Hopefully Steve will chime in here, but I just ordered one of his clamps and
had some of the same questions.
First, the clamp is designed for a 2" mast, and is not adjustable.
Second, there's a hole in the base of Steve's clamp for the 1/4-20 bolt. The
prototype shown on the Champion Radio Products website doesn't have the
hole, but it's there in production units.
Third, Since Steve's clamp has holes precisely drilled to make with the
holes in the Orion top plate, it centers the mast. Therefore, you don't need
the centering wedge. I won't know until I get and install my clamp, but it
looks like the wedge would fit if oriented side-to-side. It wouldn't fit
front-to-back. If so, then it would lift the mast off the weld at the back
of the base plate.
The stock Orion clamp definitely slips. I have 16 sq ft of windload on my
mast (a Cal-AV 2D40A.) We normally don't get really high winds in our area.
Typical peak gusts on a windy day are maybe 35-40 MPH. Over a year's time,
the mast has slipped a few times, perhaps 5 degrees each time. I use a Green
Heron rotor controller (far superior to the stock Orion controller) and it
allows compensation up to the rotor overlap, which is something like 12-15
degrees. The mast finally slipped past that point, so I was headed for a
climb to reorient it. Then we had a massive (for us) windstorm a couple of
weeks ago, with 50-60 MPH winds, and the mast slipped about 60 degrees.
Again, I was able to use the GH controller to compensate by altering the
center of rotation (luckily, the rotor loop was just long enough to allow
this.) But as soon as it gets warm I'll have to go up there and reorient the
mast.
This is why I ordered Steve's clamp. I also looked at K7NV's Orion
replacement clamp. It's very nicely made and looks much prettier than
Steve's clamp. It also fits only a 2" mast. For some reason, I like the many
u-bolts on Steve's clamp better than the shorter compressed sleeve on K7NV's
clamp. Steve's clamp might have somewhat more gripping power because it
grabs onto a greater length of mast. But I'm sure K7NV's clamp will work
just as well for all practical situations. K7NV's clamp also has a hole for
the bolt, but the wedge can't be used. Steve says K7NV's clamp is
self-centering, too, but since it has oval bolt holes, it seems to me that
it can be installed out of alignment with the center of the rotor. In my
installtion, Steve's clamp will only require me to jack the mast up an inch
or two to replace the clamp. KN7V's clamp would require the mast to be
raised the entire length of the clamp.
As for using one of these clamps or pinning, others have pointed out that
bolts can shear. I've seen this happen with other rotors. If the mast clamps
loosen up, which the Orion's will definitely do, the mast rocks back and
forth, eventually causing the edges of the hole to shear off the bolt. It
can be a real pain to get that bolt out! If you're going to fix the mast, I
think either the K7LXC or K7NV clamp is the way to go.
But should you fix the mast at all? The manufacturer says let it slip, so
it's ironic that Steve is offering a product that violates his own K7LXC
Prime Directive. Steve feels the rotor gears are rugged enough to handle the
wind stress you're going to get if the mast doesn't slip. I'm sure the gears
are way more rugged than a T2X or Yaesu G2800, but they're probably not
invulnerable. In my opinion, it's a tradeoff. How many times do you want to
climb to reorient the mast? Since we don't often get very high winds in my
area, and I just get regular but small amounts of slippage, I thought it was
worth the risk to the gears.
73, Dick WC1M
> -----Original Message-----
> From: Jim Thomson [mailto:Jim.thom@telus.net]
> Sent: Wednesday, March 03, 2010 7:35 AM
> To: towertalk@contesting.com
> Subject: [TowerTalk] OR-2800 replacement clamp for 2" mast.
>
> I see that Steve, K7LXC, makes a replacement clamp for the OR-2800
rotor.
> Listed under Misc.. on his excellent website.
>
> Has anyone used these before ? It appears the clamp just bolts to the
> existing flat plate on the OR-2800 rotor. My concern is, there appears
to
> be
> no adjustments like the stock clamp. IE: the old clamp comes in from
BOTH
> sides.
>
> With Steve's clamp, it appears his retrofit clamp assy is designed for
> exactly a 2" OD
> mast. It appears to be welded across the bottom of the channel steel, so
if
> the mast
> is slid into place, the bottom of the mast would hit the weld, and not
end
> up flush
> with his [what looks like 1/2" thick steel] base plate ? This may be a
> good thing,
> allowing water to flow out the bottom of the mast.
>
> Another concern is, what about the stock 1/4-20 SS bolt, that holds the
> stock base plate
> to the internal rotor spline ?? The stock set up has an option for a
'self
> centering mast'
> which consisted of a triangle piece of 1/2" thick AL.. with a longer
1/4-20
> SS bolt.
>
> Either way, the 1/4-20 bolt is used to ensure the two splines stay mated
> together.
> With out it, the mast and the new clamp assy, is free to completely lift
> up, off the
> rotor. Perhaps the new massive 1/2" thick base plate has a recess on the
> underside
> to accommodate the thickness of the head of the 1/4-20 bolt ??
>
> The stock OR-2800 clamp, has what appears to be a flat on either side,
> designed
> to accept a 3/8" G-5 or G-8 bolt... straight through both the clamp
halves,
> AND
> the mast between em. IE: "Pinning the mast" The OR-2800 manual
warns
> NOT to pin the mast ! "just let it slip, or you will damage the rotor
> gears"
>
> Now if the stock clamp has no gripping power, and eventually slips, why
not
> pin it??
> If Steve's jumbo replacement clamp is used, [ with 6 x U-bolts/no
saddles] ,
> I doubt it
> would slip either, it's the real deal. So what's the real difference ??
>
> On 2nd thought, I think it would be VERY difficult to precisely drill a
> 3/8" hole in
> from BOTH sides of a 3/8" thick, 106 ksi chrome moly mast ?
>
> Steve, what does this clamp of yours weigh ?? Is it readily available
?
>
> Tnx... Jim VE7RF
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