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.
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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