[TowerTalk] Homebrew Tower for 500lbs load help needed

Fri Nov 3 08:44:10 EST 2006

I don't think you will reduce costs by building it yourself.  The companies that do this sort of stuff such as Bergey Wind Power in OK (Bergey.com) buy steel in quantities and at prices you couldn't.   If you are looking for a project it might be worth it.

Clint - W5CPT

  ----- Original Message ----- 
  From: John Barrett 
  To: towertalk at contesting.com 
  Sent: Friday, November 03, 2006 2:19 AM
  Subject: Re: [TowerTalk] Homebrew Tower for 500lbs load help needed

  My only real requirement is NO guy wires, and fairly easy access to the
  turbine for maintenance. I would prefer to homebrew to reduce cash cost, I
  tend to have a lotta time on my hands :)...

  I'm basing my turbine design on information from
  http://www.otherpower.com/20page1.html. They raised their 500 pounder 70
  feet on 10" x 1/8" pipe with a tilt base, but they used guy wires

  If a 12" x 1/2" pipe is sufficient for the wind loading without guy wires,
  it would be easy enough to rig a carriage to lift the turbine, eliminating
  the need for supporing the load when tilted. The turbine I'm installing is
  smaller than the one described in that link. 10ft diameter instead of 20ft.
  smaller generator, and a lighter axle system. Adding the carriage system
  will probably bring it back up into the 500lb range, and I'll have to modify
  the furling system to work with the larger diameter support.

  just on an offhand search I can easily 12.75x0.56 or 8.75x0.9 as used or
  surplus out of California (not having much luck finding sources for
  used/surplus with online inventory/price here in North Texas).. if I dont
  have to worry about supporting the load tilted over, would the 8.75x0.9 be
  enough ?? (both weigh in at about 75lbs/ft.. putting the tower at 3750 lbs)

  ----- Original Message ----- 
  From: "Jim Lux" <jimlux at earthlink.net>
  To: "John Barrett" <ke5crp at verizon.net>; <towertalk at contesting.com>
  Sent: Thursday, November 02, 2006 11:06 PM
  Subject: Re: [TowerTalk] Homebrew Tower for 500lbs load help needed

  > At 06:49 PM 11/2/2006, John Barrett wrote:
  >>I'm looking to design a freestanding tower that can support up to
  >>500lbs of load at 50 feet with a wind loading of approx 40 sqft and
  >>100 mph survivability. Guy wires are not an option for the location
  >>we must use. I have a few problems to solve and am not finding much
  >>in the way of references online to work out all the details.
  >
  > That's a pretty burly tower..  Not something you want to engineer
  > casually.. but, if you want to ballpark it, to find out how big a job
  > you're getting into...
  >
  > 100 mi/hr is 25lbs/sq ft or thereabouts, so you're looking at a wind
  > load of 1000 lbs, not counting the probably significant wind load of
  > the tower itself (it's gonna be bigger than a foot in diameter, so
  > you've got another 50 square feet of area, just for the tower).
  >
  > so let's say you've got a bending moment of, say, 1000lb*50 ft (50000
  > lb ft) + 1250lb*25 ft( 31250 lb ft).. call it 100,000 lb ft so you
  > pick up some margin.
  >
  > A piece of 12" pipe, 1/2" wall 50 ft long would weigh about 3000 lbs,
  > and would have a bending load failure of about 4000 lbs at the top,
  > so it's in the ballpark. (I assumed mild steel with a yield of 50 ksi)
  >
  > Don't forget you also need to design for seismic loads in many
  > places.  1/3 g on a 4000 lb structure is 1300 lbs.
  >
  >
  >>1> what kind of pipe/tubing to use (diameter/thickness) -- assuming
  >>that the "mast" will be a single run of pipe (welded and reinforced
  >>with smaller tube inside at the joints if needed).. This has to be
  >>able to support the 500lbs dead weight load in the tilt-down
  >>position if a tiltover is recommended. Stepping the pipe size down
  >>as we get higher is ok (unless a carraige setup is recommended)
  >
  > Since the tube has to support a 1000 lb wind load when vertical, it
  > will support a 500 lb load at the end when horizontal.
  >
  >
  >>2> footing recomendations -- how wide a hole and how deep ?
  >
  > enormous (by ham tower standards).. You've got a pretty big bending
  > moment trying to overturn that block of concrete.  Might want to
  > consider something like a vertical pier.  Drill a hole 3 or 4 ft in
  > diameter many  ft deep, fill it with rebar and concrete.  A lot
  > depends on your soil properties.
  >
  >
  >>3> should I look at a tilt and crank-up design to reduce the
  >>stresses when raising/lowering the tower ?? or perhaps a "carraige"
  >>design where the load is pulled up the tower after it is erect ??
  >>
  >>This is obviousy overkill for an antenna tower :) and while there
  >>will be antennas on it., it will mostly be used to support a wind
  >>turbine. (that is until I build the 2nd one to support a stacked beam :)
  >>
  >>now I just need the references or some advice to work out the rest :)
  >
  >
  > This is a pretty cookbook thing in the wind turbine business.  I
  > would imagine that they have standard designs, just like they do for
  > antenna towers.  Have you checked sources like Home Power magazine?
  >
  > It's not going to be cheap, but at least, in most states you can get
  > a tax credit or rebate to help pay for it.
  >
  > You could also look into commercial poles for supporting traffic
  > signals and things like lights over freeway overpasses.  50 ft is
  > fairly short in that business, and, again, they'll have stock designs
  > and design recommendations for the footing. (The stoplight down at
  > the corner near my house is probably 40 ft tall, but has a 40-50 ft
  > canteliever sticking out.  It's also held down by a dozen or so 1" or
  > larger bolts into a concrete caisson that was probably 30 ft deep
  > with a BIG rebar cage.  OTOH, they were able to install with only
  > jackhammering out one little segment of sidewalk.
  >
  > If you could possibly get away from the "monopole" type support, life
  > would be much easier.  There's a reason why farm windmills are made
  > on lattice style A-frame structures with a wide base.
  >
  >
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