I spent some time looking at the new PST61D and it looks as if they have
addressed the issues I spoke of earlier.
The wind area is the leverage applied. Looking at the rotator specs it
lists the torque and braking loads in ft lbs. Motor torque is 280 ft
lbs and braking torque is 2100 ft lbs. Vertical load is 1,870 lb. I'd
call Array Solutions and ask them about the mount. They have fixed the
water ingress for the top seal and I'd "guess" they have addressed the 4
bolt limitation between the mount and body, but could find no photos of
that. Please note the word guess is in quotes.
If they have fixed those problems, I'd go with the new PST61D without
hesitation even with that price. The old one was rated at 44 sq ft, but
I see the newer, more heavily built one is rated at a more realistic
39. There is no weakness in the internal double worm gears As far as I
cam see. after looking at the old internals.
I was impressed with them when I had the old one apart.
Photos at http://www.rogerhalstead.com/Gears.htm
73
Roger (K8RI)
On 4/26/2016 Tuesday 3:13 PM, jimlux wrote:
On 4/26/16 11:46 AM, Máximo EA1DDO_HK1H wrote:
PST-61D has 39sqft.
The one thing that still concerns me about the Orion, however, is
that it's
only rated to 35 sqft. The OB17-4 is 27 sqft, so there's not a lot of
margin there.
It's not clear to me what a "square foot" rating for a rotator would
be.. Inertia loads would be in some sort of mass *length^2.
Square foot would be for wind drag forces: Unless you're talking
about the "side" (radial) load on the bearings (which depends a LOT on
the mast length and whether there's other bearings or mounting points.
But for "turning in the wind", you'd need to know an area and a radius
from the axis of rotation to turn that into a torque (e.g. will it
overpower the brake or rip the teeth off the gears).
Maybe they're using "square feet" as a shorthand for "size of antenna
and polar moment of inertia". Square feet cross section is given for
most antennas, polar moment is not. Since most antennas are fairly
similar in construction, knowing cross sectional area (square feet)
probably correlates well with overall size and mass.
(unless you use solid steel bar as your boom, and silver plated steel
bars for the elements. <grin>)
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73
Roger (K8RI)
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