The URL that Larry K1UO sent the list leads to a tech spec page
http://www.ruland.com/axial.html . You can see that these collars have a
specification for axial loading. I suspect that most ham installations do
not exceed these figures, especially since the collars will be one of two or
three devices on a mast that actually support the vertical load (dead
weight) of the antennas and mast.
However, the muffler clamps I used actually bite into the mast a bit.
(I bought 1-7/8 inch clamps for my 2 inch diameter mast.) Besides, their
cost (< $3 each, even here in DC) is considerably less than that of the
collars. I believe they provide sufficient support for my purposes -
supporting the antenna and mast loads. (I don't plan on climbing the mast
any time soon.)
I believe the most important spec you have to analyze to determine a
tower's ability to support the mast and antenna loads is the rating of the
bearing and rotator plates. My Trylon's three plates are rated at 300
pounds each. With my smallish HF antennas (about 90 pounds total) and the
mast weight (120 pounds), I have plenty of margin using only two supports
(the rotator shelf and the top bearing shelf - 600 pounds.) I have one
muffler clamp set right on top of the bearing collar.
To your question: Will muffler clamps support the 160 pounds of my
antennas? How much does your mast weigh? Add that to the mix, then ask the
question again. The muffler clamps ought to work IF you're using a rotator
and plate as the bottommost support. Install the mast onto the rotator
clamps, then install a muffler clamp assembly to sit on the top bearing
collar. Then install your HF antennas. That will distribute your dead
weight loads between the two plates.
BOTTOM LINE: Yes, the muffler clamps will work if you have a rotator and
shelf supporting the bottom, and you distribute the weight between/among the
plates. (I'm assuming you aren't just supporting the antennas and mast in
the muffler clamps on the tower.)
Gene Smar AD3F
P.S. Don't rely on the bearing's setscrews to provide vertical support.
They could slip!
----- Original Message -----
From: "Bob Gates" <firstname.lastname@example.org>
To: "Tower Talk" <email@example.com>
Sent: Tuesday, August 05, 2003 2:07 PM
Subject: Re: [TowerTalk] Mast Collars
> I somehow missed the first posts on this subject. But I am curious if any
> the suggestions take into consideration the weight of the antennas. I am
> looking to install two yagis with a combined weight of about 160#. The
> clamps would not appear to be strong enough, but I wonder about the "split
> collar" and the "scaffolding collar". Your thoughts would be most
> Bob KG7KW
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
> TowerTalk mailing list