Sugarloaf tower in Maine

[n1ps]

Tower on mountain in Maine collapsed this afternoon in high winds and ice.  I'm sure it knocked out some FMs at the least.
Peter

[KF7WWW]

Looks mostly cellular stuff to me. Seen it before.

[K1JJ]

Nasty.

I realize that "self-supporting" skyscraper buildings in Chicago don't have guy wires but are still rated for 250+ MPH winds.... But when it comes to extreme ice and wind environments like SugarLoaf, ala Mt. Washington,  I've always preferred old school guyed towers. The geometry of a guyed tower (with torque arms as pictured in 1st picture) tells it all.

T


I use triangular, rigid  torque arms even on my own 100'  10M tower - bulletproof:  (2nd picture below)  Double the materials and work, but it will never twist. Twisting is what kills them all.  It's also called "star guying" using six guys per level.

[kb3ouk]

As far as i know, none of the broadcast towers on mount Washington are guyed, they are very short, very massive self supporters.

[W1ITT]

As far as the Mount Washington broadcast antennas, I built both of them 94.9 and 103.7.  They are each on short stout self supporting towers.  There are a couple other smaller supports for standby antennas and other services that are guyed.  When we built the  silo radomes, we cut the ends out of the ethylux cylinders, and stacked them with gaskets in between.  I salvaged some of the plastic from the cutouts and use them as open wire line spreaders.  It's been well over 20 years and they are holding up nicely in the UV.  I wish that I had grabbed more.  On Sugarloaf, there is a 105.1 antenna for WTOS that I also built, but I believe that's on another tower that didn't succumb to the breezes.
The word out there is that people won't be getting up to the site for a close inspection at least until Wednesday as it's going down below zero and the wind is still blowing. 

[K1JJ]

As far as i know, none of the broadcast towers on mount Washington are guyed, they are very short, very massive self supporters.

Yep, it's become a self-supporter world.  Everywhere ya go there's big poles.  I have two 190'er self-supporters here.  That's what I mean about buildings - you can over-build any self supporter as big and as strong as you wish.

I just like the old-school geometry and inherent strength of guyed towers, personally.  I feel much safer climbing guyed towers. My self supporters always have some wind sway built in that is unnerving the higher you go. I still remember the creeking wind sway in World Trade Center One  - when I worked there in 1985.  

T

[n1ps]

Mt Washington recorded 171 MPH gusts yesterday.  I also noticed (in the Sugarloaf pic) that all the cables were on one side, the side that buckled.  Looks like Norm your Mt W installations survived!  A new tower will likely require a new foundation (new codes).....that will be a project. 

[kb3ouk]

I believe one of those towers on mount Washington dates back to the late 40s. Self supporters have been around a long time and held up. My opinion is it isn't the design, it is today's cost engineering, build as many as you can as cheap as you can attitude that makes the design look like it sucks. There is one design difference i have noticed between a lot of older self supporters and modern ones: seems that a lot of the older towers were 4 sided and the modern ones are 3 sides. Not sure if that makes a difference, besides just making the structure more massive. One thing i can think of is coming from geometry is a square can have its sides moved and still hold a connected shape, an equilateral triangle can't without breaking apart.

[W1ITT]

https://www.fybush.com/site-030220.html

Here are some old pictures of the structures on Mt Washingon, showing old and new ways of doing things.  The two FMs on the left are my handiwork from years ago.  The Alford TV antenna was kept as a standby.  It was fed by an odd combination to 50 and 52 ohm rigid transmission line.  The outer conductors were the same, but the inners differed a bit in dimension, adapted back and forth by "whisky cup adapters".  It made for strange and interesting impedance roller coasters.  I spent a night there with a network analyzer working through it all to improve the response of the old Alford.  It looks like a vertical, but the slot configuration radiates are fairly omni horizontally polarized signal.
The article refers to a new 1666 foot tower.  That tower sits on property abutting mine on the back side of my stone wall.  Wouldn't I like to run some wires up to that!  This morning the top 1000 feet still has a shiny ice coating, so #12 probably wouldn't cut it.

