> There is one thing I caution on and that is somr rotators are designed
> to work with a load on them and a negative load can be detrimental.
Loading is not an issue with Prop Pitch rotors.
I chose the cable suspension because its easy to fabricate and does
not require any thrust bearings. The original Prop drive gear contains a
spline drive to the gearbox. The spline is long enough to compensate
for the slight lift during rotation and expansion/contraction of the
suspension cable due to temperature changes. I welded an automotive
drive shaft U joint to the Prop Pitch output shaft and coupled it to the
Pipe going up the tower. This compensates for any slight mis-alignment.
73s de Jim
W5IFP
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces@contesting.com]On Behalf Of
> Roger (K8RI) on TT
> Sent: Sunday, September 08, 2013 2:05 PM
> To: towertalk@contesting.com
> Subject: Re: [TowerTalk] Ground Level Rotators
>
>
> On 9/8/2013 1:08 PM, WA3GIN wrote:
> > I used this method on the HDBX48 and its been up for over 30
> years....
> > funny thing is I've never had to work on the rotor (Tailtwister). I
> > use a thrust bearing to keep the pipe weight off the rotor bearing
> > although I'm sure they would handle the weight. I used allen screws
> > to set the couplings. Abt 12sqft of antenna on the mast. I ran a
> > ground strap from the mast coupling, just above the rotor, to ground.
>
> I really like the innovative suggestions.
>
> There is one thing I caution on and that is somr rotators are designed
> to work with a load on them and a negative load can be detrimental.
>
> With the cable suspension, I's add a spline say from a car
> drive train.
> A good one with no slop, that would allow vertical movement of the mast
> and no negative (pull) on the rotator. The whole works would
> leave about
> 10# on the rotator so there would be no tendency to pull against metal
> with no bearings. Just keep it well greased.
>
> Mounting the rotator independent of the tower removes all the torque
> from the tower so all it has to do is hold things upright. Of course
> this does put the entire torque load on the rotator, but it was
> designed
> for that.
>
> There is, or can be, a problem with mounting the rotator to the tower
> near the base. The tower can no longer spread the torque along its
> length, but rather it now is between the rotator and the
> concrete almost
> all in shear mode. If mounted right at the bottom, it is all
> shear mode
> and unhealthy for the tower.
>
> A local ham poured the pad a bit wider than needed. He then built a
> platform to fit inside the tower, but was entirely supported by two
> heavy steel angles (facing each other) bolted to the concrete. He used
> 2" X 3/16ths or 2" X 1/4 angle IIRC.
>
> The platform was just an accessory shelf with the ears cut off to keep
> it clear of the tower. This was securely bolted to the steel angle.
>
> Just think of two steel angles about 6 to 8 inches apart (what ever is
> convenient and fits) These bolt to the concrete roughly 6 to 8 inches
> outside the tower. They then go up a foot or so, then horizontally
> through the tower and back down on the other side. If tower bracing or
> construction prevents them from being at the same level, a block or
> riser can be fashioned to go on the lower one so they are at the same
> height where the rotator shelf mounts. Dimensions are not
> critical. For
> masting he used 2" Chrome molly with 1/2" wall. Heavy and over kill
> would be an understatement. I could not lift one end of a 24'
> length and
> I was doing full squats with 205# of free weight. We had to come up
> with a different rotator and he came up with a lighter mast.
>
> One note on the mast being supported by cables that cause the mast to
> move vertically. This adds a varying percentage of the entire
> weight of
> mast and antennas to the rotational mass so the rotational
> torque varies
> through the rotational cycle. How much? I don't know as it depends not
> only the rotational angle (180 deg at max) plus the vertical angle to
> the anchor point. Higher is less.
>
> I believe the tail twister is designed to support 500# dead load
> although it might be 800#. I'm sure some one on here will have
> the figure.
>
> 73
>
> Roger (K8RI)
>
> > 73,
> > dave
> > wa3gin
> > ----- Original Message ----- From: "Wilson" <infomet@embarqmail.com>
> > To: <towertalk@contesting.com>
> > Sent: Sunday, September 08, 2013 12:41 PM
> > Subject: [TowerTalk] Ground Level Rotators
> >
> >
> >> I love the pipe mast and cable suspension.
> >
> > _______________________________________________
> >
> >
> >
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>
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