Need 50+ Feet Poles for tower supports...
 

I will be building a water tower of about 30 to 35 feet in height, which would require that I set the poles down 12 to 15 feet for the load they will be supporting. That being said I will likely need 50 feet or longer poles to do the trick.

I am looking around to see if I can find any used utility/phone poles in my area. In the past I was able to buy them for $50 a piece.

However, I am also considering other alternatives. One thought is to simply cut down 4 pine trees of the right height and trunk diameter, strip the bark and treat them. Has anyone done this before with success?

I would also consider alternative materials such as metal beams.

In any case, I would like to hear any thoughts from people that may have already done this.

For technical purposes assume the weight bearing requirement of the platform will be anywhere from 4,000 to 6,000 lbs.

Dave

Re: Need 50+ Feet Poles for tower supports...
 

can't u do footings[concrete & steel] & bolt to them? of course the tower then has to be braced more for sideways stability.

Re: Need 50+ Feet Poles for tower supports...
 

I have definitely considered that; however my concern for living in Florida is the horizontal shear stress from strong storm winds. I suppose I could oversize the base to compensate or even use guy-wires off the top of the tower.

I am open to pretty much any design as long as it is both sound and cost effective.

Dave

Re: Need 50+ Feet Poles for tower supports...
 

Why the 35ft?

Re: Need 50+ Feet Poles for tower supports...
 

if u'r tower is open underneath i would think the shears would be small, compared to the stability the weight would provide- full/halffull. u might want to get someone to run numbers on the tank/structure for hurrican forces. i do think empty would be the worse case for wind shear.

BTW i'm a rookie that built my first screenhouse recently; so i'm just sort of brainstorming. u got a serious amount of weight up pretty high too.

Re: Need 50+ Feet Poles for tower supports...
 

Do you need 35 feet for the head pressure you want? Roughly every 30 feet is 15 PSI.

Back to your tower.....35 feet is pretty tall for 6000 lbs load + wind gust loading....even at 1500 lbs per column....35 feet is pretty tall.....columns are unstable due to the geometry of relatively long length vs small sectional properties. Columns fail in buckling. This can be eliminated via cross bracing so the effective column length is greatly greatly reduced.

I have not done any calculations (by the way, I was an structural engineer years ago.....perhaps I can do some calculations if needed ...once the final design is established....) - but here is a thought.....get 4 old steel trusses TV antenna towers - lots of folks will give you theirs if you take them down.....they are pretty strong when they have 3 and even better with 4 legs per tower......you could still brace them together when you build them up.....I like steel as you can weld to it and you can fab up a steel platform up at the top to support the tank. They are also modular and each section is pretty light weight and easy to work with.

Wind loading is a big concern. Please describe the top tank and i can run some numbers for you. I've designed some shortwave antennas that I did not want to support with guy wires....and the wing load is pretty significant in thunderstorms...and when you have heave sustained winds with added gust factors......the sustained wind can bend the system in the elastic range (meaning it will come back to normal after the wind stops)....but the gust on top of the deflected sustained load will yield the structure.....in my case I designed it for 70 mph maximum....and sometimes we get gusts over this...and it bends the antenns a bit....but i have hinge on the base for servicing it and can tip it down and straighten it out....


As for the make your own pine poles......I did this up north in michigan and built an elevated hunting bling about 25 feet high....I used cedar trees to prevent rot. Brace it up and it worked very well....but I have a 300 lb blind and 500 lbs of hunters....so total of 800 lbs on 4 posts about 7 in diameter.

I would think 4 telephone poles would be plenty if sank into firm soil about 6 feet - 10 feet.

Re: Need 50+ Feet Poles for tower supports...
 

Just be careful!

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Re: Need 50+ Feet Poles for tower supports...
 

That gives me the 15 to 20 PSI I need to the house...

Dave

Re: Need 50+ Feet Poles for tower supports...
 

btw climbing towers[practice for mountain climbing ] are sometimes out of telephone poles & i do believe the base was always bigger- poles slanted in at top. this increases side stability- maybe. u might google for a picture/design of one. glad ruprick is commenting! good luck!

Re: Need 50+ Feet Poles for tower supports...
 

Excellent thoughts ruprick. I actually have a good friend that is a geo-technical engineer and we determined we could carry quite a bit of weight per pole (at least 2 tons) if we buried them at the appropriate depth based on the soil make up and resulting skin friction....

BUT... I like your idea quite a bit as I see a lot of radio/ham towers around and even know a place where I can probably pick up 200 ft of it for free. If I did four legs I could get 50 feet giving me about 22 PSI minus pipe friction.

Great thoughts.

Dave

Re: Need 50+ Feet Poles for tower supports...
 

I meant to comment on this as well.

