[TowerTalk] tower setbacks/falling trees

[Jim Lux]

On 2/4/12 12:46 PM, K8RI wrote:
> On 2/4/2012 9:53 AM, Jim Lux wrote:
>> VE7RF wrote:
>> The rules on setbacks  upsets me.  To have a tower  fall full length and
>> still remain on  your own property is pretty tough if a ham lived on a
>> typ city lot..like 50' x 120'  or  similar. Freestanding towers, like
>> Trylons  are designed to break at the 40' level..and not at the
>> base.They will not  fall full length.   A UST  crank up is the same
>> deal, they break 3 x sections up.
>>
>> Now if a 100' tall tree on my own property, falls  down on my neighbors'
>> house, the neighbors'  own house insurance covers the damage.   If the
>> neighbor does not have insurance, he is outa
>> luck. My insurance does NOT cover my neighbors' home.  Same deal with my
>> tower.
>>
>>
>> --
>> this brings up a couple interesting issues..
>>
>> You say designed to break at a particular point.  I hadn't seen that in
>> any of the drawings I've seen, but then, I wouldn't think they would put
>> a dashed line and arrow in a bubble saying>Break here.   But it is an
>> interesting concept.
>
> I've never heard that before and it'd be pretty difficult to get a tower
> made of identical sections to break at a predetermined point.
>>
>> The question would be whether it would fly in a regulatory context. It's
>> well known that tall skinny freestanding
> The keys are tall AND skinny AND free standing. That does not include
> most ham towers and you rarely find tall, skinny, and free standing
> apply to the same structure unless a guyed tower loses its guys.

yes.. I forgot to add free standing.. Guyed towers are different. 
(although, if you have a guy anchor failure...)


  Then no
> one knows where it's going and whether it'll stay in one piece or not.
> "I'd guess" that a 25 or 45G would stay in one piece...maybe.  Actually
> if it has a lot of mass on top, then I'd expect the tower to fold. A
> tower tends to accelerate at 32ft/sec^2. all along its length  Due to
> the base pivoting the top of the tower can not keep up with the bottom
> because it has farther to go in the same time while accelerating at the
> same rate and it tends to bend back out a ways from the base if the
> tower is tall enough to have enough mass to cause the tower to bend of
> break.

Same thing for chimneys, pencil points, etc.

>
>> things tend to break somewhere
>> when falling (chimneys, pencil points), but I don't know that it's
>> something that can be convincingly "designed in" in a way that will
>> cover ALL circumstances.  If the tower is strong enough, it WILL fall in
>> one intact piece.  (e.g. 200-300 foot trees fall over without breaking
>> in the middle)
> If a 100 foot ROHN 45 lost the guys on one side it'd likely stay in one
> piece. If a tree fell on one side who knows what it'd do.

Yes.. the 100 foot Rohn 45 stick is basically a "solid tree"

>
>>
>> The tower vs tree thing is more about "manmade" vs "natural feature"..
>> and, I suspect that if you had a big tree with obvious defects in it and
>> it fell on someone else's stuff, you'd wind up with liability.  All what
>> a "reasonable person" would have done to mitigate the obvious danger.
> Setbacks are considered a safety issue and I don't know of any that have
> been turned over and are more often in zoning regulations.
>


I think the point I was trying to make is that you can plant a tree that 
will grow to 100 ft tree in your side yard, 5 feet from the property 
line, because trees do that by themselves, people have an understanding 
of trees, etc.

Artificial structures are different.

And I suspect that if you tried to transplant a 100 foot palm tree into 
your 5 foot side yard, the city might have something to say about it.

I ran into strange setback rules when trying to put a fireplace in my 
back yard. There was a complicated interaction of setback rules (5 ft 
from sideline, 10 ft from back lot line), rules about chimney height 
(top must be 6 feet above nearest structure within 25? ft), and 
foundation depth and extent requirement tied to the chimney height. 
Same sort of rules apply to putting in a wood fired pizza/bread oven 
(which is the sort of kind of thing I was looking at)  It would have 
been the weirdest looking thing you've ever seen, because I would had a 
30 foot chimney and have to have been installed in the middle of the 
yard, in the middle of an enormous concrete slab.  (I now know why 
people do those odd looking pizza ovens on "carts"... I ask you a 2000 
pound clay and brick thing on a movable cart that rapidly will sink into 
the soil under it)

Basically, you could trivially have a chimney on a house (oddly the 
chimney itself can extend past the 5 foot setback line,if it protrudes 
from the side of the house, so there's 3 ft between the back of my 
house's chimney and the lot line), but anything else is probably impossible.

So much for building a cupola furnace from Lindsay Books and making 
steel. Or smelting bronze. Ah well, the neighbors probably would have 
objected to the truckload of limestone and coke and iron ore anyway.

They object to good clean(?) pre-industrial age fun, and set up rules 
that encourage indoor hydroponic farming instead.