[TowerTalk] Tilt-over Tower/Rotator Question
Don Moman VE6JY
ve6jy.1 at gmail.com
Thu Apr 20 16:07:26 EDT 2017
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.
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.
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
> semi-permanent location at our club station. The top of 3 tower sections
> 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
> 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
> 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
> 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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