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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