[TowerTalk] Real numbers for Rohn BX-64 Re: guying

[Steve Maki]

Jim Lux wrote:

>> If I had three bathroom scales I'd go do a little experiment, but
>> I don't. So let me ask you what I'd find if I did this:
>> 
>> Take a 10' three legged tripod, and put a scale under each leg.
>> 
>> Back guy the tripod using a 45º guy angle.
>> 
>> Pull on the top of the tripod horizontally away from the guy.
>> 
>> If the tripod face width at the base is 3', and you pull with
>> 10 pounds of force, what do you read on the three scales?

> Hmmm.. ok..this sounds like a problem from my first semester physics
> class.  Let's assume you've got the guy lined up with the leg,  so you've
> got one leg pointing directly back, away from your horizontal load.  The guy
> load will be 1.4 times the horizontal or vertical force.
> 
> Now, the horizontal force is 10 pounds. The guy will resist this with a 10
> pound horizontal force, resulting in a 14 pound tension in the guy. The guy
> will push down on the top of the tripod with 10 pounds, as well.
> Since everything is balanced, and there's no other forces on the tripod, the
> load on each of the three legs will be the same, 10/3 pounds.

OK, good.

> If you put a load on the tripod itself , then, you'll get a moment and shear
> force on the base of the tripod

Here's where I'm unclear. Let's say, in addition to the 10 lb load at
the top, you put a 10 lb load in the middle of the tripod.

What do you see on the scales?

Steve K8LX