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[W3LFR]

I'm looking into a Hexbeam and figuring out a mounting scheme. It will be on a mast and somehow attached to my patio. I want to mount the rotator close to the ground and install a thrust bearing at about eight feet above the ground at the top of the patio cover. How long can the mast be above the thrust bearing without being guyed? I don't have enough room for guys in this plan, and if I can't get the beam at least ten feet above the TB without guys, I'll find an alternative mounting method. We don't get much high wind here, so I'm thinking it would be safe at ten feet if I use a sturdy mast.

Thanks.

[K6AER]

The problem is not the thrust bearing but the strength of the mast with the antenna wind loading. Almost any mast will bend and fail well before the thrust bearing becomes a problem.
I would consider 30 feet of Rohn 25 mounted next to the house. you can mount the rotor with a mast going up the tower inside for maintenance. With a hex beam your wind loading will be small.

[K5LXP]

The side loads can be calculated based on antenna cross section, and placement distance above the bearing.  The mast material and wall thickness can then be selected to best fit your loading and weight .  Chrome moly steel and extruded aluminum tubing (not pipe) will both have spec hardness and tensile strength spec's.

As a data point, I have a large tribander, 6M beam, 2M and 440 long boom yagi's and a 6M ringo on the mast on my tower.  1/8" wall 6061 T6 15' OAL, 3' inside the tower below the bearing to a ham IV rotor.  Installed 19 years ago and no hardware issues.

Mark K5LXP
Albuquerque, NM

[W3LFR]

Thanks for the info gents. I don't want to install a tower due to the necessity for a permanent cement base. Also, it would need to be freestanding, connected to a patio support at eight feet, and be short enough to not need guying. Any arrangement that could give me 15 feet from the TB to the beam would be great. The masts that support my 40 meter dipole are thin wall TV mast, but I wouldn't trust one for this setup. The 1/8" wall thickness sounds better.

[N4UFO]

Any arrangement that could give me 15 feet from the TB to the beam would be great.

Remember that pressure from wind loading acts as a force on a 'lever' with the fulcrum being at the highest mounting point, whether that is a thrust bearing or a guy point. And with every foot increase that you extend away from the fulcrum the force increases exponentially. So while five feet might be doable, understand that ten feet is not just twice the force and fifteen feet is not just three times the force... it's WAAYYY more. A hexbeam at 15 feet above the mounting point without guying?!! No way in hades. And you'll see that as soon as (if) you get it up. 

I've seen guys that have put hexbeams on the side of two story homes. The rotor is on the ground and there is a support that comes off the roof or roof edge. It extends a few feet above that, but that's all. Here are some pics of a lot of various hexbeam installations... note that they are almost all guyed within a few feet below the antenna if not immediately right at the base: https://www.k4kio.com/gallery/

Not want you want to hear, I know, but it's the way it is... sorry can't change it. To quote Scotty from Start Trek...

[VR2AX]

Remember that the thrust bearing functions to relieve the axial force, in other words the force along the line of the mast. Not the radial or sideways force. It's the total length of the mast that should be considered from a guying point of view.

[K5LXP]

I wouldn't be too concerned about the radial force on the bearing.  The ball or roller bearings in there can likely deal with a terrific amount of static pressure.  It's not like an axle that must support the load while rotating. 

Mark K5LXP
Albuquerque, NM

[K5MO]

As a data point, I have a large tribander, 6M beam, 2M and 440 long boom yagi's and a 6M ringo on the mast on my tower.  1/8" wall 6061 T6 15' OAL, 3' inside the tower below the bearing to a ham IV rotor.  Installed 19 years ago and no hardware issues.

Mark K5LXP
Albuquerque, NM

Did it make it through yesterdays winds? :-)

[W3LFR]

There is a reason why I can't place a support at the side of the house. It would be too far from the wall and would interfere with anyone walking from the front to the back. However, I could place the mast base on top of the patio cover and use a bracket/thrust bearing to secure it to the peak of the roof. That way I would only need a very short mast above the roof. I could place the rotator at or near the base. I'll need to think some more about that method. It would also let me use a tilt fixture.

[K5LXP]

Since I've lived here I've lost 2 trees to high wind, one hit the tower but the tower won.  The recent squalls have brought power outages and tumbleweeds/trash in the yard but the tower stands tall. 

Mark K5LXP
Albuquerque, NM

[KH6AQ]

Mast ideas

Mast design requirements?

Hexbeam (5.5 sq. ft. projected area)
Upper mounting point = 8' above ground
Mast height above the upper mounting point >=10'
Wind survivial, see below

Rotator
Yaesu G-450ADC
Maximum vertical load, 100 kg
Maximum mast diameter, 2.48"

Mast #1
Antenna mounting height 22' above ground
21' x 2" schedule 40 galvanized water pipe
OD = 2.375"
Wall = 0.154"
Tensile strength = 30 kpsi
Freestanding length is 22' - 8' = 14'
The rotator and ground mounting add 1'
Wind survivial = 67 mph

Mast #2
Antenna mounting height 27' above ground
21' x 2" schedule 40 galvanized water pipe + aluminum tubing
OD = 2.375"
Wall = 0.154"
Tensile strength = 30 kpsi

6" x 2.000" x 0.120" wall 6063-T832 aluminum tubing, DX Engineering Aluminum Tubing DXE-AT1313, $79

Freestanding length is 19'
The aluminum tubing telescopes 1' into the top of the steel pipe. Thin aluminum shims make it fit tightly.
Wind survival = 55 mph


Mast #3
DX Engineering Heavy-Duty 4130 Chromoly Steel Masts DXE-ST200CM-22, $1200 plus shipping
(2 in. Mast, Chrome-Moly 4130 Steel Tubing, 100K PSI Min. Yield, 2 in. OD, 0.250 in Wall, 22 ft. Length)

15' free standing
Wind survival, 119 mph

Mast #3
Aluminum Tubing, to be designed

Disclaimer:
I am not a mechanical engineer.

