ad: GNOHF-1

Good locally available antenna mast material

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by W0XX, Jun 3, 2019.

ad: L-HROutlet
ad: l-rl
ad: Left-3
ad: K5AB-Elect-1
ad: Subscribe
ad: L-MFJ
ad: MessiPaoloni-1
ad: Left-2
  1. W0XX

    W0XX Ham Member QRZ Page

    My mast got severely bent by a tornado and what I had was a piece of cyclone fence pipe cut about 14 feet long (3 feet is inside the tower to rotor)

    So now looking for something strong enough to withstand the horrible winds here. I don't think EMT Conduit would work and haven't located a fence outfit willing to sell me some of the material.

    So, what is locally available that might work okay? If I have to use a 10 foot length, will compress the distances between the antennas (6, Warc and HF Yagi) a lot.
     
  2. W1TRY

    W1TRY XML Subscriber QRZ Page

    It may be worth checking with a local metal supplier and ask for their advice. I've seen recommendations for both chromoly steel (strength) and AL 6061 hollowbar (lightness) over the years but neither option will be inexpensive. I do know that thin/thick wall EMT or water pipe/black pipe are not meant for structural support but a lot of us make do with the materials available. I'll step back now and wait for those smarter than me to correct me.
     
    WA7PRC, K2CAJ and N2EY like this.
  3. W7CJD

    W7CJD Ham Member QRZ Page

    1-1/4 diameter thick-wall steel ? used ?

    This is available from suppliers around oilfields.
     
    NH7RO and N0TZU like this.
  4. W0XX

    W0XX Ham Member QRZ Page

    Conduit, EMT is pretty thin. I think you want minimally 1/8 inch thick walled...
     
  5. AE1N

    AE1N Ham Member QRZ Page

    How about plastic PVC pipes with thick walls?
    Strong, insulated...
     
  6. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    It’s called “drill stem” pipe, used for oil and gas drilling . Should be readily available used in TX.
     
    K0UO, NH7RO and W1TRY like this.
  7. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    1N:

    PVC pipe is NOT structurally sound! It will bend, or break, with only very moderate force.

    Drill stem is very strong but is also very heavy. However, there are several companies out in Weatherford that should have used drill stem piled up.

    Glen, K9STH
     
    N2EY and NH7RO like this.
  8. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Mast strength increases with the square of the diameter, so 1-1/4" no matter what it's made of (unless it's solid and not tubing) is never strong enough for high loads.

    Most "big" beams can't even clamp down on anything that small. And while Yaesu rotators will, the Hy-Gain rotators will not rotate concentrically with such a small diameter mast: You have to "shim" the mast at the rotator to beef up its diameter to 2-1/16" OD for it to rotate properly.

    To the OP, I'd go for a 2" OD mast. I use a 15' length of 2" aluminum hollowbar (extruded tubing) with .250" wall thickness, so the I.D. is 1.5". It's very, very, very strong and also pretty lightweight and supports three beams over a 12' length above the thrust bearing through very strong winds just fine.

    HCS (high carbon steel) at 1.75" - 2.00" OD with a .120" wall is just as strong but may be heavier.

    Mast "diameter" is pretty important.
     
    KI4AX, K0UO, WA7PRC and 3 others like this.
  9. AI3V

    AI3V Ham Member QRZ Page

    https://sciencing.com/strength-tubing-vs-steel-tubing-7811536.html

    Paging Mr Young.

    A aluminum mast needs to be 3 times as thick as a steel mast to have the same strength.

    Also consider a steel mast cyclicly loaded to just under its yield point has essentially infinite resistance to fatigue failure.

    A pound of aluminum will be stronger than a pound of steel, thats why airplanes are made of aluminum and not steel

    A dollars worth of steel is stronger than a dollars worth of aluminum, thats why bulldozers are made of steel.

    Rege
     
    K0UO, KP4SX, KT5WB and 3 others like this.
  10. NH7RO

    NH7RO Ham Member QRZ Page

    I like your metallurgical poetry there, Rege; it really shines!
     

Share This Page