[TowerTalk] Shimming "1.5" inch water pipe to fit 2 inch mast clamp (was: Re: Mast diameter)

[Richard (Rick) Karlquist]

On 12/23/2015 11:18 AM, Howard Hoyt wrote:
> TTalkians,
>
> I have a 20' long steel mast (looks like chrome moly) with 0.25" walls,
> which until today I assumed was 2" in diameter.  I had taken it down
> from the tower where it was in service, so at the time I assumed (!!!!)

You have "1 1/2 inch trade size (IPS)" water pipe, or at least
tubing that is the size of water pipe.  So-called 1 1/2 inch
pipe has an actual OD of 1.900 inches, and the ID depends
on whether it is Schedule 40 or 80, etc.  In the past when
I needed to interface 1 1/2 inch water pipe to 2 inch mast
clamps, I used a shim made out of 2 inch aluminum irrigation
tubing, which has an OD that actually is 2.000 inches.
The standard wall thickness of  0.050 inch means that
the ID is 1.900 inches.  Slit the shim lengthwise and
clamp it to the 1.5 inch shaft using hose clamps.
Then install it in the mast clamp and tighten that.
Between the hose clamps and the mast clamp, there will
be enough purchase to keep the irrigation pipe shim
from slipping.  This works perfectly whenever I have
tried it. The dissimilar metals issue doesn't seem
to be a big deal at least at this QTH, which is 50
miles from any salt water.  The irrigation pipe as
used for that purpose has galvanized water pipes attached
to it that have spriklers on them, so I guess it must be OK.

I have a bunch of the irrigation pipe.  I can send you a
scrap about a foot long for postage.

Rick N6RK