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
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