At 03:18 PM 3/1/1999 EST, Chanel1096@aol.com wrote:
>
>>Question for the MEs out there -- how would you combine wind torque and
>>measured inertia/momentum to produce a real number, that could be compared
>>with rotating and braking torque specs to determine if a given rotator will
>>do the job reliably?
> >
>>
>>73, Pete Smith N4ZR
>>n4zr@contesting.com
>
>In trying to combine wind forces and starting torque needed to overcome
>inertia, it would be relatively easy to look at the combination of the two
>based on a set wind velocity (speed and direction) however there is the crux
>the problem. In looking at a wind speed, we are approximating the wind and
>the often quoted 70 mph figure is a fastest mile wind which is currently
being
>phased out as all new wind data is based on 3-second gusts in which 90 mph is
>the new base wind speed. Even your previous 70 mph numbers had to use Gust
>Effect factors to obtain wind forces. So our wind forces which get
>approximated as static forces are not static but dynamic. In addition wind
>can fluctuate greatly over a small area as well, in the national building
>codes they have two different wind loads, one for an entire structure and
>another for individual components of the structure. All of this really boils
>down to the fact that you can add the 'base' wind load torque created and the
>required starting torque but I doubt this new number will mean anymore to
real
>world operation then the current 'K' factor which seems to be causing so many
>problems.
Bill makes a good point. Virtually any "standard wind environment" is
going to be, at best, just an approximation. However, since the current K
factor makes no allowance for wind forces at all, I think that any
benchmark that includes both wind and inertial components has to be an
improvement.
73, Pete N4ZR
Loud is good
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|