So-called "2 1/2 inch" water pipe or conduit has an
OD of 2 7/8 inches. Thinwall 3 inch conduit has an ID
of 2.9 inches. This allows for a 12.5 mil gap, theoretically.
This might work for tubing in perfect condition, although
you need to understand that they really don't specific "roundness"
so there is no guarantee it will fit. If you have used irrigation
tubing like I do (the price was right, hi), there will be a coating
of dirt on the inside, and probably a few dings. Next thing
you know you are having to use a rubber mallet and grease to get the
insert inside. Been there, done that.
It is far easier to just take a couple of feet of the
3 inch irrigation tubing and slit it length wise using
a sabre saw with a nonferrous metal blade. This piece
can then be slipped over the joint and clamped with
hose clamps. The strength is quite adequate. If over
stressed, the tubing next to the joint will buckle first.
The joint won't fail.
If you want an insulated joint, make the sleeve from 3 inch
sch 40 PVC pipe, and put in a spacer made from 2 1/2 inch
PVC pipe. Put a slight ding in the irrigation tubing to prevent
it from entering the spacer.
Rick N6RK
k1xx@cfl.rr.com wrote:
> Pat:
> For 3" irrigation tubing, I used EMT conduit bought at a local
> electrical supply house. At this time, I do not remember the exact
> size I used. However, one of the standard sizes fits very nicely as a
> splice. If you check, make sure you get the OD measurements since I
> think this was another potential ID/OD, pipe/tubing issue. I also seem
> to remember the conduit coming in 8 foot lengths.
>
> 73 charlie, k1xx/4
>
>
> ----- Original Message -----
> From: Pat Chiles <chilesp@adelphia.net>
> Date: Friday, November 3, 2006 10:28 am
> Subject: [TowerTalk] Questions about Irrigation Pipe for Verticals
> To: towertalk@contesting.com
>
>> I am in the process of putting together a project that will
>> consist of phased 1/4 wave verticals for 80 meters. For my QTH
>> the most cost effective resource of aluminum tubing is 3 inch
>> irrigation pipe. The wall thickness is .050 and it comes in 10,
>> 20, and 30 foot lengths. Since I will have to transport it myself
>> I will probably buy the 20 ft lengths. I am wondering what some
>> of you have done to splice sections together? How you varied the
>> length of the vertical for adjusting the SWR.? Finally, How did
>> you get it vertical? Thanks
>>
>> Pat, K8PC
>> _______________________________________________
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