I have not picked a tank design but was definitely thinking about choosing something with the least amount of wind resistance thus reducing my wind loads. Obviously a sphere would be the ideal shape. Even if the tank is simply a round cylinder I could place a dome over the top to reduce the drag effect; however I will have to contend with the bottom (maybe a similar solution?).

Being that I live in Florida I would need to plan for sustained winds of probably 75 to 100 mph (hurricane or tropical storm). Obviously since you square the wind velocity to calculate force that 25 mph range from 75 to 100 is pretty significant.

Dave

Re: Need 50+ Feet Poles for tower supports...
 

Are you trying to live off grid? Do you want the PSI without use of electricity? How will you pump the water up there?

If you have power.....why not just use a ground based storage tank and hook it to a 30 or 50 gal well tank with a pressurized head of compressed air......

Sorry for all the questions...but your tower is going to be a big project to make it safe....3 tons x 35 feet up......I'm not sure i wanty to be around when the wind blows....

I'm crunching some numbers....I'll be right back....

Re: Need 50+ Feet Poles for tower supports...
 

Dave, I would run this by the County building Dept. first.

35' is pretty high and they may have some concerns. At best they will tell you how it would need to be built/braced.

Hate to see you build it then have the fuz tell you to take it down. Hurricanes are nothing to fool with as you probably know.

I know they have been very helpful to some bizarre ideas I have had. I live in WPB.

Re: Need 50+ Feet Poles for tower supports...
 

Just had a quick idea. I know living in florida, the land grade is pretty flat, but up near you, its better.

Dont know if you have any high grades on your property, and if you dont, maybe you could make one after you finish clearing and grading for the house. Then put a tank on top of the hill/slant and run a pipe down to the house. Could give you the pressure you need without having to go 35 feet up. Might only need to go 15 or 20 feet, which would certainly be easier and could possibly be done atop a solid building rather than supported as a tower.

Re: Need 50+ Feet Poles for tower supports...
 

6000 lbs......lets just say you have 600 lbs of tank and tank support structure up there....thus 5400 lbs water.....8 lbs/gal = 675 gal water....call it a 700 gal tank......about 7.5 gal/ cu ft.......tank will be just under 100 cu ft......lets assume a cylinderical tank of diameter = height.....

Vol = 100 cu ft = height x [(diameter x diameter) x 78%] = 0.78 x h^3.......height = 5 feet....

So, 5 feet tall x 5 feet diam will be a 700 gal tank easily holding 600 gal or 5400 lbs of water.

I'll be back with the wind loads in a minute....

Re: Need 50+ Feet Poles for tower supports...
 

Dave -

Meataxe engineering, here.

I build really, really big boats for a living, which require

Steel framed metal siding buildings.

With 40' - 45' sidewall heights which have to be

Impervious to 110 MPH winds,

According to code.

The trick here is to have monstro concrete footings.

The wind shear will literally pull the building out of the ground

Before it breaks the shell of the building,

Without the requisite weight beneath the ground.

Second point is, the bigger your footing footprint,

As compared to the dimensions of your tank -

We're talking the point loading on our tank being transferred to

Your foundations, here -

The more stable you are.

However, I'm not an accredited engineer.

Anyway, I'd look into just how heavy the footings would

Need to be, whether you use phone poles or I-Beams or whatever.


Scyth

Re: Need 50+ Feet Poles for tower supports...
 

In a nut shell, I am trying to be as grid free as possible. I plan to pump water to the tower on a continuous basis with a solar pump. The tower would then spill over into a ground based cistern I will use for mostly irrigation, and over flow there would be directed to a pond.

This obviously would be the most straight forward solution and would be a fall back if my tower project gets too big.

If I need to decrease the water storage to 500 gallons that will bring us closer to 4,000 lbs mark perhaps giving us more options. Additionally, as I am laying out my land, there is some elevation differences (not many, we are talking about Florida here) so I could potentially see if I can gain any height advantages.

Dave

Re: Need 50+ Feet Poles for tower supports...
 

You beat me too it... I will have some land contours determined in a couple of weeks when I bush-hog the land.

Dave

Re: Need 50+ Feet Poles for tower supports...
 

Scyth,

Wind shear stress is EXACTLY my concern. I know I could build a structure that would easily hold the vertical force but as you well know, those horizontal forces translate into massive vertical forces when the wind basically uses your rigid structure like a leverage against it's footers. The problem isn't so much the downward pressure but the upward pressure created by horizontal forces as you pointed out.

Good points on foundation especially considering your back ground.

This upwards and downward pressure issue is one of the reasons why I was thinking about large utility poles. By setting the poles near 15 feet deep most of the support strength will be from skin friction of the pole against the ground it is buried in. Unlike the one way advantage of a foundation against ground, the pole would also have the same upwards resistance from the skin friction thus potentially negating the horizontal forces from wind.

Dave

Re: Need 50+ Feet Poles for tower supports...
 

