I placed 2 questions as a new subscriber out on the reflector yesterday.
One generated a lot of comment and the second a lot of sources. Some were
copied to the net, others weren't so thought I would share the information I
received.
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The first question, where can I get a two-way locking winch for raising and
lowering (tilting over) my motorized crank up. Sources suggested:
Fulton and others (carried by W. W. Grainger or Northern Electric)
US Tower
Northern Hydraulics/Tools/Equipment 1-800-533-5545
Farmtek (www.farmtek.com)
I will check each of these out and thanks to all for generously sharing this
information.
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The second question had to do with my 24 foot piece of 1/4" wall 2" OD
6061-T6 tubing which I planned to use as mast material.
Many suggested throwing it away (can't do that of course, it isn't cheap
even at the mill price). Most favored the use of a chromolly mast. Well
all I got is what I got at this time. I had not intended to have but just
enough mast sticking out of the thrust bearing to hold the KLM 40M monopole
(not a 2-element folks), the TH7DXX and hopefully, a small 12/17 beam (OK,
and a small 12 el 2M yagi). My intent was put the rotator plate down about
4 more feet within the tower and put a simple thrust bearing on a plate
where the rotator would originally have gone.
Yield strength for the 6061-T6 was stated by one commenter as 35,000 psi as
opposed to 118,000 (no one indicated the wall size of this 118,000 psi ys
tubing?) for the chromolloy and that the windload I was proposing was a
situation demanding a mast with 50-60,000 psi yield strength. I will assume
this is correct. A statement was also made that the windspeed spec for
Washington County OR was 80 MPH. Now I've lived here even through the '64
Columbus Day storm and have never seen winds even near this, but I'll accept
this as an engineering design spec the county has (who set the spec?).
Everyone generally agrees that the 6061-T6 1/4 mast will have less yield
strength than a chromolly mast of the same diameter but that the 6061-T6 1/4
wall 2" OD mast will suffice if my wind load is within the yield strength of
the mast. It appears that I may have to put the wind-load numbers together
and go to my old text books to see if I'm ok and what I may not be mounting
for now.
I want to thank all of your for your input and advice.
Don W7WLL
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