The following is summary of replies that I received to my inquiry
about gin pole strength. Thanks to all who replied - the information
is greatly appreciated.
73 de Mike, W4EF.................
Can anyone out there give me advice (anecdotal, analytical, or otherwise)
on sizing a gin pole for structural integrity? I have a requirement to drop 24'
of 1/4" wall
4130 chrome moly into a Rohn 25G tower (estimate wt ~120 lbs). I currently have
in hand a 20'
section of schedule 40 6061-T6 water pipe (1.915" OD; 0.158" wall) which I hope
to use for the job
in conjuction with WB0W gin pole fixtures (pulley and bracket). The actual
working length
(measured from the bracket to the pulley) would be around 15' to allow for
raising the the
moly masts center of gravity (z=+12') above the top of the tower.
My feeling is that the aluminum pipe should be adequate to the job provided
that we take reasonable precautions to keep the load (mast) roughly collinear
with the
gin pole (e.g. minimize side load). Any comments on my assumptions would be
appreciated,
especially from those who have already performed similar feats.
Thanks,
Mike, W4EF/6
----------
From: KF8KW@aol.com[SMTP:KF8KW@aol.com]
Sent: Monday, March 15, 1999 9:04 AM
To: W4EF@pacbell.net
Subject: Re: [TowerTalk] Gin Pole Strength
Mike,
Would you post the results of your query on the gin pole strength to the
reflector or send me a copy of what you receive. Also have the same gin pole
and used a piece of roller stock as the main pole. Very heavy and hard to
handle on the tower even though the tower is up and running. Plan on putting
up a second tower in the near future and don't want to have to hassle with
this heavy horse again if I don't have to.
Gaylen also sells the poles made out of aluminum for around $60.00 but after
you figure in the shipping for a 12 foot piece, is almost cost prohibitive.
Can't seem to find a local source for this type of aluminum.
Dave
KF8KW
Bowling Green, KY
----------
From: Scott R Detloff[SMTP:sdetloff@metlife.com]
Sent: Tuesday, March 16, 1999 1:43 AM
To: w4ef@pacbell.net
Subject: RE: Gin Pole Strength
Hi Mike,
I built my 170' tower of R55 with a 14' gin pole made of 6061-T6 and
.375 wall. It wasn't a lot of fun to look at when a tower section is over
your head, but it worked. It flexed about 3-4 inches, which is more
than I would have liked to have seen, but we started at the ten foot
level and went from there. If at all possible I'd advise you to do the
same. Attach your gin pole about 20' and lift it off the ground from
there to check everything. Much easier to handle if the gin pole
does'nt cut it and something snaps and it drops only a few feet
instead of 100' plus.
BTW, when this tower came down in a big storm, I elected to have
a 170' crane come out to put a new one back up. I'd much rather
have 80' of R55 hanging over my head by a crane that 10' by my
gin pole :-)
GL...Scott K8DX
----------
From: K7LXC@aol.com[SMTP:K7LXC@aol.com]
Sent: Tuesday, March 16, 1999 2:26 AM
To: W4EF@pacbell.net; towertalk@contesting.com
Subject: Re: [TowerTalk] Gin Pole Strength
In a message dated 99-03-15 02:08:11 EST, W4EF@pacbell.net writes:
> Can anyone out there give me advice (anecdotal, analytical, or otherwise) on
> sizing a gin pole for structural integrity?
Not really but I'll share my thoughts.
The standard Rohn ginpole is fine for 25G and 45G but is not "factory
rated" for 55G plus it only has a 12 foot mast. This means that it isn't
entirely usefull for anything other than 25G or 45G.
> I have a requirement to drop 24' of 1/4" wall 4130
> chrome moly into
> a Rohn 25G tower (estimate wt ~120 lbs). I currently have in hand a 20'
> section of schedule 40
> 6061-T6 water pipe (1.915" OD; 0.158" wall) which I hope to use for the job
> in conjuction with
> WB0W gin pole fixtures (pulley and bracket). The actual working length (
> measured from the
> bracket to the pulley) would be around 15' to allow for raising the the
moly
> masts center of
> gravity (z=+12') above the top of the tower.
The WB0W fixture is more robust than the Rohn so coupled with an
appropriate mast will give you more capability. What you're describing is what
I use for BIG loads but my mast is 2 inch OD and has 1/4 inch wall. I'd talk
to Gaylen to see if your 1.915" mast will work - I think his fixture is
designed for 2 inch. A fifteen foot ginpole mast will just handle a 24 foot
long tower mast.
>
> My feeling is that the aluminum pipe should be adequate to the job provided
> that we take
> reasonable precautions to keep the load (mast) roughly collinear with the
> gin pole (e.g.minimize side load).
I'm really leary of your mast. I'd prefer using a 2 incher with a
thicker wall. I don't have any scientific reason - just gut feel.
Cheers, Steve K7LXC
----------
From: Jim White, K4OJ[SMTP:k4oj@ij.net]
Reply To: Jim White, K4OJ
Sent: Monday, March 15, 1999 1:08 PM
To: Michael Tope; 'TowerTalk'
Subject: Re: [TowerTalk] Gin Pole Strength
Elmer,
I have had much luck with using the following technique to get more than
half the length of the gin pole above the pick point.
