While on the subject of tower bolts, why does Rohn 25g tower use two
differant size bolts on the legs ?



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On Wed, 15 Jan 2014 19:55:05 -0500, Ralph Mowery wrote:
While on the subject of tower bolts, why does Rohn 25g tower use two
differant size bolts on the legs ?

My first thought was that it would promote more activity in r.r.a.a.
But, then I realized the Rohn 25G predates the internet!! HI!HI!

Jonesy W3DHJ

"Ralph Mowery" wrote in message
m...
While on the subject of tower bolts, why does Rohn 25g tower use two
differant size bolts on the legs ?


Perhaps it is because on the smaller cross-sectional component, the
larger bolt would not leave enough structural metal?

(sight unseen)

"gareth" wrote in message
...
"Ralph Mowery" wrote in message
m...
While on the subject of tower bolts, why does Rohn 25g tower use two
differant size bolts on the legs ?


Perhaps it is because on the smaller cross-sectional component, the
larger bolt would not leave enough structural metal?

(sight unseen)


Actually, just googled for the beastie; wow!

Do you left-pondians need to get planning or zonal permission for such
things as we do here in the land that is still plagued by the Normano-Viking
invaders and their spawn?

There is an engineering compromise in choosing bolt sizes for tower leg applications. You want to go with large bolts for more strength in bolt shear. You want to go with small bolts so the tower leg retains most of its strength . . . every bit of material removed by the drill bit for tower leg bolt holes weakens the tower leg a little more.

I suspect that using two of the smaller size bolts would not provide enough bolt shear and using two of the larger size would weaken the joint too much / A good compromise is to use two different sizes of bolts in each leg.

I also asked why they used fine thread bolts in 25G but not in 45G or 55G.
Again, the decision was made so long ago that nobody remembers why . .

I have used coarse thread bolts in 25G many times with absolutely no problems. Coarse thread bolts have the advantage that they can be "mechanically galvanized" rather than plated.

25G tower leg bolts are well known to rust after a relatively short time exposed to the elements.

45G and 55G bolts are coarse threaded and hot dip galvanized and hold up much better in the weather.

Hot dip galvanized threads tend to fill up with zinc during the hot dip
galvanizing process and sometimes the nuts won't go on without removing some of the galvanization or galling.

Mechanically galvanized bolts hold up like hot dipped bolts but work smoothly like plated bolts, but mechanically galvanized bolts for 25G are necessarily coarse threaded, rather than fine threaded and plated - like supplied by Rohn.

"gareth" wrote in message
...
Do you left-pondians need to get planning or zonal permission for such
things as we do here in the land that is still plagued by the
Normano-Viking
invaders and their spawn?


It all depends on where the station is located at in the US. I live in
North Carolina and out from the city. There is no requirement in the county
I live in for any kind of permit for a ham tower. About 8 years ago I put
up a 60 foot tower and did not need any permits or any other offical paper
work.

I am thinking the FCC limits the tower to 200 feet and some restrictioins if
near an airport in all parts of the country.

Some areas you can not put up a tower of any kind, and some areas need to
have permits and limit the tower to how tall it can be. Some areas require
some enginering paperwork to make sure the tower will not fall under
ordinary use.



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"Ralph Mowery" wrote in message
...

"gareth" wrote in message
...
Do you left-pondians need to get planning or zonal permission for such
things as we do here in the land that is still plagued by the
Normano-Viking
invaders and their spawn?


It all depends on where the station is located at in the US. I live in
North Carolina and out from the city. There is no requirement in the
county I live in for any kind of permit for a ham tower. About 8 years
ago I put up a 60 foot tower and did not need any permits or any other
offical paper work.

Green eyes of envy from this side of the pond

Are my eyes shining bright enough to attempt a Morse QSO? :-)

On 1/17/2014 10:35 AM, Ralph Mowery wrote:
"gareth" wrote in message
...
Do you left-pondians need to get planning or zonal permission for such
things as we do here in the land that is still plagued by the
Normano-Viking
invaders and their spawn?


It all depends on where the station is located at in the US. I live in
North Carolina and out from the city. There is no requirement in the county
I live in for any kind of permit for a ham tower. About 8 years ago I put
up a 60 foot tower and did not need any permits or any other offical paper
work.

I am thinking the FCC limits the tower to 200 feet and some restrictioins if
near an airport in all parts of the country.

Some areas you can not put up a tower of any kind, and some areas need to
have permits and limit the tower to how tall it can be. Some areas require
some enginering paperwork to make sure the tower will not fall under
ordinary use.



Actually, the FCC doesn't limit towers to 200'. But anything over 200'
has to be lighted and registered so it can appear on air navigation
charts. Then there are all kinds of other hassles like ensuring the
lights are always working at nighttime and having to climb a tower in 10
degree F weather with a 20mph wind (on the ground) to replace a burned
out light bulb (I know - I had to do it when I was young and stupid and
worked on towers ).

For most hams, it's just not worth the hassle.

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Remove the "x" from my email address
Jerry Stuckle

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"Jerry Stuckle" wrote in message
...

Actually, the FCC doesn't limit towers to 200'. But anything over 200'
has to be lighted and registered so it can appear on air navigation
charts. Then there are all kinds of other hassles like ensuring the
lights are always working at nighttime and having to climb a tower in 10
degree F weather with a 20mph wind (on the ground) to replace a burned out
light bulb (I know - I had to do it when I was young and stupid and worked
on towers ).


Over here, we have always been limited to 50' within half a mile of any
aerodrome,
but that does not imply local authority permission for anything up to that
height!

On 1/17/2014 12:22 PM, gareth wrote:
"Jerry Stuckle" wrote in message
...

Actually, the FCC doesn't limit towers to 200'. But anything over 200'
has to be lighted and registered so it can appear on air navigation
charts. Then there are all kinds of other hassles like ensuring the
lights are always working at nighttime and having to climb a tower in 10
degree F weather with a 20mph wind (on the ground) to replace a burned out
light bulb (I know - I had to do it when I was young and stupid and worked
on towers ).


Over here, we have always been limited to 50' within half a mile of any
aerodrome,
but that does not imply local authority permission for anything up to that
height!



Yes, there are additional limitations when close to airports, heliports,
etc. But rather than a fixed height like you have, ours varies
depending on the distance from the airport or heliport, and the size of
the longest runway of the airport. It varies from 25:1 (1 foot of
height for every 25 feet away) ratio for heliports to 100:1 for large
airports.

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Remove the "x" from my email address
Jerry, AI0K

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