[TowerTalk] Mast slipping

[K8RI]

On 7/23/2012 1:32 AM, K8RI wrote:
> On 7/22/2012 11:43 PM, Grant Saviers wrote:
>> I'll second the motion that the DX Eng saddle clamps are the way to go.
>
> I use many of their saddle clamps, but I'd not use those for large
> antenna to mast clamps or rotator to mast clamps.  There just isn't
> enough surface area.
>
>> Lots of surface area of the saddle in contact with the mast and
>> stainless u-bolts are provided. Use a SS nylock nut backing up the
>> (provided) regular heavy hex nut.
>
> The same for Nylock nuts.  The nylon does not stand up well to the
> elements.  I get 2 or 3 years out of them at most and I use a lot of
> them. Usually after a couple of years I can take them off with my
> fingers. More than that and they are just loose on the bolt.
>
>    On the under side of antennas pointed down so the sun can't get at the
> nylon they do fairly well, but horizontally on a mast clamp or worse,
> vertically they do not do well at all.  There are stainless Steel
> locking nuts that work very well, but be sure to use never seize as they
> will become part of the bolt in just a year other wise.
>
> I usually purchase this kind of hardware by the box of 100 at the local
> industrial supply "Prime Fastener" and they have bvery good prices, just
> be sure you don't get aircraft grade as they cost a fortune. I think it
> was near $70 or $80 USD for a box of 100 3/8" SS nuts. I said "I'll
> pass" give me the regular grade.
>
>     The only downside is they are only
>> made in tube sizes, no pipe (IPS) sizes, when last I bought them.  Your
>> mast to boom plate needs to be thick enough to handle the stress, I use
>> 1/2" thick 6061 T651 x 8" wide x 20" long and that has enough room for
>> four saddle clamps for a 2.5" boom to three saddle clamps for a 2" or 3"
>> mast.
>
> Go to a small machine shop and have them make up some mast clamps that
> are like double sided mast clamps, but wide enough to take 2, 3, 4, or
> even 5 U-bolts. The saddles should extend much farther around the mast.

On both sides!

73

Roger (K8RI)

>
> If you test the gripping force for a 2" saddle clamp which is only about
> an inch wide I think you will find it on par with normal mast clamps.
> Using 2, 3 or 4 mast clamps is a good start, but custom made clamps are
> far stronger and have considerably more gripping force.
>
> 73
>
> Roger (K8RI)
>
>
>
>>
>> Grant KZ1W
>>
>> On 7/22/2012 7:00 PM, Gregg Seidl wrote:
>>> I just got down from my tower after turning my XM-240 in line to match the rotor and other antenna AGAIN.
>>> I have done this several times now and I just can't get a grip on why this continues to happen. I haven't had trouble with any other of my antennas,some have more windload than the XM-240.
>>> As I was up there enjoying the view and thinking why this one turns I had an idea and wanted to ask others ideas.
>>> First it is up 85 feet and has been up for 6 years and I think it works great. It is much more stout than the 40-2CD that I had up before but came down piece by piece in a bad windstorm.
>>> I am using the stock clamp which seems to be great,the only thing that I haven't used one other antennas but did on this one was a galvanized mast from Texas Towers. Could it be that the mast is too "smooth" to grip? The U-bolts are not loose when I go up to straighten the antenna. It only happens once a year or so nd always after a 70-80 MPH windstorm which we get here sometimes.
>>> Looking for ideas.
>>> Gregg  K9KL
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