By weighting the bottom end of the gin pole you can pick from lower than the
middle and will not have the top be top heavy per se, granted this makes the
heavy mast even heavier but it offers you additional control.
I have taped a sledge hammer onto the bottom of the mast amongst other
heavy/dense materials on hand at the time.
Even more important I have found is a temporary rope tie at the top of the
mast. Once the pipe is oriented vertically, take a short length of rope and
tie it around the top end of the pipe along with the lifting rope. When you
get the top of the mast even with your top plate you can untie this loop
since it is about to travel out of your reach.
This will aide in keeping the pipe vertical for all but the last few feet of
the trip...by now you are steering the mast for that critical moment of
insertion. Without doubt this is the toughest thing to do on a tower in my
opinion. Your inability to be anywhere but below an ideal work height
forces you to be working with your arms over your shoulders and muscling the
pipe in place.
A point of caution, stay in control of the pipe as it descends through the
top bearing...it is easy for the mast to go at an angle - I have seen
instances where the pipe can hit the cross brace on the way in - this is a
royal pain to fix...keep it going in vertically as best you can for as long
as you can - suddenly you will hit that sweet spot where you find yourself
breathing again and you find yourself questioning whether or not you soiled
your shorts!
b b b DI...that's all folks!
73,
Jim, K4OJ
k4oj@ij.net
From: Jim MILLER[SMTP:k4sqr@juno.com]
Sent: Monday, March 15, 1999 11:39 AM
To: W4EF@pacbell.net
Subject: Re: [TowerTalk] Gin Pole Strength
Mike;
In the early 1980's, after raising 25G to 80', I used my stock Rohn gin
pole to install 21' of sked 80 steel into top of the tower w/ help of one
man w/ me on the tower and 4 ground crew. It was a bear, but no danger to
anyone. (With 105Ba at top of tower and a 15-4 on 20' boom stacked 14'
above it, Hurricane Hugo bent the mast at the top of the tower in 1989!
So all those club members who had damage, replaced masts with 6061-T6,
.250 wall, 24 ft long & no failures 10 yrs. later.)
Based on your description, it should work for you.
GL-Be safe !
Jim Miller, K4SQR
Charlotte, NC
----------
From: K7LXC@aol.com[SMTP:K7LXC@aol.com]
Sent: Tuesday, March 16, 1999 2:36 AM
To: k4oj@ij.net; W4EF@pacbell.net; towertalk@contesting.com
Subject: Re: [TowerTalk] Gin Pole Strength
In a message dated 99-03-15 07:10:40 EST, k4oj@ij.net writes:
> By weighting the bottom end of the gin pole you can pick from lower than the
> middle and will not have the top be top heavy per se, granted this makes
the
> heavy mast even heavier but it offers you additional control.
>
> I have taped a sledge hammer onto the bottom of the mast amongst other
> heavy/dense materials on hand at the time.
>
Taking a heavy mast and adding more weight to it doesn't make for a happy
ground crew but is a reasonable technique.
> Even more important I have found is a temporary rope tie at the top of the
> mast. Once the pipe is oriented vertically, take a short length of rope
and
> tie it around the top end of the pipe along with the lifting rope. When
you
> get the top of the mast even with your top plate you can untie this loop
> since it is about to travel out of your reach.
>
> This will aide in keeping the pipe vertical for all but the last few feet
of
> the trip...by now you are steering the mast for that critical moment of
> insertion. Without doubt this is the toughest thing to do on a tower in my
> opinion. Your inability to be anywhere but below an ideal work height
> forces you to be working with your arms over your shoulders and muscling
the
> pipe in place.
You can also just tape the top of the mast to the haul rope and cut the
tape as it passes by you. Another technique is to have the pick point on the
mast above the midpoint; then it goes up vertically with no problem. What you
do at the top of the tower when the haul line knot hits the top of the ginpole
is to flip the mast 180 degrees. Since you've got it captured at the ginpole,
it'll just rotate until you have the short end in your hand (a short rope
attached to the 'top' will allow you to pull it down to you). Then you just
lower it through the thrust bearing/tower top. This produces the maximum
'pucker factor' when dealing with masts but it does work well. It actually is
easier than it sounds.
Cheers, Steve K7LXC
----------
From: Jim Froemke[SMTP:froemke@ibm.net]
Reply To: froemke@ibm.net
Sent: Tuesday, March 16, 1999 4:19 AM
To: Michael Tope
Subject: Re: [TowerTalk] Gin Pole Strength
Mike, I'm going to be doing the same thing in late May. Would be interested in
what you find out.
Also, where did you buy your mast from ?
Thanks,
Jim, K0MHC
Austin, TX
----------
From: Richard McGaver[SMTP:mcgaver@execpc.com]
Sent: Tuesday, March 16, 1999 9:43 PM
To: Michael Tope
Subject: Re: [TowerTalk] Gin Pole Strength
I have lifted about 110# with 3/16' OD 6061T6 but what you have is
considered pipe, I know because I just bought a piece 20' long and the 2" OD
is classified different.
Anyway you look at it , it sounds like your set and be SAFE
73
Rick NK 9G
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