In need of  a calculator or the formula to calculate the forces on the base of a tower.    In the design phase of my antenna support structure.  I can get the windloading, weight, and dimensions easy enough.  Just need to know how much concrete I need at the bottom to keep it from tipping over.

links? 

Contact that manufacturer. They will have detailed engineering specs, to include footing. Rohn has excellent documentation.

Its not a tower but I will try.  

How big is the tower? I am looking at relocating a 100' self supporting tower and the base for that needs to be 4'4" deep by 10' square. About 16sq yards of concrete.

Well, to be honest, its not a "tower".  A while back when i realized i would likely end up in a city with a height requirement of 35', I started to figure out the probelm of "how much shit can I make happen in 35'".  I struggled and thought about multiple masts and maybe some utility poles, but that just had me with the same problem. I had to face facts of "I have one shot at 35' that HAS to fall in my yard hitting nothing (cant piss the wife off (red headed nurse that loves horses (see GD for the joke)))."   Then it dawned on me.  

SCAFFOLDING!!!   

I started researching and the more I did, i absolutly fell in love with the idea of a 5'x7' platform that I could easily climb and would have FOUR mini masts to mount all sorts of shit off of.  I love to experiment with antennas, espically VHF stuff (mostly sats), and I could cram a boat load off the support structure of a simple scaffold setup.  Even if it only got to 20', i could throw up 10' masts with antennas on top and it would be 'RF redneck nerdvana'.  

So thats when the actual physical requirements started to dawn on me of, "if theres an ice loaded 50mph north wind blowing on the fat side of this thing, how much will the skinny side hold before it says 'enough is enough' and goes on vacation."  

Which leads me to my post here.   So yea, i want to put up 20'-30' of scaffolding, freestanding, for my radio tower to hold anything I decide to put on it shy of anything crazy like stacked HF beams.  

And yes, the idea of making it isolated to use as a 40M vertical did cross my mind.  


So, thoughts?  

Wow, talk about being inventive.  Scaffolding as a support, what a great idea!!!!

Assuming that the scaffolding itself doesn't fail (rack), then you need enough concrete to keep the center of gravity low with the max antenna/ice/people load on the scaffolding.  As long as the scaffolding/extra masts don't fail, it won't fall over unless the center of gravity moves beyond the the edge of the base.   The lower the center of gravity, the further it has to tip, before the center of gravity is no longer over the base, and it falls.

*racking is when a rectangle up on edge (like a bookcase) leans to the side and becomes a parallelogram

The scaffolding seems like a weak point, if side load causes it to rack, it's coming down.  Likewise, if side load causes an upper section to lift up, it will bend the connectors on the other side and come down (just the part above where it lifted).  So your scaffolding will need stout cross bracing, and the levels need to be securely connected together.

Cool idea.

  It will end up being a chat with a SE.  All the stuff I've read said most of the scaffolding is designed to be taken down in winds above 50mph.  Cant determine if its a tipping reason or a crumbling down reason.  Luckily thru random BSing at work with my point blank questions to people "what do you know about scaffolding and concrete" netted me "nothing, but my brother is a SE specializing in concrete."  Couple text messages back and forth and I was told once i know the location and the soil type to get back in touch.  Simple job for him, no charge. 

All that said, looking at 2 houses tomorrow.  Eyes set on one with trees and no neighbors behind it.   Might be able to get a traditional mast up but after hatching the brain fart thats in this thread, i dont want one unless i need to get above the trees.  


Eta: part of my thought for keeping it from lifting would be to run cables from top of one corner to the the bottom opposite.   Interior guying, if you will.  Once i can source the scaffolding i'll make sure that there is a way to hardfasten the section together.  Self tapping screws or dilled and pinned.  

I'd love to help but last time I did this was when I was going to an engineering school, 25 years ago. I have not done anything like this ever since. All of my work has been in electrical. We did all those calculations by hand. I'm sure there are software applications for this nowadays.
You either need to find a structural engineer or someone fresh out of college. Find out exact dimensions of your structure and exact material characteristics the scaffolding is made of.
I'd be more concerned about the scaffoldin braking before concrete in the ground gives way. Don't forget to provide appropriate drainage for the piping that will be buried in the concrete.

It will be fun if I can make it happen.   Been shooting emails with the manufacture of the scaffold I have easier access to purchase.  30ft might not happen but i think 15-20 is going to and I can mast-up from there.   Looked at two houses, and completely flipped on which one I preferred.  Just gotta figure out how to do it and keep the wife happy.

Marriage, like all antennae are compromises.  

Seriously OP, good luck and please take lots'a pics-if you live through it, maybe I'll have you on the show to help teach us about your technique!

She isnt opposed to it.  She kind of assumes shes going to sacrafice some of the space in the yard to my antennas.  Just gotta do it and make it look decent.  And yea, photos will happen.