[TowerTalk] Calculating Forces for Tilting tower

[charlie at thegallos.com]

Thanks Jim,
That makes 100% sense, was wondering where the "Magic" 2x and 4x came 
from, as I was expecting to see a COS in there somewhere, and moment 
arms (I know enough to know that)

It is a case of "Show your work", and you did, so I get it.

On 2019-05-29 12:51, jimlux wrote:
> On 5/29/19 8:15 AM, charlie at thegallos.com wrote:
>> Hey Gang,
>> 
>> This isn't a snark answer - this is me trying to learn, I'm NOT an 
>> engineer (although some call me a 'software engineer' - bah)
>> 
>> Where do those 2x and 4x numbers come from?  I _ASSUME_ it is standard 
>> engineering "stuff".  Now I have a Machinery's Handbook, and a Marks 
>> Manual sitting here - is there a section where I can look this up, so 
>> I can understand it?
> 
> 
> You analyze this in terms of the moments which are Force times 
> distance.
> 
> The tower is 160 lb (4* 40lb/sec, and you can assume it's uniformly
> distributed along the length, so it's the same as a point mass at half
> the length.
> 
> The load is 50lb and at the end of the 40 ft tower.
> 
> So the moment is
> 
> 160 *20 = 3200 ft lb
> 50 * 40 = 2000 ft lb
> 
> or 5200 ft lb.
> 
> In order to just lift it, you need to figure out what force is applied
> at the 10 ft mark.
> 
> 5200/10 = 520 lb (pulling straight up).
> 
> You're not pulling straight up, though, you're using a cable from a
> winch attached to the garage wall.
> 
> For simplicity, let's assume the winch is at 10 ft also, so the cable
> is at 45 degrees when the tower is on the ground.
> 
> The tension in the cable is 520 lb/cos(45) =  735 lb.
> 
> Now, what's the horizontal force on the garage wall?  Since it's 45
> degrees, it's exactly equal to the vertical force on the tower.  520
> lb.
> 
> 
> 
>> 
>> I'm assuming it is the simple ftlb model, with the ratio of the 10ft 
>> and 40 ft, but that doesn't seem to take into account any vectors on 
>> the load too (of course that gives you a nice safety factor, always a 
>> GOOD thing)
>> 
>> 73 de KG2V
>> 
>> 
>>