[K1JJ]

It's true that for a given material thickness and overall tower diameter, the more sides, the stronger.  A two sided tower is weak. (a ladder)   A three sided tower is stronger.  A four sided tower is stronger yet. … Until we come to a single large rounded pipe that has infinite sides and is the strongest of all. The common monopole towers we see today take advantage of this, as do underground pipes and submarines...    But more material is required to cover the gaps.

When it comes to 3-sided vs: 4-sided, the strength advantage is not worth the labor and cost to put Rohn 3-sided towers out of biz. Users would rather upgrade to Rohn 55 instead of Rohn 45, though all 3-sided.   It really does come down to spending as few American Dollars as possible to get the job done!

Today it's screw the poor climbers who have to crawl up on frick'in tower pegs.   (Has anyone here ever climbed a 190'er on pegs?)

T

[K1JJ]

Now here's the real question when it comes to multi-sided towers.... a short exercise:

What if you were given 10,000 pounds of raw steel. You could build any tower structure you wanted as long as it was 100' tall, with guy wires included in the weight, if used. Guyed or self supported permitted.    No load - strength measured by wind slowly increased up to 500 mph and ice up to 1" radial dia.

Multi-sided towers would require you to make the material thickness thinner as you increased the number of sides.  So a 4-sided tower to weigh as much as a 3-sided tower would require thinner legs, etc.

Now what would be the strongest most efficient design?  If we included guy wires as material weight too, my guess is the strongest structure for 10,000 pounds of material to stand 100' tall would be a single TAPERED round monopole guyed at three levels with guy wires.  The diameter of the pole and material thickness would have to be optimized in software, as well as the guy wire thickness and spacing levels.

The only thing that bugs me about this design is that "self-supporters" are designed to sway and guy wires can actually load them down. So should the pole be the same diameter the whole way up, I dunno.

Or maybe it's a wash... as we increase the number of sides to infinity, the thinning material does not let us gain an advantage. Something like an immutable physics law...


Any ideas?

T

[W1ITT]

Hi Tom..
One thing I learned from working with the mechanical engineers is that tower design is spooky and not at all amenable to intuitive solutions.  There is some interesting proprietary software out there that shows the stresses and loads for various tower designs, antenna loads,  guy placements and tensions etc, in a graphical format, and sometimes it shows forces stacking up in ways that defy my limited logic.  So if I were to "design" a tower on my own, without really knowing what I was doing (I don't) I'd just make it as big  and scroteful as I could afford and hope for the best.
My all time favorite tower, the one I'd like to have in my back yard (I don't),  is the old Stainless G5.  The company name is Stainless, and it's a galvanized steel tower, 5 feet on a triangular face.  It's big enough to climb inside with a ladder in the corner, but not so huge that you don't feel nice and comfy unlike the 10 footers that feel like elevator shafts.  With a safety-climb cable on the ladder you could climb it, albeit slower every year, well into your elderly times.   A couple rest platforms on the way up and lunch and a cold drink in your bag and it would be ham heaven.  Lovely stuff, it is.
I haven't heard any news today, Wednesday, about anyone getting a close-up look at the Sugarloaf fall.  What a mess to untangle!
Norm

[DMOD]

For Tom's scenario I would choose a Monopole any day over a lattice tower.

See PDF.

I prefer the cacti tower or the Pine tree concealment myself. Gives you that warm, fuzzy feeling.

https://ehresmannengineering.com/towers-and-poles/concealment/


Phel

[K1JJ]

Yep, the tower modeling can be non-intuitive for sure.

When I put up my towers, the State of CT  rule was for TWO civil engr companies to review the plans, not just one. ($$)  There was a bad construction accident a few years before that killed a number of construction workers, so CT overreacted, of course.

The warning NOT to use guy wires on self spporters threw me.  Heavy steel guy wires can pull down a self supporter, not being designed for that kind of load.  Maybe a single set of light Phillystran  3/4 way up the tower would be a better solution.

Another advantage of lattice towers over monopoles  (for hams especially) is lattice allows you many places to bolt on brackets, mount antennas, tie ropes, etc.  Also, I would think the wind load is less being able to blow thru the tower.  

T