[TowerTalk] Antenna & Tower Wind Load Ratings

[Kurt Andress]

On 6/16/2017 11:34 PM, Kurt Andress wrote:
> Hi Jim,
> Thank you for you contributions to the discussion!
> How you may decide to solve some problems is not necessarily how I 
> would chose to solve them....but that is probably not critically 
> important.
>
> We are pre-assembling three 16 element tribanders and two full size 
> 40's for a very large new rotating tower system for a client, with 
> several other antennas on it. I have determined what needs to be done 
> to the antennas to maintain wind torque & gravitational balance on all 
> the antennas, as they can actually be installed on the tower system, 
> and we have made the counterweights and compensators to do that. No 
> antenna builder out there is capable of doing that!
> We just do it for our clients, when they decide they want things done 
> right....
>
> Be mindful that even when antennas are properly torque balanced the 
> best they can be.....there are certain sites that produce unbalanced 
> wind loads on them due to the near field terrain!!!!
>
> Rating rotators for the incorrect or correct antenna areas is totally 
> useless! Rotators only care about the torque developed by the antenna 
> system they need to control!
>
> Jim, when you have developed the software to perform non-linear 
> analyses of antenna members continually inclined to different attack 
> angles in the increasing wind speeds, please let us know! Most of my 
> pro colleagues would like to have that capability, there is no 
> non-linear platform that can do it today....
> I know how I approach that, it takes many tons of time to even 
> approximate it, but it can be done if one is dedicated enough to spend 
> the time to approximate it! If you have finite element software and 
> are a capable practitioner with it, you can do this, it just takes 
> more time than following 222-G standards......
> On reflectors there are always people that say things, then there are 
> people that appear to know things, then there are people that actually 
> do the things they know......
> Nothing I have ever designed from scratch has ever failed, I've had 
> plenty of failures trying to make things delivered/built by others 
> survive!
>
> The linear analyses of EIA/TIA 222G do a pretty good job according to 
> the hordes of professional engineers that developed it, for us to use 
> as a guide to do what we do! I'm sure you have never ever even seen 
> it! But, you might learn something if you did........but, since this 
> is certified to be Amateur Experimental Radio, we all have free 
> license to just be Amateurs and experiment with what we think we know ;-)
> How the individual parts of antennas are designed and built is up to 
> the designer that is responsible for that, nothing I have designed 
> from scratch for any clients have ever failed, because I have fully 
> vetted them for the loads the were expected to encounter, for the 
> EIA-222-G rating I certified them for. I have no knowledge of what 
> others have done....
>
> There is one simple principle, that my first year engineering 
> professor drilled into our minds.....things only fail when they are 
> inadequate, there is always a reason for that, Our job is to 
> understand it and figure out how to not let that happen! What it takes 
> to do that is a bit more complicated.......
>
> 73, Kurt, K7NV