What I would do is put a thrust bearing where the rotor
normally would be located, allowing a mast of 10' or so
to extend below it. THEN, I would use thinwall irrigation
pipe as a 'torque tube' down to the rotor, in the bottom
section. Select a pipe just big enough to slip over
the mast, and pin to it.
Irrigation pipe is light and somewhat flexible, and will translate
the torque load down to the strongest part of the tower.
As for a rotor plate, look for a local metalworking shop,
and see what they'll charge you for one which fits the
lower section. You'll probably have to draw it for them...
and you may want to actually bring them the lower section, so
they can check the fit. My guess is, you could get away with
The reason for the 10' caveat is that Rohn had hbdx's fail due
to rivets coming out, when larger beams were allowed to slam into
the rotor brakes. The resulting torque impulse tore out the rivets.
Rohn was heavily driven by insurance company's requirements, at that time.
On 7/15/06, Paul Ferguson <Paul@paulferguson.us> wrote:
> I am putting up a Rohn HDBX 48 foot tower. I will put a 3 element
> SteppIR on it.
> The SteppIR specs are 42 lbs, 6.1 square feet of maximum wind load,
> and 16 foot boom.
> The HDBX 48 antenna load specs "Antenna types should be limited to
> those having a maximum boom length of 10 feet. No engineering data
> relating to the use of boom lengths in excess of 10 feet is available
> and the use of such boom lengths is not recommended."
> Would there be much advantage to lowering the rotor plate down to the
> next lower 8-foot section?
> Has anyone done this and have any tips on fabricating a new larger
> rotor plate?
> Raleigh, NC
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