I'm with Steve. I got a neighbor to build me one (he was a talented
fabricator) after making sure that my second C-3E had enough
inter-element clearance to swing fully. Put pieces of radiator hose on
the legs to serve as stops. 300 degrees it was, almost to a degree.
73, Pete N4ZR
On 1/30/2023 11:06 PM, Steve Maki wrote:
I was only talking about the gate itself. Of course the wider the
tower face, the longer the gate needs to be. And the more thought one
needs to put into the element spacing and boom-to-mast clamp location
on the boom, especially for 10M yagis. But it's a very good solution
for many scenarios.
-73, Steve K8LX
On 1/30/2023 8:03 PM, Grant Saviers wrote:
I'm not sure about the swing. Best to draw it out on the exact tower
dimensions. Also how the elements clear.
Grant KZ1W
On 1/30/2023 15:23, Steve Maki wrote:
Yes - the X configured bracing, which gets all three legs involved,
is how we made all our swing gate mounts and collars in the late
90's. That puts the rotor straight off the leg, which automatically
gets you 300° rotation, right?
-Steve K8LX
On 1/30/2023 6:08 PM, Grant Saviers wrote:
Might be better as a new topic "swing arm mounts"
Some expert advice I got was to use crossed A36 angle steel
(2x2x1/4 or 1.5x1.5x3/16) U-bolted to all three legs and mount the
rotator close to the tower on a 3/16 plate bolted in the V in the
outside gap.
Repeat for the top bearing, xx feet above the rotator. Could use a
stock "thrust" bearing or a simple UHMW block with all the load on
the rotator.
The swing arms were about 33" long mounted the the mast, which was
going to be 1-7/8" x 0.188" 1026 DOM. The mast was to be 13ft
between mounts so able to mount 2 yagis. A triangular brace mast
to arm and a stub mast welded on the arm to mount the antenna with
a stock mast-boom clamp. Of course YMMV.
It's important to have all three legs capture the loading.
Ideally get it all hot dip galvanized or do a good pant job.
And find a PE to recommend a design for the planned yagis.
Grant KZ1W
On 1/30/2023 11:32, Steve Maki wrote:
On 1/30/2023 2:23 PM, Lux, Jim wrote:
On 1/30/23 11:10 AM, Steve Maki wrote:
On 1/30/2023 1:48 PM, Lux, Jim wrote:
On 1/30/23 9:46 AM, Grant Saviers wrote:
I agree side mount + swing arm is a good option.
Although my 7 K0XG R65 rings have worked great minus one motor
failure, I would do side mounts for future (unlikely) towers.
The advantages of side mounts are lower cost & weight, using
standard rotators, and if desired with multiple beams on a
long mast between rotator and top support.
The side mount disadvantages are less rotation (but still can
get ~250*), some offset load on the tower (use 6 guys or star
brackets), and easily fabricated or purchased unique parts,
although you/PE need a design.
I think the updated Orion 2800 is a better choice than the
Yaesu for very big beams.
I've been thinking about this, and I wonder if there were some
"not too complex" scheme with an extra hinge point on the arm
that would get you 360 degrees. Not that I would build such a
thing (would that I had room for it) - but I was thinking if
you had an arm that is the length of a "face" of the tower, and
some sort of offset crank linkage, you could get 360 of
rotation from 240 degrees (or less) of movement from the
primary arm. My mind's eye has this as like a "wrist" that
reaches around the tower. Yeah, you'd have the mass of the
antenna as a cantilever load, which would put a bending moment
on the tower.
A swing arm where the rotor is mounted straight off a tower leg
is good for 300° easy. That's plenty as long as you have another
antenna to cover the dead zone.
Oh yeah, I figured that.. I was just contemplating "clever
mechanical solutions" - The swing arm is actually a nice solution
in general - simple, uses off the shelf stuff, can be added after
the tower is up, etc.
It's like the hinge plates for mounting an antenna on a
tower/mast that pivots from horizontal to vertical - a simple
clever solution.
Of course, the other solution is to mount two (or three) Yagis
and a combining network to phase them (or just switch). <grin>
Yep, I was trying to picture your idea. Back when linear actuators
were cheap (used in the satellite dish industry) I put some time
into thinking about a way to use one or two to turn a large yagi
on a swing gate. It never got past day dreaming and a little
pencil scratching.
-Steve K8LX
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