[TowerTalk] Tilt-over Tower/Rotator Question

[Don Moman VE6JY]

John, I wouldn't worry about that amount of side loading on the Rak.
Somewhere in my Dayton HamVention archives I have a picture of Mitch VE6OH
doing chin ups on the USTower/SteppIR tower there, with our AlfaSPid RAK
and several feet of mast out horizontally during the install process.
Everything survived.

I found it and I'll send it to you as an attached copy but it will get
stripped for the reflectors I'm sure.

73 Don
VE6JY

On Thu, Apr 20, 2017 at 3:18 PM, John Brodie <brodiejb at shaw.ca> wrote:

> I just joined this group and can imagine my question has come up before.
> Our club has a tilt-over crank-up tower on a trailer which we are using in
> a
> semi-permanent location at our club station.  The top of 3 tower sections
> is
> very narrow with about 5 in. between vertical legs with a thin plate and
> sleeve-type bearing welded on top of the 3 legs.  A 2 in. diameter pipe
> extends about 4 ft. down from the top bearing to a lower bearing and plate
> and the pipe is free to turn.  A TH7 beam (weighing 75 lb) is mounted on
> the
> pipe close to the top sleeve bearing.  The spacing of the verticals leaves
> no room for a rotator mounted inside the tower so normally the beam is
> turned with a rope.  Our plan is to shorten the pipe, restrain it from
> turning, then install an Alfa Spid RAK rotator on the shortened pipe with
> the beam and VHF antenna on a second pipe immediately above the rotator.
> Our concern is that when the tower is lowered to a horizontal position for
> beam maintenance etc., the weight of the antenna and anything  mounted
> above
> it will place a large bending moment on the rotator and damage it (we have
> no doubt about the ability of the rotator to withstand forces when in the
> normal vertical position).  We have seen this concern expressed before, and
> note that others have constructed a "cage" to house the rotator above the
> top of the tower and thereby provide some bearing support above the
> rotator.
> The RAK appears to be very robust so I would appreciate informed opinions
> about the necessity to do this (and how best to do it). Thanks in advance
> for any advice.
>
> John VA7XB for VE7SAR  (Surrey ARC )
>
> Email: sarc at ve7sar.net
>
>
>
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