OK......5' diam x 5' tall cylinder in 100 mph wind = nearly 8000 lbs wind load...and this does not include the wind load of the tower support structure. The leg will probably add another 1500 lbs of wind load but down much lower....averaging the 1500 lbs at mid leg (15' up).

Most folks do not appreciate the force of 100 mph wind on even a small 5'x5' area.

Drop down to 75 mph = 4500 lbs.

50 mph = 2000 lbs force.

Steel TV tower will only handle this level of bending load if the are guyed.....Telephone poles deep in the ground probably will take this load.....poles have a lot of drag from braces, transformers and wires.....they can take the wind.....so can your tower.

Re: Need 50+ Feet Poles for tower supports...
 

Dave -

Monster Garage kind of stuff,here, but

If you drilled you phone poles through and through

For 1/2" rebar which stuck out, say

Two feet from either side of the pole,

And those drilled holes were set up so that

The Rebar stuck out in a spiral pattern

It would lock you into your footings pretty well.

Rather than going 15' deep, I think you could

Go a lot shallower.


scyth

Re: Need 50+ Feet Poles for tower supports...
 

Why not build a ground cistern and use the solar pump to reach head pressure just like everyone on a well does?

If you plan to build a tower, I would advise you to get a professional involved. Consult your local building codes, zoning height restrictions, homeowners insurance requirements, soil borings and/or test piling, etc... If you wanted a professional opinion, you just got one.

Re: Need 50+ Feet Poles for tower supports...
 

ruprick,

I can't thank you enough for the calculations. Not having much of an engineering background aside from common sense, I knew the wind load would exceed the actual vertical loads at high wind speeds and your calculations confirm that.

That being said, perhaps four phone poles with bracing between them would provide adequate strength. I will likely have to rent a large auger to dig the holes for the poles but considering the area I am in I probably won't have that hard of a time getting my hands on one.

50 foot phone poles at one point weren't too hard to get so I will keep looking. I know the local power and telephone companies have been replacing most of their wood poles with concrete so there is probably some huge surplus yard where they are dying to get rid of them.

In either case, I will run some of the final numbers by you once I get all of the measurements together. Ideally, I will try and find a height advantage to help reduce the tower height somewhere on the land. I will try and get some skin friction numbers based on buried poles as well.

Dave

Re: Need 50+ Feet Poles for tower supports...
 

Your monster garage gut is correct!

Keep in mind.....when the wind blows on the side of this structure...it will try to lift the upwind legs on one side and push the downwind legs deeper into the ground. At the same time....all legs will share equal bending loads.

The problem is the height vs the base footprint.....because it is 30 feet high...and the base is only 5 feet x 5 feet square......an 8000 lb wind load....30ft/2.5ft = 12X the force per each leg.....each of the 4 legs will share the 8000 lbs.....or 2000 lbs per leg.....2000 x 12 = 24,000.....so, there will be 24,000 lbs of force trying to pull the upwind leg and 24000 lbs planting the downwind leg.

You will need a lot of attachment into the ground.

I say go to an alternative design for a ground based system. I'll post some ideas in a minute.....

Re: Need 50+ Feet Poles for tower supports...
 

The only problem with using the solar pump for head pressure is it wouldn't do well for on demand use, especially at night; which is what lead me to the tower concept.

I will definitely take your advice and consult the local building codes and zoning folks before proceeding forward with anything. Are you a geo-tech ?

Dave

Re: Need 50+ Feet Poles for tower supports...
 

scyth,

I definitely wouldn't mind a more shallow solution to the base! Renting an auger big enough to do the drill would probably cost me just as much as the concrete needed to build the foundation.

Good thoughts again.

Dave

Re: Need 50+ Feet Poles for tower supports...
 

No offense to the creative thinkers posting here. You are getting really bad advice in both not understanding the difference between spread footings and friction pilings, as well as the fact wind forces increase with elevation. You must have a design that will counteract overturning moment under a horizontal load even when empty.

Build a ground cistern...

Re: Need 50+ Feet Poles for tower supports...
 

I have never seen a SILO damaged by wind in the midwest. The Round shape is the key IMHO.http://sk1.yt-thm-a01.yimg.com/image/111048f629bd289a

Maybe a form of SILO would be good---also makes an excelent anti-Zombie position.

E-A

Re: Need 50+ Feet Poles for tower supports...
 

That was the original intent behind the phone poles was to take advantage of the skin friction based on a deep setting. I will find out what the actual performance is based on our soil type next time I talk to my geo-tech friend.

Dave

Re: Need 50+ Feet Poles for tower supports...
 

OK.....here is your solution......just let the solar powered pump fill a ground based tank with no pressure....the pump will require less power to fill the ground tank since it is not pumping against the 30' - 35' head pressure.....not pumping against the 15-20 PSI.

