[TowerTalk] How to stiffen a mast

[Pete Smith]

I believe there is a writeup on K7NV's web site about the mechanics of 
masts; I think he explains that the modulus of elasticity for aluminum is a 
LOT higher than steel, so for given physical parameters an aluminum mast 
will always be a lot whippier than steel.  Worth a look, anyway.


73, Pete

At 05:30 PM 1/31/2005, Jim Lux wrote:

>At 12:12 PM 1/31/2005, Rick Karlquist wrote:
>>Stiffness (not strength) is proportional to the quantity:
>>
>>OD^4 - ID^4.
>>
>>In your current case, this is 2.5^4 - 1.5^4 = 39 - 5 = 34
>>
>>The best you could possibly do with an aluminum insert is to emulate
>>a solid rod, in which case the stiffness would be higher by
>>a factor of 39/34 which is a 15% increase in stiffness.  I
>>believe steel is about 3 times stiffer than aluminum, so
>>a solid steel rod would get you a factor of 49/34 or 44%.
>
>Or, even a steel tube.. the 4th power making tubes almost as stiff as a 
>solid bar works for all materials..  A thin wall steel tube is probably 
>stiffer than a solid aluminum bar of the same OD (or weight).
>
>
>
>>Rick N6RK
>>
>>Barkey, Patrick M. said:
>> > I've been using 24 foot, half inch wall, 2.5 inch OD aluminum masts
>> > on all of my towers for quite a few years, with no failures or real
>> > problems.  During the recent ice storm, however, a couple of them
>> > flexed a little more than I'd like to see (they've since sprung back).
>> >
>> > Now that I have the opportunity to think this over, I am wondering
>> > if it would be of any value to try to add a little more stiffness to
>> > the existing mast by driving something into the hollow center.
>> > I've got a 1.5 inch ID hole to work with - perhaps some pipe or
>> > solid rod could be driven into it?
>>
>>
>>_______________________________________________
>>
>>See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless 
>>Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with 
>>any questions and ask for Sherman, W2FLA.
>>
>>_______________________________________________
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>
>
>_______________________________________________
>
>See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless 
>Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with 
>any questions and ask for Sherman, W2FLA.
>
>_______________________________________________
>TowerTalk mailing list
>TowerTalk at contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk