Mr. Russell,
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. 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. 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!
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.
As far as your observations of bad tower experiences, I am not saying they
can't happen. But again, you have to make accurate comparisons. The tower
you mentioned may or may not have been a Heights tower. It could have been
another tower. There is at least one product that puts out a product very
similar in appearance as our old design, but appearance does not always
count for much. Only people familiar with the details of the product
involved can spot seemingly small differences that have potentially huge
ramifications. You can make great products out of steel, aluminum or vinyl,
and you can make not so good products out of the same exact materials.
Could you find out who produced those towers, sir? I would appreciate it.
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.
Enough for now. If you can get a make and model on that fallen tower, I'd
like to know. Also, can you tell me how much windload the antenna(s)
created, in terms of square feet? Tnx,
Drake Dimitry
Heights Tower Sys.
You wrote:
> See intersperced comments and observations below
>regarding Aluminum Towers de Tom N4KG
>
>On Wed, 07 Oct 1998 20:35:00 -0500 "d.dimitry" <d.dimitry@mci2000.com>
>writes:
>>
>>
>>Dear Mr. Hider and friends,
>>
>>I beg to differ with the opinion you expressed. It is not uncommon
>>for my
>>office to hear from many hams (yes, customers) who have had their
>>aluminum
>>towers up for well over 20 years, some even approaching 40 years.
>>Crank-ups have an especially high survival rate, even in hurricanes,
>etc.
>>It's not surprising to hear these testimonials anymore; that's how the
>towers
>>were designed.
>>
>>Needless to say, most of these guys have aluminum masts with the
>>towers. I think it is true that some aluminum masts are on the light
>side.
>>However, several years ago we started offering HAMS heavier walled
>material.
>>No doubt, many chrome-moly masts would still have a greater yield
>>strength.
>
>>The question is: Is it necessary, and are you willing to pay the
>>extra change? Consider also, that you may be paying more for a nearly
>>invincible mast, only to have your antenna torn to shreds in serious
>winds.
>>
> Are you suggesting it is better to use an inferior mast
> that will fold over in lighter winds? It is a lot easier to
> remove a damaged antenna from an intact straight
> mast than to remove intact antennas from a bent mast.
> de N4KG
>
>>Aluminum towers in general have stood the test of time.
>
> One of the locals installed a KT34XA on an 80 ft
> self-supporting 80 ft. ALUMINUM tower, against
> the advice of experienced locals.
>
> Three weeks later, it was laying in the street following
> a summer storm. One of the inward tapering legs at
> the top of either the bottom or next higher section, folded
> inward, bringing the whole tower down.
>
> I have never understood why the ALUMINUM tower
> manufacturers do NOT use a horizontal brace at the
> top of their tower sections, especially on tapered sections
> where the weight of the upper sections is pushing downward
> AND inward on the bent upper leg. In my humble opinion,
> this seems like an accident waiting to happen. de N4KG
>
>>In addition to their strength, they offer the corrosion resistance and
>>light-weight, that some owners both want and need.
>
> My father's 40 ft ALUMINUM tower exhibited some leg
> joints which would not separate during removal. A car
> jack was used to facilitate separation and two leg ends
> broke off, leaving the unbolted junction intact. Would
> penetrox have prevented this problem? de N4KG
>
> I have never understood why some ALUMINUM tower
> manufacturers place the upper leg INSIDE the top of
> the next lower section, allowing rain water to run down
> the tower leg into the junction. All of the STEEL towers
> I have seen put the top of the legs INSIDE the bottom of the
> next section, forming a protective hood over the junction.
> de Tom N4KG
>
>
>No one can
>>reasonably argue that they fill
>>a niche, but even that is a large understatement. One last comment:
>>like in
>>anything else, compare apples to apples. There are different
>>manufacturers
>>of aluminum towers, just as there are different car manufacturers,
>>everything from Chevies to Cadillacs. Do your homework.
>>
>>I would be happy to provide thorough calculations to any interested
>>HAMs
>>about contemporary designs that meet strict up-to-date engineering
>>codes.
>>
>>Drake Dimitry
>>DDimitry@HeightsTowers.com
>
>
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