Use the extra solar energy to charge a battery bank that can be used to power a pump and a conventional well tank.

I would think that for most applications....you do not need 20 - 40 psi water....toilets, sinks, things like that only need low pressure. Only the shower might need pressurized water....or the ability to drive a second floor shower.

You are probably going to have a central battery system for the rest of the home????

We had an off-grid cottage up in Canada....just used tanks in the roof trusses....worked for pretty much everything...,.

Re: Need 50+ Feet Poles for tower supports...
 

For the time and money your gonna spend buy or make a little pressure tank system like a DAVEY....http://www.daveypumps.com.au/products/household.aspx


I have the luxury (if you wanna call it that LOL) of living in a mountainous region so gravity set up is not so hard for me . For about 4yrs. after building my new house at a higher location than my old abode I utilized a pressure set up same as the link.Two years ago I punched a new well and cut a new pad 110' higher than my new house and set a 5000 gallon tank on it I then connected it to my lower elevation tanks for a total capacity of over 12000 gallons.Just from my new well to the new tank and down to my new house took a 1/2 mile of 2" pvc.....what a party that was.

I ran the Davey off my solar system ,I'm 100% off grid have been for over 20 years. My house is 3000sq ft and ran off a Davey 110volt system that drew 9 amps max......I would take a good hard look at a pressure set up cuz it looks like your gonna spend a ton of dough & time trying to go gravity fed....JMTC
Either way, good luck to , it's a long row to hoe :ok:

Re: Need 50+ Feet Poles for tower supports...
 

Sorry I didn't read Rupricks post above mine before writing , but I think he's talking along the same lines. I may not post or convey as well as others but I have all the experience in the world, brains don't hurt though Haha, what I lack in smarts I make up for with tenacity ....remember the old saying about not being able to see the forest for the trees.

Re: Need 50+ Feet Poles for tower supports...
 

Dave, 12 to 15 feet deep sounds excessively deep, however I'm not in Florida. Illinois power always told us 3feet plus 10%. So if you have a 30 foot pole you need to put it in 6 feet. At that depth it would snap before it pulled over.

That assumes very little load though. You could always put a concrete pad in the bottom to increase that though.

sb

Re: Need 50+ Feet Poles for tower supports...
 

nub,

Great links. I will take a look at the pressure system. The purpose of this conversation is based on the feasibility of what I am trying to accomplish. Naturally, living in Florida I don't have the benefit of 100+ feet deviations in my property boundaries allowing me to take advantage of geographic features for gravity driven system. However, in Florida water towers are used pretty extensively for the reliability it provides for water supply not to say your above system is any less reliable. Obviously you have issues that can arise in water towers as well.

Thanks for the information..

Dave

Re: Need 50+ Feet Poles for tower supports...
 

ruprick,

You are providing a good alternative to the tower. As I mentioned at the start of the thread I am not stuck on the tower concept but I am willing to embark on the project provided I can get the materials inexpensively enough.

I will not have a battery system immediately since funds will not permit an investment in solar power at the start but this is something I will be pursuing and adding to my homestead. I am hoping that solar options will have come down in price by the time I begin this part of the project.

There are three big things that are going to be my major power users.

1) Mechanical (cooling mostly)
2) Water Heater
3) Water Supply

I know for a fact I can address 2 and 3 pretty easily. Being in Florida a solar water system is EXTREMELY feasible and I know people that use solar heating system that provide them all the hot water they need even through winter. The water supply system of course I am trying to address with a passive approach in water supply versus a dependency on pump for pressure. However, if I can come up with a cost effective way to use solar for the pump I will definitely be open to that.

Mechanical will be a new thread entirely! At the start, I will add as many passive cooling features to my home as possible such as crawl space foundation, cupola for convection air flow, property positioning of the home as related to the sun and so on.

BTW: I found a great site that discussed skin and base friction of a pile: http://www.sbe.napier.ac.uk/projects...e/chapter4.htm

I am going to work with my geo-tech friend to calculate skin friction assuming I pile the poles in to a 15 foot depth. Off the top of his head he thinks we can achieve upwards to 4 tons capacity per pole of up/down vertical force assuming we are using 12'' diameter poles and we have a thick sand towards the base of the pile. Based on the results of our calculations which are pretty heavily dependent on my property soil conditions we should have an answer to the foundation requirements.

Ultimately, to give me the extra horizontal shear support I will likely need to have guy-wires that I can install prior to storms. Perhaps some concrete anchored hooks around the tower that I can latch too in preparation for strong winds. The guy-wire system may not be needed depending the result of the skin and base friction calculations of the piles.

Dave

Re: Need 50+ Feet Poles for tower supports...
 

Why not put it on or underground and then pressurize the tank or use a pressure pump on your water lines/ well pumps do this all the time.
Bill cook