Greetings, TowerTalkians --
I forwarded a couple of our on-going discussion posts to Tom Schiller,
N6BT, chief designer at Force 12. Here's his reply:
In a message dated 99-03-02 11:20:55 EST, you write:
> Appreciate the information. I was impressed that apparently nobody has
> noticed the 70 mph mast torque spec in Force 12 specs for the last several
> years. I spend a lot of effort to keep this number below 1000 inch pounds.
> Kurt mentioned that the bulk of the antenna design time is on electrical and
> not mechanical. In our case, this is not so and never has been. I began the
"
> balanced antenna quest" back in 1978. The one I used for several years had a
> 48' boom 4el 20 with a 2el 40 on it, then a 36' boom 6el 15 above it, with a
> 36' boom 8el 10 at the top of the mast. I turned all of this with a
> TailTwister and still have the rotator - never touched it. I wrote my own
> software to compute the moments and fins, if necessary, which I did not use
> on my installation.
> In production designs, I average more than three fold the time on
> mechanical as electrical design, which is why they take so long. There are
> many cases where the mechanical drives the electrical. Some of the
> mechanical issues are more than balance, such as the 30" open area in the C-
> 31XR. That took me 6 months and was a combination of mechanical and
> electrical solutions.
> If you want to share some or all of this, that's all right. Besides the
> standard 70 mph mast torque spec in the Force 12 brochure, maybe we should
> add another at 50 mph, or some other velocity. The latest request we have is
> from Europeans who want the torque in Newtons.
>
> 73, Tom, N6BT
> Force 12, Inc.
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