In a message dated 98-10-10 16:48:50 EDT, d.dimitry@mci2000.com writes:
> Thanks for the comments. I'll offer a couple responses.
> To your first question: No, I am not suggesting using an 'inferior' mast,
> just an appropriate one. Sure it's probably somewhat easier getting a
> damaged antenna off a straight mast rather than a bent one, but what is the
> difference in price you are willing to pay for that mast.
Hold on a minute. The goal of ALL tower owners and manufacturers should
be to build a reliable tower/antenna system that is designed, engineered and
installed so that a minimum of maintenance is involved to provide ZERO
mechanical failures. For YEARS.
Installation of a component that could/will fail is perposterous. OF
COURSE you should invest in a mast (among other components) that will not
fail. A bent mast is the sign of using substandard materials along with 'hip
pocket' engineering. Both are wrong and dangerous.
Removing antennas from a bent mast is one of the 2 or 3 most dangerous
tower activities you could under take (no pun intended). Either be VERY sure
of your skills or get professionals in to dismantle everything in this case.
> If you get a
> chrome-moly, you'll probably pay around $200.00 or more than for a heavy
> wall aluminum mast. Specifically, this is probably the price difference
> between a moly-chrome mast less than 2" O.D. with less than .150 wall and
> an aluminum 2" x 1/4" wall mast. But to get off the point for a second, I
> doubt that that aluminum mast will fail much ahead a time of a typical
> chrome-moly.
Please enlighten me how a 118K psi yield strength chromoly mast will fail
before a 35K psi 6061-T6 aluminum mast? When did they change the laws of
physics? Wall thickness has little to do with it.
Have you missed the posts regarding calculations of windspeeds, antenna
loads and bending moments?
> As everyone has pointed out, there are many variables here.
> I'm not going to try to reiterate them all here. I know I can supply Hams
> with superior values in masts, measured in $ for strength, flexibility and
> longevity. The previous sentence is not really a full-blown ad. The
reason
> I express this as a seller of masts, is because there are widely varying
> masts to buy. Some vendors charge radically different prices even for the
> same material, materials which also has many shades of variation.
> I can find masts sold by competitors at 2 to 3 times the price. It's hard
> to
> believe. I think this is why people are always asking me the exact
> alloy of my masts; they may not believe that I can sell the same stuff
> (yes, certified by the producers) so cheaply. My point is that our
> conclusions in this little practical contention on the best value in masts
> can change dramatically, depending on what vendor is selling you what
> material at what price!
What specifically are you talking about? Feel free to post the alloy,
certification and other specifications of the aforementioned masts along with
the price. Broad allusions to the "best value in masts" doesn't give us any
information.
> Much more could be said. One point I want to echo is that I think because
> of its elasticity and flexibility, I think an aluminum mast, in terms
> of tensile strength, may tend to bounce back and not completely fold or
> break like steel and stainless would under similar pressure.
>
Please let us know what the calculations you used to reach the above
conclusion.
>
> I'll try to answer one more q for you. Yes, the connections between some
> old style aluminum sections has been a problem after several years
outdoors.
> They can be very difficult to pull apart. There are precautions and
> maintenance steps that can be done to help this problem. First, coat the
> section ends you are joining together with an anti-seize lubricant made for
> aluminum surfaces. This can be gotten at electrical, hardware and bearing
> stores, as well as antenna and some tower mfrs. Then take your tower apart
> every 3 to 5 years to check the joints. Do you need to apply more
> lubricant? Also, on this issue, do not over-torque the nuts on
> your leg
> connecting bolts when assembling the tower; this can egg-shape the legs and
> wedge them more tightly together.
>
Good advice about ovalizing the legs and the use of anti-seize in the
leg joints. But are you serious about taking your tower apart every 3-5 years?
It is my opinion that you are undermining your credibility as the
president of a tower manufacturing company and contributer to TowerTalk with
the incorrect advice and conclusions that you're presented here. I'm still
waiting for an answer to the availability of tower engineering data that you
mentioned previously.
Cheers, Steve K7LXC
Tower Tech
Champion Radio Products
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