sets of guys.....
Mark N1UK
----- Original Message -----
From: "EZ Rhino" <ezrhino@fastmovers.biz>
To: "Gary Joe Mayfield" <gary_mayfield@hotmail.com>
Cc: <towertalk@contesting.com>
Sent: Saturday, 14 May, 2011 4:53 PM
Subject: Re: [TowerTalk] concrete bases for freestanding towers
> OK, this happened to a close friend of mine about 10 years ago. The names
> are withheld to protect the guilty. Or ignorant, in this case. :-)
>
> He had 53 feet of Rohn 45, house bracketed at 10'. He had a 3'x3'x3'
> concrete base, and two C3's and a shorty fourty on top. No guys. A
> microburst wind took it all down, which actually upturned the concrete
> base along with it.
>
> Now I don't think I would categorize this as a base failure, as a single
> set (or two) of guys would likely have prevented this.
>
> Chris
> KF7P
>
>
>
>
>
>
>
> On May 13, 2011, at 19:56 , Gary Joe Mayfield wrote:
>
> I was referring to the cylinder (dirt) bases that are for the BX
> freestanding towers. The newer catalogs say they are not recommended and
> are provided for convenience. Again I think the only thing to change is
> the
> liability. I really like the question someone else asked. Have you ever
> heard of a tower base failing? I would think that once the base is strong
> enough the tower always fails first, there would be no point in having the
> base any stronger....
>
> 73,
> Joe kk0sd
>
> -----Original Message-----
> From: towertalk-bounces@contesting.com
> [mailto:towertalk-bounces@contesting.com] On Behalf Of K8RI on TT
> Sent: Friday, May 13, 2011 4:27 PM
> To: towertalk@contesting.com
> Subject: Re: [TowerTalk] concrete bases for freestanding towers
>
> On 5/13/2011 11:02 AM, Dick Green WC1M wrote:
>> I would bet that Rohn's specs for its dirt base required a certain soil
>> consistency and limited the windload. You might be able to get away with
>> using a base like that in some locations, but not others, such as places
>> with loose, sandy soil.
>
> They work quite well in most any soil except mud/swamp. However I'd have
> any soil evaluated where the use of one is contemplated. They are for
> *guyed towers only* where the base serves only to keep the tower from
> sinking or the base from sliding sideways out from under it. Depending
> on the design of the base, *most* sand works quite well for this. OTOH
> I'd certainly not use one on a sand dune. <:-)) Another point for a dirt
> base in sand, the tower needs to be guyed very well ( rigidly ) as any
> movement can cause the base to *work* its way down into the sand. This
> *typically* is not a problem with well shorter, guyed towers.
>
> In the past I've used them under towers holding 5L 20 and 6L 15 meter
> beams.
>
> I would not use them under a heavy tower, or one that will support a
> heavy load. I'd not use on any tower larger than a 25G or a 25G taller
> than 60 feet. That is based on the vertical load that base must support.
>
> I'd rephrase Joe's statement to, "The old installations were based on
> what worked (was sufficient) while today's are based on a large safety
> factor due to liability".
>
> The typical guyed ham tower installation (not the larger ones most of us
> on TT use) would work just fine with a dirt base. Yes, I put a dirt base
> under a 50' 25G on the West end of my shop. But all it supports is a
> C19-XR and a 7L 6-meter yagi for the time being. The plans are to
> replace it with a 60 or 70 foot crank up and that will definitely not be
> on a dirt base. <:-))
>
> 73
>
> Roger (K8RI)
>
>> 73, Dick WC1M
>>
>> -----Original Message-----
>> From: Gary "Joe" Mayfield [mailto:gary_mayfield@hotmail.com]
>> Sent: Friday, May 13, 2011 8:58 AM
>> To: 'WA8JXM'; towertalk@contesting.com
>> Subject: Re: [TowerTalk] concrete bases for freestanding towers
>>
>> Ken,
>>
>> I just put in a base for a HDBX-48 on Wednesday. Several people
>> here on the list thought the 5 yards of concrete specified by Rohn was
>> not
>> enough and the rebar specified by Rohn was completely in adequate. Most
> of
>> the local old timers thought I was putting in crazy too much concrete, as
>> their towers had been put in with at most 3 yards and had been up for
> years.
>> One local in particular whom I know has put up many towers (all of which
> are
>> still up) advised me all that was really needed a little under 2 yards of
>> concrete. I respect this guy because I know for a fact he has been there
>> and done that. It was kind of difficult to go against years of local
>> experience and wisdom, but in the end I chose to follow the prime
> directive.
>> At $93 per cubic yard is was not an easy decision to make on my budget.
>> I
>> was able to save some $ by hand digging the hole myself the day before,
>> which was a lot of work for a fat aging man.
>>
>> The strange thing is Rohn sells or at least used to sell a cylinder
>> "dirt" base for these towers that has/had a very small volume. I suspect
>> the true answer is a little of both. The old numbers were used to sell
>> towers - look how easy this is, and you only need to a 2 yards of
> concrete!
>> The new numbers are driven by liability.
>>
>> 73,
>> Joe kk0sd
>>
>>
>> -----Original Message-----
>> From: towertalk-bounces@contesting.com
>> [mailto:towertalk-bounces@contesting.com] On Behalf Of WA8JXM
>> Sent: Friday, May 13, 2011 7:18 AM
>> To: towertalk@contesting.com
>> Subject: [TowerTalk] concrete bases for freestanding towers
>>
>> Many years ago I had a 64' freestanding tower with a 3el triband beam
>> (TA-33) on it. The base was only 2 cu yards of concrete. As far as I
>> remember, that was all the manufacturer (Heights) recommended at the
>> time.
>>
>> Now when I look at anyone's recommendations, the base requirements are
> much
>> larger. Rohn (and others) recommends 3 cu yards even for a 40' BX tower.
>> I had used only 1 cu yard for a freestanding 40' tower.
>>
>> Is my memory faulty, or have the recommended bases grown over the years?
>> Were the old recommendations inadequate, or has everyone grown super
>> conservative over the years? "If one yard is adequate, three will be
>> better, so let's use five yards"???
>>
>> As one ham commented on the air yesterday, the only failures he has ever
>> heard of were in the tower itself, not the base falling over.
>>
>> Ken
>> _______________________________________________
>>
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