Galvanized water pipe is not recommended for antenna masts yet many of use use them for such.

[VR2AX]

Take a look at the last page of this advert which is a typical urban arrangement in Asia (for people lucky to have a house rather than apartment)

http://www.cd-corp.com/eng/ama/rtt/erc5x_eng.pdf

If you bracket your mast arrangement to the house at low height (a partial substitute for guying higher up), with or without thrust bearing, there will be a risk of structural damage to the property at the bracket area.

The hex beam has low weight but moderate-high wind surface area. A ham near me has one on what I guess to be a 30 feet high unsupported/unguyed steel pole (I don't know him but observe it comes down and goes back up quite regularly).

Rotator specs could be taken with a pinch of salt. The thrust bearing is unlikely to make things worse but it does not does not fix spec issues.

[W1MOW]

Have you run any of these ideas through your local building department? Due to the close proximity to your neighbors, I would ask them before doing anything.

You mentioned placing the base of the mast/rotor ontop of your patio cover, what is it made of?

Gary P.E. W1MOW

[W3LFR]

Have you run any of these ideas through your local building department? Due to the close proximity to your neighbors, I would ask them before doing anything.

You mentioned placing the base of the mast/rotor ontop of your patio cover, what is it made of?

Gary P.E. W1MOW

My neighbors are cool with my antennas. I've had various antennas for 20 years. The patio cover uses three 4X4 vertical supports with a
 4X8 truss connecting them at the top and sixteen 2X6 rafters fastened to the side of the house and the other ends fastened to the truss. The top is an array of 2X2s  with 2" spacing. It is a sturdy structure.

[VE7RF]

Mast ideas

Mast design requirements?

Hexbeam (5.5 sq. ft. projected area)
Upper mounting point = 8' above ground
Mast height above the upper mounting point >=10'
Wind survivial, see below

Rotator
Yaesu G-450ADC
Maximum vertical load, 100 kg
Maximum mast diameter, 2.48"

Mast #1
Antenna mounting height 22' above ground
21' x 2" schedule 40 galvanized water pipe
OD = 2.375"
Wall = 0.154"
Tensile strength = 30 kpsi
Freestanding length is 22' - 8' = 14'
The rotator and ground mounting add 1'
Wind survivial = 67 mph

Mast #2
Antenna mounting height 27' above ground
21' x 2" schedule 40 galvanized water pipe + aluminum tubing
OD = 2.375"
Wall = 0.154"
Tensile strength = 30 kpsi

6" x 2.000" x 0.120" wall 6063-T832 aluminum tubing, DX Engineering Aluminum Tubing DXE-AT1313, $79

Freestanding length is 19'
The aluminum tubing telescopes 1' into the top of the steel pipe. Thin aluminum shims make it fit tightly.
Wind survival = 55 mph


Mast #3
DX Engineering Heavy-Duty 4130 Chromoly Steel Masts DXE-ST200CM-22, $1200 plus shipping
(2 in. Mast, Chrome-Moly 4130 Steel Tubing, 100K PSI Min. Yield, 2 in. OD, 0.250 in Wall, 22 ft. Length)

15' free standing
Wind survival, 119 mph

Mast #3
Aluminum Tubing, to be designed

Disclaimer:
I am not a mechanical engineer.

Galvanized water pipe is not recommended for antenna masts yet many of use use them for such.

Plan 'B'.... use sched 80 Galvanized water pipe.  BTW, tensile strength does not enter into the equation, only the yield strength.

Another option would be to use 2.875" OD galvanized water pipe, in either sched 40 or sched 80.  In sched 80, it's .276" wall thickness.

Bending moment =  yield strength X section modulus of the pipe / tubing.   Bigger diameter + thinner wall has a lot bigger section modulus  vs  smaller OD and a thicker wall.

EG: 3.00" CM tubing with a .25" wall  has a much bigger section modulus   vs a 2.00" OD CM tube, with a .375" wall. IF both have the same yield strength, the 3" tubing wins  hands down.  But both weigh the same, and cost the same. 

Water pipe is typ 35-36 ksi yield strength.   CM is typ 105-120 ksi yield strength, but only if heat treated. Un heat treated CM is only 70 ksi yield strength.   Aluminum is typ 39/40 ksi yield strength.  (6063-T832 / 6061-T6/T8).   Galvanized DOM tubing is yet another option..and is typ 75-87 ksi.

As you can see, the stronger alloys are a helluva lot stronger vs  35/36 ksi water pipe.   Another option is galvanized fence post material.... which comes in as high as 52 ksi yield strength..and as big as 2.875"  OD.  KM1H has been using the galvanized 52 ksi fence post for masts for a looong time. They are cost effective.

The issue with aluminum is.... it flexs  3  X as much as steel.  (Modulus of elasticity is triple that of steel).

Your issue will be  2 x fold.  How much will it bend above..and below the bearing ?  It's a fulcrum at that point.