I built a full size dipole for 40M and put it at 105 feet on my rotating
tower this Summer ... THREE times. The last time it stayed up until this
moment. I started with 1.625 inch, triple wall tubing in the center and
also have the struts out using 3/16 Dacron, doubled. I used eyebolts
through the element to tie the strut ropes to the element. I also used
Yagi Mechanical from DX Engineering to determine that the element needed
triple wall to survive.
So far, all I have seen is some 45 mph gusts.
BTW, the antenna works great!.
73,
Dave, K4TO
On Tue, Aug 14, 2018 at 1:54 PM Joe Partlow <joe.w6jwp@gmail.com> wrote:
> Sorry wrong thread.
>
> On Tue, Aug 14, 2018 at 10:52 AM, Joe Partlow <joe.w6jwp@gmail.com> wrote:
>
> > I cheat: http://ac6v.com/swrmeter.html
> >
> >
> > On Tue, Aug 14, 2018 at 9:56 AM, Jim Thomson <jim.thom@telus.net> wrote:
> >
> >> Date: Mon, 13 Aug 2018 16:40:04 -0700 (PDT)
> >> From: terry burge <ki7m@comcast.net>
> >> To: TowerTalk@contesting.com, terry burge <ki7m@comcast.net>
> >> Subject: [TowerTalk] supporting a 40 meter rotatable dipole with
> >> trusses
> >>
> >> <Been working on my 40 meter rotatable dipole I plan to put up at 124
> >> feet or so. But I'm worried about making sure whatever I come up with to
> >> fix the 3/16" dacron truss lines to the elements out about 20' or so are
> >> secure. Dealing with the DXE tubing when <it gets down below 1" or so I
> >> don't want anything too heavy. Also don't want to drill and weaken the
> >> dipole. I actually came up with some 'rings' from Wilco just about the
> >> right size that would slip over the 0.5", 0.625", 0.750" to I believe
> the
> >> 0.875". There I <could use 1/2"-1 1/4" hose clamps to make sure the ring
> >> doesn't slip further up. Just the dacron wrapped around the ring might
> be
> >> enough to keep that from happening but I don't trust it.
> >>
> >>
> >> <I'm not sure I could trust just using the hose clamps to hold the
> dacron
> >> line but I don't want to drill and weaken the tubing in any way.
> >>
> >>
> >> <Any better idea? You can see a few pictures of what I'm building on my
> >> QRZ/KI7M page.
> >>
> >>
> >> <Terry
> >>
> >> <KI7M
> >>
> >> ## Ken, W3JK, uses a 2 piece machined aluminum clamp, thick,
> >> rectangular, that goes around the tubing in question.
> >> On the top part of the clamp, a piece of 1 x 1 x .125 angle aluminum
> >> is bolted, using the same pair of ss bolts as the
> >> 2 x piece clamp. The vertical part of the angle al is where the truss
> >> terminates... with just a hole in the vert portion of the
> >> angle al. Use a small thimble etc, so the dacron does not bear down on
> >> the edges of the hole. Ken will make a couple of pairs
> >> for you, if he knows the exact tubing OD in question. Then they wont
> >> slip.
> >>
> >> ## I looked at your pix. I would use better mast to rectangular plate
> >> clamps.... vs the muffler style clamps you show in the pix.
> >> Use a pair of the dx eng style muffler clamps.. the ones that have the
> >> SOLID al saddle, then they have loads of surface area. The SS
> >> u bolts that come with them are extra long threads, that will handle any
> >> thickness al plate. You also
> >> need a solid fiberglass center insulator. Without it, you have way
> too
> >> much stress right in the middle.
> >>
> >> ## heres the real concern. Did you run the design through
> something
> >> like the DX eng yagi mech software program ???
> >> 66 ft long and starting with just 1.25..and down to the typ .375
> >> even with thick, inboard sections, is going to have a tough
> >> time with high winds... esp with dipole broadside to the wind. If we
> >> knew the exact tubing schedule used, which means exposed
> >> tubing lengths and also overlaps, and wall thickness, or if any inner
> >> liners used etc, etc, then it can all be run through the dx eng mech
> >> software very quickly.
> >>
> >> ## Your pair of over head truss lines wont buy you anything for
> >> increased wind speed, only sag, and sag from snow and ice loading.
> >> You also require horizontal dacron truss lines to handle increased
> wind
> >> speeds. Horz truss lines will also minimize horizontal
> >> deflection for XXX wind speed. If the ele deflects too much, then
> >> you also get this effect called... wind induced swr.
> >>
> >> ## The dx eng yagi mech program will spit out how much vertical..and
> >> horz deflection you will get..and also factor in both vert
> >> and horz truss lines.
> >>
> >> ## At 1st glance, I just cant see your 66 ft long ele
> >> surviving...when its only 1.25 inch OD in the middle. 1.25 is what
> you
> >> would typ
> >> use for the center of a 20m ele. For a 66 ft long dipole, 2.00 inch
> is
> >> typ used..then tapering down to .375 at the tips. Even then, the
> inboard
> >> 15 ft on either side of mast is typ heavy walled material, like .125.
> >> And thats just to get it to survive a 85-90 mph gust. Without a
> horz
> >> truss,
> >> the ele deflection is insane with high winds. Typ a single horz truss
> >> is used, and terminates 15 ft from the mast.
> >>
> >> Jim VE7RF
> >>
> >> _______________________________________________
> >>
> >>
> >>
> >> _______________________________________________
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> >> TowerTalk@contesting.com
> >> http://lists.contesting.com/mailman/listinfo/towertalk
> >>
> >
> >
> >
> > --
> > - 73 -
> > - Joe W6JWP
> >
>
>
>
> --
> - 73 -
> - Joe W6JWP
> _______________________________________________
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