Homemade sch40 Tower questions

Discussion in 'Frame Construction' started by TKa, Nov 1, 2011.

  1. TKa


    Please critique my tower plan for a Wintura750 in a not so windy area but sometimes gusts can hit 50mph.

    Total hieght 24ft. 2 lengths of 10ft Sch40, and a 4ft top piece of sch80 to mount it.
    3 Steel 1/8" guy wires attached to the top coupler 20ft up and 4ft down from the turbine.

    Is this strong enough or should I add guy wires at the 10ft coupler also? 1/8" wire strong enough?

  2. windyguru

    windyguru WindyNation Expert

    What is the load rating of the cables?

    One set of guy wires should be sufficient but you may need to go thicker. If you can, try to get the tower 20 feet above any obstroctution within a 100 foot radius.
  3. TKa


    1/8 cable (7strand x 7wire) is 340lb max (Home Depot cable). Is that enough? I have no idea what the loads are on the wintura sitting 25ft up. Cables will probably be at a 60deg angle at the ground.
  4. murray2paddles

    murray2paddles WindyNation Engineer

    If you Google there are many sites offering load ratings for wire cable but unfortunately we do not have a load rating for mph for all the different size turbines / blades we are using. So Safety first and to protect your investment I would recommend 3/16 wire ( check to see if it is rust resistant) with 3 clamps per loop. Make sure the round part of the clamp is on the live side of the cable loop. ( live side would be the short length when looped). Wire attachments at approximately 20 ft high on your tower, 12-15 ft out from your tower base would be adequate for your cable anchors. ( even a 40-45 ft tower would only require 20 ft anchor from your tower base)
    If your location allows you would be surprised at how much cleaner wind there would be at just 10 more feet higher. Why don't you tell us more about your location, any close obstructions / trees etc .
  5. TKa


    My location is on a hill side with the nearest tree about 50ft away. The tower will be on the hillside behind the house so at 25ft high +~8ft up the hilll from the house. This puts the turbine ~15ft above the roof ridge and maybe ~40ft horizontally away from the roof ridge.

    I could add another 10ft sch40 section and move the single set of guy wires up to 30ft then add the 4ft piece of sch80 for the turbine. I was under the impression that the guy wires should be as close to the turbine as possible?
  6. murray2paddles

    murray2paddles WindyNation Engineer

    TKa, heads up,,, don't let any of us tell you what to do, we might suggest something but bottom line it's your decision because you qknow your own site better !
    There was also nothing wrong with your first design, that would have given you 28 ft and with no obstructions it may do you good. I had three towers at 32 ft high, which is close to your suggested height for a number of years and they produced well.
    When we start to suggest higher it is better because you will capture more clean air which gives more watts. The down side of going higher ( adding 10 ft) now you are at 38 ft which will require a second set of guy wires and may take you back to re thinking how to raise / lower your tower.
    The lower set of wires stabilizes the tower while the higher set takes all the force from the wind.
    Top set of wires should be 1/4 inch and bottom set 3/16 inch. At 38 ft high you would be setting your ground wire attachments at appox 20 ft from the tower base.
    If this is your first tower you might choose to make it a little more user friendly on the build and stay with your original 28 ft., if you do I would suggest that you place your ground anchors at 20 ft from the base and you would be set up if you add another 10 ft later.
  7. TKa


    Yep, this my first tower. I found some 3/16 (7x19) Galv cable rated to 840lbs. Will use that and start at 28ft tall and raise it later if needed.

  8. windyguru

    windyguru WindyNation Expert

    That sounds better. I roughly calculated about ~215 pounds of force on the tower if you were to consider the blades a ~35 square foot wall that a 35 mph wind was running into. Now, that does not take into account the incredible torque generated by the spinning blades which is substanial (Think of trying to change the direction of a fastly spinning gyroscope. It is not easy to do.)

    Of course, the tower pipe is also contributing to the strength of the tower so the 3/16 inch wire is not absorbing 100% of the load.

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